The complete VSI C Run-Time Library (C RTL) needed for use with
the VSI C compiler is distributed with the OpenVMS operating
system, which runs on Intel[R] Itanium[R] processors.
The C RTL provides routines to perform input/output, character
and string handling, mathematical computations, memory
allocation, error detection, subprocess creation, system access,
and emulation of selected UNIX[R] features. These routines are
provided both in shared image and object module library form.
The C RTL contains XPG4-compliant internationalization support,
providing functions to help you develop software that can run in
different languages and cultures.
This online help describes the C RTL routines available with this
version of the OpenVMS system.
For help on the socket routines used for writing Internet
application programs for the TCP/IP Services protocol, use the
following:
$ HELP TCPIP_Services Programming_Interfaces Sockets_API
Also see the "HP TCP/IP Services for OpenVMS" product
documentation.
1 – Feature-Test Macros
Feature-test macros provide a means for writing portable
programs. They ensure that the C RTL symbolic names used
by a program do not clash with the symbolic names supplied by the
implementation.
The C RTL header files are coded to support the use of
a number of feature-test macros. When an application defines a
feature-test macro, the C RTL header files supply the
symbols and prototypes defined by that feature-test macro and
nothing else. If a program does not define such a macro, the
C RTL header files define symbols without restriction.
The feature-test macros supported by the C RTL fall into
the following broad categories for controlling the visibility of
symbols in header files according to the following:
o Standards
o Multiple-version support
o Compatibility
1.1 – Standards Macros
The C RTL implements parts of the following standards:
o X/Open CAE Specification, System Interfaces and Headers, Issue
4, Version 2, also known as XPG4 V2.
o X/Open CAE Specification, System Interfaces and Headers, Issue
4, also known as XPG4.
o Standard for Information Technology - Portable Operating
System Interface (POSIX) - Part 1: System Application Program
Interface (API)-Amendment 2: Threads Extension [C Language],
also known as POSIX 1003.1c-1995 or IEEE 1003.1c-1995.
o ISO/IEC 9945-2:1993 - Information Technology - Portable
Operating System Interface (POSIX) - Part 2: Shell and
Utilities, also known as ISO POSIX-2.
o ISO/IEC 9945-1:1990 - Information Technology - Portable
Operating System Interface (POSIX) - Part 1: System
Application Programming Interface (API) (C Language), also
known as ISO POSIX-1.
o ANSI/ISO/IEC 9899:1999 - The C99 standard, published by ISO in
December, 1999 and adopted as an ANSI standard in April, 2000.
o ISO/IEC 9899:1990-1994 - Programming Languages - C, Amendment
1: Integrity, also known as ISO C, Amendment 1.
o ISO/IEC 9899:1990 - Programming Languages - C, also known as
ISO C. The normative part is the same as X3.159-1989, American
National Standard for Information Systems - Programming
Language C, also known as ANSI C.
1.2 – Selecting a Standard
You can define a feature-test macro to select each standard. You
can do this either with a #define preprocessor directive in your
C source before the inclusion of any header file, or with the
/DEFINE qualifier on the CC command line.
Features not defined by one of the previously named standards are
considered VSI C extensions and are selected by not defining
any standards-related, feature-test macros.
If you do not explicitly define feature test macros to control
header file definitions, you implicitly include all defined
symbols as well as VSI C extensions.
1.2.1 – XOPEN SOURCE EXTENDED
Makes visible XPG4-extended features, including traditional UNIX
based interfaces not previously adopted by X/Open.
Standard Selected: XPG4 V2
Other Standards Implied: XPG4, ISO POSIX-2, ISO POSIX-1, ANSI C
1.2.2 – XOPEN SOURCE
Makes visible XPG4 standard symbols and causes _POSIX_C_SOURCE
to be set to 2 if it is not already defined with a value greater
than 2.
Notes:
o Where the ISO C Amendment 1 includes symbols not specified by
XPG4, defining __STDC_VERSION__ == 199409 and _XOPEN_SOURCE
(or _XOPEN_SOURCE_EXTENDED) selects both ISO C and XPG4 APIs.
Conflicts that arise when compiling with both XPG4 and ISO C
Amendment 1 resolve in favor of ISO C Amendment 1.
o Where XPG4 extends the ISO C Amendment 1, defining _XOPEN_
SOURCE or _XOPEN_SOURCE_EXTENDED selects ISO C APIs as well as
the XPG4 extensions available in the header file. This mode of
compilation makes XPG4 extensions visible.
Standard Selected: XPG4
Other Standards Implied: XPG4, ISO POSIX-2, ISO POSIX-1, ANSI C
1.2.3 – POSIX C SOURCE==199506
Header files defined by ANSI C make visible those symbols
required by IEEE 1003.1c-1995.
Standard Selected: IEEE 1003.1c-1995
Other Standards Implied: ISO POSIX-2, ISO POSIX-1, ANSI C
1.2.4 – POSIX C SOURCE==2
Header files defined by ANSI C make visible those symbols
required by ISO POSIX-2 plus those required by ISO POSIX-1.
Standard Selected: ISO POSIX-2
Other Standards Implied: ISO POSIX-1, ANSI C
1.2.5 – POSIX C SOURCE==1
Header files defined by ANSI C make visible those symbols
required by ISO POSIX-1.
Standard Selected: ISO POSIX-1
Other Standards Implied: ANSI C
1.2.6 – STDC VERSION ==199409
Makes ISO C Amendment 1 symbols visible.
Standard Selected: ISO C Amendment 1
Other Standards Implied: ANSI C
1.2.7 – ANSI C SOURCE
Makes ANSI C standard symbols visible.
Standard Selected: ANSI C
Other Standards Implied: None.
1.2.8 – Interactions with the /STANDARD Qualifier
The /STANDARD qualifier selects the dialect of the C language
supported.
With the exception of /STANDARD=ANSI89 and /STANDARD=ISOC94, the
selection of C dialect and the selection of C RTL APIs to
use are independent choices. All other values for /STANDARD cause
the entire set of APIs to be available, including extensions.
Specifying /STANDARD=ANSI89 restricts the default API set to the
ANSI C set. In this case, to select a broader set of APIs, you
must also specify the appropriate feature-test macro. To select
the ANSI C dialect and all APIs, including extensions, undefine
__HIDE_FORBIDDEN_NAMES before including any header file.
Compiling with /STANDARD=ISOC94 sets __STDC_VERSION__ to
199409. Conflicts that arise when compiling with both XPG4 and
ISO C Amendment 1 resolve in favor of ISO C Amendment 1. XPG4
extensions to ISO C Amendment 1 are selected by defining _XOPEN_
SOURCE.
The following examples help clarify these rules:
o The fdopen function is an ISO POSIX-1 extension to <stdio.h>.
Therefore, <stdio.h> defines fdopen only if one or more of the
following is true:
- The program including it is not compiled in strict ANSI C
mode (/STANDARD=ANSI89).
- _POSIX_C_SOURCE is defined as 1 or greater.
- _XOPEN_SOURCE is defined.
- _XOPEN_SOURCE_EXTENDED is defined.
o The popen function is an ISO POSIX-2 extension to <stdio.h>.
Therefore, <stdio.h> defines popen only if one or more of the
following is true:
- The program including it is not compiled in strict ANSI C
mode (/STANDARD=ANSI89).
- _POSIX_C_SOURCE is defined as 2 or greater.
- _XOPEN_SOURCE is defined.
- _XOPEN_SOURCE_EXTENDED is defined.
o The getw function is an X/Open extension to <stdio.h>.
Therefore, <stdio.h> defines getw only if one or more of the
following is true:
- The program is not compiled in strict ANSI C mode
(/STANDARD=ANSI89).
- _XOPEN_SOURCE is defined.
- _XOPEN_SOURCE_EXTENDED is defined.
o The X/Open Extended symbolic constants _SC_PAGESIZE,
_SC_PAGE_SIZE, _SC_ATEXIT_MAX, and _SC_IOV_MAX were added
to <unistd.h> to support the sysconf function. However, these
constants are not defined by _POSIX_C_SOURCE.
The <unistd.h> header file defines these constants only if
a program does not define _POSIX_C_SOURCE and does define
_XOPEN_SOURCE_EXTENDED.
If _POSIX_C_SOURCE is defined, these constants are not visible
in <unistd.h>. Note that _POSIX_C_SOURCE is defined only for
programs compiled in strict ANSI C mode.
o The fgetname function is a C RTL extension to
<stdio.h>. Therefore, <stdio.h> defines fgetname only
if the program is not compiled in strict ANSI C mode
(/STANDARD=ANSI89).
o The macro _PTHREAD_KEYS_MAX is defined by POSIX 1003.1c-1995.
This macro is made visible in <limits.h> when compiling for
this standard with _POSIX_C_SOURCE == 199506 defined, or
by default when compiling without any standards-defining,
feature-test macros.
o The macro WCHAR_MAX defined in <wchar.h> is required by ISO C
Amendment 1 but not by XPG4. Therefore:
- Compiling for ISO C Amendment 1 makes this symbol visible,
but compiling for XPG4 compliance does not.
- Compiling for both ISO C Amendment 1 and XPG4 makes this
symbol visible.
Similarly, the functions wcsftime and wcstok in <wchar.h>
are defined slightly differently by the ISO C Amendment 1 and
XPG4:
- Compiling for ISO C Amendment 1 makes the ISO C Amendment 1
prototypes visible.
- Compiling for XPG4 compliance makes the XPG4 prototypes
visible.
- Compiling for both ISO C Amendment 1 and XPG4 selects the
ISO C prototypes because conflicts resulting from this mode
of compilation resolve in favor of ISO C.
- Compiling without any standard selecting feature test
macros makes ISO C Amendment 1 features visible.
In this example, compiling with no standard-selecting
feature-test macros makes WCHAR_MAX and the ISO C Amendment 1
prototypes for wcsftime and wcstok visible.
o The wcswidth and wcwidth functions are XPG4 extensions to
ISO C Amendment 1. Their prototypes are in <wchar.h>.
These symbols are visible if:
- Compiling for XPG4 compliance by defining _XOPEN_SOURCE or
_XOPEN_SOURCE_EXTENDED.
- Compiling for DEC C Version 4.0 compatibility or on pre-
OpenVMS Version 7.0 systems.
- Compiling with no standard-selecting feature-test macros.
- Compiling for both ISO C Amendment 1 and XPG4 compilance
because these symbols are XPG4 extensions to ISO C
Amendment 1.
Compiling for strict ISO C Amendment 1 does not make them
visible.
1.3 – Multiple-Version-Support Macro
By default, the header files enable APIs in the C RTL
provided by the version of the operating system on which the
compilation occurs. This is accomplished by the predefined
setting of the __VMS_VER macro, as described in the VSI C
User's Guide for OpenVMS Systems. For example, compiling on
OpenVMS Version 6.2 causes only C RTL APIs from Version
6.2 and earlier to be made available.
Another example of the use of the __VMS_VER macro is support
for the 64-bit versions of C RTL functions available
with OpenVMS Alpha Version 7.0 and higher. In all header files,
functions that provide 64-bit support are conditionalized so that
they are visible only if __VMS_VER indicates a version of OpenVMS
that is greater than or equal to 7.0.
To target an older version of the operating system, do the
following:
1. Define a logical DECC$SHR to point to the old version of
DECC$SHR. The compiler uses a table from DECC$SHR to perform
routine name prefixing.
2. Define __VMS_VER appropriately, either with the /DEFINE
qualifier or with a combination of the #undef and #define
preprocessor directives. With /DEFINE, you may need to disable
the warning regarding redefinition of a predefined macro.
Targeting a newer version of the operating system might not
always be possible. For some versions, you can expect that the
new DECC$SHR.EXE will require new features of the operating
system that are not present. For such versions, the defining
if the logical DECC$SHR in Step 1 would cause the compilation to
fail.
To override the value of __VMS_VER, define __VMS_VER_OVERRIDE on
the compiler command line. Defining __VMS_VER_OVERRIDE without a
value sets __VMS_VER to the maximum value.
1.4 – Compatibility Modes
The following predefined macros are used to select header-file
compatibility with previous versions of DEC C or the OpenVMS
operating system:
o _DECC_V4_SOURCE
o _VMS_V6_SOURCE
There are two types of incompatibilities that can be controlled
in the header files:
o To conform to standards, some changes are source-code
incompatible but binary compatible. To select DEC C Version
4.0 source compatibility, use the _DECC_V4_SOURCE macro.
o Other changes to conform to standards introduce a binary or
run-time incompatibility.
In general, programs that recompile get new behaviors. In
these cases, use the _VMS_V6_SOURCE feature test macro to
retain previous behaviors.
However, for the exit, kill, and wait functions, the OpenVMS
Version 7.0 changes to make these routines ISO POSIX-1
compliant were considered too incompatible to become the
default. Therefore, in these cases the default behavior is
the same as on pre-OpenVMS Version 7.0 systems. To access the
versions of these routines that comply with ISO POSIX-1, use
the _POSIX_EXIT feature test macro.
The following examples help clarify the use of these macros:
o To conform to the ISO POSIX-1 standard, typedefs for the
following have been added to <types.h>:
dev_t off_t
gid_t pid_t
ino_t size_t
mode_t ssize_t
nlink_t uid_t
Previous development environments using a version of DEC C
earlier than Version 5.2 may have compensated for the lack
of these typedefs in <types.h> by adding them to another
module. If this is the case on your system, then compiling
with the <types.h> provided with DEC C Version 5.2 might cause
compilation errors.
To maintain your current environment and include the DEC C
Version 5.2 <types.h>, compile with _DECC_V4_SOURCE defined.
This will omit incompatible references from the DEC C Version
5.2 headers. In <types.h>, for example, the previously listed
typedefs will not be visible.
o As of OpenVMS Version 7.0, the C RTL getuid and
geteuid functions are defined to return an OpenVMS UIC (user
identification code) that contains both the group and member
portions of the UIC. In previous versions of the DEC C RTL,
these functions returned only the member number from the UIC
code.
Note that the prototypes for getuid and geteuid in <unistd.h>
(as required by the ISO POSIX-1 standard) and in <unixlib.h>
(for C RTL compatibility) have not changed. By default,
newly compiled programs that call getuid and geteuid get
the new definitions. That is, these functions will return
an OpenVMS UIC.
To let programs retain the pre-OpenVMS Version 7.0 behavior of
getuid and geteuid, compile with the _VMS_V6_SOURCE feature-
test macro defined.
o As of OpenVMS Version 7.0, the C RTL exit function is
defined with ISO POSIX-1 semantics. As a result, the input
status argument to exit takes a number between 0 and 255.
(Prior to this, exit could take an OpenVMS condition code in
its status parameter.)
By default, the behavior for exit on OpenVMS systems is the
same as before: exit accepts an OpenVMS condition code. To
enable the ISO POSIX-1 compatible exit function, compile with
the _POSIX_EXIT feature-test macro defined.
1.5 – Curses and Socket Compatibility Macros
The following feature-test macros are used to control the Curses
and Socket subsets of the C RTL library:
o _BSD44_CURSES
This macro selects the Curses package from the 4.4BSD Berkeley
Software Distribution.
o _VMS_CURSES
This macro selects a Curses package based on the VAX C
compiler. This is the default Curses package.
o _SOCKADDR_LEN
This macro is used to select 4.4BSD-compatible and XPG4 V2-
compatible socket interfaces. These interfaces require support
in your underlying TCP/IP software. Contact your TCP/IP vendor
to inquire if the version of TCP/IP software you run supports
4.4BSD sockets.
Strict XPG4 V2 compliance requires the 4.4BSD-compatible socket
interface. Therefore, if _XOPEN_SOURCE_EXTENDED is defined on
OpenVMS Version 7.0 or higher, _SOCKADDR_LEN is defined to be 1.
The following examples help clarify the use of these macros:
o Symbolic constants like AE, AL, AS, AM, BC, which represent
pointers to termcap fields used by the BSD Curses package, are
only visible in <curses.h> if _BSD44_CURSES is defined.
o The <socket.h> header file defines a 4.4BSD sockaddr structure
only if _SOCKADDR_LEN or _XOPEN_SOURCE_EXTENDED is defined.
Otherwise, <socket.h> defines a pre-4.4BSD sockaddr structure.
If _SOCKADDR_LEN is defined and _XOPEN_SOURCE_EXTENDED is not
defined,
The <socket.h> header file also defines an osockaddr
structure, which is a 4.3BSD sockaddr structure to be used
for compatibility purposes. Since XPG4 V2 does not define
an osockaddr structure, it is not visible in _XOPEN_SOURCE_
EXTENDED mode.
1.6 – 2 GB File Size Macro
The C RTL provides support for compiling applications to use file
sizes and offsets that are 2 GB and larger. This is accomplished
by allowing file offsets of 64-bit integers.
The fseeko and ftello functions, which have the same behavior
as fseek and ftell, accept or return values of type off_t, which
allows for a 64-bit variant of off_t to be used.
C RTL functions lseek, mmap, ftuncate, truncate, stat, fstat, and
ftw can also accommodate a 64-bit file offset.
The new 64-bit interfaces can be selected at compile time by
defining the _LARGEFILE feature macro.
1.7 – 32-Bit UID and GID Macro (Integrity servers, Alpha)
The C RTL supports 32-bit User Identification (UID) and Group
Identification (GID). When an application is compiled to use
32-bit UID/GID, the UID and GID are derived from the UIC as in
previous versions of the operating system.
To compile an application for 16-bit UID/GID support on systems
that by default use 32-bit UIDs/GIDs, define the _DECC_SHORT_GID_
T macro to 1.
Not specifying _DECC_SHORT_GID_T provides long (32-bit) UID/GID.
Compiling on older OpenVMS systems where long UID/GID is not
supported, or compiling for legacy compatibility (_DECC_V4_SOURCE
for VSI C Version 4 or _VMS_V6_SOURCE for OpenVMS Version 6),
forces use of short (16-bit) UID/GID.
1.8 – Standard-Compliant stat Structure (Integrity servers, Alpha)
The C RTL supports an X/Open standard-compliant definition of
the stat structure and associated definitions. To use these new
definitions, applications must compile with the _USE_STD_STAT
feature-test macro defined. Use of _USE_STD_STAT specifies long
(32-bit) GIDs.
When compiled with _USE_STD_STAT, the stat structure includes
these changes:
o Type ino_t is defined as an unsigned quadword int. Without _
USE_STD_STAT, it is an unsigned short.
o Type dev_t is defined as a 64-bit integer. Without _USE_STD_
STAT, it is a 32-bit character pointer.
o Type off_t is defined as a 64-bit integer, as if the _
LARGEFILE macro has been defined. Without _USE_STD_STAT, off_t
is a 32-bit integer.
o Fields st_dev and st_rdev will have unique values per device.
Without _USE_STD_STAT, uniqueness is not assured.
o Fields st_blksize and st_blocks are added. Without _USE_STD_
STAT, these fields do not exist.
1.9 – Using Legacy toupper and tolower Behavior (Integrity servers, Alpha)
As of OpenVMS Version 8.3, to comply with the C99 ANSI standard
and X/Open Specification, the _tolower and _toupper macros by
default do not evaluate their parameter more than once. They
simply call their respective tolower or toupper function. This
avoids side effects (such as i++ or function calls) where the
user can tell how many times an expression is evaluated.
To retain the older, optimized behavior of the _tolower and _
toupper macros, compile with /DEFINE=_FAST_TOUPPER. Then, as
in previous releases, these macros optimize the call to avoid
the overhead of a runtime call. However, the macro's parameter
is evaluated more than once to determine how to calculate the
result, possibly creating unwanted side effects.
1.10 – Using Faster, Inlined Put and Get Functions (Integrity servers, Alpha)
Compiling with the __UNIX_PUTC macro defined enables an
optimization that sets the following I/O functions to use faster,
inlined functions:
fgetc
fputc
putc
putchar
fgetc_unlocked
fputc_unlocked
putc_unlocked
putchar_unlocked
1.11 – POSIX Style exit (Integrity servers, Alpha)
The VSI C and C++ Version 7.1 and higher compilers have a
/MAIN=POSIX_EXIT qualifier that defines the _POSIX_EXIT macro
and causes the main program to call __posix_exit instead of exit
when returning from the main program.
This qualifier should be used with programs ported from UNIX that
do not explicitly call exit and do not use OpenVMS specific exit
codes.
For older compilers, the following sample code can be used to
force the existing main module to have a different name so that a
simple main program will call it but force the exit status to be
through the __posix_exit call.
The replacement main function can be in a different module, so
that /DEFINE="main=real_main" is all that is needed for modifying
the build of the existing main function.
#define _POSIX_EXIT 1
#include <stdlib.h>
int real_main(int argc, char **argv);
/* Make sure POSIXized exit is used */
int main(int argc, char **argv)
{
int ret_status;
ret_status = real_main(argc, argv);
exit (ret_status);
}
#define main real_main
Unless your C program is intentionally using OpenVMS status codes
for exit values, it is strongly recommended that both the _POSIX_
EXIT macro be defined and, if needed, the /MAIN=POSIX_EXIT or the
alternative main replacement be used so that DCL, BASH, and the
accounting file get usable exit values.
2 – Feature Logical Names
The C RTL provides an extensive list of feature switches that
can be set using DECC$ logical names. These switches affect the
behavior of a C application at run time.
The feature switches introduce new behaviors and also preserve
old behaviors that have been deprecated.
You enable most features by setting a logical name to ENABLE and
disable a feature by setting the logical name to DISABLE:
$ DEFINE DECC$feature ENABLE
$ DEFINE DECC$feature DISABLE
Some feature logical names can be set to a numeric value. For
example:
$ DEFINE DECC$PIPE_BUFFER_SIZE 32768
NOTES
o Do not set C RTL feature logical names for the system.
Set them only for the applications that need them,
because other applications including OpenVMS components
depend on the default behavior of these logical names.
o Older feature logicals from earlier releases of the
C Run-Time Library were documented as supplying "any
equivalence string" to enable a feature. While this was
true at one time, we now strongly recommend that you use
ENABLE for setting these feature logicals and DISABLE for
disabling them. Failure to do so may produce unexpected
results.
The reason for this is twofold:
- In previous versions of the C RTL, any equivalence
string, even DISABLE, may have enabled a feature
logical.
- In subsequent and current versions of the C RTL, the
following equivalence strings will disable a feature
logical. Do not use them to enable a feature logical.
DISABLE
0 (zero)
F
FALSE
N
NO
Any other string not on this list will enable a
feature logical. The unintentionally misspelled string
"DSABLE", for example, will enable a feature logical.
The C RTL also provides several functions to manage feature
logicals within your applications:
decc$feature_get
decc$feature_get_value
decc$feature_get_index
decc$feature_get_name
decc$feature_set
decc$feature_set_value
decc$feature_show
decc$feature_show_all
See the reference section for more information on these
functions.
The C RTL feature logical names are listed below, grouped by the
type of features they control:
Feature Logical Name Default
------- ------- ---- -------
Performance Optimizations:
DECC$ENABLE_GETENV_CACHE DISABLE
DECC$LOCALE_CACHE_SIZE 0
DECC$TZ_CACHE_SIZE 2
Legacy Behaviors:
DECC$ALLOW_UNPRIVILEGED_NICE DISABLE
DECC$NO_ROOTED_SEARCH_LISTS DISABLE
DECC$PRINTF_USES_VAX_ROUND DISABLE
DECC$THREAD_DATA_AST_SAFE DISABLE
DECC$V62_RECORD_GENERATION DISABLE
DECC$WRITE_SHORT_RECORDS DISABLE
DECC$XPG4_STRPTIME DISABLE
File Attributes:
DECC$DEFAULT_LRL 32767
DECC$DEFAULT_UDF_RECORD DISABLE
DECC$FIXED_LENGTH_SEEK_TO_EOF DISABLE
DECC$ACL_ACCESS_CHECK DISABLE
Mailboxes:
DECC$MAILBOX_CTX_STM DISABLE
Changes for UNIX Conformance:
DECC$SELECT_IGNORES_INVALID_FD DISABLE
DECC$STRTOL_ERANGE DISABLE
DECC$VALIDATE_SIGNAL_IN_KILL DISABLE
General UNIX Enhancements:
DECC$UNIX_LEVEL DISABLE
DECC$ARGV_PARSE_STYLE DISABLE
DECC$PIPE_BUFFER_SIZE 512
DECC$PIPE_BUFFER_QUOTA 512
DECC$STREAM_PIPE DISABLE
DECC$POPEN_NO_CRLF_REC_ATTR DISABLE
DECC$STDIO_CTX_EOL DISABLE
DECC$USE_RAB64 DISABLE
DECC$GLOB_UNIX_STYLE DISABLE
Enhancements for UNIX Style Filenames:
DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION DISABLE
DECC$EFS_CHARSET DISABLE
DECC$ENABLE_TO_VMS_LOGNAME_CACHE ENABLE
DECC$FILENAME_ENCODING_UTF8 DISABLE
DECC$FILENAME_UNIX_NO_VERSION DISABLE
DECC$FILENAME_UNIX_REPORT DISABLE
DECC$READDIR_DROPDOTNOTYPE DISABLE
DECC$RENAME_NO_INHERIT DISABLE
DECC$RENAME_ALLOW_DIR DISABLE
Enhancements for UNIX Style File Attributes:
DECC$EFS_FILE_TIMESTAMPS DISABLE
DECC$EXEC_FILEATTR_INHERITANCE DISABLE
DECC$FILE_OWNER_UNIX DISABLE
DECC$FILE_PERMISSION_UNIX DISABLE
DECC$FILE_SHARING DISABLE
UNIX Compliance Mode:
DECC$DETACHED_CHILD_PROCESS DISABLE
DECC$FILENAME_UNIX_ONLY DISABLE
DECC$POSIX_STYLE_UID DISABLE
DECC$USE_JPI$_CREATOR DISABLE
New Behaviors for POSIX Conformance:
DECC$ALLOW_REMOVE_OPEN_FILES DISABLE
DECC$POSIX_SEEK_STREAM_FILE DISABLE
DECC$UMASK RMS default
Filename Handling:
DECC$POSIX_COMPLIANT_PATHNAMES DISABLE
DECC$DISABLE_POSIX_ROOT ENABLE
DECC$EFS_CASE_PRESERVE DISABLE
DECC$EFS_CASE_SPECIAL DISABLE
DECC$EFS_NO_DOTS_IN_DIRNAME DISABLE
DECC$READDIR_KEEPDOTDIR DISABLE
DECC$UNIX_PATH_BEFORE_LOGNAME DISABLE
2.1 – DECC$ACL_ACCESS_CHECK
The DECC$ACL_ACCESS_CHECK feature logical controls the behavior
of the access function.
With DECC$ACL_ACCESS_CHECK enabled, the access function checks
both UIC protection and OpenVMS Access Control Lists (ACLs).
With DECC$ACL_ACCESS_CHECK disabled, the access function checks
only UIC protection.
2.2 – DECC$ALLOW_REMOVE_OPEN_FILES
The DECC$ALLOW_REMOVE_OPEN_FILES feature logical controls the
behavior of the remove function on open files. Ordinarily, the
operation fails. However, POSIX conformance dictates that the
operation succeed.
With DECC$ALLOW_REMOVE_OPEN_FILES enabled, this POSIX conformant
behavior is achieved.
2.3 – DECC$ALLOW_UNPRIVILEGED_NICE
With DECC$ALLOW_UNPRIVILEGED_NICE enabled, the nice function
exhibits its legacy behavior of not checking the privilege of
the calling process (that is, any user may lower the nice value
to increase process priorities). Also, when the caller sets a
priority above MAX_PRIORITY, the nice value is set to the base
priority.
With DECC$ALLOW_UNPRIVILEGED_NICE disabled, the nice function
conforms to the X/Open standard of checking the privilege of the
calling process (only users with ALTPRI privilege can lower the
nice value to increase process priorities), and when the caller
sets a priority above MAX_PRIORITY, the nice value is set to MAX_
PRIORITY.
2.4 – DECC$ARGV_PARSE_STYLE
With DECC$ARGV_PARSE_STYLE enabled, case is preserved in command-
line arguments when the process has been set up for extended DCL
parsing using SET PROCESS/PARSE_STYLE=EXTENDED.
DECC$ARGV_PARSE_STYLE must be defined externally as a logical
name or set in a function called using the LIB$INITIALIZE
mechanism because it is evaluated before function main is
called.
2.5 – DECC$DEFAULT_LRL
DECC$DEFAULT_LRL specifies the default value for the RMS
attribute for the longest record length. The default value 32767
is the largest record size supported by RMS.
Default: 32767
Maximum: 32767
2.6 – DECC$DEFAULT_UDF_RECORD
With DECC$DEFAULT_UDF_RECORD enabled, file access mode defaults
to RECORD instead of STREAM mode for all files except STREAMLF.
2.7 – DECC$DETACHED_CHILD_PROCESS
With DECC$DETACHED_CHILD_PROCESS enabled, child processes created
using vfork and exec are created as detached processes instead of
subprocesses.
This feature has only limited support. In some cases the console
cannot be shared between the parent process and the detached
process, which can cause exec to fail.
2.8 – DECC$DISABLE_POSIX_ROOT
With DECC$DISABLE_POSIX_ROOT enabled, support for the POSIX root
directory defined by SYS$POSIX_ROOT is disabled.
With DECC$DISABLE_POSIX_ROOT disabled, the SYS$POSIX_ROOT logical
name is interpreted as the equivalent of the file path "/". If
a UNIX path starting with a slash (/) is given and the value
after the leading slash cannot be translated as a logical name,
SYS$POSIX_ROOT is used as the parent directory for the specified
UNIX file path.
The C RTL supports a UNIX style root that behaves like a real
directory. This allows such actions as:
% cd /
% mkdir /dirname
% tar -xvf tarfile.tar /dirname
% ls /
Previously, the C RTL did not recognize "/" as a directory name.
The normal processing for a file path starting with "/" was to
interpret the first element as a logical name or device name. If
this failed, there was special processing for the name /dev/null
and names starting with /bin and /tmp:
/dev/null NLA0:
/bin SYS$SYSTEM:
/tmp SYS$SCRATCH:
These behaviors are retained for compatibility purposes. In
addition, support has been added to the C RTL for the logical
name SYS$POSIX_ROOT as an equivalent to "/".
To enable this feature for use by the C RTL, define SYS$POSIX_
ROOT as a concealed logical name. For example:
$ DEFINE/TRANSLATION=(CONCEALED,TERMINAL) SYS$POSIX_ROOT -
"$1$DKA0:[SYS0.abc.]"
To disable this feature:
$ DEFINE DECC$DISABLE_POSIX_ROOT DISABLE
Enabling SYS$POSIX_ROOT results in the following behavior:
o If the existing translation of a UNIX path starting with "/"
fails and SYS$POSIX_ROOT is defined, the name is interpreted
as if it starts with /sys$posix_root.
o When converting from an OpenVMS to a UNIX style filename,
and the OpenVMS name starts with "SYS$POSIX_ROOT:", then
the "SYS$POSIX_ROOT:" is removed. For example, SYS$POSIX_
ROOT:[dirname] becomes /dirname. If the resulting name
could be interpreted as a logical name or one of the special
cases previously listed, the result is /./dirname instead of
/dirname.
2.9 – DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION
With DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION enabled, the
conversion routine decc$to_vms will only treat the first element
of a UNIX style name as a logical name if there is a leading
slash (/).
2.10 – DECC$EFS_CASE_PRESERVE
With DECC$EFS_CASE_PRESERVE enabled, case is preserved for
filenames on ODS-5 disks.
With DECC$EFS_CASE_PRESERVE disabled, UNIX style filenames are
always reported in lowercase.
However, note that enabling DECC$EFS_CASE_SPECIAL overrides the
setting for DECC$EFS_CASE_PRESERVE.
2.11 – DECC$EFS_CASE_SPECIAL
With DECC$EFS_CASE_SPECIAL enabled, case is preserved only for
filenames containing lowercase. If an element of a filename
contains all uppercase letters, it is reported in all lowercase
in UNIX style.
When enabled, DECC$EFS_CASE_SPECIAL overrides the value of
DECC$EFS_CASE_PRESERVE.
2.12 – DECC$EFS_CHARSET
With DECC$EFS_CHARSET enabled, UNIX names can contain ODS-5
extended characters. Support includes multiple dots and all ASCII
characters in the range 0 to 255, except the following:
<NUL>
/ *
" ?
Unless DECC$FILENAME_UNIX_ONLY is enabled, some characters can be
interpreted as OpenVMS characters depending on context. They are:
: ^
[ ;
<
DECC$EFS_CHARSET might be necessary for existing applications
that make assumptions about filenames based on the presence
of certain characters, because the following nonstandard and
undocumented C RTL extensions do not work when EFS extended
character-set support is enabled:
o $HOME is interpreted as the user's login directory
With DECC$EFS_CHARSET enabled, $HOME is treated literally and
may be in an OpenVMS or UNIX style filename.
o ~name is interpreted as the login directory for user name
With DECC$EFS_CHARSET enabled, ~name is treated literally and
can be in an OpenVMS or UNIX style filename.
o Wild card regular expressions in the form [a-z]
With DECC$EFS_CHARSET enabled, square brackets are acceptable
in OpenVMS and UNIX style filenames. For instance, in a
function such as open, abc[a-z]ef.txt is interpreted as a
UNIX style name equivalent to the OpenVMS style name abc^[a-
z^]ef.txt, and [a-z]bc is interpreted as an OpenVMS style name
equivalent to the UNIX style name /sys$disk/a-z/bc.
With DECC$EFS_CHARSET enabled, the following encoding for EFS
extended characters is supported when converting from an OpenVMS
style filename to a UNIX style filename:
o All ODS-2 compatible names
o All encoding for 8-bit characters, either as single byte or
using two-digit hexadecimal form ^ab. In a UNIX path these are
always represented as a single byte.
o Encoding for DEL (^7F)
o The following characters when preceded by a caret:
space ! , _ & ' ( ) + @ { } ; # [ ] % ^ = $ - ~ .
o The following characters when not preceded by a caret:
$ - ~ .
o The implementation supports the conversion from OpenVMS to
UNIX needed for functions readdir, ftw, getname, fgetname,
getcwd, and others.
NOTE
There are some special cases in C RTL filename processing.
For example:
o Pathnames ending in ^.dir are treated as directories, and
when translated, these characters are truncated from the
string.
o Pathnames begining with ^/ treat the next token as a
logical name or a directory from the root.
The following sample program shows these nuances:
#include <stdio.h>
#include <dirent.h>
#include <unixlib.h>
#include <string.h>
main()
{
char adir[80];
DIR *dir;
struct dirent *dp;
int decc_feature_efs_charset_index = 0;
int decc_feature_efs_charset_default_val = 0;
if (
( (decc_feature_efs_charset_index =
decc$feature_get_index("DECC$EFS_CHARSET")) == -1 )
||
( (decc_feature_efs_charset_default_val =
decc$feature_get_value(decc_feature_efs_charset_index, 0)) == -1 )
||
( (decc$feature_set_value(decc_feature_efs_charset_index, 1, TRUE) == -1))
)
{
printf("Error setting up DECC$EFS_CHARSET macro\n");
}
strcpy(adir, "SYS$SYSDEVICE:[SSHTEST.TEST.a^,test^.dir^;22]");
printf("\n\nFor %s\n", adir);
mrb: dir = opendir(adir);
if(dir)
{
do
{
dp = readdir(dir);
if(dp->d_name) printf("%s\n", dp->d_name);
} while (dp);
}
closedir(dir);
strcpy(adir, "SYS$SYSDEVICE:[SSHTEST.TEST.a^,test^.dir]");
printf("\n\nFor %s\n", adir);
dir = opendir(adir);
if(dir)
{
do
{
dp = readdir(dir);
if(dp->d_name) printf("%s\n", dp->d_name);
} while (dp);
}
closedir(dir);
strcpy(adir, "SYS$SYSDEVICE:[SSHTEST.TEST.a^\\test]");
printf("\n\nFor %s\n", adir);
dir = opendir(adir);
if(dir)
{
do
{
dp = readdir(dir);
if(dp->d_name) printf("%s\n", dp->d_name);
} while (dp);
}
strcpy(adir, "SYS$SYSDEVICE:[SSHTEST.TEST.copies]");
printf("\n\nFor %s\n", adir);
dir = opendir(adir);
if(dir)
{
do
{
dp = readdir(dir);
if(dp->d_name) printf("%s\n", dp->d_name);
} while (dp);
}
closedir(dir);
strcpy(adir, "/SYS$SYSDEVICE/SSHTEST/TEST/copies");
printf("\n\nFor %s\n", adir);
dir = opendir(adir);
if(dir)
{
do
{
dp = readdir(dir);
if(dp->d_name) printf("%s\n", dp->d_name);
} while (dp);
}
closedir(dir);
}
2.13 – DECC$EFS_FILE_TIMESTAMPS
With DECC$EFS_FILE_TIMESTAMPS enabled, stat and fstat report
new ODS-5 access time (st_atime), attribute revision time
(st_ctime) and modification time (st_mtime) for files on ODS-5
volumes that have the extended file times enabled using SET
VOLUME/VOLUME=ACCESS_DATES.
If DECC$EFS_FILE_TIMESTAMPS is disabled, or the volume is not
ODS-5, or the volume does not have support for these additional
times enabled, st_ctime continues to be the file creation time
and st_atime the same as the st_mtime.
The utime and utimes functions support these ODS-5 times in the
same way as stat.
2.14 – DECC$EFS_NO_DOTS_IN_DIRNAME
With support for extended characters in filenames for ODS-5,
a name such as NAME.EXT can be interpreted as NAME.EXT.DIR.
Determining if directory [.name^.ext] exists adds overhead to
UNIX name translation when support for extended character support
in UNIX filenames is enabled.
Enabling the DECC$EFS_NO_DOTS_IN_DIRNAME feature logical
suppresses the interpretation of a filename containing dots as
a directory name. With this logical enabled, NAME.EXT is assumed
to be a filename; no check is made for directory [.name^.ext].
2.15 – DECC$ENABLE_GETENV_CACHE
The C RTL supplements the list of environment variables in the
environ table with all logical names and DCL symbols available to
the process.
By default, whenever getenv is called for a name not in the
environ table, an attempt is made to resolve this as a logical
name and, if this fails, as a DCL symbol.
With DECC$ENABLE_GETENV_CACHE enabled, once a logical name or
DCL name has been successfully translated, its value is stored
in a cache. When the same name is requested in a future call
to getenv, the value is returned from the cache instead of
reevaluating the logical name or DCL symbol.
2.16 – DECC$ENABLE_TO_VMS_LOGNAME_CACHE
Use the DECC$ENABLE_TO_VMS_LOGNAME_CACHE to improve the
performance of UNIX name translation. The value is the life of
each cache entry in seconds. The equivalence string ENABLE is
evaluated as 1 second.
Define DECC$ENABLE_TO_VMS_LOGNAME_CACHE to 1 to enable the cache
with a 1-second life for each entry.
Define DECC$ENABLE_TO_VMS_LOGNAME_CACHE to 2 to enable the cache
with a 2-second life for each entry.
Define DECC$ENABLE_TO_VMS_LOGNAME_CACHE to -1 to enable the cache
without a cache entry expiration.
2.17 – DECC$EXEC_FILEATTR_INHERITANCE
The DECC$EXEC_FILEATTR_INHERITANCE feature logical affects child
processes that are C programs.
For versions of OpenVMS before Version 7.3-2, DECC$EXEC_FILEATTR_
INHERITANCE is either enabled or disabled:
o With DECC$EXEC_FILEATTR_INHERITANCE enabled, the current file
pointer and the file open mode is passed to the child process
in exec calls.
o With this logical name disabled, the child process does not
inherit append mode or the file position.
For OpenVMS Version 7.3-2 and higher, DECC$EXEC_FILEATTR_
INHERITANCE can be defined to 1 or 2, or be disabled:
o With DECC$EXEC_FILEATTR_INHERITANCE defined to 1, a child
process inherits file positioning for all file access modes
except append.
o With DECC$EXEC_FILEATTR_INHERITANCE defined to 2, a child
process inherits file positioning for all file access modes
including append.
o With DECC$EXEC_FILEATTR_INHERITANCE disabled, a child process
does not inherit the file position for any access modes.
2.18 – DECC$FILENAME_ENCODING_UTF8
C RTL routines that deal with filenames now support filenames in
UTF-8 encoding when given in UNIX style.
For example, on an ODS-5 disk the OpenVMS DIRECTORY command
supports a filename with the following characters:
disk:[mydir]^U65E5^U672C^U8A9E.txt
This filename contains three UCS-2 characters (call them xxx,
yyy, and zzz for typographical purposes) meaning "day", "origin",
and "language", respectively.
With UTF-8 support enabled, a C program can now read the filename
from the VMS directory and use that filename as an UTF-8 encoded
string.
For example, opendir("/disk/mydir") followed by a readdir will
place the following into the d_name field of the supplied dirent
structure:
"\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E.txt"
One of the following calls can then open this file:
open("/disk/mydir/\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E.txt",O_RDWR,0)
open("/disk/mydir/xxxyyyzzz.txt", O_RDWR,0)
The "\xE6\x97\xA5" above is the byte stream E697A5, which
represents the xxx character in UTF-8 encoding.
This feature enhances the UNIX portability of international
software that uses UTF-8 encoded filenames.
The DECC$FILENAME_ENCODING_UTF8 feature logical controls whether
or not the C RTL allows and correctly interprets Unicode UTF-8
encoding for filenames given in UNIX style.
This logical is undefined by default, and the C RTL behavior is
to accept filenames as ASCII and Latin-1 format.
This feature works only on ODS-5 disks. Therefore, to enable
Unicode UTF-8 encoding, you must define both the DECC$FILENAME_
ENCODING_UTF8 and DECC$EFS_CHARSET logicals to ENABLE.
2.19 – DECC$FILENAME_UNIX_ONLY
With DECC$FILENAME_UNIX_ONLY enabled, filenames are never
interpreted as OpenVMS style names. This prevents any
interpretation of the following as OpenVMS special characters:
: [ ^
2.20 – DECC$FILENAME_UNIX_NO_VERSION
With DECC$FILENAME_UNIX_NO_VERSION enabled, OpenVMS version
numbers are not supported in UNIX style filenames.
With DECC$FILENAME_UNIX_NO_VERSION disabled, in UNIX style names,
version numbers are reported preceded by a period (.).
2.21 – DECC$FILENAME_UNIX_REPORT
With DECC$FILENAME_UNIX_REPORT enabled, all filenames are
reported in UNIX style unless the caller specifically selects
OpenVMS style. This applies to getpwnam, getpwuid, argv[0],
getname, fgetname, and tempnam.
With DECC$FILENAME_UNIX_REPORT disabled, unless specified in the
function call, filenames are reported in OpenVMS style.
2.22 – DECC$FILE_PERMISSION_UNIX
With DECC$FILE_PERMISSION_UNIX enabled, the file permissions
for new files and directories are set according to the file
creation mode and umask. This includes mode 0777. When an earlier
version of the file exists, the file permissions for the new file
are inherited from the earlier version. This mode sets DELETE
permission for a new directory when WRITE permission is enabled.
With DECC$FILE_PERMISSION_UNIX disabled, modes 0 and 0777
indicate using RMS default protection or protection from the
previous version of the file. Permissions for new directories
also follow OpenVMS rules, including disabling DELETE
permissions.
2.23 – DECC$FILE_SHARING
With DECC$FILE_SHARING enabled, all files are opened with full
sharing enabled (FAB$M_DEL | FAB$M_GET | FAB$M_PUT | FAB$M_UPD).
This is set as a logical OR with any sharing mode specified by
the caller.
2.24 – DECC$FIXED_LENGTH_SEEK_TO_EOF
With DECC$FIXED_LENGTH_SEEK_TO_EOF enabled, lseek, fseeko, and
fseek with the direction parameter set to SEEK_END will position
relative to the last byte in the file for files with fixed-length
records.
With DECC$FIXED_LENGTH_SEEK_TO_EOF disabled, lseek, fseek, and
fseeko when called with SEEK_EOF on files with fixed-length
records, will position relative to the end of the last record
in the file.
2.25 – DECC$GLOB_UNIX_STYLE
Enabling DECC$GLOB_UNIX_STYLE selects the UNIX mode of the glob
function, which uses UNIX style filenames and wildcards instead
of OpenVMS style filenames and wildcards.
2.26 – DECC$LOCALE_CACHE_SIZE
DECC$LOCALE_CACHE_SIZE defines how much memory, in bytes, to
allocate for caching locale data. The default value is 0, which
disables the locale cache.
Default: 0
Maximum: 2147483647
2.27 – DECC$MAILBOX_CTX_STM
By default, an open on a local mailbox that is not a pipe treats
mailbox records as having a record attribute of FAB$M_CR.
With DECC$MAILBOX_CTX_STM enabled, the record attribute FAB$M_CR
is not set.
2.28 – DECC$NO_ROOTED_SEARCH_LISTS
When the decc$to_vms function evaluates a UNIX style path string,
if it determines the first element to be a logical name, then:
o For rooted logicals or devices, it appends ":[000000]" to the
logical name.
For example, if log1 is a rooted logical ($DEFINE LOG1
[DIR_NAME.]) then /log1/filename.ext translates to
LOG1:[000000]FILENAME.EXT.
o For nonrooted logicals, it appends just a colon (:) to the
logical name.
For example, if log2 is a nonrooted logical ($ DEFINE
LOG2 [DIR_NAME]), then /log2/filename.ext translates to
LOG2:FILENAME.EXT.
o If the first element is a search-list logical, the translation
proceeds by evaluating the first element in the search list,
and translating the path as previously described.
The preceding three cases lead to predictable, expected results.
In the case where the first element is a search list that
consists of a mixture of rooted and nonrooted logicals,
translating paths as described previously can lead to different
behavior from that of older versions of OpenVMS (before OpenVMS
Version 7.3-1):
o Before OpenVMS Version 7.3-1, regardless of the contents of
the logical, the decc$to_vms function appended only a colon
(:). For search lists that consisted of a mixture of rooted
and nonrooted logicals, this resulted in certain expected
behaviors.
o For OpenVMS Version 7.3-1 and later, if the first element
of the mixed search list is a rooted logical, then decc$to_
vms appends ":[000000]" to the logical name, resulting in
different behavior from that of OpenVMS releases prior to
Version 7.3-1.
DECC$NO_ROOTED_SEARCH_LISTS controls how the decc$to_vms function
resolves search-list logicals and provides a means to restore the
OpenVMS behavior prior to Version 7.3-1.
With DECC$NO_ROOTED_SEARCH_LISTS enabled:
o If a logical is detected in a file specification, and it is
a search list, then a colon (:) is appended when forming the
OpenVMS file specification.
o If it is not a search list, the behavior is the same as with
DECC$NO_ROOTED_SEARCH_LISTS disabled.
Enabling this feature logical provides the pre-Version 7.3-1
behavior for search list logicals.
With DECC$NO_ROOTED_SEARCH_LISTS disabled:
o If a logical is detected in a file specification, and it is
a rooted logical (or a search list whose first element is a
rooted logical), then ":[000000]" is appended when forming the
OpenVMS file specification.
o If it is a nonrooted logical (or a search list whose first
element is a nonrooted logical), then just a colon (:) is
appended.
Disabling this feature logical provides the behavior for OpenVMS
Version 7.3-1 and later.
2.29 – DECC$PIPE_BUFFER_QUOTA
OpenVMS Version 7.3-2 adds an optional fourth argument of type
int to the pipe function to specify the buffer quota of the
pipe's mailbox. In previous OpenVMS versions, the buffer quota
was equal to the buffer size.
DECC$PIPE_BUFFER_QUOTA lets you specify a buffer quota to use
for the pipe function if the optional fourth argument of that
function is omitted.
If the optional pipe fourth argument is omitted and DECC$PIPE_
BUFFER_QUOTA is not defined, then the buffer quota defaults to
the buffer size, as before.
Default: 512
Minimum: 512
Maximum: 2147483647
2.30 – DECC$PIPE_BUFFER_SIZE
The system default buffer size of 512 bytes for pipe write
operations can limit performance and generate extra line feeds
when handling messages longer than 512 bytes.
DECC$PIPE_BUFFER_SIZE allows a larger buffer size to be used for
pipe functions such as pipe and popen. A value of 512 to 65535
bytes can be specified.
If DECC$PIPE_BUFFER_SIZE is not specified, the default buffer
size 512 is used.
Default: 512
Minimum: 512
Maximum: 65535
2.31 – DECC$POPEN_NO_CRLF_REC_ATTR
With DECC$POPEN_NO_CRLF_REC_ATTR disabled, a pipe opened with the
popen function has its record attributes set to CR/LF carriage
control (fab$b_rat |= FAB$M_CR). This is the default behavior.
With DECC$POPEN_NO_CRLF_REC_ATTR enabled, CR/LF carriage control
is prevented from being added to the pipe records. This is
compatible with UNIX behavior, but be aware that enabling this
feature might result in undesired behavior from other functions,
such as gets, that rely on the carriage-return character.
2.32 – DECC$POSIX_COMPLIANT_PATHNAMES
With DECC$POSIX_COMPLIANT_PATHNAMES enabled, an application
is allowed to present POSIX-compliant pathnames to any C RTL
function that accepts a pathname.
By default DECC$POSIX_COMPLIANT_PATHNAMES is disabled, and the
usual C RTL behavior prevails. This disabled mode includes
interpretation of pathnames as UNIX style specifications and
uses rules that are different and unrelated to POSIX-compliant
pathname processing.
To enable DECC$POSIX_COMPLIANT_PATHNAMES, set it to one of the
following values:
1 All pathnames are designated as POSIX style.
2 Pathnames that end in ":" or contain any of the bracket
characters "[]<>", and that can be successfully parsed by
the SYS$FILESCAN service, are designated as OpenVMS style.
Otherwise, they are designated as POSIX style.
3 The pathnames "." and "..", or pathnames that contain "/" are
designated as POSIX style. Otherwise, they are designated as
OpenVMS style.
4 All pathnames are designated as OpenVMS style.
See Chapter 12 of the VSI C Run-Time Library Reference Manual
for OpenVMS Systems for more information on POSIX-compliant
pathnames and symbolic links.
2.33 – DECC$POSIX_SEEK_STREAM_FILE
With DECC$POSIX_SEEK_STREAM_FILE enabled, positioning beyond
end-of-file on STREAM files does not write to the file until the
next write. If the write is beyond the current end-of-file, this
positions beyond the old end-of-file, and the start position for
the write is filled with zeros.
With DECC$POSIX_SEEK_STREAM_FILE disabled, positioning beyond
end-of-file will immediately write zeros to the file from the
current end-of-file to the new position.
2.34 – DECC$POSIX_STYLE_UID
With DECC$POSIX_STYLE_UID enabled, 32-bit UIDs and GIDs are
interpreted as POSIX style identifiers.
With this logical name disabled, UIDs and GIDs are derived from
the process UIC.
This feature is only available on OpenVMS systems providing POSIX
style UID and GID support.
2.35 – DECC$PRINTF_USES_VAX_ROUND
With DECC$PRINTF_USES_VAX_ROUND enabled, the F and E format
specifiers of printf use VAX rounding rules for programs compiled
with IEEE float.
2.36 – DECC$READDIR_DROPDOTNOTYPE
With DECC$READDIR_DROPDOTNOTYPE enabled, readdir when reporting
files in UNIX style only reports the trailing period (.) for
files with no file type when the filename contains a period.
With this logical name disabled, all files without a file type
are reported with a trailing period.
2.37 – DECC$READDIR_KEEPDOTDIR
The default behavior when reporting files in UNIX style from
readdir is to report directories without a file type.
With DECC$READDIR_KEEPDOTDIR enabled, directories are reported in
UNIX style with a file type of ".DIR".
2.38 – DECC$RENAME_NO_INHERIT
DECC$RENAME_NO_INHERIT provides more UNIX compliant behavior in
the rename function. With DECC$RENAME_NO_INHERIT enabled, the
following behaviors are enforced:
o If the old argument points to the pathname of a file that
is not a directory, the new argument will not point to the
pathname of a directory.
o The new argument cannot point to a directory that exists.
o If the old argument points to the pathname of a directory, the
new argument will not point to the pathname of a file that is
not a directory.
o The new name for the file does not inherit anything from
the old name. The new name must be specified completely. For
example:
Renaming "A.A" to "B" yields "B"
With this logical name disabled, you get the expected OpenVMS
behavior. For example:
Renaming "A.A" to "B" yields "B.A"
2.39 – DECC$RENAME_ALLOW_DIR
Enabling DECC$RENAME_ALLOW_DIR restores the prior OpenVMS
behavior of the rename function by allowing conversion to a
directory specification when the second argument is an ambiguous
file specification passed as a logical name. The ambiguity is
whether the logical name is a UNIX or OpenVMS file specification.
Consider the following example with DECC$RENAME_ALLOW_DIR
enabled:
rename("file.ext", "logical_name")
/*where logical_name = dev:[dir.subdir]*/
/* and :[dir.subdir] exists. */
This results in:
dev:[dir.subdir]file.ext
This example renames a file from one directory into another
directory, which is the same behavior as in legacy versions
of OpenVMS (versions before 7.3-1). Also in this example, if
dev:[dir.subdir] does not exist, rename returns an error.
Disabling DECC$RENAME_ALLOW_DIR provides a more UNIX compliant
conversion of the "logical_name" argument of rename. Consider the
following example with DECC$RENAME_ALLOW_DIR disabled:
rename("file.ext", "logical_name")
/* where logical_name = dev:[dir.subdir] */
This results in:
dev:[dir]subdir.ext
This example renames the file using the subdir part of the
"logical_name" argument as the new filename because on UNIX
systems, renaming a file to a directory is not allowed. So
rename internally converts the "logical_name" to a filename, and
dev:[dir]subdir is the most reasonable conversion it can perform.
This new feature switch has a side effect of causing rename to a
directory to take precedence over rename to a file. Consider this
example:
rename ( "file1.ext", "dir2" ) /* dir2 is not a logical */
With DECC$RENAME_ALLOW_DIR disabled, this example results in
dir2.ext, regardless of whether or not subdirectory [.dir2]
exists.
With DECC$RENAME_ALLOW_DIR enabled, this example results in
dir2.ext only if subdirectory [.dir2] does not exist. If
subdirectory [.dir2] does exist, the result is [.dir2]file1.ext.
NOTE
If DECC$RENAME_NO_INHERIT is enabled, UNIX compliant
behavior is expected, so DECC$RENAME_ALLOW_DIR is ignored,
and renaming a file to a directory is not allowed.
2.40 – DECC$SELECT_IGNORES_INVALID_FD
With DECC$SELECT_IGNORES_INVALID_FD enabled, select fails with
errno set to EBADF when an invalid file descriptor is specified
in one of the descriptor sets.
With DECC$SELECT_IGNORES_INVALID_FD disabled, select ignores
invalid file descriptors.
2.41 – DECC$STDIO_CTX_EOL
With DECC$STDIO_CTX_EOL enabled, writing to stdout and stderr
for stream access is deferred until a terminator is seen or the
buffer is full.
With DECC$STDIO_CTX_EOL disabled, each fwrite generates a
separate write, which for mailbox and record files generates a
separate record.
2.42 – DECC$STREAM_PIPE
With DECC$STREAM_PIPE enabled, the C RTL pipe function uses the
more UNIX compatible stream I/O.
With DECC$STREAM_PIPE disabled, pipe uses the OpenVMS legacy
record I/O. This is the default.
2.43 – DECC$STRTOL_ERANGE
With DECC$STRTOL_ERANGE enabled, the strtol behavior for an
ERANGE error is corrected to consume all remaining digits in
the string.
With DECC$STRTOL_ERANGE disabled, the legacy behavior of leaving
the pointer at the failing digit is preserved.
2.44 – DECC$THREAD_DATA_AST_SAFE
The C RTL has a mode that allocates storage for thread-specific
data allocated by threads at non-AST level separate for data
allocated for ASTs. In this mode, each access to thread-
specific data requires a call to LIB$AST_IN_PROG, which can add
significant overhead when accessing thread-specific data in the
C RTL.
The alternate mode protects thread-specific data only if another
function has it locked. This protects data that is in use within
the C RTL, but does not protect the caller from an AST changing
the data pointed to.
This latter mode is now the C RTL default for the strtok, ecvt,
and fcvt functions.
You can select the legacy AST safe mode by enabling DECC$THREAD_
DATA_AST_SAFE.
2.45 – DECC$TZ_CACHE_SIZE
DECC$TZ_CACHE_SIZE specifies the number of time zones that can be
held in memory.
Default: 2
Maximum: 2147483647
2.46 – DECC$UMASK
DECC$UMASK specifies the default value for the permission mask
umask. By default, a parent C program sets the umask from the RMS
default permissions for the process. A child process inherits the
parent's value for umask.
To enter the value as an octal value, add the leading zero;
otherwise, it is translated as a decimal value. For example:
$ DEFINE DECC$UMASK 026
Maximum: 0777
2.47 – DECC$UNIX_LEVEL
With the DECC$UNIX_LEVEL logical name, you can manage multiple
C RTL feature logical names at once. By setting a value for
DECC$UNIX_LEVEL from 1 to 100, you determine the default value
for groups of feature logical names. The value you set has a
cumulative effect: the higher the value, the more groups that
are affected. Setting a value of 20, for example, enables all the
feature logicals associated with a DECC$UNIX_LEVEL of 20, 10, and
1.
The principal logical names affecting UNIX like behavior are
grouped as follows:
1 General corrections
10 Enhancements
20 UNIX style filenames
30 UNIX style file attributes
90 Full UNIX behavior - No concessions to OpenVMS
Level 30 is appropriate for UNIX like programs such as BASH and
GNV.
The DECC$UNIX_LEVEL values and associated groups of affected
feature logical names are:
General Corrections (DECC$UNIX_LEVEL 1)
DECC$FIXED_LENGTH_SEEK_TO_EOF 1
DECC$POSIX_SEEK_STREAM_FILE 1
DECC$SELECT_IGNORES_INVALID_FD 1
DECC$STRTOL_ERANGE 1
DECC$VALIDATE_SIGNAL_IN_KILL 1
General Enhancements (DECC$UNIX_LEVEL 10)
DECC$ARGV_PARSE_STYLE 1
DECC$EFS_CASE_PRESERVE 1
DECC$STDIO_CTX_EOL 1
DECC$PIPE_BUFFER_SIZE 4096
DECC$USE_RAB64 1
UNIX style filenames (DECC$UNIX_LEVEL 20)
DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION 1
DECC$EFS_CHARSET 1
DECC$FILENAME_UNIX_NO_VERSION 1
DECC$FILENAME_UNIX_REPORT 1
DECC$READDIR_DROPDOTNOTYPE 1
DECC$RENAME_NO_INHERIT 1
DECC$GLOB_UNIX_STYLE
UNIX like file attributes (DECC$UNIX_LEVEL 30)
DECC$EFS_FILE_TIMESTAMPS 1
DECC$EXEC_FILEATTR_INHERITANCE 1
DECC$FILE_OWNER_UNIX 1
DECC$FILE_PERMISSION_UNIX 1
DECC$FILE_SHARING 1
UNIX compliant behavior (DECC$UNIX_LEVEL 90)
DECC$FILENAME_UNIX_ONLY 1
DECC$POSIX_STYLE_UID 1
DECC$USE_JPI$_CREATOR 1
DECC$DETACHED_CHILD_PROCESS 1
NOTES
o Defining a logical name for an individual feature logical
supersedes the default value established by DECC$UNIX_
LEVEL for that feature.
o Future revisions of the C RTL may add new feature
logicals to a given DECC$UNIX_LEVEL. For applications
that specify that UNIX level, the effect is to enable
those new feature logicals by default.
2.48 – DECC$UNIX_PATH_BEFORE_LOGNAME
With DECC$UNIX_PATH_BEFORE_LOGNAME enabled, when translating
a UNIX filename not starting with a leading slash (/), an
attempt is made to match this to a file or directory in the
current directory. If this is not found and the name is valid
as a logical name in an OpenVMS filename, an attempt is made to
translate the logical name and, if found, is used as part of the
resulting filename.
Enabling DECC$UNIX_PATH_BEFORE_LOGNAME overrides the setting for
DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION.
2.49 – DECC$USE_JPI$_CREATOR
When enabled, DECC$USE_JPI$_CREATOR determines the parent process
ID in getppid by calling $GETJPI using item JPI$_CREATOR instead
of JPI$_OWNER.
This feature is only available on systems supporting POSIX style
session identifiers.
2.50 – DECC$USE_RAB64
With DECC$USE_RAB64 enabled, open functions allocate a RAB64
structure instead of the traditional RAB structure.
This provides latent support for file buffers in 64-bit memory.
2.51 – DECC$VALIDATE_SIGNAL_IN_KILL
With DECC$VALIDATE_SIGNAL_IN_KILL enabled, a signal value that
is in the range 0 to _SIG_MAX but is not supported by the C RTL
generates an error with errno set to EINVAL, which makes the
behavior the same as for raise.
With this logical name disabled, validation of signals is
restricted to checking that the signal value is in the range 0 to
_SIG_MAX. If sys$sigprc fails, errno is set based on sys$sigprc
exit status.
2.52 – DECC$V62_RECORD_GENERATION
OpenVMS Versions 6.2 and higher can output record files using
different rules.
With DECC$V62_RECORD_GENERATION enabled, the output mechanism
follows the rules used for OpenVMS Version 6.2.
2.53 – DECC$WRITE_SHORT_RECORDS
The DECC$WRITE_SHORT_RECORDS feature logical supports a previous
change to the fwrite function (to accommodate writing records
with size less than the maximum record size), while retaining
the legacy way of writing records to a fixed-length file as the
default behavior:
With DECC$WRITE_SHORT_RECORDS enabled, short-sized records
(records with size less than the maximum record size) written at
EOF are padded with zeros to align records on record boundaries.
This is the behavior seen in OpenVMS Version 7.3-1 and some ACRTL
ECOs of that time period.
With DECC$WRITE_SHORT_RECORDS disabled, the legacy behavior
of writing records with no padding is implemented. This is the
recommended and default behavior.
2.54 – DECC$XPG4_STRPTIME
XPG5 support for strptime introduces pivoting year support so
that years in the range 0 to 68 are in the 21st century, and
years in the range 69-99 are in the 20th century.
With DECC$XPG4_STRPTIME enabled, XPG5 support for the pivoting
year is disabled and all years in the range 0 to 99 are in the
current century.
3 – a64l
Converts a character string to a long integer.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdlib.h>
long a64l (const char *s);
3.1 – Argument
s
Pointer to the character string that is to be converted to a long
integer.
3.2 – Description
The a64l and l64a functions are used to maintain numbers stored
in base-64 ASCII characters as follows:
o a64l converts a character string to a long integer.
o l64a converts a long integer to a character string.
Each character used for storing a long integer represents a
numeric value from 0 through 63. Up to six characters can be
used to represent a long integer.
The characters are translated as follows:
o A period (.) represents 0.
o A slash (/) represents 1.
o The numbers 0 through 9 represent 2 through 11.
o Uppercase letters A through Z represent 12 through 37.
o Lowercase letters a through z represent 38 through 63.
The a64l function takes a pointer to a base-64 representation,
in which the first digit is the least significant, and returns
a corresponding long value. If the string pointed to by the s
parameter exceeds six characters, a64l uses only the first six
characters.
If the first six characters of the string contain a null
terminator, a64l uses only characters preceding the null
terminator.
The a64l function translates a character string from left to
right with the least significant number on the left, decoding
each character as a 6-bit base-64 number.
If s is the NULL pointer or if the string pointed to by s was
not generated by a previous call to l64a, the behavior of a64l is
unspecified.
See also l64a.
3.3 – Return Values
n Upon successful completion, the long value
resulting from conversion of the input string.
0L Indicates that the string pointed to by s is
an empty string.
4 – abort
Sends the signal SIGABRT that terminates execution of the
program.
Format
#include <stdlib.h>
void abort (void);
5 – abs
Returns the absolute value of an integer.
Format
#include <stdlib.h>
int abs (int x);
5.1 – Argument
x
An integer.
5.2 – Return Value
x The absolute value of the input argument. If
the argument is LONG_MIN, abs returns LONG_
MIN because -LONG_MIN cannot fit in an int
variable.
6 – access
Checks a file to see whether a specified access mode is allowed.
NOTE
The access function does not accept network files as
arguments.
Format
#include <unistd.h>
int access (const char *file_spec, int mode);
6.1 – Arguments
file_spec
A character string that gives an OpenVMS or UNIX style file
specification. The usual defaults and logical name translations
are applied to the file specification.
mode
Interpreted as shown in Interpretation of the mode Argument.
Table REF-1 Interpretation of the mode Argument
Mode
Argument Access Mode
F_OK Tests to see if the file exists
X_OK Execute
W_OK Write (implies delete access)
R_OK Read
Combinations of access modes are indicated by ORing the values.
For example, to check to see if a file has RWED access mode,
invoke access as follows:
access (file_spec, R_OK | W_OK | X_OK);
6.2 – Description
The access function checks a file to see whether a specified
access mode is allowed. If the DECC$ACL_ACCESS_CHECK feature
logical is enabled, this function checks OpenVMS Access Control
Lists (ACLs) as well as the UIC protection.
6.3 – Return Values
0 Indicates that the access is allowed.
-1 Indicates that the access is not allowed.
6.4 – Example
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
main()
{
if (access("sys$login:login.com", F_OK)) {
perror("ACCESS - FAILED");
exit(2);
}
}
7 – acos
Returns the arc cosine of its argument.
Format
#include <math.h>
double acos (double x);
float acosf (float x); (Integrity servers, Alpha)
long double acosl (long double x); (Integrity servers, Alpha)
double acosd (double x); (Integrity servers, Alpha)
float acosdf (float x); (Integrity servers, Alpha)
long double acosdl (long double x);
(Integrity servers, Alpha)
7.1 – Argument
x
A radian expressed as a real value in the domain [-1,1].
7.2 – Description
The acos functions compute the principal value of the arc cosine
of x in the range [0,pi] radians for x in the domain [-1,1].
The acosd functions compute the principal value of the arc cosine
of x in the range [0,180] degrees for x in the domain [-1,1].
For abs(x) > 1, the value of acos(x) is 0, and errno is set to
EDOM.
8 – acosh
Returns the hyperbolic arc cosine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double acosh (double x);
float acoshf (float x);
long double acoshl (long double x);
8.1 – Argument
x
A radian expressed as a real value in the domain [1, +Infinity].
8.2 – Description
The acosh functions return the hyperbolic arc cosine of x for x
in the domain [1, +Infinity], where acosh(x) = ln(x + sqrt(x**2 -
1)).
The acosh function is the inverse function of cosh where
acosh(cosh(x)) = |x|.
x < 1 is an invalid argument.
9 – [w]addch
Add a character to the window at the current position of the
cursor.
Format
#include <curses.h>
int addch (char ch);
int waddch (WINDOW *win, char ch);
9.1 – Arguments
win
A pointer to the window.
ch
The character to be added. A new-line character (\n) clears the
line to the end, and moves the cursor to the next line at the
same x coordinate. A return character (\r) moves the cursor to
the beginning of the line on the window. A tab character (\t)
moves the cursor to the next tabstop within the window.
9.2 – Description
When the waddch function is used on a subwindow, it writes the
character onto the underlying window as well.
The addch routine performs the same function as waddch, but on
the stdscr window.
The cursor is moved after the character is written to the screen.
9.3 – Return Values
OK Indicates success.
ERR Indicates that writing the character would
cause the screen to scroll illegally. For more
information, see the scrollok function.
10 – [w]addstr
Add the string pointed to by str to the window at the current
position of the cursor.
Format
#include <curses.h>
int addstr (char *str);
int waddstr (WINDOW *win, char *str);
10.1 – Arguments
win
A pointer to the window.
str
A pointer to a character string.
10.2 – Description
When the waddstr function is used on a subwindow, the string is
written onto the underlying window as well.
The addstr routine performs the same function as waddstr, but on
the stdscr window.
The cursor position changes as a result of calling this routine.
10.3 – Return Values
OK Indicates success.
ERR Indicates that the function causes the screen
to scroll illegally, but it places as much of
the string onto the window as possible. For
more information, see the scrollok function.
11 – alarm
Sends the signal SIGALRM (defined in the <signal.h> header file)
to the invoking process after the number of seconds indicated by
its argument has elapsed.
Format
#include <unistd.h>
unsigned int alarm (unsigned int seconds); (ISO POSIX-1)
int alarm (unsigned int seconds); (Compatibility)
11.1 – Argument
seconds
Has a maximum limit of LONG_MAX seconds.
11.2 – Description
Calling the alarm function with a 0 argument cancels any pending
alarms.
Unless it is intercepted or ignored, the signal generated by
alarm terminates the process. Successive alarm calls reinitialize
the alarm clock. Alarms are not stacked.
Because the clock has a 1-second resolution, the signal may
occur up to 1 second early. If the SIGALRM signal is intercepted,
resumption of execution may be held up due to scheduling delays.
When the SIGALRM signal is generated, a call to SYS$WAKE is
generated whether or not the process is hibernating. The pending
wake causes the current pause() to return immediately (after
completing any function that catches the SIGALRM).
11.3 – Return Value
n The number of seconds remaining from a
previous alarm request.
12 – asctime
Converts a broken-down time in a tm structure into a 26-character
string in the following form:
Sun Sep 16 01:03:52 1984\n\0
All fields have a constant width.
Format
#include <time.h>
char *asctime (const struct tm *timeptr);
char *asctime_r (const struct tm *timeptr, char *buffer);
(ISO POSIX-1)
12.1 – Arguments
timeptr
A pointer to a structure of type tm, which contains the broken-
down time.
The tm structure is defined in the <time.h> header file, and also
shown in tm Structure in the description of localtime.
buffer
A pointer to a character array that is at least 26 bytes long.
This array is used to store the generated date-and-time string.
12.2 – Description
The asctime and asctime_r functions convert the contents of tm
into a 26-character string and returns a pointer to the string.
The difference between asctime_r and asctime is that the former
puts the result into a user-specified buffer. The latter puts
the result into thread-specific static memory allocated by the
C RTL, which can be overwritten by subsequent calls to
ctime or asctime; you must make a copy if you want to save it.
On success, asctime returns a pointer to the string; asctime_r
returns its second argument. On failure, these functions return
the NULL pointer.
See the localtime function for a list of the members in tm.
NOTE
Generally speaking, UTC-based time functions can affect in-
memory time-zone information, which is processwide data.
However, if the system time zone remains the same during
the execution of the application (which is the common case)
and the cache of timezone files is enabled (which is the
default), then the _r variant of the time functions asctime_
r, ctime_r, gmtime_r and localtime_r, is both thread-safe
and AST-reentrant.
If, however, the system time zone can change during the
execution of the application or the cache of timezone files
is not enabled, then both variants of the UTC-based time
functions belong to the third class of functions, which are
neither thread-safe nor AST-reentrant.
12.3 – Return Values
x A pointer to the string, if successful.
NULL Indicates failure.
13 – asin
Returns the arc sine of its argument.
Format
#include <math.h>
double asin (double x);
float asinf (float x); (Integrity servers, Alpha)
long double asinl (long double x); (Integrity servers, Alpha)
double asind (double x); (Integrity servers, Alpha)
float asindf (float x); (Integrity servers, Alpha)
long double asindl (long double x);
(Integrity servers, Alpha)
13.1 – Argument
x
A radian expressed as a real number in the domain [-1,1].
13.2 – Description
The asin functions compute the principal value of the arc sine of
x in the range [-pi/2,pi/2] radians for x in the domain [-1,1].
The asind functions compute the principal value of the arc sine
of x in the range [-90,90] degrees for x in the domain [-1,1].
When abs(x) is greater than 1.0, the value of asin(x) is 0, and
errno is set to EDOM.
14 – asinh
Returns the hyperbolic arc sine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double asinh (double x);
float asinhf (float x);
long double asinhl (long double x);
14.1 – Argument
x
A radian expressed as a real value in the domain [-Infinity,
+Infinity].
14.2 – Description
The asinh functions return the hyperbolic arc sine of x for x
in the domain [-Infinity, +Infinity], where asinh(x) = ln(x +
sqrt(x**2 + 1)).
The asinh function is the inverse function of sinh where
asinh(sinh(x)) = x.
15 – assert
Used for implementing run-time diagnostics in programs.
Format
#include <assert.h>
void assert (int expression);
15.1 – Argument
expression
An expression that has an int type.
15.2 – Description
When assert is executed, if expression is false (that is, it
evaluates to 0), assert writes information about the particular
call that failed (including the text of the argument, the name of
the source file, and the source line number; the latter two are,
respectively, the values of the preprocessing macros __FILE__
and __LINE__) to the standard error file in an implementation-
defined format. Then, it calls the abort function.
The assert function writes a message in the following form:
Assertion failed: expression, file aaa, line nnn
If expression is true (that is, it evaluates to nonzero) or if
the signal SIGABRT is being ignored, assert returns no value.
NOTE
If a null character ('\0') is part of the expression being
asserted, then only the text up to and including the null
character is printed, since the null character effectively
terminates the string being output.
Compiling with the CC command qualifier /DEFINE=NDEBUG or with
the preprocessor directive #define NDEBUG ahead of the #include
assert statement causes the assert function to have no effect.
15.3 – Example
#include <stdio.h>
#include <assert.h>
main()
{
printf("Only this and the assert\n");
assert(1 == 2); /* expression is FALSE */
/* abort should be called so the printf will not happen. */
printf("FAIL abort did not execute");
}
16 – atan
Format
#include <math.h>
double atan (double x);
float atanf (float x); (Integrity servers, Alpha)
long double atanl (long double x); (Integrity servers, Alpha)
double atand (double x); (Integrity servers, Alpha)
float atandf (float x); (Integrity servers, Alpha)
long double atandl (long double x);
(Integrity servers, Alpha)
16.1 – Argument
x
A radian expressed as a real number.
16.2 – Description
The atan functions compute the principal value of the arc tangent
of x in the range [-pi/2,pi/2] radians.
The atand functions compute the principal value of the arc
tangent of x in the range [-90,90] degrees.
17 – atan2
Format
#include <math.h>
double atan2 (double y, double x);
float atan2f (float y, float x); (Integrity servers, Alpha)
long double atan2l (long double y, long double x);
(Integrity servers, Alpha)
double atand2 (double y, double x);
(Integrity servers, Alpha)
float atand2f (float y, float x); (Integrity servers, Alpha)
long double atand2l (long double y, long double x);
(Integrity servers, Alpha)
17.1 – Arguments
y
A radian expressed as a real number.
x
A radian expressed as a real number.
17.2 – Description
The atan2 functions compute the principal value of the arc
tangent of y/x in the range [-pi,pi] radians. The sign of
atan2 and atan2f is determined by the sign of y. The value of
atan2(y,x) is computed as follows, where f is the number of
fraction bits associated with the data type:
Value of Input
Arguments Angle Returned
x = 0 or y/x > pi/2 * (sign y)
2**(f+1)
x > 0 and y/x <= atan(y/x)
2**(f+1)
x < 0 and y/x <= pi * (sign y) + atan(y/x)
2**(f+1)
The atand2 functions compute the principal value of the arc
tangent of y/x in the range [-180,180] degrees. The sign of
atand2 and atand2f is determined by the sign of y.
The following are invalid arguments for the atan2 and atand2
functions:
Function Exceptional Argument
atan2, atan2f, atan2l x = y = 0
atan2, atan2f, atan2l |x| = |y| = Infinity
atand2, atand2f, atand2l x = y = 0
atand2, atand2f, atand2l |x| = |y| = Infinity
18 – atanh
Returns the hyperbolic arc tangent of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double atanh (double x);
float atanhf (float x);
long double atanhl (long double x);
18.1 – Argument
x
A radian expressed as a real value in the domain [-1,1].
18.2 – Description
The atanh functions return the hyperbolic arc tangent of x.
The atanh function is the inverse function of tanh where
atanh(tanh(x)) = x.
|x| > 1 is an invalid argument.
19 – atexit
Registers a function that is called without arguments at program
termination.
Format
#include <stdlib.h>
int atexit (void (*func) (void));
19.1 – Argument
func
A pointer to the function to be registered.
19.2 – Return Values
0 Indicates that the registration has succeeded.
nonzero Indicates failure.
19.3 – Restriction
The longjmp function cannot be executed from within the handler,
because the destination address of the longjmp no longer exists.
19.4 – Example
#include <stdlib.h>
#include <stdio.h>
static void hw(void);
main()
{
atexit(hw);
}
static void hw()
{
puts("Hello, world\n");
}
Running this example produces the following output:
Hello, world
20 – atof
Converts an ASCII character string to a double-precision number.
Format
#include <stdlib.h>
double atof (const char *nptr);
20.1 – Argument
nptr
A pointer to the character string to be converted to a double-
precision number. The string is interpreted by the same rules
that are used to interpret floating constants.
20.2 – Description
The string to be converted has the following format:
[white-spaces][+|-]digits[radix-character][digits][e|E[+|-]integer]
Where radix-character is defined in the current locale.
The first unrecognized character ends the conversion.
This function is equivalent to strtod(nptr, (char**) NULL).
20.3 – Return Values
x The converted value.
0 Indicates an underflow or the conversion could
not be performed. The function sets errno to
ERANGE or EINVAL, respectively.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
21 – atoi,atol
Convert strings of ASCII characters to the appropriate numeric
values.
Format
#include <stdlib.h>
int atoi (const char *nptr);
long int atol (const char *nptr);
21.1 – Argument
nptr
A pointer to the character string to be converted to a numeric
value.
21.2 – Description
The atoi and atol functions convert the initial portion of a
string to its decimal int or long int value, respectively. The
atoi and atol functions do not account for overflows resulting
from the conversion. The string to be converted has the following
format:
[white-spaces][+|-]digits
The function call atol (str) is equivalent to strtol (str,
(char**)NULL, 10), and the function call atoi (str) is equivalent
to (int) strtol (str, (char**)NULL, 10), except, in both cases,
for the behavior on error.
21.3 – Return Value
n The converted value.
22 – atoq,atoll
Convert strings of ASCII characters to the appropriate numeric
values. atoll is a synonym for atoq.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdlib.h>
__int64 atoq (const char *nptr);
__int64 atoll (const char *nptr);
22.1 – Argument
nptr
A pointer to the character string to be converted to a numeric
value.
22.2 – Description
The atoq (or atoll) function converts the initial portion of
a string to its decimal __int64 value. This function does not
account for overflows resulting from the conversion. The string
to be converted has the following format:
[white-spaces][+|-]digits
The function call atoq (str) is equivalent to strtoq (str,
(char**)NULL, 10), except for the behavior on error.
22.3 – Return Value
n The converted value.
23 – basename
Returns the last component of a pathname.
Format
#include <libgen.h>
char *basename (char *path);
23.1 – Function Variants
The basename function has variants named _basename32 and
_basename64 for use with 32-bit and 64-bit pointer sizes,
respectively.
23.2 – Argument
path
A UNIX style pathname from which the base pathname is extracted.
23.3 – Description
The basename function takes the UNIX style pathname pointed to
by path and returns a pointer to the pathname's final component,
deleting any trailing slash (/) characters.
If path consists entirely of the slash (/) character, the
function returns a pointer to the string "/".
If path is a NULL pointer or points to an empty string, the
function returns a pointer to the string ".".
The basename function can modify the string pointed to by path.
23.4 – Return Values
x A pointer to the final component of path.
"/" If path consists entirely of the '/'
character.
"." If path is a NULL pointer or points to an
empty string.
24 – bcmp
Compares byte strings.
Format
#include <strings.h>
void bcmp (const void *string1, const void *string2, size_t length);
24.1 – Arguments
string1, string2
The byte strings to be compared.
length
The length (in bytes) of the strings.
24.2 – Description
The bcmp function compares the byte string in string1 against the
byte string in string2.
Unlike the string functions, there is no checking for null bytes.
Zero-length strings are always identical.
Note that bcmp is equivalent to memcmp, which is defined by
the ANSI C Standard. Therefore, using memcmp is recommended for
portable programs.
24.3 – Return Values
0 The strings are identical.
Nonzero The strings are not identical.
25 – bcopy
Copies byte strings.
Format
#include <strings.h>
void bcopy (const void *source, void *destination, size_t length);
25.1 – Arguments
source
Pointer to the source string.
destination
Pointer to the destination string.
length
The length (in bytes) of the string.
25.2 – Description
The bcopy function operates on variable-length strings of bytes.
It copies the value of the length argument, in bytes, from the
string in the source argument to the string in the destination
argument.
Unlike the string functions, there is no checking for null bytes.
If the length argument is 0 (zero), no bytes are copied.
Note that bcopy is equivalent to memcpy, which is defined by
the ANSI C Standard. Therefore, using memcpy is recommended for
portable programs.
26 – box
Draws a box around the window using the character vert as the
character for drawing the vertical lines of the rectangle, and
hor for drawing the horizontal lines of the rectangle.
Format
#include <curses.h>
int box (WINDOW *win, char vert, char hor);
26.1 – Arguments
win
The address of the window.
vert
The character for the vertical edges of the window.
hor
The character for the horizontal edges of the window.
26.2 – Description
The box function copies boxes drawn on subwindows onto the
underlying window. Use caution when using functions such as
overlay and overwrite with boxed subwindows. Such functions copy
the box onto the underlying window.
26.3 – Return Values
OK Indicates success.
ERR Indicates an error.
27 – brk
Determines the lowest virtual address that is not used with the
program.
Format
#include <stdlib.h>
void *brk (unsigned long int addr);
27.1 – Argument
addr
The lowest address, which the function rounds up to the next
multiple of the page size. This rounded address is called the
break address.
27.2 – Description
An address that is greater than or equal to the break address
and less than the stack pointer is considered to be outside the
program's address space. Attempts to reference it will cause
access violations.
When a program is executed, the break address is set to the
highest location defined by the program and data storage areas.
Consequently, brk is needed only by programs that have growing
data areas.
27.3 – Return Values
n The new break address.
(void *)(-1) Indicates that the program is requesting too
much memory. errno and vaxc$errno are updated.
27.4 – Restriction
Unlike other C library implementations, the C RTL memory
allocation functions (such as malloc) do not rely on brk or
sbrk to manage the program heap space. Consequently, on OpenVMS
systems, calling brk or sbrk can interfere with memory allocation
routines. The brk and sbrk functions are provided only for
compatibility purposes.
28 – bsearch
Performs a binary search. It searches an array of sorted objects
for a specified object.
Format
#include <stdlib.h>
void *bsearch (const void *key, const void *base, size_t
nmemb, size_t size, int (*compar)
(const void *, const void *));
28.1 – Function Variants
The bsearch function has variants named _bsearch32 and _bsearch64
for use with 32-bit and 64-bit pointer sizes, respectively.
28.2 – Arguments
key
A pointer to the object to be sought in the array. This pointer
should be of type pointer-to-object and cast to type pointer-to-
void.
base
A pointer to the initial member of the array. This pointer should
be of type pointer-to-object and cast to type pointer-to-void.
nmemb
The number of objects in the array.
size
The size of an object, in bytes.
compar
A pointer to the comparison function.
28.3 – Description
The array must first be sorted in increasing order according to
the specified comparison function pointed to by compar.
Two arguments are passed to the comparison function pointed to
by compar. The two arguments point to the objects being compared.
Depending on whether the first argument is less than, equal to,
or greater than the second argument, the comparison function must
return an integer less than, equal to, or greater than 0.
It is not necessary for the comparison function (compar) to
compare every byte in the array. Therefore, the objects in the
array can contain arbitrary data in addition to the data being
compared.
Since it is declared as type pointer-to-void, the value returned
must be cast or assigned into type pointer-to-object.
28.4 – Return Values
x A pointer to the matching member of the array
or a null pointer if no match is found.
NULL Indicates that the key cannot be found in the
array.
28.5 – Example
#include <stdio.h>
#include <stdlib.h>
#define SSIZE 30
extern int compare(); /* prototype for comparison function */
int array[SSIZE] = {30, 1, 29, 2, 28, 3, 27, 4, 26, 5,
24, 6, 23, 7, 22, 8, 21, 9, 20, 10,
19, 11, 18, 12, 17, 13, 16, 14, 15, 25};
/* This program takes an unsorted array, sorts it using qsort, */
/* and then calls bsearch for each element in the array, */
/* making sure that bsearch returns the correct element. */
main()
{
int i;
int failure = FALSE;
int *rkey;
qsort(array, SSIZE, sizeof (array[0]), &compare);
/* search for each element */
for (i = 0; i < SSIZE - 1; i++) {
/* search array element i */
rkey = bsearch((array + i), array, SSIZE,
sizeof(array[0]), &compare);
/* check for successful search */
if (&array[i] != rkey) {
printf("Not in array, array element %d\n", i);
failure = TRUE;
break;
}
}
if (!failure)
printf("All elements successfully found!\n");
}
/* Simple comparison routine. */
/* */
/* Returns: = 0 if a == b */
/* < 0 if a < b */
/* > 0 if a > b */
int compare(int *a, int *b)
{
return (*a - *b);
}
This example program outputs the following:
All elements successfully found!
29 – btowc
Converts a one-byte multibyte character to a wide character in
the initial shift state.
Format
#include <wchar.h>
wint_t btowc (int c);
29.1 – Argument
c
The character to be converted to a wide-character representation.
29.2 – Description
The btowc function determines whether (unsigned char)c is a valid
one-byte multibyte character in the initial shift state, and if
so, returns a wide-character representation of that character.
29.3 – Return Values
x The wide-character representation of unsigned
char c.
WEOF Indicates an error. The c argument has the
value EOF or does not constitute a valid one-
byte multibyte character in the initial shift
state.
30 – bzero
Copies null characters into byte strings.
Format
#include <strings.h>
void bzero (void *string, size_t length);
30.1 – Arguments
string
Specifies the byte string into which you want to copy null
characters.
length
Specifies the length (in bytes) of the string.
30.2 – Description
The bzero function copies null characters ('\0') into the byte
string pointed to by string for length bytes. If length is 0
(zero), then no bytes are copied.
31 – cabs
Returns the absolute value of a complex number.
Format
#include <math.h>
double cabs (cabs_t z);
float cabsf (cabsf_t z); (Integrity servers, Alpha)
long double cabsl (cabsl_t z); (Integrity servers, Alpha)
31.1 – Argument
z
A structure of type cabs_t, cabsf_t, or cabsl_t. These types are
defined in the <math.h> header file as follows:
typedef struct {double x,y;} cabs_t;
typedef struct { float x, y; } cabsf_t; (Integrity servers, Alpha)
typedef struct { long double x, y; } cabsl_t; (Integrity servers, Alpha)
31.2 – Description
The cabs functions return the absolute value of a complex number
by computing the Euclidean distance between its two points as the
square root of their respective squares:
sqrt(x2 + y2)
On overflow, the return value is undefined.
The cabs, cabsf, and cabsl functions are equivalent to the hypot,
hypotf, and hypotl functions, respectively.
32 – cacos
Returns the complex arc cosine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex cacos (double complex z);
float complex cacosf (float complex z);
long double complex cacosl (long double complex z);
32.1 – Argument
z
A complex value.
32.2 – Description
The cacos functions compute the complex arc cosine of z, with
branch cuts outside the interval [-1, +1] along the real axis.
32.3 – Return Values
n The complex arc cosine value, in the range
of a strip mathematically unbounded along the
imaginary axis and in the interval [0, π]
along the real axis.
33 – cacosh
Returns the complex arc hyperbolic cosine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex cacosh (double complex z);
float complex cacoshf (float complex z);
long double complex cacoshl (long double complex z);
33.1 – Argument
z
A complex value.
33.2 – Description
The cacosh functions compute the complex arc hyperbolic cosine of
z, with a branch cut at values less than 1 along the real axis.
33.3 – Return Values
n The complex arc hyperbolic cosine value, in
the range of a half-strip of non-negative
values along the real axis and in the interval
[-iπ, +iπ] along the imaginary axis.
34 – calloc
Allocates an area of zeroed memory. This function is AST-
reentrant.
Format
#include <stdlib.h>
void *calloc (size_t number, size_t size);
34.1 – Function Variants
The calloc function has variants named _calloc32 and _calloc64
for use with 32-bit and 64-bit pointer sizes, respectively.
34.2 – Arguments
number
The number of items to be allocated.
size
The size of each item.
34.3 – Description
The calloc function initializes the items to 0. The maximum
amount of memory allocated at once is limited to 0xFFFFD000.
See also malloc and realloc.
34.4 – Return Values
x The address of the first byte, which
is aligned on a quadword boundary
(Alpha only) or an octaword boundary
(Integrity servers(ONLY)) .
NULL Indicates an inability to allocate the space.
35 – carg
Returns the phase angle of its complex argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double carg (double complex z);
float cargf (float complex z);
long double cargl (long double complex z);
35.1 – Argument
z
A complex value.
35.2 – Description
The carg functions compute the argument (also called phase angle)
of z, with a branch cut along the negative real axis.
35.3 – Return Values
n The value of the argument of z, in the
interval [-π, +π].
36 – casin
Returns the complex arc sine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex casin (double complex z);
float complex casinf (float complex z);
long double complex casinl (long double complex z);
36.1 – Argument
z
A complex value.
36.2 – Description
The casin functions compute the complex arc sine of z, with
branch cuts outside the interval [-1, +1] along the real axis.
36.3 – Return Values
n The complex arc sine value, in the range of
a strip mathematically unbounded along the
imaginary axis and in the interval [-π/2,
+π/2] along the real axis.
37 – casinh
Returns the complex arc hyperbolic sine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex casinh (double complex z);
float complex casinhf (float complex z);
long double complex casinhl (long double complex z);
37.1 – Argument
z
A complex value.
37.2 – Description
The casinh functions compute the complex arc hyperbolic sine
of z, with branch cuts outside the interval [-i, +i] along the
imaginary axis.
37.3 – Return Values
n The complex arc hyperbolic sine value, in the
range of a strip mathematically unbounded
along the real axis and in the interval
[-iπ/2, +iπ/2] along the imaginary
axis.
38 – catan
Returns the complex arc tangent of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex catan (double complex z);
float complex catanf (float complex z);
long double complex catanl (long double complex z);
38.1 – Argument
z
A complex value.
38.2 – Description
The catan functions compute the complex arc tangent of z, with
branch cuts outside the interval [-i, +i] along the imaginary
axis.
38.3 – Return Values
n The complex arc tangent value, in the range
of a strip mathematically unbounded along the
imaginary axis and in the interval [-π/2,
+π/2] along the real axis.
39 – catanh
Returns the complex arc hyperbolic tangent of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex catanh (double complex z);
float complex catanhf (float complex z);
long double complex catanhl (long double complex z);
39.1 – Argument
z
A complex value.
39.2 – Description
The catanh functions compute the complex arc hyperbolic tangent
of z, with branch cuts outside the interval [-1, +1] along the
imaginary axis.
39.3 – Return Values
n The complex arc hyperbolic tangent value, in
the range of a strip mathematically unbounded
along the real axis and in the interval
[-iπ/2, +iπ/2] along the imaginary
axis.
40 – catclose
Closes a message catalog.
Format
#include <nl_types.h>
int catclose (nl_catd catd);
40.1 – Argument
catd
A message catalog descriptor. This is returned by a successful
call to catopen.
40.2 – Description
The catclose function closes the message catalog referenced by
catd and frees the catalog file descriptor.
40.3 – Return Values
0 Indicates that the catalog was successfully
closed.
-1 Indicates that an error occurred. The function
sets errno to the following value:
o EBADF - The catalog descriptor is not
valid.
41 – catgets
Retrieves a message from a message catalog.
Format
#include <nl_types.h>
char *catgets (nl_catd catd, int set_id, int msg_id, const char *s);
41.1 – Function Variants
The catgets function has variants named _catgets32 and _catgets64
for use with 32-bit and 64-bit pointer sizes, respectively.
41.2 – Arguments
catd
A message catalog descriptor. This is returned by a successful
call to catopen.
set_id
An integer set identifier.
msg_id
An integer message identifier.
s
A pointer to a default message string that is returned by the
function if the message cannot be retrieved.
41.3 – Description
The catgets function retrieves a message identified by set_id
and msg_id, in the message catalog catd. The message is stored in
a message buffer in the nl_catd structure, which is overwritten
by subsequent calls to catgets. If a message string needs to
be preserved, it should be copied to another location by the
program.
41.4 – Return Values
x Pointer to the retrieved message.
s Pointer to the default message string.
Indicates that the function is not able
to retrieve the requested message from
the catalog. This condition can arise if
the requested pair (set_d, msg_id) does
not represent an existing message from the
open catalog, or it indicates that an error
occurred. If an error occurred, the function
sets errno to one of the following values:
o EBADF - The catalog descriptor is not
valid.
o EVMSRR - An OpenVMS I/O read error;
the OpenVMS error code can be found in
vaxc$errno.
41.5 – Example
#include <nl_types.h>
#include <locale.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <unixio.h>
/* This test makes use of all the message catalog routines. catopen */
/* opens the catalog ready for reading, then each of the three */
/* messages in the catalog are extracted in turn using catgets and */
/* printed out. catclose closes the catalog after use. */
/* The catalog source file used to create the catalog is as follows: */
/* $ This is a message file
* $
* $quote "
* $ another comment line
* $set 1
* 1 "First set, first message"
* 2 "second message - This long message uses a backslash \
* for continuation."
* $set 2
* 1 "Second set, first message" */
char *default_msg = "this is the first message.";
main()
{
nl_catd catalog;
int msg1,
msg2,
retval;
char *cat = "sys$disk:[]catgets_example.cat"; /*Force local catalog*/
char *msgtxt;
char string[128];
/* Create the message test catalog */
system("gencat catgets_example.msgx catgets_example.cat") ;
if ((catalog = catopen(cat, 0)) == (nl_catd) - 1) {
perror("catopen");
exit(EXIT_FAILURE);
}
msgtxt = catgets(catalog, 1, 1, default_msg);
printf("%s\n", msgtxt);
msgtxt = catgets(catalog, 1, 2, default_msg);
printf("%s\n", msgtxt);
msgtxt = catgets(catalog, 2, 1, default_msg);
printf("%s\n", msgtxt);
if ((retval = catclose(catalog)) == -1) {
perror("catclose");
exit(EXIT_FAILURE);
}
delete("catgets_example.cat;") ; /* Remove the test catalog */
}
Running the example program produces the following result:
First set, first message
second message - This long message uses a backslash for
continuation.
Second set, first message
42 – catopen
Opens a message catalog.
Format
#include <nl_types.h>
nl_catd catopen (const char *name, int oflag);
42.1 – Arguments
name
The name of the message catalog to open.
oflag
An object of type int that determines whether the locale set for
the LC_MESSAGES category in the current program's locale or the
logical name LANG is used to search for the catalog file.
42.2 – Description
The catopen function opens the message catalog identified by
name.
If name contains a colon (:), a square opening bracket ([), or
an angle bracket (<), or is defined as a logical name, then it
is assumed that name is the complete file specification of the
catalog.
If it does not include these characters, catopen assumes that
name is a logical name pointing to an existing catalog file. If
name is not a logical name, then the logical name NLSPATH is used
to define the file specification of the message catalog. NLSPATH
is defined in the user's process. If the NLSPATH logical name is
not defined, or no message catalog can be opened in any of the
components specified by the NLSPATH, then the SYS$NLSPATH logical
name is used to search for a message catalog file.
Both NLSPATH and SYS$NLSPATH are comma-separated lists of
templates. The catopen function uses each template to construct a
file specification. For example, NLSPATH could be defined as:
DEFINE NLSPATH SYS$SYSROOT:[SYS$I18N.MSG]%N.CAT,SYS$COMMON:[SYSMSG]%N.CAT
In this example, catopen first searches the directory
SYS$SYSROOT:[SYS$I18N.MSG] for the named catalog. If the named
catalog is not found there, the directory SYS$COMMON:[SYSMSG] is
searched. The catalog name is constructed by substituting %N with
the name passed to catopen, and adding the .cat suffix. %N is
known as a substitution field. The following substitution fields
are valid:
Field Meaning
%N Substitute the name passed to catopen
%L Substitute the locale name.
The period (.) and at-sign (@) characters in the locale
name are replaced by an underscore (_) character.
For example, the "zh_CN.dechanzi@radical" locale name
results in a substitution of ZH_CN_DECHANZI_RADICAL.
%l Substitute the language part of the locale name. For
example, the language part of the en_GB.ISO8859-1 locale
name is en.
%t Substitute the territory part of the locale name. For
example, the territory part of the en_GB.ISO8859-1 locale
is GB.
%c Substitute the codeset name from the locale name. For
example, the codeset name of the en_GB.ISO8859-1 locale
name is ISO8859-1.
If the oflag argument is set to NL_CAT_LOCALE, then the
current locale as defined for the LC_MESSAGES category is
used to determine the substitution for the %L, %l, %t, and %c
substitution fields. If the oflag argument is set to 0, then the
value of the LANG environment variable is used as a locale name
to determine the substitution for these fields. Note that using
NL_CAT_LOCALE conforms to the XPG4 specification while a value of
0 (zero) exists for the purpose of preserving XPG3 compatibility.
Note also, that catopen uses the value of the LANG environment
variable without checking whether the program's locale can be set
using this value. That is, catopen does not check whether this
value can serve as a valid locale argument in the setlocale call.
If the substitution value is not defined, an empty string is
substituted.
A leading comma or two adjacent commas (,,) is equivalent to
specifying %N. For example,
DEFINE NLSPATH ",%N.CAT,SYS$COMMON:[SYSMSG.%L]%N.CAT"
In this example, catopen searches in the following locations in
the order shown:
1. name (in the current directory)
2. name.cat (in the current directory)
3. SYS$COMMON:[SYSMSG.locale_name]name.cat
42.3 – Return Values
x A message catalog file descriptor. Indicates
the call was successful. This descriptor is
used in calls to catgets and catclose.
(nl_catd) -1 Indicates an error occurred. The function sets
errno to one of the following values:
o EACCES - Insufficient privilege or file
protection violation, or file currently
locked by another user.
o EMFILE - Process channel count exceeded.
o ENAMETOOLONG - The full file specification
for message catalog is too long
o ENOENT - Unable to find the requested
message catalog.
o ENOMEM - Insufficient memory available.
o ENOTDIR - Part of the name argument is not
a valid directory.
o EVMSERR - An error occurred that does not
match any errno value. Check the value of
vaxc$errno.
43 – cbrt
Returns the rounded cube root of y.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double cbrt (double y);
float cbrtf (float y);
long double cbrtl (long double y);
43.1 – Argument
y
A real number.
44 – ccos
Returns the complex cosine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex ccos (double complex z);
float complex ccosf (float complex z);
long double complex ccosl (long double complex z);
44.1 – Argument
z
A complex value.
44.2 – Description
The ccos functions return the complex cosine of z.
44.3 – Return Values
x The complex cosine value.
45 – ccosh
Returns the complex hyperbolic cosine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex ccosh (double complex z);
float complex ccoshf (float complex z);
long double complex ccoshl (long double complex z);
45.1 – Argument
z
A complex value.
45.2 – Description
The ccosh functions return the complex hyperbolic cosine of z.
45.3 – Return Values
x The complex hyperbolic cosine value.
46 – ceil
Returns the smallest integer that is greater than or equal to its
argument.
Format
#include <math.h>
double ceil (double x);
float ceilf (float x); (Integrity servers, Alpha)
long double ceill (long double x); (Integrity servers, Alpha)
46.1 – Argument
x
A real value.
46.2 – Return Value
n The smallest integer greater than or equal to
the function argument.
47 – cexp
Returns the complex exponent of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex cexp (double complex z);
float complex cexpf (float complex z);
long double complex cexpl (long double complex z);
47.1 – Argument
z
A complex value.
47.2 – Description
The cexp functions compute the complex exponential value of
z, defined as e**z, where e is the constant used as a base for
natural logarithms.
47.3 – Return Values
x The complex exponential value of the argument.
48 – cfree
Makes available for reallocation the area allocated by a previous
calloc, malloc, or realloc call. This function is AST-reentrant.
Format
#include <stdlib.h>
void cfree (void *ptr);
48.1 – Argument
ptr
The address returned by a previous call to malloc, calloc, or
realloc.
48.2 – Description
The contents of the deallocated area are unchanged.
In VSI C for OpenVMS Systems, the free and cfree functions
are equivalent. Some other C implementations use free with malloc
or realloc, and cfree with calloc. However, since the ANSI C
standard does not include cfree, using free may be preferable.
See also free.
49 – chdir
Changes the default directory.
Format
#include <unistd.h>
int chdir (const char *dir_spec); (ISO POSIX-1)
int chdir (const char *dir_spec, . . . ); (DEC C Extension)
49.1 – Arguments
dir_spec
A null-terminated character string naming a directory in either
an OpenVMS or UNIX style specification.
. . .
This argument is an VSI C extension available when not
defining any of the standards-related feature-test macros and not
compiling in strict ANSI C mode (/STANDARD=ANSI89). The argument
is an optional flag of type int that is significant only when
calling chdir from USER mode.
If the value of the flag is 1, the new directory is effective
across images. If the value is not 1, the original default
directory is restored when the image exits.
49.2 – Description
The chdir function changes the default directory. The change can
be permanent or temporary. Permanent means that the new directory
remains as the default directory after the image exits. Temporary
means that on image exit, the default is set to whatever it was
before the execution of the image.
There are two ways of making the change permanent:
o Call chdir from USER mode with the second argument set to 1.
o Call chdir from SUPERVISOR or EXECUTIVE mode, regardless of
the value of the second argument.
Otherwise, the change is temporary.
49.3 – Return Values
0 Indicates that the directory is successfully
changed to the given name.
-1 Indicates that the change attempt has failed.
50 – chmod
Changes the file protection of a file.
Format
#include <stat.h>
int chmod (const char *file_spec, mode_t mode);
50.1 – Arguments
file_spec
The name of an OpenVMS or UNIX style file specification.
mode
A file protection. Modes are constructed by performing a bitwise
OR on any of the values shown in File Protection Values and Their
Meanings.
Table REF-2 File Protection Values and Their Meanings
Value Privilege
0400 OWNER:READ
0200 OWNER:WRITE
0100 OWNER:EXECUTE
0040 GROUP:READ
0020 GROUP:WRITE
0010 GROUP:EXECUTE
0004 WORLD:READ
0002 WORLD:WRITE
0001 WORLD:EXECUTE
When you supply a mode value of 0, the chmod function gives the
file the user's default file protection.
The system is given the same privileges as the owner. A WRITE
privilege also implies a DELETE privilege.
50.2 – Description
You must have a WRITE privilege for the file specified to change
the mode.
The C RTL does not support the S_ISVTX bit. Setting the S_ISVTX
mode has no effect.
50.3 – Return Values
0 Indicates that the mode is successfully
changed.
-1 Indicates that the change attempt has failed.
51 – chown
Changes the user ID and group ID of the specified file.
Format
#include <unistd.h>
int chown (const char *file_spec, uid_t owner, gid_t group);
51.1 – Arguments
file_spec
The address of an ASCII filename.
owner
The new user ID of the file.
group
The new group ID of the file.
51.2 – Return Values
0 Indicates success.
-1 Indicates failure.
52 – cimag
Returns the imaginary part of its complex argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double cimag (double complex z);
float cimagf (float complex z);
long double cimagl (long double complex z);
52.1 – Argument
z
A complex value.
52.2 – Description
The cimag functions return the imaginary part of z as a real
number.
52.3 – Return Values
x The imaginary part value.
53 – [w]clear
Erase the contents of the specified window and reset the cursor
to coordinates (0,0). The clear function acts on the stdscr
window.
Format
#include <curses.h>
int clear();
int wclear (WINDOW *win);
53.1 – Argument
win
A pointer to the window.
53.2 – Return Values
OK Indicates success.
ERR Indicates an error.
54 – clearerr
Resets the error and end-of-file indicators for a file (so that
ferror and feof will not return a nonzero value).
Format
#include <stdio.h>
void clearerr (FILE *file_ptr);
54.1 – Argument
file_ptr
A file pointer.
55 – clearerr_unlocked
Same as the clearerr function, except used only within a scope
protected by flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
void clearerr_unlocked (FILE *file_ptr);
55.1 – Argument
file_ptr
A file pointer.
55.2 – Description
The reentrant version of the clearerr function is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the stream. The unlocked version of this
call, clearerr_unlocked can be used to avoid the overhead. The
clearerr_unlocked macro is functionally identical to the clearerr
macro, except that it is not required to be implemented in a
thread-safe manner. The clearerr_unlocked function can be safely
used only within a scope that is protected by the flockfile and
funlockfile functions used as a pair. The caller must ensure that
the stream is locked before clearerr_unlocked is used.
See also flockfile, ftrylockfile, and funlockfile.
56 – clearok
Sets the clear flag for the window.
Format
#include <curses.h>
clearok (WINDOW *win, bool boolf);
56.1 – Arguments
win
The entire size of the terminal screen. You can use the windows
stdscr and curscr with clearok.
boolf
A Boolean value of TRUE or FALSE. If the argument is TRUE, this
forces a clearscreen to be printed on the next call to refresh,
or stops the screen from being cleared if boolf is FALSE.
The type bool is defined in the <curses.h> header file as
follows:
#define bool int
56.2 – Description
Unlike the clear function, the clearok function does not alter
the contents of the window. If the win argument is curscr, the
next call to refresh causes a clearscreen, even if the window
passed to refresh is not a window the size of the entire terminal
screen.
57 – clock
Determines the CPU time (in 10-millisecond units) used since the
beginning of the process. The time reported is the sum of the
user and system times of the calling process and any terminated
child processes for which the calling process has executed wait
or system.
Format
#include <time.h>
clock_t clock (void);
57.1 – Description
The value returned by the clock function must be divided by the
value of the CLK_TCK, as defined in the standard header file
<time.h>, to obtain the time in seconds.
The type clock_t is defined in the <time.h> header file as
follows:
typedef long int clock_t;
Only the accumulated times for child processes running a C main
program or a program that calls VAXC$CRTL_INIT or DECC$CRTL_INIT
are included.
A typical usage of the clock function is to call it after a
program does its initial setup, and then again after the program
executes the code to be timed. Then subtract the two values to
give elapsed CPU time.
57.2 – Return Values
n The processor time used.
-1 Indicates that the processor time used is not
available.
58 – clock_getres
Gets the resolution for the specified clock.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <time.h>
int clock_getres (clockid_t clock_id, struct timespec *res);
58.1 – Arguments
clock_id
The clock type used to obtain the resolution. The CLOCK_REALTIME
clock is supported and represents the TIME-OF-DAY clock for the
system.
res
A pointer to the timespec data structure that receives the value
of the clock's resolution.
58.2 – Description
The clock_getres function obtains the resolution value for the
specified clock. Clock resolutions are implementation-dependent
and cannot be set by a process.
If the res argument is not NULL, the resolution of the specified
clock is stored in the location pointed to by res.
If res is NULL, the clock resolution is not stored.
If the time argument (tp) of clock_settime is not a multiple of
res, then the value is truncated to a multiple of res.
On success, the function returns 0.
On failure, the function returns -1 and sets errno to indicate
the error.
See also clock_gettime, clock_settime, time, and ctime.
58.3 – Return Values
0 Indicates success.
-1 Indicates failure; errno is set to the
following value:
o EINVAL - The clock_id argument does not
specify a known clock.
59 – clock_gettime
Returns the current time (in seconds and nanoseconds) for the
specified clock.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <time.h>
int clock_gettime (clockid_t clock_id, struct timespec *tp);
59.1 – Arguments
clock_id
The clock type used to obtain the time for the clock that is
set. The CLOCK_REALTIME clock is supported and represents the
TIME-OF-DAY clock for the system.
tp
A pointer to a timespec data structure.
59.2 – Description
The clock_gettime function returns the current tp value for the
specified clock, clock_id.
On success, the function returns 0.
On failure, the function returns -1 and sets errno to indicate
the error.
See also clock_getres, clock_settime, time, and ctime.
59.3 – Return Values
0 Indicates success.
-1 Indicates failure; errno is set to the
following value:
o EINVAL - The clock_id argument does not
specify a known clock, or the tp argument
specifies a nanosecond value less than 0 or
greater than or equal to 1 billion.
60 – clock_settime
Sets the specified clock.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <time.h>
int clock_settime (clockid_t clock_id, const struct timespec *tp);
60.1 – Arguments
clock_id
The clock type used for the clock that is to be set. The CLOCK_
REALTIME clock is supported and represents the TIME-OF-DAY clock
for the system.
tp
A pointer to a timespec data structure.
60.2 – Description
The clock_settime function sets the specified clock, clock_id,
to the value specified by tp. Time values that are between two
consecutive non-negative integer multiples of the resolution of
the specified clock are truncated down to the smaller multiple of
the resolution.
A clock can be systemwide (that is, visible to all processes)
or per-process (measuring time that is meaningful only within a
process).
The CLOCK_REALTIME clock, defined in <time.h>, represents the
realtime clock for the system. For this clock, the values
specified by clock_settime and returned by clock_gettime
represent the amount of time elapsed, in seconds and nanoseconds,
since the Epoch. The Epoch is defined as 00:00:00:00 January 1,
1970 Greenwich Mean Time (GMT).
You must have OPER, LOG_IO, and SYSPRV privileges to use the
clock_settime function.
On success, the function returns 0.
On failure, the function returns -1 and sets errno to indicate
the error.
See also clock_getres, clock_gettime, time, and ctime.
60.3 – Return Values
0 Indicates success.
-1 Indicates failure; errno is set to the
following value:
o EINVAL - The clock_id argument does not
specify a known clock, or the tp argument
is outside the range for the given clock_id
or specifies a nanosecond value less than 0
or greater than or equal to 1 billion.
o EPERM - The requesting process does not
have the appropriate privilege to set the
specified clock.
61 – clog
Returns the complex natural (base e) logarithm of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex clog (double complex z);
float complex clogf (float complex z);
long double complex clogl (long double complex z);
61.1 – Argument
z
A complex value.
61.2 – Description
The clog functions return the complex natural (base e) logarithm
of z, with a branch cut along the negative real axis.
61.3 – Return Values
x The complex natural logarithm value in the
range of a strip mathematically unbounded
along the real axis and in the interval [-
iπ, +iπ] along the imaginary axis.
62 – close
Closes the file associated with a file descriptor.
Format
#include <unistd.h>
int close (int file_desc);
62.1 – Argument
file_desc
A file descriptor.
62.2 – Description
The close function tries to write buffered data by using an
implicit call to fflush. If the write fails (because the disk
is full or the user's quota was exceeded, for example), close
continues executing. It closes the OpenVMS channel, deallocates
any buffers, and releases the memory associated with the file
descriptor (or FILE pointer). Any buffered data is lost, and the
file descriptor (or FILE pointer) no longer refers to the file.
If your program needs to recover from errors when flushing
buffered data, it should make an explicit call to fsync (or
fflush) before calling close.
62.3 – Return Values
0 Indicates that the file is properly closed.
-1 Indicates that the file descriptor is
undefined or an error occurred while the file
was being closed (for example, if the buffered
data cannot be written out).
62.4 – Example
#include <unistd.h>
int fd;
.
.
.
fd = open ("student.dat", 1);
.
.
.
close(fd);
63 – closedir
Closes directories.
Format
#include <dirent.h>
int closedir (DIR *dir_pointer);
63.1 – Argument
dir_pointer
Pointer to the dir structure of an open directory.
63.2 – Description
The closedir function closes a directory stream and frees
the structure associated with the dir_pointer argument. Upon
return, the value of dir_pointer does not necessarily point to an
accessible object of the type DIR.
The type DIR, which is defined in the <dirent.h> header file,
represents a directory stream that is an ordered sequence of
all the directory entries in a particular directory. Directory
entries represent files. You can remove files from or add files
to a directory asynchronously to the operation of the readdir
function.
NOTE
An open directory must always be closed with the closedir
function to ensure that the next attempt to open the
directory is successful.
63.3 – Example
The following example shows how to search a directory for the
entry name, using the opendir, readdir, and closedir functions:
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define FOUND 1
#define NOT_FOUND 0
static int dir_example(const char *name, unsigned int unix_style)
{
DIR *dir_pointer;
struct dirent *dp;
if ( unix_style )
dir_pointer = opendir(".");
else
dir_pointer = opendir(getenv("PATH"));
if ( !dir_pointer ) {
perror("opendir");
return NOT_FOUND;
}
/* Note, that if opendir() was called with UNIX style file */
/* spec like ".", readdir() will return only a single */
/* version of each file in the directory. In this case the */
/* name returned in d_name member of the dirent structure */
/* will contain only file name and file extension fields, */
/* both lowercased like "foo.bar". */
/* If opendir() was called with OpenVMS style file spec, */
/* readdir() will return every version of each file in the */
/* directory. In this case the name returned in d_name */
/* member of the dirent structure will contain file name, */
/* file extension and file version fields. All in upper */
/* case, like "FOO.BAR;1". */
for ( dp = readdir(dir_pointer);
dp && strcmp(dp->d_name, name);
dp = readdir(dir_pointer) )
;
closedir(dir_pointer);
if ( dp != NULL )
return FOUND;
else
return NOT_FOUND;
}
int main(void)
{
char *filename = "foo.bar";
FILE *fp;
remove(filename);
if ( !(fp = fopen(filename, "w")) ) {
perror("fopen");
return (EXIT_FAILURE);
}
if ( dir_example( "FOO.BAR;1", 0 ) == FOUND )
puts("OpenVMS style: found");
else
puts("OpenVMS style: not found");
if ( dir_example( "foo.bar", 1 ) == FOUND )
puts("UNIX style: found");
else
puts("UNIX style: not found");
fclose(fp);
remove(filename);
return( EXIT_SUCCESS );
}
63.4 – Return Values
0 Indicates success.
-1 Indicates an error and is further specified in
the global errno.
64 – [w]clrattr
Deactivate the video display attribute attr within the window.
The clrattr function acts on the stdscr window.
Format
#include <curses.h>
int clrattr (int attr);
int wclrattr (WINDOW *win, int attr);
64.1 – Arguments
win
A pointer to the window.
attr
Video display attributes that can be blinking, boldface, reverse
video, and underlining; they are represented by the defined
constants _BLINK, _BOLD, _REVERSE, and _UNDERLINE. To clear
multiple attributes, separate them with a bitwise OR operator
(|) as follows:
clrattr(_BLINK | _UNDERLINE);
64.2 – Description
These functions are specific to VSI C for OpenVMS Systems and
are not portable.
64.3 – Return Values
OK Indicates success.
ERR Indicates an error.
65 – [w]clrtobot
Erase the contents of the window from the current position of the
cursor to the bottom of the window. The clrtobot function acts on
the stdscr window.
Format
#include <curses.h>
int clrtobot();
int wclrtobot (WINDOW *win);
65.1 – Argument
win
A pointer to the window.
65.2 – Return Values
OK Indicates success.
ERR Indicates an error.
66 – [w]clrtoeol
Erase the contents of the window from the current cursor position
to the end of the line on the specified window. The clrtoeol
function acts on the stdscr window.
Format
#include <curses.h>
int clrtoeol();
int wclrtoeol (WINDOW *win);
66.1 – Argument
win
A pointer to the window.
66.2 – Return Values
OK Indicates success.
ERR Indicates an error.
67 – confstr
Determines the current value of a specified system variable
defined by a string value.
Format
#include <unistd.h>
size_t confstr (int name, char *buf, size_t len);
67.1 – Arguments
name
The system variable setting. Valid values for the name argument
are the _CS_X names defined in the <unistd.h> header file.
buf
Pointer to the buffer where the confstr function copies the name
value.
len
The size of the buffer storing the name value.
67.2 – Description
The confstr function allows an application to determine the
current setting of certain system parameters, limits, or options
that are defined by a string value. The function is mainly used
by applications to find the system default value for the PATH
environment variable.
If the following conditions are true, then the confstr function
copies that value into a len-byte buffer pointed to by buf:
o The len argument can be 0 (zero).
o The name argument has a system-defined value.
o The buf argument is not a NULL pointer.
If the returned string is longer than len bytes, including the
terminating null, then the confstr function truncates the string
to len - 1 bytes and adds a terminating null to the result. The
application can detect that the string was truncated by comparing
the value returned by the confstr function with the value of the
len argument.
The <limits.h> header file contains system-defined limits. The
<unistd.h> header file contains system-defined environmental
variables.
Also, confstr supports the following three HP-UX symbolic
constants, which are added to header file <unistd.h>:
o _CS_MACHINE_IDENT
o _CS_PARTITION_IDENT
o _CS_MACHINE_SERIAL
67.3 – Example
To find out how big a buffer is needed to store the string
value of name, enter:
confstr(_CS_PATH, NULL, (size_t) 0)
The confstr function returns the size of the buffer necessary.
67.4 – Return Values
0 Indicates an error. When the specified name
value:
o Is invalid, errno is set to EINVAL.
o Does not have a system-defined value, errno
is not set.
n The size of the buffer needed to hold the
value.
o When the value of the name argument is
system-defined, confstr returns the size of
the buffer needed to hold the entire value.
If this return value is greater than the
len value, the string returned as the buf
value is truncated.
o When the value of the len argument is set
to 0 or the buf value is NULL, confstr
returns the size of the buffer needed to
hold the entire system-defined value. The
string value is not copied.
68 – conj
Returns the complex conjugate of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex conj (double complex z);
float complex conjf (float complex z);
long double complex conjl (long double complex z);
68.1 – Argument
z
A complex value.
68.2 – Description
The conj functions return the complex conjugate of z, by
reversing the sign of its imaginary part.
68.3 – Return Values
x The complex conjugate value.
69 – copysign
Returns x with the same sign as y.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double copysign (double x, double y);
float copysignf (float x, float y);
(Integrity servers, Alpha)
long double copysignl (long double x, long double y);
(Integrity servers, Alpha)
69.1 – Arguments
x
A real value.
y
A real value.
69.2 – Description
The copysign functions return x with the same sign as y. IEEE 754
requires copysign(x,NaN), copysignf(x,NaN), and copysignl(x,NaN)
to return +x or -x.
69.3 – Return Value
x The value of x with the same sign as y.
70 – cos
Returns the cosine of its radian argument.
Format
#include <math.h>
double cos (double x);
float cosf (float x); (Integrity servers, Alpha)
long double cosl (long double x); (Integrity servers, Alpha)
double cosd (double x); (Integrity servers, Alpha)
float cosdf (float x); (Integrity servers, Alpha)
long double cosdl (long double x); (Integrity servers, Alpha)
70.1 – Argument
x
A radian expressed as a real value.
70.2 – Description
The cos functions return the cosine of their argument, measured
in radians.
The cosd functions return the cosine of their argument, measured
in degrees.
|x| = Infinity is an invalid argument.
70.3 – Return Values
x The cosine of the argument.
HUGE_VAL Indicates that the argument is too large;
errno is set to ERANGE.
71 – cosh
Returns the hyperbolic cosine of its radian argument.
Format
#include <math.h>
double cosh (double x);
float coshf (float x); (Integrity servers, Alpha)
long double coshl (long double x); (Integrity servers, Alpha)
71.1 – Argument
x
A radian expressed as a real number.
71.2 – Description
The cosh functions return the hyperbolic cosine of x and are
defined as (e**x + e**(-x))/2.
71.3 – Return Values
x The hyperbolic cosine of the argument.
HUGE_VAL Indicates that the argument is too large;
errno is set to ERANGE.
72 – cot
Returns the cotangent of its radian argument.
Format
#include <math.h>
double cot (double x);
float cotf (float x); (Integrity servers, Alpha)
long double cotl (long double x); (Integrity servers, Alpha)
double cotd (double x); (Integrity servers, Alpha)
float cotdf (float x); (Integrity servers, Alpha)
long double cotdl (long double x); (Integrity servers, Alpha)
72.1 – Argument
x
A radian expressed as a real number.
72.2 – Description
The cot functions return the cotangent of their argument,
measured in radians.
The cotd functions return the cotangent of their argument,
measured in degrees.
x = 0 is an invalid argument.
72.3 – Return Values
x The cotangent of the argument.
HUGE_VAL Indicates that the argument is zero; errno is
set to ERANGE.
73 – cpow
Returns the complex power function x**y.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex cpow (double complex x, double complex y);
float complex cpowf (float complex x, float complex y);
long double complex cpowl (long double complex x, long double complex y);
73.1 – Argument
x
A complex value.
y
A complex value.
73.2 – Description
The cpow functions return the complex power function x**y, with a
branch cut for the first parameter along the negative real axis.
73.3 – Return Values
x The complex power function value.
74 – cproj
Returns a projection of its argument onto the Riemann sphere.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex cproj (double complex z);
float complex cprojf (float complex z);
long double complex cprojl (long double complex z);
74.1 – Argument
z
A complex value.
74.2 – Description
The cproj functions compute and return a projection of z onto
the Riemann sphere: z projects to z, except that all complex
infinities (even those with one infinite part and one NaN part)
project to positive infinity on the real axis. If z has an
infinite part, then cproj(z) is equivalent to:
INFINITY + I * copysign(0.0, cimag(z))
74.3 – Return Values
x The value of the projection onto the Riemann
sphere.
75 – creal
Returns the real part of its complex argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double creal (double complex z);
float crealf (float complex z);
long double creall (long double complex z);
75.1 – Argument
z
A complex value.
75.2 – Description
The creal functions return the real part of z.
75.3 – Return Values
x The real part value.
76 – creat
Creates a new file.
Format
#include <fcntl.h>
int creat (const char *file_spec, mode_t mode); (ISO POSIX-1)
int creat (const char *file_spec, mode_t mode, . . . );
(DEC C Extension)
76.1 – Arguments
file_spec
A null-terminated string containing any valid file specification.
mode
An unsigned value that specifies the file-protection mode. The
compiler performs a bitwise AND operation on the mode and the
complement of the current protection mode.
You can construct modes by using the bitwise OR operator (|) to
create mode combinations. The modes are:
0400 OWNER:READ
0200 OWNER:WRITE
0100 OWNER:EXECUTE
0040 GROUP:READ
0020 GROUP:WRITE
0010 GROUP:EXECUTE
0004 WORLD:READ
0002 WORLD:WRITE
0001 WORLD:EXECUTE
The system is given the same privileges as the owner. A WRITE
privilege implies a DELETE privilege.
NOTE
To create files with OpenVMS RMS default protections using
the UNIX system-call functions umask, mkdir, creat, and
open, call mkdir, creat, and open with a file-protection
mode argument of 0777 in a program that never specifically
calls umask. These default protections include correctly
establishing protections based on ACLs, previous versions of
files, and so on.
In programs that do vfork/exec calls, the new process image
inherits whether umask has ever been called or not from
the calling process image. The umask setting and whether
the umask function has ever been called are both inherited
attributes.
. . .
An optional argument list of character strings of the following
form:
"keyword = value", . . . ,"keyword = value"
Or in the case of "acc" or "err", this form:
"keyword"
Here, keyword is an RMS field in the file access block (FAB) or
record access block (RAB); value is valid for assignment to that
field. Some fields permit you to specify more than one value. In
these cases, the values are separated by commas.
The RMS callback keywords "acc" and "err" are the only keywords
that do not take values. Instead, they are followed by a pointer
to the callback routine to be used, followed by a pointer to a
user-specified value to be used as the first argument of the
callback routine. For example, to set up an access callback
routine called acc_callback whose first argument is a pointer
to the integer variable first_arg in a call to open, you can use
the following statement:
open("file.dat", O_RDONLY, 0 ,"acc", acc_callback, &first_arg)
The second and third arguments to the callback routine must be
pointers to a FAB and RAB, respectively, and the routine must
have a return type of int. If the callback returns a value less
than 0, the open, creat, or fopen fails. The error callback can
correct the error condition and return a status greater than
or equal to 0 to continue the creat call. Assuming the previous
open statement, the function prototype for acc_callback would be
similar to the following statement:
#include <rms.h>
int acc_callback(int *first_arg, struct FAB *fab, struct RAB *rab);
FAB and RAB are defined in the <rms.h> header file, and the
actual pointers passed to the routine are pointers to the RAB
and FAB being used to open the file file.dat.
If an access callback routine is established, then it will be
called in the open-type routine immediately before the call to
the RMS function sys$create or sys$open. If an error callback
routine is established and an error status is returned from the
sys$create or sys$open function, then the callback routine will
be invoked immediately after the status is checked and the error
value is discovered.
NOTE
Any manipulation of the RAB or FAB in a callback function
could lead to serious problems in later calls to the
C RTL I/O functions.
RMS Valid Keywords and Values describes the RMS keywords and
values.
Table REF-3 RMS Valid Keywords and Values
Keyword Value Description
"acc" callback Access callback routine.
"alq = n" decimal Allocation quantity.
"bls = n" decimal Block size.
"ctx = bin" string No translation of '\n' to the terminal.
Use this for writing binary data to
files.
"ctx = cvt" string Negates a previous setting of
"ctx=nocvt". This is the default.
"ctx = string No conversion of Fortran carriage-control
nocvt" bytes.
"ctx = rec" string Forces record mode access.
"ctx = stm" string Forces stream mode access.
"ctx = string Causes records to be written only when
xplct" explicitly specified by a call to fflush,
close, or fclose.
"deq = n" decimal Default extension quantity.
"dna = string Default file-name string.
filespec"
"err" callback Error callback routine.
"fop = val, File-processing options:
val , . . . "
ctg Contiguous.
cbt Contiguous-best-try.
dfw Deferred write; only applicable to files
opened for shared access.
dlt Delete file on close.
tef Truncate at end-of-file.
cif Create if nonexistent.
sup Supersede.
scf Submit as command file on close.
spl Spool to system printer on close.
tmd Temporary delete.
tmp Temporary (no file directory).
nef Not end-of-file.
rck Read check compare operation.
wck Write check compare operation.
mxv Maximize version number.
rwo Rewind file on open.
pos Current position.
rwc Rewind file on close.
sqo File can only be processed in a
sequential manner.
"fsz = n" decimal Fixed header size.
"gbc = n" decimal The requested number of global buffers
for a file.
"mbc = n" decimal Multiblock count.
"mbf = n" decimal Multibuffer count.
"mrs = n" decimal Maximum record size.
"pmt=usr- string Prompts for terminal input. Any RMS input
prmpt" from a terminal device will be preceded
by "usr-prmpt" when this option and
"rop=pmt" are specified.
"rat = val, Record attributes:
val . . . "
cr Carriage-return control.
blk Disallow records to span block
ftn boundaries.
none Fortran print control.
prn Explicitly forces no carriage control.
Print file format.
"rfm = val" Record format:
fix Fixed-length record format.
stm RMS stream record format.
stmlf Stream format with line-feed terminator.
stmcr Stream format with carriage-return
terminator.
var Variable-length record format.
vfc Variable-length record with fixed
udf control.
Undefined.
"rop = val, Record-processing operations:
val . . . "
asy Asynchronous I/O.
cco Cancels Ctrl/O (used with Terminal I/O).
cvt Capitalizes characters on a read from the
terminal.
eof Positions the record stream to the end-
of-file for the connect operation only.
nlk Do not lock record.
pmt Enables use of the prompt specified
by "pmt=usr-prmpt" on input from the
terminal.
pta Eliminates any information in the type-
ahead buffer on a read from the terminal.
rea Locks record for a read operation for
this process, while allowing other
accessors to read the record.
rlk Locks record for write.
rne Suppresses echoing of input data on the
screen as it is entered on the keyboard.
rnf Indicates that Ctrl/U, Ctrl/R, and DELETE
are not to be considered control commands
on terminal input, but are to be passed
to the application program.
rrl Reads regardless of lock.
syncsts Returns a success status of RMS$_SYNCH if
the requested service completes its task
immediately.
tmo Timeout I/O.
tpt Allows put/write services using
sequential record access mode to occur
at any point in the file, truncating the
file at that point.
ulk Prohibits RMS from automatically
unlocking records.
wat Wait until record is available, if
currently locked by another stream.
rah Read ahead.
wbh Write behind.
"rtv=n" decimal The number of retrieval pointers that RMS
has to maintain in memory (0 to 127,255).
"shr = val, File sharing options:
val, . . . "
del Allows users to delete.
get Allows users to read.
mse Allows multistream connects.
nil Prohibits file sharing.
put Allows users to write.
upd Allows users to update.
upi Allows one or more writers.
nql No query locking (file level).
"tmo = n" decimal I/O timeout value.
In addition to these options, any option that takes a key value
(such as "fop" or "rat") can be negated by prefixing the value
with "no". For example, specify "fop=notmp" to clear the "tmp"
bit in the "fop" field.
NOTES
o While these options provide much flexibility and
functionality, many of them can also cause severe
problems if not used correctly.
o You cannot share the default VSI C for OpenVMS stream
file I/O. If you wish to share files, you must specify
"ctx=rec" to force record access mode. You must also
specify the appropriate "shr" options depending on the
type of access you want.
o If you intend to share a file opened for append, you must
specify appropriate share and record-locking options, to
allow other accessors to read the record. The reason for
doing this: the file is positioned at the end-of-file by
reading records in a loop until end-of-file is reached.
For more information on these options, see the OpenVMS Record
Management Services Reference Manual.
76.2 – Description
The C RTL opens the new file for reading and writing, and
returns the corresponding file descriptor.
If the file exists:
o A version number one greater than any existing version is
assigned to the newly created file.
o By default, the new file inherits certain attributes from
the existing version of the file unless those attributes are
specified in the creat call. The following attributes are
inherited:
- Record format (FAB$B_RFM)
- Maximum record size (FAB$W_MRS)
- Carriage control (FAB$B_RAT)
- File protection
o When a new version of a file is created, and the named file
already exists as a symbolic link, the file to which the
symbolic link refers is created.
If the file did not previously exist:
o It is given the file protection that results from performing
a bitwise AND on the mode argument and the complement of the
current protection mask.
o It defaults to stream format with line-feed record separator
and implied carriage-return attributes.
See also open, close, read, write, and lseek in this section.
76.3 – Return Values
n A file descriptor.
-1 Indicates errors, including protection
violations, undefined directories, and
conflicting file attributes.
77 – [no]crmode
In the UNIX system environment, the crmode and nocrmode functions
set and unset the terminal from cbreak mode. In cbreak mode, a
single input character can be processed without pressing Return.
This mode of single-character input is only supported with the
Curses input routine getch.
Format
#include <curses.h>
crmode()
nocrmode()
77.1 – Example
/* Program to demonstrate the use of crmod() and curses */
#include <curses.h>
main()
{
WINDOW *win1;
char vert = '.',
hor = '.',
str[80];
/* Initialize standard screen, turn echo off. */
initscr();
noecho();
/* Define a user window. */
win1 = newwin(22, 78, 1, 1);
/* Turn on reverse video and draw a box on border. */
setattr(_REVERSE);
box(stdscr, vert, hor);
mvwaddstr(win1, 2, 2, "Test cbreak input");
refresh();
wrefresh(win1);
/* Set cbreak, do some input, and output it. */
crmode();
getch();
nocrmode(); /* Turn off cbreak. */
mvwaddstr(win1, 5, 5, str);
mvwaddstr(win1, 7, 7, "Type something to clear the screen");
wrefresh(win1);
/* Get another character, then delete the window. */
getch();
wclear(win1);
touchwin(stdscr);
endwin();
}
In this example, the first call to getch returns as soon as one
character is entered, because crmode was called before getch
was called. The second time getch is called, it waits until the
Return key is pressed before processing the character entered,
because nocrmode was called before getch was called the second
time.
78 – crypt
The password encryption function.
Format
#include <unistd.h>
#include <stdlib.h>
char *crypt (const char *key, const char *salt;)
78.1 – Function Variants
The crypt function has variants named _crypt32 and _crypt64 for
use with 32-bit and 64-bit pointer sizes, respectively.
78.2 – Argument
key
A user's typed password.
salt
A 2-character string.
78.3 – Description
The crypt function generates an encoded version of a password.
It is based on the NBS Data Encryption Standard, with variations
intended to frustrate use of hardware implementations of the DES
for key search.
The first argument to crypt is normally a user's typed password.
The second is a 2-character string chosen from the set [a-zA-Z0-
9./]. The salt string is used to perturb the DES algorithm in one
of 4096 different ways, after which the password is used as the
key to encrypt repeatedly a constant string. The returned value
points to the encrypted password, in the same alphabet as the
salt. The first two characters are the salt itself.
The return value from crypt points to a static data area whose
content is overwritten by each call.
See also encrypt and setkey.
78.4 – Return Value
pointer Pointer to the encrypted password.
79 – csin
Returns the complex sine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex csin (double complex z);
float complex csinf (float complex z);
long double complex csinl (long double complex z);
79.1 – Argument
z
A complex value.
79.2 – Description
The csin functions compute the complex sine value of z.
79.3 – Return Values
x The complex sine value.
Returns the complex hyperbolic sine of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex csinh (double complex z);
float complex csinhf (float complex z);
long double complex csinhl (long double complex z);
79.4 – Argument
z
A complex value.
79.5 – Description
The csinh functions compute the complex hyperbolic sine of z.
79.6 – Return Values
x The complex hyperbolic sine value.
80 – csqrt
Returns the complex square root of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex csqrt (double complex z);
float complex csqrtf (float complex z);
long double complex csqrtl (long double complex z);
80.1 – Argument
z
A complex value.
80.2 – Description
The csqrt functions compute the complex square root of z, with a
branch cut along the negative real axis.
80.3 – Return Values
x The complex square root value in the range of
the right half-plane (including the imaginary
axis).
81 – ctan
Returns the complex tangent of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex ctan (double complex z);
float complex ctanf (float complex z);
long double complex ctanl (long double complex z);
81.1 – Argument
z
A complex value.
81.2 – Description
The ctan functions compute the complex tangent value of z.
81.3 – Return Values
x The complex tangent value.
82 – ctanh
Returns the complex hyperbolic tangent of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <complex.h>
double complex ctanh (double complex z);
float complex ctanhf (float complex z);
long double complex ctanhl (long double complex z);
82.1 – Argument
z
A complex value.
82.2 – Description
The ctanh functions compute the complex hyperbolic tangent value
of z.
82.3 – Return Values
x The complex hyperbolic tangent value.
83 – ctermid
Returns a character string giving the equivalence string of
SYS$COMMAND. This is the name of the controlling terminal.
Format
#include <stdio.h>
char *ctermid (char *str);
83.1 – Function Variants
The ctermid function has variants named _ctermid32 and _ctermid64
for use with 32-bit and 64-bit pointer sizes, respectively.
83.2 – Argument
str
Must be a pointer to an array of characters. If this argument is
NULL, the filename is stored internally and might be overwritten
by the next ctermid call. Otherwise, the filename is stored
beginning at the location indicated by the argument. The argument
must point to a storage area of length L_ctermid (defined by the
<stdio.h> header file).
83.3 – Return Value
pointer Points to a character string.
84 – ctime
Converts a time in seconds, since 00:00:00 January 1, 1970, to an
ASCII string in the form generated by the asctime function.
Format
#include <time.h>
char *ctime (const time_t *bintim);
char *ctime_r (const time_t *bintim, char *buffer);
(ISO POSIX-1)
84.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to
this function that is equivalent to the behavior before OpenVMS
Version 7.0.
84.2 – Arguments
bintim
A pointer to a variable that specifies the time value (in
seconds) to be converted.
buffer
A pointer to a character array that is at least 26 bytes long.
This array is used to store the generated date-and-time string.
84.3 – Description
The ctime and ctime_r functions convert the time pointed to by
bintim into a 26-character string, and return a pointer to the
string.
The difference between the ctime_r and ctime functions is that
the former puts its result into a user-specified buffer. The
latter puts its result into thread-specific static memory
allocated by the C RTL, which can be overwritten by
subsequent calls to ctime or asctime; you must make a copy if
you want to save it.
On success, ctime returns a pointer to the string; ctime_r
returns its second argument. On failure, these functions return
the NULL pointer.
The type time_t is defined in the <time.h> header file as
follows:
typedef long int time_t
The ctime function behaves as if it called tzset.
NOTE
Generally speaking, UTC-based time functions can affect in-
memory time-zone information, which is processwide data.
However, if the system time zone remains the same during
the execution of the application (which is the common case)
and the cache of timezone files is enabled (which is the
default), then the _r variant of the time functions asctime_
r, ctime_r, gmtime_r, and localtime_r, is both thread-safe
and AST-reentrant.
If, however, the system time zone can change during the
execution of the application or the cache of timezone files
is not enabled, then both variants of the UTC-based time
functions belong to the third class of functions, which are
neither thread-safe nor AST-reentrant.
84.4 – Return Values
x A pointer to the 26-character ASCII string, if
successful.
NULL Indicates failure.
85 – cuserid
Returns a pointer to a character string containing the name of
the user initiating the current process.
Format
#include <unistd.h> (X/Open, POSIX-1)
#include <stdio.h> (X/Open)
char *cuserid (char *str);
85.1 – Function Variants
The cuserid function has variants named _cuserid32 and _cuserid64
for use with 32-bit and 64-bit pointer sizes, respectively.
85.2 – Argument
str
If this argument is NULL, the user name is stored internally. If
the argument is not NULL, it points to a storage area of length
L_cuserid (defined by the <stdio.h> header file), and the name is
written into that storage. If the user name is a null string, the
function returns NULL.
85.3 – Return Values
pointer Points to a string.
NULL If the user name is a null string.
86 – DECC$CRTL_INIT
Allows you to call the C RTL from other languages or to
use the C RTL when your main function is not in C. It
initializes the run-time environment and establishes both an exit
and condition handler. VAXC$CRTL_INIT is a synonym for DECC$CRTL_
INIT. Either name invokes the same routine.
Format
#include <signal.h>
void DECC$CRTL_INIT(void);
86.1 – Description
The following example shows a Pascal program that calls the
C RTL using the DECC$CRTL_INIT function:
$ PASCAL EXAMPLE1
$ LINK EXAMPLE1
$ TY EXAMPLE1.PAS
PROGRAM TESTC(input, output);
PROCEDURE DECC$CRTL_INIT; extern;
BEGIN
DECC$CRTL_INIT;
END
A shareable image need only call this function if it contains
an VSI C function for signal handling, environment variables,
I/O, exit handling, a default file protection mask, or if it is a
child process that should inherit context.
Although many of the initialization activities are performed only
once, DECC$CRTL_INIT can safely be called multiple times.
At least one frame in the current call stack must have that
handler established for OpenVMS exceptions to get mapped to UNIX
signals.
87 – decc$feature_get
Calls decc$feature_get_value with a character-string feature
name, rather than an index.
Format
#include <unixlib.h>
int decc$feature_get (const char *name, int mode);
87.1 – Argument
name
Pointer to a character string passed as a name in the list of
supported features.
mode
An integer indicating which feature value to return. The values
for mode are:
__FEATURE_MODE_DEFVAL Default value
__FEATURE_MODE_CURVAL Current value
__FEATURE_MODE_MINVAL Minimum value
__FEATURE_MODE_MAXVAL Maximum value
__FEATURE_MODE_INIT_STATE Initialization state
87.2 – Description
The decc$feature_get function allows you to call the
decc$feature_get_value function with a character-string feature
name, rather than an index into an internal C RTL table.
On error, -1 is returned and errno is set to indicate the error.
See also decc$feature_get_value, decc$feature_get_index,
decc$feature_get_name, decc$feature_set, decc$feature_set_value,
decc$feature_show, and decc$feature_show_all.
87.3 – Return Values
n An integer corresponding to the specified name
and mode arguments.
-1 Indicates an error; errno is set.
88 – decc$feature_get_index
Returns an index for accessing feature values.
Format
#include <unixlib.h>
int decc$feature_get_index (char *name);
88.1 – Argument
name
Pointer to a character string passed as a name in the list of
supported features.
88.2 – Description
The decc$feature_get_index function looks up the string passed
as name in the list of supported features. If the name is found,
decc$feature_get_index returns a (nonnegative) index that can
be used to set or retrieve the values for the feature. The
comparison for name is case insensitive.
On error, -1 is returned and errno is set to indicate the error.
See also decc$feature_get, decc$feature_get_value, decc$feature_
get_name, decc$feature_set, decc$feature_set_value, decc$feature_
show, and decc$feature_show_all.
88.3 – Return Values
n A nonnegative index that can be used to set or
retrieve the specified values for the feature.
-1 Indicates an error; errno is set.
89 – decc$feature_get_name
Returns a feature name.
Format
#include <unixlib.h>
char *decc$feature_get_name (int index);
89.1 – Argument
index
An integer value from 0 to the highest allocated feature.
89.2 – Description
The decc$feature_get_name function returns a pointer to a null-
terminated string containing the name of the feature for the
entry specified by index. The index value can be 0 to the highest
allocated feature. If there is no feature corresponding to the
index value, then the function returns a NULL pointer.
On error, NULL is returned and errno is set to indicate the
error.
See also decc$feature_get, decc$feature_get_index, decc$feature_
get_value, decc$feature_set, decc$feature_set_value,
decc$feature_show, and decc$feature_show_all.
89.3 – Return Values
x Pointer to a null-terminated string containing
the name of the feature for the entry
specified by index.
NULL Indicates an error; errno is set.
90 – decc$feature_get_value
Returns a feature value specified by the index and mode
arguments.
Format
#include <unixlib.h>
int decc$feature_get_value (int index, int mode);
90.1 – Arguments
index
An integer value from 0 to the highest allocated feature.
mode
An integer indicating which feature value to return. The values
for mode are:
__FEATURE_MODE_DEFVAL Default value
__FEATURE_MODE_CURVAL Current value
__FEATURE_MODE_MINVAL Minimum value
__FEATURE_MODE_MAXVAL Maximum value
__FEATURE_MODE_INIT_STATE Initialization state
90.2 – Description
The decc$feature_get_value function retrieves a value for the
feature specified by index. The mode determines which value is
returned.
The default value is what is used if not set by a logical name or
overridden by a call to decc$feature_set_value.
If mode = 4, then the initialization state is returned. Values
for the initialization state are:
0 not initialized
1 set by logical name
2 forced by decc$feature_set_value
-1-initialized to default value
On error, -1 is returned and errno is set to indicate the error.
See also decc$feature_get, decc$feature_get_index, decc$feature_
get_name, decc$feature_set, decc$feature_set_value, decc$feature_
show, and decc$feature_show_all.
90.3 – Return Values
n An integer corresponding to the specified
index and mode arguments.
-1 Indicates an error; errno is set.
91 – decc$feature_set
Calls decc$feature_set_value with a character-string feature
name, rather than an index.
Format
#include <unixlib.h>
int decc$feature_set (const char *name, int mode, int value);
91.1 – Argument
name
Pointer to a character string passed as a name in the list of
supported features.
mode
An integer indicating which feature value to return. The values
for mode are:
__FEATURE_MODE_DEFVAL Default value
__FEATURE_MODE_CURVAL Current value
__FEATURE_MODE_MINVAL Minimum value
__FEATURE_MODE_MAXVAL Maximum value
__FEATURE_MODE_INIT_STATE Initialization state
value
The feature value to be set.
91.2 – Description
The decc$feature_set function allows you to call the
decc$feature_set_value function with a character-string feature
name, rather than an index into an internal C RTL table.
If successful, the function returns the previous value.
On error, -1 is returned and errno is set to indicate the error.
See also decc$feature_set_value, decc$feature_get, decc$feature_
get_index, decc$feature_get_name, decc$feature_get_value.
decc$feature_show, and decc$feature_show_all.
91.3 – Return Values
n The previous feature value.
-1 Indicates an error; errno is set.
92 – decc$feature_set_value
Sets the default value or the current value for the feature
specified by index.
Format
#include <unixlib.h>
int decc$feature_set_value (int index, int mode, int value);
92.1 – Arguments
index
An integer value from 0 to the highest allocated feature.
mode
An integer indicating whether to set the default or current
feature value. The values for mode are:
0 default value
1 current value
value
The feature value to be set.
92.2 – Description
The decc$feature_set_value function sets the default value or
the current value (as determined by the mode argument) for the
feature specified by index.
If this function is successful, it returns the previous value.
On error, -1 is returned and errno is set to indicate the error.
See also decc$feature_get, decc$feature_get_index, decc$feature_
get_name, decc$feature_get_value, decc$feature_set, decc$feature_
show, and decc$feature_show_all.
92.3 – Return Values
n The previous feature value.
-1 Indicates an error; errno is set.
93 – decc$feature_show
Displays all feature values for the specified feature name.
Format
#include <unixlib.h>
int decc$feature_show (const char *name);
93.1 – Argument
name
Pointer to a character string passed as a name in the list of
supported features.
93.2 – Description
The decc$feature_show function displays to stdout all values for
the specified feature name. For example:
--------- C RTL Feature Name --------- Cur Def Min Max Ini
DECC$V62_RECORD_GENERATION 0 0 0 1 -1
On error, -1 is returned and errno is set to indicate the error.
See also decc$feature_get, decc$feature_get_index, decc$feature_
get_name, decc$feature_get_value, decc$feature_set, decc$feature_
set_value, and decc$feature_show_all.
93.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set.
94 – decc$feature_show_all
Displays all feature values for all feature names.
Format
#include <unixlib.h>
int decc$feature_show_all (void);
94.1 – Description
The decc$feature_show_all function displays to stdout all values
for all feature names.
On error, -1 is returned and errno is set to indicate the error.
See also decc$feature_get, decc$feature_get_index, decc$feature_
get_name, decc$feature_get_value, decc$feature_set, decc$feature_
set_value, and decc$feature_show.
94.2 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set.
95 – decc$fix_time
Converts OpenVMS binary system times to UNIX binary times.
Format
#include <unixlib.h>
unsigned int decc$fix_time (void *vms_time);
95.1 – Argument
vms_time
The address of a quadword containing an OpenVMS binary time:
unsigned int quadword[2];
unsigned int *vms_time = quadword;
95.2 – Description
The decc$fix_time routine converts an OpenVMS binary system time
(a 64-bit quadword containing the number of 100-nanosecond ticks
since 00:00 November 17, 1858) to a UNIX binary time (a longword
containing the number of seconds since 00:00 January 1, 1970).
This routine is useful for converting binary times returned by
OpenVMS system services and RMS services to the format used by
some C RTL routines, such as ctime and localtime.
95.3 – Return Values
x A longword containing the number of seconds
since 00:00 January 1, 1970.
(unsigned Indicates an error. Be aware, that a return
int)(-1) value of (unsigned int)(-1) can also represent
a valid date of Sun Feb 7 06:28:15 2106.
95.4 – Example
#include <unixlib.h>
#include <stdio.h>
#include <starlet.h> /* OpenVMS specific SYS$ routines) */
main()
{
unsigned int current_vms_time[2];
/*quadword for OpenVMS time*/
unsigned int number_of_seconds; /* number of seconds */
/* first get the current system time */
sys$gettim(¤t_vms_time[0]);
/* fix the time */
number_of_seconds = decc$fix_time(¤t_vms_time[0]);
printf("Number of seconds since 00:00 January 1, 1970 = %d",
number_of_seconds);
}
This example shows how to use the decc$fix_time routine in
VSI C. It also shows the use of the SYS$GETTIM system
service.
96 – decc$from_vms
Converts OpenVMS file specifications to UNIX style file
specifications.
Format
#include <unixlib.h>
int decc$from_vms (const char *vms_filespec, int
action_routine, int wild_flag);
96.1 – Arguments
vms_filespec
The address of a null-terminated string containing a name in
OpenVMS file specification format.
action_routine
The address of a routine that takes as its only argument a null-
terminated string containing the translation of the given OpenVMS
filename to a valid UNIX style filename.
If the action_routine returns a nonzero value (TRUE), file
translation continues. If it returns a zero value (FALSE), no
further file translation takes place.
wild_flag
Either 0 or 1, passed by value. If a 0 is specified, wildcards
found in vms_filespec are not expanded. Otherwise, wildcards
are expanded and each one is passed to action_routine. Only
expanded filenames that correspond to existing UNIX style files
are included.
96.2 – Description
The decc$from_vms routine converts the given OpenVMS file
specification into the equivalent UNIX style file specification.
It allows you to specify OpenVMS wildcards, which are translated
into a list of corresponding existing files in UNIX style file
specification format.
96.3 – Return Value
x The number of filenames that result from the
specified OpenVMS file specification.
96.4 – Example
/* This example must be run as a foreign command */
/* and be supplied with an OpenVMS file specification. */
#include <unixlib.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
int number_found; /* number of files found */
int print_name(); /* name printer */
printf("Translating: %s\n", argv[1]);
number_found = decc$from_vms(argv[1], print_name, 1);
printf("\n%d files found", number_found);
}
/* print the name on each line */
print_name(char *name)
{
printf("\n%s", name);
/* will continue as long as success status is returned */
return (1);
}
This example shows how to use the decc$from_vms routine in
VSI C. It produces a simple form of the ls command that
lists existing files that match an OpenVMS file specification
supplied on the command line. The matching files are displayed
in UNIX style file specification format.
97 – decc$match_wild
Matches a string to a pattern.
Format
#include <unixlib.h>
int decc$match_wild (char *test_string, char *string_pattern);
97.1 – Arguments
test_string
The address of a null-terminated string.
string_pattern
The address of a string containing the pattern to be matched.
This pattern can contain wildcards (such as asterisks (*),
question marks (?), and percent signs (%) as well as regular
expressions (such as the range [a-z]).
97.2 – Description
The decc$match_wild routine determines whether the specified
test string is a member of the set of strings specified by the
pattern.
97.3 – Return Values
1 (TRUE) The string matches the pattern.
0 (FALSE) The string does not match the pattern.
97.4 – Example
/* Define as a foreign command and then provide */
/* two arguments: test_string, string_pattern. */
#include <unixlib.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
if (decc$match_wild(argv[1], argv[2]))
printf("\n%s matches %s", argv[1], argv[2]);
else
printf("\n%s does not match %s", argv[1], argv[2]);
}
98 – decc$record_read
Reads a record from a file.
Format
#include <stdio.h>
int decc$record_read (FILE *fp, void *buffer, int nbytes);
98.1 – Arguments
fp
A file pointer. The specified file pointer must refer to a file
currently opened for reading.
buffer
The address of contiguous storage in which the input data is
placed.
nbytes
The maximum number of bytes involved in the read operation.
98.2 – Description
The decc$record_read function is specific to OpenVMS systems and
should not be used when writing portable applications.
This function is equivalent to the read function, except that the
first argument is a file pointer, not a file descriptor.
98.3 – Return Values
x The number of characters read.
-1 Indicates a read error, including physical
input errors, illegal buffer addresses,
protection violations, undefined file
descriptors, and so forth.
99 – decc$record_write
Writes a record to a file.
Format
#include <stdio.h>
int decc$record_write (FILE *fp, void *buffer, int nbytes);
99.1 – Arguments
fp
A file pointer. The specified file pointer must refer to a file
currently opened for writing or updating.
buffer
The address of contiguous storage from which the output data is
taken.
nbytes
The maximum number of bytes involved in the write operation.
99.2 – Description
The decc$record_write function is specific to OpenVMS systems and
should not be used when writing portable applications.
This function is equivalent to the write function, except that
the first argument is a file pointer, not a file descriptor.
99.3 – Return Values
x The number of bytes written.
-1 Indicates errors, including undefined file
descriptors, illegal buffer addresses, and
physical I/O errors.
100 – decc$set_child_default_dir
Sets the default directory for a child process spawned by a
function from the exec family of functions.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unixlib.h>
int decc$set_child_default_dir (const char *default_dir);
100.1 – Arguments
default_dir
The default directory specification for child processes, or NULL.
100.2 – Description
By default, child processes created by one of the exec family of
functions inherit the default (working) directory of their parent
process.
The decc$set_child_default_dir function lets you set the
default directory for a child process. After calling decc$set_
child_default_dir, newly spawned child processes have their
default directory set to default_dir as they begin execution.
The default_dir argument must represent a valid directory
specification, or results of the call are unpredictable
(subsequent calls to the child process might fail without
notification). Both OpenVMS and UNIX style file specifications
are supported for this function call.
You can reestablish the default behavior by specifying default_
dir as NULL. Subsequently, newly created child processes will
inherit their parent's working directory.
100.3 – Return Values
0 Successful completion. The new inherited
default directory was established.
-1 Indicates failure. No new default directory
was established for child processes. The
function sets errno to one of the following
values:
o ENOMEM - Insufficient memory
o ENAMETOOLONG - default_dir is too long to
issue the required SET DEFAULT command.
101 – decc$set_child_standard_streams
For a child spawned by a function from the exec family of
functions, associates specified file descriptors with a child's
standard streams: stdin, stdout, and stderr.
Format
#include <unixlib.h>
int decc$set_child_standard_streams (int fd1, int fd2, int fd3);
101.1 – Arguments
fd1
The file associated with this file descriptor in the parent
process is associated with file descriptor number 0 (stdin) in
the child process. If -1 is specified, the file associated with
the parent's file descriptor number 0 is used (the default).
fd2
The file associated with this file descriptor in the parent
process is associated with file descriptor number 1 (stdout) in
the child process. If -1 is specified, the file associated with
the parent's file descriptor number 1 is used (the default).
fd3
The file associated with this file descriptor in the parent
process is associated with file descriptor number 2 (stderr) in
the child process. If -1 is specified, the file associated with
the parent's file descriptor number 2 is used (the default).
101.2 – Description
The decc$set_child_standard_streams function allows mapping of
specified file descriptors to the child's stdin/stdout/stderr
streams, thereby compensating, to a certain degree, the lack of a
real fork function on OpenVMS systems.
On UNIX systems, the code between fork and exec is executed in
the context of the child process:
parent:
create pipes p1, p2 and p3
fork
child:
map stdin to p1 like dup2(p1, stdin);
map stdout to p2 like dup2(p2, stdout);
map stderr to p3 like dup2(p3, stderr);
exec (child reads from stdin and writes to stdout and stderr)
exit
parent:
communicates with the child using pipes
On OpenVMS systems, the same task could be achieved as follows:
parent:
create pipes p1, p2 and p3
decc$set_child_standard_streams(p1, p2, p3);
vfork
exec (child reads from stdin and writes to stdout and stderr)
parent:
communicates with the child using pipes
Once established through the call to decc$set_child_standard_
streams, the mapping of the child's standard streams remains in
effect until explicitly disabled by one of the following calls:
decc$set_child_standard_streams(-1, -1, -1);
Or:
decc$set_child_standard_streams(0, 1, 2);
Usually, the child process inherits all its parent's open file
descriptors. However, if file descriptor number n was specified
in the call to decc$set_child_standard_streams, it is not
inherited by the child process as file descriptor number n;
instead, it becomes one of the child's standard streams.
NOTES
o Standard streams can be redirected only to pipes.
o If the parent process redefines the DCL DEFINE command,
this redefinition is not in effect in a subprocess with
user-defined channels. The subprocess always sees the
standard DCL DEFINE command.
o It is the responsibility of the parent process to consume
all the output written by the child process to stdout and
stderr. Depending on how the subprocess writes to stdout
and stderr-in wait or nowait mode-the subprocess might be
placed in LEF state waiting for the reader. For example,
DCL writes to SYS$OUTPUT and SYS$ERROR in a wait mode,
so a child process executing a DCL command procedure will
wait until all the output is read by the parent process.
Recommendation: Read the pipes associated with the child
process' stdout and stderr in a loop until an EOF message
is received, or declare write attention ASTs on these
mailboxes.
o The amount of data written to SYS$OUTPUT depends on the
verification status of the process (SET VERIFY/NOVERIFY
command); the subprocess inherits the verification status
of the parent process. It is the caller's responsibility
to set the verification status of the parent process to
match the expected amount of data written to SYS$OUTPUT
by the subprocess.
o Some applications, like DTM, define SYS$ERROR as
SYS$OUTPUT. If stderr is not redefined by the caller,
it is set in the subprocess as the parent's SYS$ERROR,
which in this case translates to the parent's SYS$OUTPUT.
If the caller redefines stdout to a pipe and does not
redefine stderr, output sent to stderr goes to the pipe
associated with stdout, and the amount of data written
to this mailbox may be more than expected. Although
redefinition of any subset of standard channels is
supported, it is always safe to explicitly redefine all
of them (or at least stdout and stderr) to avoid this
situation.
o For a child process executing a DCL command procedure,
SYS$COMMAND is set to the pipe specified for the child's
stdin so that the parent process can feed the child
requesting data from SYS$COMMAND through the pipe. For
DCL command procedures, it is impossible to pass data
from the parent to the child by means of the child's
SYS$INPUT because for a command procedure, DCL defines
SYS$INPUT as the command file itself.
101.3 – Return Values
x The number of file descriptors set for the
child. This number does not include file
descriptors specified as -1 in the call.
-1 indicates that an invalid file descriptor was
specified; errno is set to EBADF.
101.4 – Example
parent.c
#include <stdio.h>
#include <string.h>
#include <unistd.h>
int decc$set_child_standard_streams(int, int, int);
main()
{
int fdin[2], fdout[2], fderr[2];
char msg[] = "parent writing to child's stdin";
char buf[80];
int nbytes;
pipe(fdin);
pipe(fdout);
pipe(fderr);
if ( vfork() == 0 ) {
decc$set_child_standard_streams(fdin[0], fdout[1], fderr[1]);
execl( "child", "child" );
}
else {
write(fdin[1], msg, sizeof(msg));
nbytes = read(fdout[0], buf, sizeof(buf));
buf[nbytes] = '\0';
puts(buf);
nbytes = read(fderr[0], buf, sizeof(buf));
buf[nbytes] = '\0';
puts(buf);
}
}
child.c
#include <stdio.h>
#include <unistd.h>
main()
{
char msg[] = "child writing to stderr";
char buf[80];
int nbytes;
nbytes = read(0, buf, sizeof(buf));
write(1, buf, nbytes);
write(2, msg, sizeof(msg));
}
child.com
$ read sys$command s
$ write sys$output s
$ write sys$error "child writing to stderr"
This example program returns the following for both child.c and
child.com:
$ run parent
parent writing to child's stdin
child writing to stderr
Note that in order to activate child.com, you must explicitly
specify execl("child.com", ...) in the parent.c program.
102 – decc$set_reentrancy
Controls the type of reentrancy that reentrant C RTL
routines will exhibit.
Format
#include <reentrancy.h>
int decc$set_reentrancy (int type);
102.1 – Argument
type
The type of reentrancy desired. Use one of the following values:
o C$C_MULTITHREAD - Designed to be used in conjunction with the
DECthreads product. It performs DECthreads locking and never
disables ASTs. DECthreads must be available on your system to
use this form of reentrancy.
o C$C_AST - Uses the __TESTBITSSI (Integrity servers, Alpha)
built-in function to perform simple locking around critical
sections of RTL code, and it may additionally disable
asynchronous system traps (ASTs) in locked regions of
code. This type of locking should be used when AST code
contains calls to C RTL I/O routines, or when the user
application disables ASTs.
o C$C_TOLERANT - Uses the
__TESTBITSSI (Integrity servers, Alpha) built-in function
to perform simple locking around critical sections of RTL
code, but ASTs are not disabled. This type of locking should
be used when ASTs are used and must be delivered immediately.
TOLERANT is the default reentrancy type.
o C$C_NONE - Gives optimal performance in the C RTL, but
does absolutely no locking around critical sections of RTL
code. It should only be used in a single-threaded environment
when there is no chance that the thread of execution will be
interrupted by an AST that would call the C RTL.
The reentrancy type can be raised but never lowered. The ordering
of reentrancy types from low to high is C$C_NONE, C$C_TOLERANT,
C$C_AST and C$C_MULTITHREAD. For example, once an application
is set to multithread, a call to set the reentrancy to AST is
ignored. A call to decc$set_reentrancy that attempts to lower the
reentrancy type returns a value of -1.
102.2 – Description
Use the decc$set_reentrancy function to change the type of
reentrancy exhibited by reentrant routines.
decc$set_reentrancy must be called exclusively at the non-AST
level.
In an application using DECthreads, DECthreads automatically sets
the reentrancy to multithread.
102.3 – Return Value
type The type of reentrancy used before this call.
-1 The reentrancy was set to a lower type.
103 – decc$to_vms
Converts UNIX style file specifications to OpenVMS file
specifications.
Format
#include <unixlib.h>
int decc$to_vms (const char *unix_style_filespec,
int (*action_routine)
(char *OpenVMS_style_filespec, int type_of_file),
int allow_wild, int no_directory);
103.1 – Arguments
unix_style_filespec
The address of a null-terminated string containing a name in UNIX
style file specification format.
action_routine
The address of a routine called by decc$to_vms that accepts the
following arguments:
o A pointer to a null-terminated string that is the result of
the translation to OpenVMS format.
o An integer that has one of the following values:
Value Translation
0 (DECC$K_FOREIGN) A file on a remote system that is not
running the OpenVMS or VAXELN operating
system.
1 (DECC$K_FILE) The translation is a file.
2 (DECC$K_ The OpenVMS translation of the UNIX style
DIRECTORY) filename is a directory.
These values can be defined symbolically with the symbols
DECC$K_FOREIGN, DECC$K_FILE, and DECC$K_DIRECTORY. See the
example for more information.
If action_routine returns a nonzero value (TRUE), file
translation continues. If it returns a 0 value (FALSE), no
further file translation takes place.
allow_wild
Either 0 or 1, passed by value. If a 0 is specified, wildcards
found in unix_style_filespec are not expanded. Otherwise,
wildcards are expanded and each one is passed to action_routine.
Only expanded filenames that correspond to existing OpenVMS files
are included.
no_directory
An integer that has one of the following values:
Value Translation
0 Directory allowed.
1 Prevent expansion of the string as a directory
name.
2 Forced to be a directory name.
103.2 – Description
The decc$to_vms function converts the given UNIX style file
specification into the equivalent OpenVMS file specification
(in all uppercase letters). It allows you to specify UNIX style
wildcards, which are translated into a list of corresponding
OpenVMS files.
Note that the following feature logicals can affect the behavior
of decc$to_vms:
DECC$DISABLE_TO_VMS_LOGNAME_TRANSLATION
DECC$NO_ROOTED_SEARCH_LISTS
103.3 – Return Value
x The number of filenames that result from the
specified UNIX style file specification.
103.4 – Example
/* Translate "UNIX" wildcard file names to OpenVMS names.*/
/* Define as a foreign command and provide the name as */
/* an argument. */
#include <unixlib.h>
#include <stdio.h>
int print_name(char *, int);
int main(int argc, char *argv[])
{
int number_found; /* number of files found */
printf("Translating: %s\n", argv[1]);
number_found = decc$to_vms(argv[1], print_name, 1, 0);
printf("%d files found\n", number_found);
}
/* action routine that prints name and type on each line */
int print_name(char *name, int type)
{
if (type == DECC$K_DIRECTORY)
printf("directory: %s\n", name);
else if (type == DECC$K_FOREIGN)
printf("remote non-VMS: %s\n", name);
else
printf("file: %s\n", name);
/* Translation continues as long as success status is returned */
return (1);
}
This example shows how to use the decc$to_vms routine in
VSI C. It takes a UNIX style file specification argument
and displays, in OpenVMS file specification format, the name of
each existing file that matches it.
104 – decc$translate_vms
Translates OpenVMS file specifications to UNIX style file
specifications.
Format
#include <unixlib.h>
char *decc$translate_vms (const char *vms_filespec);
104.1 – Argument
vms_filespec
The address of a null-terminated string containing a name in
OpenVMS file specification format.
104.2 – Description
The decc$translate_vms function translates the given OpenVMS file
specification into the equivalent UNIX style file specification,
whether or not the file exists. The translated name string is
stored in a thread-specific memory, which is overwritten by each
call to decc$translate_vms from the same thread.
This function differs from the decc$from_vms function, which does
the conversion for existing files only.
104.3 – Return Values
x The address of a null-terminated string
containing a name in UNIX style file
specification format.
0 Indicates that the filename is null or
syntactically incorrect.
-1 Indicates that the file specification contains
an ellipsis (for example, [ . . . ]a.dat), but
is otherwise correct. You cannot translate
the OpenVMS ellipsis syntax into a valid UNIX
style file specification.
104.4 – Example
/* Demonstrate translation of a "UNIX" name to OpenVMS */
/* form, define a foreign command, and pass the name as */
/* the argument. */
#include <unixlib.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
char *ptr; /* translation result */
ptr = decc$translate_vms( argv[1] );
if ((int) ptr == 0 || (int) ptr == -1)
printf( "could not translate %s\n", argv[1]);
else
printf( "%s is translated to %s\n", argv[1], ptr );
}
105 – decc$validate_wchar
Confirms that its argument is a valid wide character in the
current program's locale.
Format
#include <unistd.h>
int decc$validate_wchar (wchar_t wc);
105.1 – Argument
wc
Wide character to be validated.
105.2 – Description
The decc$validate_wchar function provides a convenient way to
verify whether a specified argument of wchar_t type is a valid
wide character in the current program's locale.
One reason to call decc$validate_wchar is that the isw* wide-
character classification functions and macros do not validate
their argument before dereferencing the classmask array
describing character properties. Passing an isw* function a value
that exceeds the maximum wide-character value for the current
program's locale can result in an attempt to access memory beyond
the allocated classmask array.
A standard way to validate a wide character is to call the wctomb
function, but this way is less convenient because it requires
declaring a multibyte character array of sufficient size and
passing it to wctomb.
105.3 – Return Values
1 Indicates that the specified wide character
is a valid wide character in the current
program's locale.
0 Indicates that the specified wide character
is not a valid wide character in the current
program's locale. errno is not set.
106 – decc$write_eof_to_mbx
Writes an end-of-file message to the mailbox.
Format
#include <unistd.h>
int decc$write_eof_to_mbx (int fd);
106.1 – Argument
fd
File descriptor associated with the mailbox.
106.2 – Description
The decc$write_eof_to_mbx function writes end-of-file message to
the mailbox.
For a mailbox that is not a pipe, the write function called with
an nbytes argument value of 0 sends an end-of-file message to the
mailbox. For a pipe, however, the only way to write an end-of-
file message to the mailbox is to close the pipe.
If the child's standard input is redirected to a pipe through a
call to the decc$set_child_standard_streams function, the parent
process can call decc$write_eof_to_mbx for this pipe to send an
EOF message to the child. It has the same effect as if the child
read the data from a terminal, and Ctrl/Z was pressed.
After a call to decc$write_eof_to_mbx, the pipe can be reused
for communication with another child, for example. This is
the purpose of decc$write_eof_to_mbx: to allow reuse of the
pipe instead of having to close it just to send an end-of-file
message.
106.3 – Return Values
0 Indicates success.
-1 Indicates failure; errno and vaxc$errno are
set according to the failure status returned
by SYS$QIOW.
106.4 – Example
/* decc$write_eof_to_mbx_example.c */
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <unixio.h>
#include <descrip.h>
#include <ssdef.h>
#include <starlet.h>
int decc$write_eof_to_mbx( int );
main()
{
int status, nbytes, failed = 0;
int fd, fd2[2];
short int channel;
$DESCRIPTOR(mbxname_dsc, "TEST_MBX");
char c;
/* first try a mailbox created by SYS$CREMBX */
status = sys$crembx(0, &channel, 0, 0, 0, 0, &mbxname_dsc, 0, 0);
if ( status != SS$_NORMAL ) {
printf("sys$crembx failed: %s\n",strerror(EVMSERR, status));
failed = 1;
}
if ( (fd = open(mbxname_dsc.dsc$a_pointer, O_RDWR, 0)) == -1) {
perror("? open mailbox");
failed = 1;
}
if ( decc$write_eof_to_mbx(fd) == -1 ) {
perror("? decc$write_eof_to_mbx to mailbox");
failed = 1;
}
if ( (nbytes = read(fd, &c, 1)) != 0 || errno != 0 ) {
perror("? read mailbox");
printf("? nbytes = %d\n", nbytes);
failed = 1;
}
if ( close(fd) == -1 ) {
perror("? close mailbox");
failed = 1;
}
/* Now do the same thing with a pipe */
errno = 0; /* Clear errno for consistency */
if ( pipe(fd2) == -1 ) {
perror("? opening pipe");
failed = 1;
}
if ( decc$write_eof_to_mbx(fd2[1]) == -1 ) {
perror("? decc$write_eof_to_mbx to pipe");
failed = 1;
}
if ( (nbytes = read(fd2[0], &c, 1)) != 0 || errno != 0 ) {
perror("? read pipe");
printf("? nbytes = %d\n", nbytes);
failed = 1;
}
/* Close both file descriptors involved with the pipe */
if ( close(fd2[0]) == -1 ) {
perror("close(fd2[0])");
failed = 1;
}
if ( close(fd2[1]) == -1 ) {
perror("close(fd2[1])");
failed = 1;
}
if ( failed )
puts("?Example program failed");
else
puts("Example ran to completion");
}
This example program produces the following result:
Example ran to completion
107 – [w]delch
Delete the character on the specified window at the current
position of the cursor. The delch function operates on the stdscr
window.
Format
#include <curses.h>
int delch();
int wdelch (WINDOW *win);
107.1 – Argument
win
A pointer to the window.
107.2 – Description
All of the characters to the right of the cursor on the same line
are shifted to the left, and a blank character is appended to the
end of the line.
107.3 – Return Values
OK Indicates success.
ERR Indicates an error.
108 – delete
Deletes a file.
Format
#include <unixio.h>
int delete (const char *file_spec);
108.1 – Argument
file_spec
A pointer to the string that is an OpenVMS or UNIX style file
specification. The file specification can include a wildcard in
its version number (but not in any other part of the file spec).
So, for example, files of the form filename.txt;* can be deleted.
108.2 – Description
If you specify a directory in the filename and it is a search
list that contains an error, VSI C for OpenVMS Systems
interprets it as a file error.
When delete is used to delete a symbolic link, the link itself is
deleted, not the file to which it refers.
The remove and delete functions are functionally equivalent in
the C RTL.
See also remove.
NOTE
The delete routine is not available to C++ programmers
because it conflicts with the C++ reserved word delete.
C++ programmers should use the ANSI/ISO C standard function
remove instead.
108.3 – Return Values
0 Indicates success.
nonzero value Indicates that the operation has failed.
109 – [w]deleteln
Delete the line at the current position of the cursor. The
deleteln function acts on the stdscr window.
Format
#include <curses.h>
int deleteln();
int wdeleteln (WINDOW *win);
109.1 – Argument
win
A pointer to the window.
109.2 – Description
Every line below the deleted line moves up, and the bottom line
becomes blank. The current (y,x) coordinates of the cursor remain
unchanged.
109.3 – Return Values
OK Indicates success.
ERR Indicates an error.
110 – delwin
Deletes the specified window from memory.
Format
#include <curses.h>
int delwin (WINDOW *win);
110.1 – Argument
win
A pointer to the window.
110.2 – Description
If the window being deleted contains a subwindow, the subwindow
is invalidated. Delete subwindows before deleting their parent.
The delwin function refreshes all windows covered by the deleted
window.
110.3 – Return Values
OK Indicates success.
ERR Indicates an error.
111 – difftime
Computes the difference, in seconds, between the two times
specified by the time1 and time2 arguments.
Format
#include <time.h>
double difftime (time_t time2, time_t time1);
111.1 – Arguments
time2
A time value of type time_t.
time1
A time value of type time_t.
111.2 – Description
The type time_t is defined in the <time.h> header file as
follows:
typedef unsigned long int time_t
111.3 – Return Value
n time2 - time1 in seconds expressed as a
double.
112 – dirname
Reports the parent directory name of a file pathname.
Format
#include <libgen.h>
char *dirname (char *path);
112.1 – Function Variants
The dirname function has variants named _dirname32 and _dirname64
for use with 32-bit and 64-bit pointer sizes, respectively.
112.2 – Argument
path
The file pathname.
112.3 – Description
The dirname function takes a pointer to a character string that
contains a UNIX pathname and returns a pointer to a string that
is a pathname of the parent directory of that file. Trailing
slash (/) characters in the path are not counted as part of the
path.
This function returns a pointer to the string "." (dot), when the
path argument:
o Does not contain a slash (/).
o Is a NULL pointer.
o Points to an empty string.
The dirname function can modify the string pointed to by the path
argument.
The dirname and basename functions together yield a complete
pathname. The expression dirname(path) obtains the pathname of
the directory where basename(path) is found.
See also basename.
112.4 – Return Values
x A pointer to a string that is the parent
directory of the path argument.
"." The path argument:
o Does not contain a slash (/).
o Is a NULL pointer.
o Points to an empty string.
112.5 – Example
Using the dirname function, the following example reads a
pathname, changes the current working directory to the parent
directory, and opens a file.
char path [MAXPATHLEN], *pathcopy;
int fd;
fgets(path, MAXPATHLEN, stdin);
pathcopy = strdup(path);
chdir(dirname(pathcopy));
fd = open(basename(path), O_RDONLY);
113 – div
Returns the quotient and the remainder after the division of its
arguments.
Format
#include <stdlib.h>
div_t div (int numer, int denom);
113.1 – Arguments
numer
A numerator of type int.
denom
A denominator of type int.
113.2 – Description
The type div_t is defined in the standard header file <stdlib.h>
as follows:
typedef struct
{
int quot, rem;
} div_t;
114 – dlclose
Deallocates the address space for a shared library.
Format
#include <dlfcn.h>
void dlclose (void *handle);
114.1 – Argument
handle
Pointer to the shared library.
114.2 – Description
The dlclose function deallocates the address space allocated by
the C RTL for the handle.
There is no way on OpenVMS systems to unload a shareable image
dynamically loaded by the LIB$FIND_IMAGE_SYMBOL routine, which
is the routine called by the dlsym function. In other words,
there is no way on OpenVMS systems to release the address space
occupied by the shareable image brought into memory by dlsym.
115 – dlerror
Returns a string describing the last error that occurred from a
call to dlopen, dlclose, or dlsym.
Format
#include <dlfcn.h>
char *dlerror (void);
115.1 – Return Value
x A string describing the last error that
occurred from a call to dlopen, dlclose, or
dlsym.
116 – dlopen
Provides an interface to the dynamic library loader to allow
shareable images to be loaded and called at run time.
Format
#include <dlfcn.h>
void *dlopen (char *pathname, int mode);
116.1 – Arguments
pathname
The name of the shareable image. This name is saved for
subsequent use by the dlsym function.
mode
This argument is ignored on OpenVMS systems.
116.2 – Description
The dlopen function provides an interface to the dynamic library
loader to allow shareable images to be loaded and called at run
time.
This function does not load a shareable image but rather saves
its pathname argument for subsequent use by the dlsym function.
dlsym is the function that actually loads the shareable image
through a call to LIB$FIND_IMAGE_SYMBOL.
The pathname argument of the dlopen function must be the name
of the shareable image. This name is passed as-is by the dlsym
function to the LIB$FIND_IMAGE_SYMBOL routine as the filename
argument. No image-name argument is specified in the call
to LIB$FIND_IMAGE_SYMBOL, so default file specification of
SYS$SHARE:.EXE is applied to the image name.
The dlopen function returns a handle that is used by a dlsym or
dlclose call. If an error occurs, a NULL pointer is returned.
116.3 – Return Values
x A handle to be used by a dlsym or dlclose
call.
NULL Indicates an error.
117 – dlsym
Returns the address of the symbol name found in a shareable
image.
Format
#include <dlfcn.h>
void *dlsym (void *handle, char *name);
117.1 – Arguments
handle
Pointer to the shareable image.
name
Pointer to the symbol name.
117.2 – Description
The dlsym function returns the address of the symbol name found
in the shareable image corresponding to handle. If the symbol is
not found, a NULL pointer is returned.
As of OpenVMS Version 7.3-2, library symbols containing
lowercase characters can be loaded using the dlsym function. More
generally, the functions that dynamically load libraries (dlopen,
dlsym, dlclose, dlerror) are enhanced to provide the following
capabilities:
o Support for libraries with mixed-case symbol names
o Ability to pass a full file path to dlopen
o Validation of the specified library name
117.3 – Return Values
x Address of the symbol name found.
NULL Indicates that the symbol was not found.
118 – drand48
Generates uniformly distributed pseudorandom-number sequences.
Returns 48-bit, nonnegative, double-precision floating-point
values.
Format
#include <stdlib.h>
double drand48 (void);
118.1 – Description
The drand48 function generates pseudorandom numbers using the
linear congruential algorithm and 48-bit integer arithmetic.
It returns nonnegative, double-precision, floating-point values
uniformly distributed over the range of y values such that 0.0
y < 1.0.
Before you call drand48, use either srand48, seed48, or lcong48
to initialize the random-number generator. You must initialize
prior to invoking the drand48 function because it stores the last
48-bit Xi generated into an internal buffer. (Although it is not
recommended, constant default initializer values are supplied
automatically if the drand48, lrand48, or mrand48 functions are
called without first calling an initialization function.)
The drand48 function works by generating a sequence of 48-bit
integer values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n >= 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke lcong48, the multiplier value a
and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The values returned by drand48 are computed by first generating
the next 48-bit Xi in the sequence. Then the appropriate bits,
according to the type of returned data item, are copied from the
high-order (most significant) bits of Xi and transformed into the
returned value.
See also srand48, seed48, lcong48, lrand48, and mrand48.
118.2 – Return Value
n A nonnegative, double-precision, floating-
point value.
119 – dup,dup2
Allocate a new descriptor that refers to a file specified by a
file descriptor returned by open, creat, or pipe.
Format
#include <unistd.h>
int dup (int file_desc1);
int dup2 (int file_desc1, int file_desc2);
119.1 – Arguments
file_desc1
The file descriptor being duplicated.
file_desc2
The new file descriptor to be assigned to the file designated by
file_desc1.
119.2 – Description
The dup function causes a previously unallocated descriptor to
refer to its argument, while the dup2 function causes its second
argument to refer to the same file as its first argument.
The argument file_desc1 is invalid if it does not describe an
open file; file_desc2 is invalid if the new file descriptor
cannot be allocated. If file_desc2 is connected to an open file,
that file is closed.
119.3 – Return Values
n The new file descriptor.
-1 Indicates that an invalid argument was passed
to the function.
120 – [no]echo
Set the terminal so that characters may or may not be echoed on
the terminal screen. This mode of single-character input is only
supported with Curses.
Format
#include <curses.h>
void echo (void);
void noecho (void);
120.1 – Description
The noecho function may be helpful when accepting input from the
terminal screen with wgetch and wgetstr; it prevents the input
characters from being written onto the screen.
121 – ecvt
Converts its argument to a null-terminated string of ASCII digits
and returns the address of the string. The string is stored in a
thread-specific memory location created by the C RTL.
Format
#include <stdlib.h>
char *ecvt (double value, int ndigits, int *decpt, int *sign);
121.1 – Arguments
value
An object of type double that is converted to a null-terminated
string of ASCII digits.
ndigits
The number of ASCII digits to be used in the converted string.
decpt
The position of the decimal point relative to the first character
in the returned string. A negative int value means that the
decimal point is decpt number of spaces to the left of the
returned digits (the spaces being filled with zeros). A 0 value
means that the decimal point is immediately to the left of the
first digit in the returned string.
sign
An integer value that indicates whether the value argument is
positive or negative. If value is negative, the function places
a nonzero value at the address specified by sign. Otherwise, the
function assigns 0 to the address specified by sign.
121.2 – Description
The ecvt function converts value to a null-terminated string
of length ndigits, and returns a pointer to it. The resulting
low-order digit is rounded to the correct digit for outputting
ndigits digits in C E-format. The decpt argument is assigned the
position of the decimal point relative to the first character in
the string.
Repeated calls to the ecvt function overwrite any existing
string.
The ecvt, fcvt, and gcvt functions represent the following
special values specified in the IEEE Standard for floating-point
arithmetic:
Value Representation
Quiet NaN NaNQ
Signalling NaNS
NaN
+Infinity Infinity
-Infinity -Infinity
The sign associated with each of these values is stored into the
sign argument. In IEEE floating-point representation, a value
of 0 (zero) can be positive or negative, as set by the sign
argument.
See also gcvt and fcvt.
121.3 – Return Value
x The value of the converted string.
122 – encrypt
Encrypts a string using the key generated by the setkey function.
Format
#include <unistd.h>
#include <stdlib.h>
void encrypt (char *block[64], int edflag;)
122.1 – Argument
block
A character array of length 64 containing 0s and 1s.
edflag
An integer. If edflag is 0, the argument is encrypted; if
nonzero, it is decrypted.
122.2 – Description
The encrypt function encrypts a string using the key generated by
the setkey function.
The first argument to encrypt is a character array of length 64
containing 0s and 1s. The argument array is modified in place
to a similar array representing the bits of the argument after
having been subjected to the DES algorithm using the key set by
setkey.
The second argument, edflag, determines whether the first
argument is encrypted or decrypted: if edflag is 0, the first
argument array is encrypted; if nonzero, it is decrypted.
No value is returned.
See also crypt and setkey.
122.3 – Return Value
pointer Pointer to the encrypted password.
123 – endgrent
Closes the group database when processing is complete.
Format
#include <grp.h>
void endgrent (void);
123.1 – Description
The endgrent function closes the group database.
This function is always successful. No value is returned, and
errno is not set.
124 – endpwent
Closes the user database and any private stream used by getpwent.
Format
#include <pwd.h>
void endpwent (void);
124.1 – Description
The endpwent function closes the user database and any private
stream used by getpwent.
No value is returned. If an I/O error occurred, the function sets
errno to EIO.
See also getpwent, getpwuid, getpwnam, and setpwent.
125 – endwin
Clears the terminal screen and frees any virtual memory allocated
to Curses data structures.
Format
#include <curses.h>
void endwin (void);
125.1 – Description
A program that calls Curses functions must call the endwin
function before exiting to restore the previous environment of
the terminal screen.
126 – erand48
Generates uniformly distributed pseudorandom-number sequences.
Returns 48-bit nonnegative, double-precision, floating-point
values.
Format
#include <stdlib.h>
double erand48 (unsigned short int xsubi[3]);
126.1 – Argument
xsubi
An array of three short ints, which form a 48-bit integer when
concatenated together.
126.2 – Description
The erand48 function generates pseudorandom numbers using the
linear congruential algorithm and 48-bit integer arithmetic.
It returns nonnegative, double-precision, floating-point values
uniformly distributed over the range of y values, such that 0.0
<= y < 1.0.
The erand48 function works by generating a sequence of 48-bit
integer values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n >= 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke the lcong48 function, the multiplier
value a and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The erand48 function requires that the calling program pass an
array as the xsubi argument. For the first call, the array must
be initialized to the value of the pseudorandom-number sequence.
Unlike the drand48 function, it is not necessary to call an
initialization function prior to the first call.
By using different arguments, the erand48 function allows
separate modules of a large program to generate several
independent sequences of pseudorandom numbers; for example, the
sequence of numbers that one module generates does not depend
upon how many times the function is called by other modules.
126.3 – Return Value
n A nonnegative, double-precision, floating-
point value.
127 – [w]erase
Erases the window by painting it with blanks. The erase function
acts on the stdscr window.
Format
#include <curses.h>
int erase();
int werase (WINDOW *win);
127.1 – Argument
win
A pointer to the window.
127.2 – Description
Both the erase and werase functions leave the cursor at the
current position on the terminal screen after completion; they
do not return the cursor to the home coordinates of (0,0).
127.3 – Return Values
OK Indicates success.
ERR Indicates an error.
128 – erf
Returns the error function of its argument.
Format
#include <math.h>
double erf (double x);
float erff (float x); (Integrity servers, Alpha)
long double erfl (long double x); (Integrity servers, Alpha)
double erfc (double x); (Integrity servers, Alpha)
float erfcf (float x); (Integrity servers, Alpha)
long double erfcl (long double x); (Integrity servers, Alpha)
128.1 – Argument
x
A radian expressed as a real number.
128.2 – Description
The erf functions return the error function of x, where erf(x),
erff(x), and erfl(x) equal 2/sqrt(pi) times the area under the
curve e**(-t**2) between 0 and x.
The erfc functions return (1.0 - erf(x)). The erfc function can
result in an underflow as x gets large.
128.3 – Return Values
x The value of the error function (erf) or
complementary error function (erfc).
NaN x is NaN; errno is set to EDOM.
0 Underflow occurred; errno is set to ERANGE.
129 – execl
Passes the name of an image to be activated in a child process.
This function is nonreentrant.
Format
#include <unistd.h>
int execl (const char *file_spec, const char *arg0, . . . ,
(char *)0); (ISO POSIX-1)
int execl (char *file_spec, . . . ); (Compatibility)
129.1 – Arguments
file_spec
The full file specification of a new image to be activated in the
child process.
arg0, ...
A sequence of pointers to null-terminated character strings.
If the POSIX-1 format is used, at least one argument must be
present and must point to a string that is the same as the new
process filename (or its last component). (This pointer can also
be the NULL pointer, but then execle would accomplish nothing.)
The last pointer must be the NULL pointer. This is also the
convention if the compatibility format is used.
129.2 – Description
To understand how the exec functions operate, consider how
the OpenVMS system calls any VSI C program, as shown in the
following syntax:
int main (int argc, char *argv[], char *envp[]);
The identifier argc is the argument count; argv is an array
of argument strings. The first member of the array (argv[0])
contains the name of the image. The arguments are placed in
subsequent elements of the array. The last element of the array
is always the NULL pointer.
An exec function calls a child process in the same way that
the run-time system calls any other VSI C program. The exec
functions pass the name of the image to be activated in the
child; this value is placed in argv[0]. However, the functions
differ in the way they pass arguments and environment information
to the child:
o Arguments can be passed in separate character strings (execl,
execle, and execlp) or in an array of character strings
(execv, execve, and execvp).
o The environment can be explicitly passed in an array (execle
and execve) or taken from the parent's environment (execl,
execv, execlp, and execvp).
If vfork was called before invoking an exec function, then when
the exec function completes, control is returned to the parent
process at the point of the vfork call. If vfork was not called,
the exec function waits until the child has completed execution
and then exits the parent process. See vfork.
129.3 – Return Value
-1 Indicates failure.
130 – execle
Passes the name of an image to be activated in a child process.
This function is nonreentrant.
Format
#include <unistd.h>
int execle (char *file_spec, char *arg0, . . . , (char *)0,
char *envp[]); (ISO POSIX-1)
int execle (char *file_spec, . . . ); (Compatibility)
130.1 – Arguments
file_spec
The full file specification of a new image to be activated in the
child process.
arg0, ...
A sequence of pointers to null-terminated character strings.
If the POSIX-1 format is used, at least one argument must be
present and must point to a string that is the same as the new
process filename (or its last component). (This pointer can also
be the NULL pointer, but then execle would accomplish nothing.)
The last pointer must be the NULL pointer. This is also the
convention if the compatibility format is used.
envp
An array of strings that specifies the program's environment.
Each string in envp has the following form:
name = value
The name can be one of the following names and the value is a
null-terminated string to be associated with the name:
o HOME-Your login directory
o TERM-The type of terminal being used
o PATH-The default device and directory
o USER-The name of the user who initiated the process
The last element in envp must be the NULL pointer.
When the operating system executes the program, it places a copy
of the current environment vector (envp) in the external variable
environ.
130.2 – Description
See execl for a description of how the exec functions operate.
130.3 – Return Value
-1 Indicates failure.
131 – execlp
Passes the name of an image to be activated in a child process.
This function is nonreentrant.
Format
#include <unistd.h>
int execlp (const char *file_name, const char *arg0, . . . ,
(char *)0); (ISO POSIX-1)
int execlp (char *file_name, . . . ); (Compatibility)
131.1 – Arguments
file_name
The filename of a new image to be activated in the child process.
The device and directory specification for the file is obtained
by searching the VAXC$PATH environment name.
argn
A sequence of pointers to null-terminated character strings. By
convention, at least one argument must be present and must point
to a string that is the same as the new process filename (or its
last component).
. . .
A sequence of pointers to strings. At least one pointer must
exist to terminate the list. This pointer must be the NULL
pointer.
131.2 – Description
See execl for a description of how the exec functions operate.
131.3 – Return Value
-1 Indicates failure.
132 – execv
Passes the name of an image to be activated in a child process.
This function is nonreentrant.
Format
#include <unistd.h>
int execv (char *file_spec, char *argv[]);
132.1 – Arguments
file_spec
The full file specification of a new image to be activated in the
child process.
argv
An array of pointers to null-terminated character strings.
These strings constitute the argument list available to the new
process. By convention, argv[0] must point to a string that is
the same as the new process filename (or its last component).
argv is terminated by a NULL pointer.
132.2 – Description
See execl for a description of how the exec functions operate.
132.3 – Return Value
-1 Indicates failure.
133 – execve
Passes the name of an image to be activated in a child process.
This function is nonreentrant.
Format
#include <unistd.h>
int execve (const char *file_spec, char *argv[], char *envp[]);
133.1 – Arguments
file_spec
The full file specification of a new image to be activated in the
child process.
argv
An array of pointers to null-terminated character strings.
These strings constitute the argument list available to the new
process. By convention, argv[0] must point to a string that is
the same as the new process filename (or its last component).
argv is terminated by a NULL pointer.
envp
An array of strings that specifies the program's environment.
Each string in envp has the following form:
name = value
The name can be one of the following names and the value is a
null-terminated string to be associated with the name:
o HOME-Your login directory
o TERM-The type of terminal being used
o PATH-The default device and directory
o USER-The name of the user who initiated the process
The last element in envp must be the NULL pointer.
When the operating system executes the program, it places a copy
of the current environment vector (envp) in the external variable
environ.
133.2 – Description
See execl for a description of how the exec functions operate.
133.3 – Return Value
-1 Indicates failure.
134 – execvp
Passes the name of an image to be activated in a child process.
This function is nonreentrant.
Format
#include <unistd.h>
int execvp (const char *file_name, char *argv[]);
134.1 – Arguments
file_name
The filename of a new image to be activated in the child process.
The device and directory specification for the file is obtained
by searching the environment name VAXC$PATH.
argv
An array of pointers to null-terminated character strings.
These strings constitute the argument list available to the new
process. By convention, argv[0] must point to a string that is
the same as the new process filename (or its last component).
argv is terminated by a NULL pointer.
134.2 – Description
See execl for a description of how the exec functions operate.
134.3 – Return Value
-1 Indicates failure.
135 – exit,_exit
Terminate execution of the program from which they are called.
These functions are nonreentrant.
Format
#include <stdlib.h>
void exit (int status);
#include <unistd.h>
void _exit (int status);
135.1 – Argument
status
For non-POSIX behavior, a status value of EXIT_SUCCESS (1), EXIT_
FAILURE (2), or a number from 3 to 255, as follows:
o A status value of 0, 1 or EXIT_SUCCESS is translated to the
OpenVMS SS$_NORMAL status code to return the OpenVMS success
value.
o A status value of 2 or EXIT_FAILURE is translated to an error-
level exit status. The status value is passed to the parent
process.
o Any other status value is left the same.
For POSIX behavior:
o A status value of 0 is translated to the OpenVMS SS$_NORMAL
status code to return the OpenVMS success value.
o Any other status is returned to the parent process as an
OpenVMS message symbol with facility set to C, severity
set to success, and with the status in the message number
field. For more information on the format of message symbols,
see "message code" in the VSI OpenVMS Command Definition,
Librarian, and Message Utilities Manual.
To get POSIX behavior, include <unistd.h> and compile with the
_POSIX_EXIT feature-test macro set (either with /DEFINE=_POSIX_
EXIT, or with #define _POSIX_EXIT at the top of your file, before
any file inclusions). This behavior is available only on OpenVMS
Version 7.0 and higher systems.
135.2 – Description
If the process was invoked by DCL, the status is interpreted by
DCL, and a message is displayed.
If the process was a child process created using vfork or an exec
function, then the child process exits and control returns to the
parent. The two functions are identical; the _exit function is
retained for reasons of compatibility with VAX C.
The exit and _exit functions make use of the $EXIT system
service. If your process is being invoked by the RUN command
using any of the hibernation and scheduled wakeup qualifiers, the
process might not correctly return to hibernation state when an
exit or _exit call is made.
The C compiler command-line qualifier /[NO]MAIN=POSIX_EXIT can be
used to direct the compiler to call __posix_exit instead of exit
when returning from main. The default is /NOMAIN.
Beginning with OpenVMS Version 8.3, C RTL contains a fix for
the problem in which a call to _exit after a failed execl really
exits but must not.
In the OpenVMS implementation of vfork, a child process is not
actually started as it is started on most UNIX systems. However,
the C RTL creates some internal data structures intended to mimic
child-process functionality (called the "child context").
A bug occurred whereby after a vfork while in the child context,
a call to an exec function justifiably fails, then calls _exit.
On UNIX systems, after the failed exec call, the child process
continues to execute. A subsequent call to _exit terminates
the child. In the OpenVMS implementation, after the failed exec
call, the child context terminates. A subsequent call to _exit
terminates the parent. The C RTL fix is enabled by a feature
logical switch, DECC$EXIT_AFTER_ FAILED_EXEC. Enabling this
feature logical allows the child context to continue execution.
With DECC$EXIT_AFTER_FAILED_EXEC disabled or not defined, the
current behavior remains the default.
NOTE
EXIT_SUCCESS and EXIT_FAILURE are portable across any
ANSI C compiler to indicate success or failure. On OpenVMS
systems, they are mapped to OpenVMS condition codes with
the severity set to success or failure, respectively. Values
in the range of 3 to 255 can be used by a child process to
communicate a small amount of data to the parent. The parent
retrieves this data using the wait, wait3, wait4, or waitpid
functions.
136 – exp
Returns the base e raised to the power of the argument.
Format
#include <math.h>
double exp (double x);
float expf (float x); (Integrity servers, Alpha)
long double expl (long double x); (Integrity servers, Alpha)
double expm1 (double x); (Integrity servers, Alpha)
float expm1f (float x); (Integrity servers, Alpha)
long double expm1l (long double x);
(Integrity servers, Alpha)
136.1 – Argument
x
A real value.
136.2 – Description
The exp functions compute the value of the exponential function,
defined as e**x, where e is the constant used as a base for
natural logarithms.
The expm1 functions compute exp(x) - 1 accurately, even for tiny
x.
If an overflow occurs, the exp functions return the largest
possible floating-point value and set errno to ERANGE. The
constant HUGE_VAL is defined in the <math.h> header file to be
the largest possible floating-point value.
136.3 – Return Values
x The exponential value of the argument.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
0 Underflow occurred; errno is set to ERANGE.
NaN x is NaN; errno is set to EDOM.
137 – exp2
Returns the value of 2 raised to the power of the argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double exp2 (double x);
float exp2f (float x);
long double exp2l (long double x); )
137.1 – Argument
x
A real value.
137.2 – Description
The exp2 functions compute the base-2 exponential of x.
If an overflow occurs, the exp functions return the largest
possible floating-point value and set errno to ERANGE. The
constant HUGE_VAL is defined in the <math.h> header file to be
the largest possible floating-point value.
137.3 – Return Values
n 2**x.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
1 x is +0 or -0; errno is set to ERANGE.
0 x is -Inf or underflow occurred; errno is set
to ERANGE.
x x is +Inf; errno is set to ERANGE.
NaN x is NaN; errno is set to EDOM.
138 – fabs
Returns the absolute value of its argument.
Format
#include <math.h>
double fabs (double x);
float fabsf (float x); (Integrity servers, Alpha)
long double fabsl (long double x); (Integrity servers, Alpha)
138.1 – Argument
x
A real value.
138.2 – Return Value
x The absolute value of the argument.
139 – fchmod
Changes file access permissions.
Format
#include <stat.h>
int fchmod (int fildes, mode_t mode);
139.1 – Arguments
fildes
An open file descriptor.
mode
The bit pattern that determines the access permissions.
139.2 – Description
The fchmod function is equivalent to the chmod function, except
that the file whose permissions are changed is specified by a
file descriptor (fildes) rather than a filename.
139.3 – Return Values
0 Indicates that the mode is successfully
changed.
-1 Indicates that the change attempt has failed.
140 – fchown
Changes the owner and group of a file.
Format
#include <unistd.h>
int fchown (int fildes, uid_t owner, gid_t group);
140.1 – Arguments
fildes
An open file descriptor.
owner
A user ID corresponding to the new owner of the file.
group
A group ID corresponding to the group of the file.
140.2 – Description
The fchown function has the same effect as chown except that the
file whose owner and group are to be changed is specified by the
file descriptor fildes.
140.3 – Return Values
0 Indicates success.
-1 Indicates failure. The function sets errno to
one of the following values:
The fchown function will fail if:
o EBADF - The fildes argument is not an open
file descriptor.
o EPERM - The effective user ID does not
match the owner of the file, or the process
does not have appropriate privilege.
o EROFS - The file referred to by fildes
resides on a read-only file system.
The fchown function may fail if:
o EINVAL - The owner or group ID is not a
value supported by the implementation.
o EIO - A physical I/O error has occurred.
o EINTR - The fchown function was interrupted
by a signal that was intercepted.
141 – fclose
Closes a file by flushing any buffers associated with the file
control block and freeing the file control block and buffers
previously associated with the file pointer.
Format
#include <stdio.h>
int fclose (FILE *file_ptr);
141.1 – Argument
file_ptr
A pointer to the file to be closed.
141.2 – Description
When a program terminates normally, the fclose function is
automatically called for all open files.
The fclose function tries to write buffered data by using an
implicit call to fflush.
If the write fails (because the disk is full or the user's quota
is exceeded, for example), fclose continues executing. It closes
the OpenVMS channel, deallocates any buffers, and releases the
memory associated with the file descriptor (or FILE pointer). Any
buffered data is lost, and the file descriptor (or FILE pointer)
no longer refers to the file.
If your program needs to recover from errors when flushing
buffered data, it should make an explicit call to fsync (or
fflush) before calling fclose.
141.3 – Return Values
0 Indicates success.
EOF Indicates that the file control block is not
associated with an open file.
142 – fcntl
Performs controlling operations on an open file.
Format
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
int fcntl (int file_desc, int request [, int arg]);
int fcntl (int file_desc, int request [, struct flock *arg]);
142.1 – Arguments
file_desc
An open file descriptor obtained from a successful open, fcntl,
or pipe function.
request
The operation to be performed.
arg
A variable that depends on the value of the request argument.
For a request of F_DUPFD, F_SETFD, or F_SETFL, specify arg as an
int.
For a request of F_GETFD and F_GETFL, do not specify arg.
For a request of F_GETLK, F_SETLK, or F_SETLKW specify arg as a
pointer to a flock structure.
142.2 – Description
The fcntl function performs controlling operations on the open
file specified by the file_desc argument.
The values for the request argument are defined in the header
file <fcntl.h>, and include the following:
F_DUPFD Returns a new file descriptor that is the lowest
numbered available (that is, not already open)
file descriptor greater than or equal to the third
argument (arg) taken as an integer of type int.
The new file descriptor refers to the same file as
the original file descriptor (file_desc). The FD_
CLOEXEC flag associated with the new file descriptor
is cleared to keep the file open across calls to one
of the exec functions.
The following two calls are equivalent:
fid = dup(file_desc);
fid = fcntl(file_desc, F_DUPFD, 0);
Consider the following call:
fid = dup2(file_desc, arg);
It is similar (but not equivalent) to:
close(arg);
fid = fcntl(file_desc, F_DUPFD, arg);
F_GETFD Gets the value of the close-on-exec flag associated
with the file descriptor file_desc. File descriptor
flags are associated with a single file descriptor
and do not affect other file descriptors that refer
to the same file. The arg argument should not be
specified.
F_SETFD Sets the close-on-exec flag associated with file_
desc to the value of the third argument, taken as
type int.
If the third argument is 0, the file remains open
across the exec functions, which means that a child
process spawned by the exec function inherits this
file descriptor from the parent.
If the third argument is FD_CLOEXEC, the file is
closed on successful execution of the next exec
function, which means that the child process spawned
by the exec function will not inherit this file
descriptor from the parent.
F_GETFL Gets the file status flags and file access modes,
defined in <fcntl.h>, for the file description
associated with file_desc. The file access modes
can be extracted from the return value using the
mask O_ACCMODE, which is defined in <fcntl.h>. File
status flags and file access modes are associated
with the file description and do not affect other
file descriptors that refer to the same file with
different open file descriptions.
F_SETFL Sets the file status flags, defined in <fcntl.h>,
for the file description associated with file_desc
from the corresponding bits in the third argument,
arg, taken as type int. Bits corresponding to the
file access mode and the file creation flags,
as defined in <fcntl.h>, that are set in arg
are ignored. If any bits in arg other than those
mentioned here are changed by the application, the
result is unspecified.
Note: The only status bit recognized is O_APPEND.
Support for O_APPEND is not standard-compliant.
The X/Open standard states that "File status flags
and file access modes are associated with the file
description and do not affect other file descriptors
that refer to the same file with different open
file descriptions." However, because the append bit
is stored in the FCB, all file descriptors using
the same FCB are using the same append flag, so
that setting this flag with fcntl(F_SETFL) will
affect all files sharing the FCB; that is, all files
duplicated from the same file descriptor.
Record Locking Requests
F_GETLK Gets the first lock that blocks the lock description
pointed to by the arg parameter, taken as a pointer
to type struct flock. The information retrieved
overwrites the information passed to the fcntl
function in the flock structure. If no lock is found
that would prevent this lock from being created,
then the structure is left unchanged except for the
lock type, which is set to F_UNLCK.
F_SETLK Sets or clears a file segment lock according to
the lock description pointed to by arg, taken as
a pointer to type struct flock. F_SETLK is used to
establish shared locks (F_RDLCK), or exclusive locks
(F_WRLCK), as well as remove either type of lock (F_
UNLCK). If a shared (read) or exclusive (write)
lock cannot be set, the fcntl function returns
immediately with a value of -1.
An unlock (F_UNLCK) request in which the l_len of
the flock structure is nonzero and the offset of the
last byte of the requested segment is the maximum
value for an object of type off_t, when the process
has an existing lock in which l_len is 0 and which
includes the last byte of the requested segment,
is treated as a request to unlock from the start
of the requested segment with an l_len equal to 0.
Otherwise, an unlock (F_UNLCK) request attempts to
unlock only the requested file.
F_SETLKW Same as F_SETLK except that if a shared or exclusive
lock is blocked by other locks, the process will
wait until it is unblocked. If a signal is received
while fcntl is waiting for a region, the function
is interrupted, -1 is returned, and errno is set to
EINTR.
File Locking
The C RTL supports byte-range file locking using the F_GETLK,
F_SETLK, and F_SETLKW commands of the fcntl function, as defined
in the X/Open specification. Byte-range file locking is supported
across OpenVMS clusters. You can only use offsets that fit into
32-bit unsigned integers.
When a shared lock is set on a segment of a file, other processes
on the cluster are able to set shared locks on that segment or
a portion of it. A shared lock prevents any other process from
setting an exclusive lock on any portion of the protected area.
A request for a shared lock fails if the file descriptor was not
opened with read access.
An exclusive lock prevents any other process on the cluster from
setting a shared lock or an exclusive lock on any portion of the
protected area. A request for an exclusive lock fails if the file
descriptor was not opened with write access.
The flock structure describes the type (l_type), starting offset
(l_whence), relative offset (l_start), size (l_len) and process
ID (l_pid) of the segment of the file to be affected.
The value of l_whence is set to SEEK_SET, SEEK_CUR or SEEK_END,
to indicate that the relative offset l_start bytes is measured
from the start of the file, from the current position, or from
the end of the file, respectively. The value of l_len is the
number of consecutive bytes to be locked. The l_len value may be
negative (where the definition of off_t permits negative values
of l_len). The l_pid field is only used with F_GETLK to return
the process ID of the process holding a blocking lock. After a
successful F_GETLK request, the value of l_whence becomes SEEK_
SET.
If l_len is positive, the area affected starts at l_start and
ends at l_start + l_len - 1. If l_len is negative, the area
affected starts at l_start + l_len and ends at l_start - 1. Locks
may start and extend beyond the current end of a file, but may
not be negative relative to the beginning of the file. If l_len
is set to 0 (zero), a lock may be set to always extend to the
largest possible value of the file offset for that file. If such
a lock also has l_start set to 0 (zero) and l_whence is set to
SEEK_SET, the whole file is locked.
Changing or unlocking a portion from the middle of a larger
locked segment leaves a smaller segment at either end. Locking
a segment that is already locked by the calling process causes
the old lock type to be removed and the new lock type to take
effect.
All locks associated with a file for a given process are removed
when a file descriptor for that file is closed by that process
or the process holding that file descriptor terminates. Locks are
not inherited by a child process.
If the request argument is F_SETLKW, the lock is blocked by
some lock from another process, and putting the calling process
to sleep to wait for that lock to become free would cause a
deadlock, then the application will hang.
142.3 – Return Values
n Upon successful completion, the value returned
depends on the value of the request argument
as follows:
o F_DUPFD - Returns a new file descriptor.
o F_GETFD - Returns FD_CLOEXEC or 0.
o F_SETFD, F_GETLK, F_SETLK, F_UNLCK - Return
a value other than -1.
-1 Indicates that an error occurred. The function
sets errno to one of the following values:
o EACCES - The request argument is F_SETLK;
the type of lock (l_type) is a shared (F_
RDLCK) or exclusive (F_WRLCK) lock, and the
segment of a file to be locked is already
exclusive-locked by another process; or
the type is an exclusive (F_WRLCK) lock and
the some portion of the segment of a file
to be locked is already shared-locked or
exclusive-locked by another process.
o EBADF - The file_desc argument is not a
valid open file descriptor and the arg
argument is negative or greater than or
equal to the per-process limit.
The request parameter is F_SETLK or F_
SETLKW, the type of lock (l_type) is a
shared lock (F_RDLCK), and file_desc is not
a valid file descriptor open for reading.
The type of lock (l_type) is an exclusive
lock (F_WRLCK), and file_desc is not a
valid file descriptor open for writing.
o EFAULT - The arg argument is an invalid
address.
o EINVAL - The request argument is F_DUPFD
and arg is negative or greater than or
equal to OPEN_MAX.
Either the OPEN_MAX value or the per-
process soft descriptor limit is checked.
An illegal value was provided for the
request argument.
The request argument is F_GETLK, F_SETLK,
or F_SETLKW and the data pointed to by arg
is invalid, or file_desc refers to a file
that does not support locking.
o EMFILE - The request argument is F_DUPFD
and too many or OPEN_MAX file descriptors
are currently open in the calling process,
or no file descriptors greater than or
equal to arg are available.
Either the OPEN_MAX value or the per-
process soft descriptor limit is checked.
o EOVERFLOW - One of the values to be
returned cannot be represented correctly.
The request argument is F_GETLK, F_SETLK,
or F_SETLKW and the smallest or, if l_
len is nonzero, the largest offset of any
byte in the requested segment cannot be
represented correctly in an object of type
off_t.
o EINTR - The request argument is F_SETLKW,
and the function was interrupted by a
signal.
o ENOLCK - The request argument is F_SETLK or
F_SETLKW, and satisfying the lock or unlock
request would exceed the configurable
system limit of NLOCK_RECORD.
o ENOMEM - The system was unable to allocate
memory for the requested file descriptor.
143 – fcvt
Converts its argument to a null-terminated string of ASCII digits
and returns the address of the string. The string is stored in a
thread-specific location created by the C RTL.
Format
#include <stdlib.h>
char *fcvt (double value, int ndigits, int *decpt, int *sign);
143.1 – Arguments
value
An object of type double that is converted to a null-terminated
string of ASCII digits.
ndigits
The number of ASCII digits after the decimal point to be used in
the converted string.
decpt
The position of the decimal point relative to the first character
in the returned string. The returned string does not contain the
actual decimal point. A negative int value means that the decimal
point is decpt number of spaces to the left of the returned
digits (the spaces are filled with zeros). A 0 value means that
the decimal point is immediately to the left of the first digit
in the returned string.
sign
An integer value that indicates whether the value argument is
positive or negative. If value is negative, the fcvt function
places a nonzero value at the address specified by sign.
Otherwise, the functions assign 0 to the address specified by
sign.
143.2 – Description
The fcvt function converts value to a null-terminated string and
returns a pointer to it. The resulting low-order digit is rounded
to the correct digit for outputting ndigits digits in C F-format.
The decpt argument is assigned the position of the decimal point
relative to the first character in the string.
In C F-format, ndigits is the number of digits desired after the
decimal point. Very large numbers produce a very long string of
digits before the decimal point, and ndigit of digits after the
decimal point. For large numbers, it is preferable to use the
gcvt or ecvt function so that E-format is used.
Repeated calls to the fcvt function overwrite any existing
string.
The ecvt, fcvt, and gcvt functions represent the following
special values specified in the IEEE Standard for floating-point
arithmetic:
Value Representation
Quiet NaN NaNQ
Signalling NaNS
NaN
+Infinity Infinity
-Infinity -Infinity
The sign associated with each of these values is stored into the
sign argument. In IEEE floating-point representation, a value
of 0 (zero) can be positive or negative, as set by the sign
argument.
See also gcvt and ecvt.
143.3 – Return Value
x A pointer to the converted string.
144 – fdim
Determines the positive difference between its arguments.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double fdim (double x, double y);
float fdimf (float x, float y);
long double fdiml (long double x, long double y);
144.1 – Argument
x
A real value.
y
A real value.
144.2 – Description
The fdim functions determine the positive difference between
their arguments. If x is greater than y, x - y is returned. If x
is less than or equal to y, +0 is returned.
144.3 – Return Values
n Upon success, the positive difference value.
HUGE_VAL If x - y is positive and overflows; errno is
set to ERANGE.
0 If x - y is positive and underflows; errno is
set to ERANGE.
NaN x or y is NaN; errno is set to EDOM.
145 – fdopen
Associates a file pointer with a file descriptor returned by an
open, creat, dup, dup2, or pipe function.
Format
#include <stdio.h>
FILE *fdopen (int file_desc, char *a_mode);
145.1 – Arguments
file_desc
The file descriptor returned by open, creat, dup, dup2, or pipe.
a_mode
The access mode indicator. See the fopen function for a
description. Note that the access mode specified must agree
with the mode used to originally open the file. This includes
binary/text access mode ("b" mode on fdopen and the "ctx=bin"
option on creat or open).
145.2 – Description
The fdopen function allows you to access a file, originally
opened by one of the UNIX I/O functions, with Standard I/O
functions. Ordinarily, a file can be accessed by either a file
descriptor or by a file pointer, but not both, depending on the
way you open it.
145.3 – Return Values
pointer Indicates that the operation has succeeded.
NULL Indicates that an error has occurred.
146 – feof
Tests a file to see if the end-of-file has been reached.
Format
#include <stdio.h>
int feof (FILE *file_ptr);
146.1 – Argument
file_ptr
A file pointer.
146.2 – Return Values
nonzero integer Indicates that the end-of-file has been
reached.
0 Indicates that the end-of-file has not been
reached.
147 – feof_unlocked
Same as feof, except used only within a scope protected by
flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int feof_unlocked (FILE *file_ptr);
147.1 – Argument
file_ptr
A file pointer.
147.2 – Description
The reentrant version of the feof function is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the stream. The unlocked version of this
call, feof_unlocked can be used to avoid the overhead. The feof_
unlocked function is functionally identical to the feof function,
except that it is not required to be implemented in a thread-
safe manner. The feof_unlocked function can be safely used only
within a scope that is protected by the flockfile and funlockfile
functions used as a pair. The caller must ensure that the stream
is locked before feof_unlocked is used.
See also flockfile, ftrylockfile, and funlockfile.
147.3 – Return Values
nonzero integer Indicates end-of-file has been reached.
0 Indicates end-of-file has not been reached.
148 – ferror
Returns a nonzero integer if an error occurred while reading or
writing a file.
Format
#include <stdio.h>
int ferror (FILE *file_ptr);
148.1 – Argument
file_ptr
A file pointer.
148.2 – Description
A call to ferror continues to return a nonzero integer until the
file is closed or until clearerr is called.
148.3 – Return Values
0 Indicates success.
nonzero integer Indicates that an error has occurred.
149 – ferror_unlocked
Same as ferror, except used only within a scope protected by
flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int ferror_unlocked (FILE *file_ptr);
149.1 – Argument
file_ptr
A file pointer.
149.2 – Description
The reentrant version of the ferror function is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the stream. The unlocked version of this
call, ferror_unlocked can be used to avoid the overhead. The
ferror_unlocked function is functionally identical to the ferror
function, except that it is not required to be implemented in a
thread-safe manner. The ferror_unlocked function can be safely
used only within a scope that is protected by the flockfile and
funlockfile functions used as a pair. The caller must ensure that
the stream is locked before ferror_unlocked is used.
See also flockfile, ftrylockfile, and funlockfile.
149.3 – Return Values
0 Indicates success.
nonzero integer Indicates that an error has occurred.
150 – fflush
Writes out any buffered information for the specified file.
Format
#include <stdio.h>
int fflush (FILE *file_ptr);
150.1 – Argument
file_ptr
A file pointer. If this argument is a NULL pointer, all buffers
associated with all currently open files are flushed.
150.2 – Description
The output files are normally buffered only if they are not
directed to a terminal, except for stderr, which is not buffered
by default.
The fflush function flushes the C RTL buffers. However,
RMS has its own buffers. The fflush function does not guarantee
that the file will be written to disk. (See the description of
fsync for a way to flush buffers to disk.)
If the file pointed to by file_ptr was opened in record mode
and if there is unwritten data in the buffer, then fflush always
generates a record.
150.3 – Return Values
0 Indicates that the operation is successful.
EOF Indicates that the buffered data cannot be
written to the file, or that the file control
block is not associated with an output file.
151 – ffs
Finds the index of the first bit set in a string.
Format
#include <strings.h>
int ffs (int iteger);
151.1 – Argument
integer
The integer to be examined for the first bit set.
151.2 – Description
The ffs function finds the first bit set (beginning with the
least significant bit) and returns the index of that bit. Bits
are numbered starting at 1 (the least significant bit).
151.3 – Return Values
x The index of the first bit set.
0 If index is 0.
152 – fgetc
Returns the next character from a specified file.
Format
#include <stdio.h>
int fgetc (FILE *file_ptr);
152.1 – Argument
file_ptr
A pointer to the file to be accessed.
152.2 – Description
The fgetc function returns the next character from the specified
file.
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
See also the fgetc_unlocked function and the getc macro.
152.3 – Return Values
x The returned character.
EOF Indicates the end-of-file or an error.
153 – fgetc_unlocked
Same as the fgetc function, except used only within a scope
protected by flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int fgetc_unlocked (FILE *file_ptr);
153.1 – Argument
file_ptr
A file pointer.
153.2 – Description
The reentrant version of the fgetc function is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the stream. The unlocked version of this
call, fgetc_unlocked can be used to avoid the overhead. The
fgetc_unlocked function is functionally identical to the fgetc
function, except that fgetc_unlocked can be safely used only
within a scope that is protected by the flockfile and funlockfile
functions used as a pair. The caller must ensure that the stream
is locked before fgetc_unlocked is used.
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
See also getc_unlocked, flockfile, ftrylockfile, and funlockfile.
153.3 – Return Values
n The returned character.
EOF Indicates the end-of-file or an error.
154 – fgetname
Returns the file specification associated with a file pointer.
Format
#include <stdio.h>
char *fgetname (FILE *file_ptr, char *buffer, . . . );
154.1 – Function Variants
The fgetname function has variants named _fgetname32 and _
fgetname64 for use with 32-bit and 64-bit pointer sizes,
respectively.
154.2 – Arguments
file_ptr
A file pointer.
buffer
A pointer to a character string that is large enough to hold the
file specification.
. . .
An optional additional argument that can be either 1 or 0. If you
specify 1, the fgetname function returns the file specification
in OpenVMS format. If you specify 0, fgetname returns the file
specification in UNIX style format. If you do not specify this
argument, fgetname returns the filename according to your current
command language interpreter.
154.3 – Description
The fgetname function places the file specification at the
address given in the buffer. The buffer should be an array large
enough to contain a fully qualified file specification (the
maximum length is 256 characters).
154.4 – Return Values
n The address of the buffer.
0 Indicates an error.
154.5 – Restriction
The fgetname function is specific to the C RTL and is not
portable.
155 – fgetpos
Stores the current file position for a given file.
Format
#include <stdio.h>
int fgetpos (FILE *stream, fpos_t *pos);
155.1 – Arguments
stream
A file pointer.
pos
A pointer to an implementation-defined structure. The fgetpos
function fills this structure with information that can be used
on subsequent calls to fsetpos.
155.2 – Description
The fgetpos function stores the current value of the file
position indicator for the stream pointed to by stream into the
object pointed to by pos.
155.3 – Return Values
0 Indicates successful completion.
-1 Indicates that there are errors.
155.4 – Example
#include <stdio.h>
#include <stdlib.h>
main()
{
FILE *fp;
int stat,
i;
int character;
char ch,
c_ptr[130],
d_ptr[130];
fpos_t posit;
/* Open a file for writing. */
if ((fp = fopen("file.dat", "w+")) == NULL) {
perror("open");
exit(1);
}
/* Get the beginning position in the file. */
if (fgetpos(fp, &posit) != 0)
perror("fgetpos");
/* Write some data to the file. */
if (fprintf(fp, "this is a test\n") == 0) {
perror("fprintf");
exit(1);
}
/* Set the file position back to the beginning. */
if (fsetpos(fp, &posit) != 0)
perror("fsetpos");
fgets(c_ptr, 130, fp);
puts(c_ptr); /* Should be "this is a test." */
/* Close the file. */
if (fclose(fp) != 0) {
perror("close");
exit(1);
}
}
156 – fgets
Reads a line from the specified file, up to one less than the
specified maximum number of characters or up to and including the
new-line character, whichever comes first. The function stores
the string in str.
Format
#include <stdio.h>
char *fgets (char *str, int maxchar, FILE *file_ptr);
156.1 – Function Variants
The fgets function has variants named _fgets32 and _fgets64 for
use with 32-bit and 64-bit pointer sizes, respectively.
156.2 – Arguments
str
A pointer to a character string that is large enough to hold the
information fetched from the file.
maxchar
The maximum number of characters to fetch.
file_ptr
A file pointer.
156.3 – Description
The fgets function terminates the line with a null character
(\0). Unlike gets, fgets places the new-line character that
terminates the input line into the user buffer if more than
maxchar characters have not already been fetched.
When the file pointed to by file_ptr is opened in record
mode, fgets treats the end of a record the same as a new-line
character, so it reads up to and including a new-line character
or to the end of the record.
156.4 – Return Values
x Pointer to str.
NULL Indicates the end-of-file or an error. The
contents of str are undefined if a read error
occurs.
156.5 – Example
#include <stdio.h>
#include <stdlib.h>
#include <unixio.h>
main()
{
FILE *fp;
char c_ptr[130];
/* Create a dummy data file */
if ((fp = fopen("file.dat", "w+")) == NULL) {
perror("open");
exit(1);
}
fprintf(fp, "this is a test\n") ;
fclose(fp) ;
/* Open a file with some data -"this is a test" */
if ((fp = fopen("file.dat", "r+")) == NULL) {
perror("open error") ;
exit(1);
}
fgets(c_ptr, 130, fp);
puts(c_ptr); /* Display what fgets got. */
fclose(fp);
delete("file.dat") ;
}
157 – fgetwc
Reads the next character from a specified file, and converts it
to a wide-character code.
Format
#include <wchar.h>
wint_t fgetwc (FILE *file_ptr);
157.1 – Argument
file_ptr
A pointer to the file to be accessed.
157.2 – Description
Upon successful completion, the fgetwc function returns the wide-
character code read from the file pointed to by file_ptr and
converted to type wint_t. If the file is at end-of-file, the
end-of-file indicator is set, and WEOF is returned. If an I/O
read error occurred, then the error indicator is set, and WEOF is
returned.
Applications can use ferror or feof to distinguish between an
error condition and an end-of-file condition.
157.3 – Return Values
x The wide-character code of the character read.
WEOF Indicates the end-of-file or an error. If a
read error occurs, the function sets errno to
one of the following:
o EALREADY - An operation is already in
progress on the same file.
o EBADF - The file descriptor is not valid.
o EILSEQ - Invalid character detected.
158 – fgetws
Reads a line of wide characters from a specified file.
Format
#include <wchar.h>
wchar_t *fgetws (wchar_t *wstr, int maxchar, FILE *file_ptr);
158.1 – Function Variants
The fgetws function has variants named _fgetws32 and _fgetws64
for use with 32-bit and 64-bit pointer sizes, respectively.
158.2 – Arguments
wstr
A pointer to a wide-character string large enough to hold the
information fetched from the file.
maxchar
The maximum number of wide characters to fetch.
file_ptr
A file pointer.
158.3 – Description
The fgetws function reads wide characters from the specified file
and stores them in the array pointed to by wstr. The function
reads up to maxchar-1 characters or until the new-line character
is read, converted, and transferred to wstr, or until an end-
of-file condition is encountered. The function terminates the
line with a null wide character. fgetws places the new-line that
terminates the input line into the user buffer, unless maxchar
characters have already been fetched.
158.4 – Return Values
x Pointer to wstr.
NULL Indicates the end-of-file or an error. The
contents of wstr are undefined if a read
error occurs. If a read error occurs, the
function sets errno. For a list of possible
errno values, see fgetwc.
158.5 – Example
#include <stdlib.h>
#include <stdio.h>
#include <locale.h>
#include <wchar.h>
main()
{
wchar_t wstr[80],
*ret;
FILE *fp;
/* Create a dummy data file */
if ((fp = fopen("file.dat", "w+")) == NULL) {
perror("open");
exit(1);
}
fprintf(fp, "this is a test\n") ;
fclose(fp) ;
/* Open a test file containing : "this is a test" */
if ((fp = fopen("file.dat", "r")) == (FILE *) NULL) {
perror("File open error");
exit(EXIT_FAILURE);
}
ret = fgetws(wstr, 80, fp);
if (ret == (wchar_t *) NULL) {
perror("fgetws failure");
exit(EXIT_FAILURE);
}
fputws(wstr, stdout);
fclose(fp);
delete("file.dat");
}
159 – fileno
Returns the file descriptor associated with the specified file
pointer.
Format
#include <stdio.h>
int fileno (FILE *file_ptr);
159.1 – Argument
file_ptr
A file pointer.
159.2 – Description
If you are using version 5.2 or lower of the C compiler, undefine
the fileno macro:
#if defined(fileno)
#undef fileno
#endif
159.3 – Return Values
x Integer file descriptor.
-1 Indicates an error.
160 – finite
Returns the integer value 1 (True) when its argument is a finite
number, or 0 (False) if not.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
int finite (double x);
int finitef (float x);
int double finitel (long double x);
160.1 – Argument
x
A real value.
160.2 – Description
The finite functions return 1 when -Infinity < x < +Infinity.
They return 0 when |x| = Infinity, or x is a NaN.
161 – flockfile
Locks a stdio stream.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
void flockfile (FILE *file_ptr);
161.1 – Argument
file_ptr
A file pointer.
161.2 – Description
The flockfile function locks a stdio stream so that a thread can
have exclusive use of that stream for multiple I/O operations.
Use the flockfile function for a thread that wants to ensure
that the output of several printf functions, for example, is not
garbled by another thread also trying to use printf.
File pointers passed are assumed to be valid; flockfile will
perform locking even on invalid file pointers. Also, the
funlockfile function will not fail if the calling thread does
not own a lock on the file pointer passed.
Matching flockfile and funlockfile calls can be nested. If the
stream has been locked recursively, it will remain locked until
the last matching funlockfile is called.
All C RTL file-pointer I/O functions lock their file pointers as
if calling flockfile and funlockfile.
See also ftrylockfile and funlockfile.
162 – floor
Returns the largest integer less than or equal to the argument.
Format
#include <math.h>
double floor (double x);
float floorf (float x); (Integrity servers, Alpha)
long double floorl (long double x);
(Integrity servers, Alpha)
162.1 – Argument
x
A real value.
162.2 – Return Value
n The largest integer less than or equal to the
argument.
163 – fma
Computes (x * y) + z, rounded as one ternary operation.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double fma (double x, double y, double z);
float fmaf (float x, float y, float z);
long double fmal (long double x, long double y, long double z);
163.1 – Argument
x,y,z
Real values.
163.2 – Description
The fma functions compute (x * y) + z, rounded as one ternary
operation: the value is computed as if to infinite precision and
rounded once to the result format, according to the rounding mode
characterized by the value of FLT_ROUNDS.
163.3 – Return Values
n Upon success, (x * y) + z, rounded as one
ternary operation.
NaN x or y is NaN; errno is set to EDOM.
164 – fmax
Returns the maximum numeric value of its arguments.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double fmax (double x, double y);
float fmaxf (float x, float y);
long double fmaxl (long double x, long double y);
164.1 – Argument
x
A real value.
y
A real value.
164.2 – Description
The fmax functions determine the maximum numeric value of their
arguments. NaN arguments are treated as missing data: if one
argument is a NaN and the other numeric, then the numeric value
is returned.
164.3 – Return Values
n Upon success, the maximum numeric value of the
arguments. If just one argument is a NaN, the
other argument is returned.
NaN Both x and y are NaNs.
165 – fmin
Returns the minimum numeric value of its arguments.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double fmin (double x, double y);
float fminf (float x, float y);
long double fminl (long double x, long double y);
165.1 – Argument
x
A real value.
y
A real value.
165.2 – Description
The fmin functions determine the minimum numeric value of their
arguments. NaN arguments are treated as missing data: if one
argument is a NaN and the other numeric, then the numeric value
is returned.
165.3 – Return Values
n Upon success, the minimum numeric value of the
arguments. If just one argument is a NaN, the
other argument is returned.
NaN Both x and y are NaNs.
166 – fmod
Computes the floating-point remainder.
Format
#include <math.h>
double fmod (double x, double y);
float fmodf (float x, float y); (Integrity servers, Alpha)
long double fmodl (long double x, long double y);
(Integrity servers, Alpha)
166.1 – Arguments
x
A real value.
y
A real value.
166.2 – Description
The fmod functions return the floating-point remainder of the
first argument divided by the second. If the second argument is
0, the function returns 0.
166.3 – Return Values
x The value f, which has the same sign as the
argument x, such that x == i * y + f for some
integer i, where the magnitude of f is less
than the magnitude of y.
0 Indicates that y is 0.
167 – fopen
Opens a file by returning the address of a FILE structure.
Format
#include <stdio.h>
FILE *fopen (const char *file_spec, const char *a_mode);
(ANSI C)
FILE *fopen (const char *file_spec, const char
*a_mode, . . . ); (DEC C Extension)
167.1 – Arguments
file_spec
A character string containing a valid file specification.
a_mode
The access mode indicator. Use one of the following character
strings: "r", "w", "a", "r+", "w+", "rb", "r+b", "rb+", "wb",
"w+b", "wb+", "ab", "a+b", "ab+", or "a+".
These access modes have the following effects:
o "r" opens an existing file for reading.
o "w" creates a new file, if necessary, and opens the file for
writing. If the file exists, it creates a new file with the
same name and a higher version number.
o "a" opens the file for append access. An existing file is
positioned at the end-of-file, and data is written there. If
the file does not exist, the C RTL creates it.
The update access modes allow a file to be opened for both
reading and writing. When used with existing files, "r+" and
"a+" differ only in the initial positioning within the file. The
modes are:
o "r+" opens an existing file for read update access. It is
opened for reading, positioned first at the beginning-of-file,
but writing is also allowed.
o "w+" opens a new file for write update access.
o "a+" opens a file for append update access. The file is first
positioned at the end-of-file (writing). If the file does not
exist, the C RTL creates it.
o "b" means binary access mode. In this case, no conversion of
carriage-control information is attempted.
. . .
Optional file attribute arguments. The file attribute arguments
are the same as those used in the creat function. For more
information, see the creat function.
167.2 – Description
If a version of the file exists, a new file created with fopen
inherits certain attributes from the existing file unless
those attributes are specified in the fopen call. The following
attributes are inherited:
Record format
Maximum record size
Carriage control
File protection
If you specify a directory in the filename and it is a search
list that contains an error, VSI C for OpenVMS Systems
interprets it as a file open error.
The file control block can be freed with the fclose function, or
by default on normal program termination.
167.3 – Return Values
x File pointer.
NULL Indicates an error. The constant NULL is
defined in the <stdio.h> header file to be
the NULL pointer value. The function returns
NULL to signal the following errors:
o File protection violations
o Attempts to open a nonexistent file for
read access
o Failure to open the specified file
168 – fp_class
Determines the class of IEEE floating-point values.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
int fp_class (double x);
int fp_classf (float x);
int fp_classl (long double x);
168.1 – Argument
x
An IEEE floating-point number.
168.2 – Description
The fp_class functions determine the class of the specified IEEE
floating-point number, returning a constant from the <fp_class.h>
header file. They never cause an exception, even for signaling
NaNs (Not-a-Number). These functions implement the recommended
class(x) function in the appendix of the IEEE 754-1985 standard
for binary floating-point arithmetic. The constants in <fp_
class.h> refer to the following classes of values:
FP_SNAN Signaling NaN (Not-a-Number)
FP_QNAN Quiet NaN
FP_POS_INF +Infinity
FP_NEG_INF -Infinity
FP_POS_NORM positive normalized
FP_NEG_NORM negative normalized
FP_POS_DENORM positive denormalized
FP_NEG_DENORM negative denormalized
FP_POS_ZERO +0.0 (positive zero)
FP_NEG_ZERO -0.0 (negative zero)
168.3 – Return Value
x A constant from the <fp_class.h> header file.
169 – fpathconf
Retrieves file implementation characteristics.
Format
#include <unistd.h>
long int fpathconf (int filedes, int name);
169.1 – Arguments
filedes
An open file descriptor.
name
The configuration attribute to query. If this attribute is
not applicable to the file specified by the filesdes argument,
fpathconf returns an error.
169.2 – Description
The fpathconf function allows an application to retrieve the
characteristics of operations supported by the file system
underlying the filenamed by the filesdes argument. Read, write,
or execute permission of the named file is not required, but you
must be able to search all directories in the path leading to the
file.
Symbolic values for the name argument are defined in the
<unistd.h> header file as follows:
_PC_LINK_MAX The maximum number of links to the file. If the
filedes argument refers to a directory, the value
returned applies to the directory itself.
_PC_MAX_ The maximum number of bytes in a canonical input
CANON line. This is applicable only to terminal devices.
_PC_MAX_ The number of types allowed in an input queue.
INPUT This is applicable only to terminal devices.
_PC_NAME_MAX Maximum number of bytes in a filename (not
including a terminating null). The byte range
value is between 13 and 255. This is applicable
only to a directory file. The value returned
applies to filenames within the directory.
_PC_PATH_MAX Maximum number of bytes in a pathname (not
including a terminating null). The value is never
larger than 65,535. This is applicable only to a
directory file. The value returned is the maximum
length of a relative pathname when the specified
directory is the working directory.
_PC_PIPE_BUF Maximum number of bytes guaranteed to be written
atomically. This is applicable only to a FIFO. The
value returned applies to the referenced object.
If the path argument refers to a directory, the
value returned applies to any FIFO that exists or
can be created within the directory.
_PC_CHOWN_ The value returned applies to any files (other
RESTRICTED than directories) that exist or can be created
within the directory. This is applicable only to a
directory file.
_PC_NO_TRUNC Returns 1 if supplying a component name longer
than allowed by NAME_MAX causes an error. Returns
0 (zero) if long component names are truncated.
This is applicable only to a directory file.
_PC_VDISABLE This is always 0 (zero); no disabling character
is defined. This is applicable only to a terminal
device.
169.3 – Return Values
x The resultant value for the configuration
attribute specified in the name argument.
-1 Indicates an error; errno is set to one of the
following values:
o EINVAL - The name argument specifies an
unknown or inapplicable characteristic.
o EBADF - the filedes argument is not a valid
file descriptor.
170 – fprintf
Performs formatted output to a specified file.
Format
#include <stdio.h>
int fprintf (FILE *file_ptr, const char *format_spec, . . . );
170.1 – Arguments
file_ptr
A pointer to the file to which the output is directed.
format_spec
A pointer to a character string that contains the format
specification.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, the output sources can
be omitted. Otherwise, the function calls must have exactly as
many output sources as there are conversion specifications, and
the conversion specifications must match the types of the output
sources.
Conversion specifications are matched to output sources in left-
to-right order. Any excess output sources are ignored.
170.2 – Example
An example of a conversion specification follows:
#include <stdio.h>
main()
{
int temp = 4, temp2 = 17;
fprintf(stdout, "The answers are %d, and %d.", temp, temp2);
}
This example outputs the following to the stdout file:
The answers are 4, and 17.
170.3 – Return Values
x The number of bytes written, excluding the
null terminator.
Negative value Indicates an error. The function sets errno to
one of the following:
o EILSEQ - Invalid character detected.
o EINVAL - Insufficient arguments.
o ENOMEM - Not enough memory available for
conversion.
o ERANGE - Floating-point calculations
overflow.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This might indicate that conversion to a
numeric value failed because of overflow.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENOSPC - No free space on the device
containing the file.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o ESPIPE - Illegal seek in a file opened for
append.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
171 – fputc
Writes a character to a specified file.
Format
#include <stdio.h>
int fputc (int character, FILE *file_ptr);
171.1 – Arguments
character
An object of type int.
file_ptr
A file pointer.
171.2 – Description
The fputc function writes a single character to the specified
file and returns the character.
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
See also the fputc_unlocked function and the putc macro.
171.3 – Return Values
x The character written to the file. Indicates
success.
EOF Indicates an output error.
172 – fputc_unlocked
Same as the fputc function, except used only within a scope
protected by flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int fputc_unlocked (int character, FILE *file_ptr);
172.1 – Arguments
character
The character to be written. An object of type int.
file_ptr
A file pointer.
172.2 – Description
See the putc_unlocked macro.
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
See also flockfile, ftrylockfile, and funlockfile.
172.3 – Return Values
n The returned character.
EOF Indicates the end-of-file or an error.
173 – fputs
Writes a character string to a file without copying the string's
null terminator (\0).
Format
#include <stdio.h>
int fputs (const char *str, FILE *file_ptr);
173.1 – Arguments
str
A pointer to a character string.
file_ptr
A file pointer.
173.2 – Description
Unlike puts, the fputs function does not append a new-line
character to the output string.
See also puts.
173.3 – Return Values
Nonnegative value Indicates success.
EOF Indicates an error.
174 – fputwc
Converts a wide character to its corresponding multibyte value,
and writes the result to a specified file.
Format
#include <wchar.h>
wint_t fputwc (wint_t wc, FILE *file_ptr);
174.1 – Arguments
wc
An object of type wint_t.
file_ptr
A file pointer.
174.2 – Description
The fputwc function writes a wide character to a file and returns
the character.
See also putwc.
174.3 – Return Values
x The character written to the file. Indicates
success.
WEOF Indicates an output error. The function sets
errno to the following:
o EILSEQ - Invalid wide-character code
detected.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENOSPC - No free space on the device
containing the file.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o ESPIPE - Illegal seek in a file opened for
append.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
175 – fputws
Writes a wide-character string to a file without copying the
null-terminating character.
Format
#include <wchar.h>
int fputws (const wchar_t *wstr, FILE *file_ptr);
175.1 – Arguments
wstr
A pointer to a wide-character string.
file_ptr
A file pointer.
175.2 – Description
The fputws function converts the specified wide-character string
to a multibyte character string and writes it to the specified
file. The function does not append a terminating null byte
corresponding to the null wide-character to the output string.
175.3 – Return Values
Nonnegative value Indicates success.
-1 Indicates an error. The function sets errno.
For a list of the values, see fputwc.
176 – fread
Reads a specified number of items from the file.
Format
#include <stdio.h>
size_t fread (void *ptr, size_t size_of_item, size_t
number_items, FILE *file_ptr);
176.1 – Arguments
ptr
A pointer to the location, within memory, where you place the
information being read. The type of the object pointed to is
determined by the type of the item being read.
size_of_item
The size of the items being read, in bytes.
number_items
The number of items to be read.
file_ptr
A pointer that indicates the file from which the items are to be
read.
176.2 – Description
The type size_t is defined in the header file <stdio.h> as
follows:
typedef unsigned int size_t
The reading begins at the current location in the file. The items
read are placed in storage beginning at the location given by
the first argument. You must also specify the size of an item, in
bytes.
If the file pointed to by file_ptr was opened in record mode,
fread will read size_of_item multiplied by number_items bytes
from the file. That is, it does not necessarily read number_items
records.
176.3 – Return Values
n The number of bytes read divided by size_of_
item.
0 Indicates the end-of-file or an error.
177 – free
Makes available for reallocation the area allocated by a previous
calloc, malloc, or realloc call.
Format
#include <stdlib.h>
void free (void *ptr);
177.1 – Argument
ptr
The address returned by a previous call to malloc, calloc, or
realloc. If ptr is a NULL pointer, no action occurs.
177.2 – Description
The ANSI C standard defines free as not returning a value;
therefore, the function prototype for free is declared with
a return type of void. However, since a free can fail, and
since previous versions of the C RTL have declared free
to return an int, the implementation of free does return 0 on
success and -1 on failure.
178 – freopen
Substitutes the filenamed by a file specification for the open
file addressed by a file pointer. The latter file is closed.
Format
#include <stdio.h>
FILE *freopen (const char *file_spec, const char *a_mode, FILE
*file_ptr, . . . );
178.1 – Arguments
file_spec
A pointer to a string that contains a valid OpenVMS or UNIX
style file specification. After the function call, the given
file pointer is associated with this file.
a_mode
The access mode indicator. See the fopen function for a
description.
file_ptr
A file pointer.
. . .
Optional file attribute arguments. The file attribute arguments
are the same as those used in the creat function.
178.2 – Description
The freopen function is typically used to associate one of the
predefined names stdin, stdout, or stderr with a file.
178.3 – Return Values
file_ptr The file pointer, if freopen is successful.
NULL Indicates an error.
179 – frexp
Calculates the fractional and exponent parts of a floating-point
value.
Format
#include <math.h>
double frexp (double value, int *eptr);
float frexpf (float value, int *eptr);
(Integrity servers, Alpha)
long double frexpl (long double value, int *eptr);
(Integrity servers, Alpha)
179.1 – Arguments
value
A floating-point number of type double, float, or long double.
eptr
A pointer to an int where frexp places the exponent.
179.2 – Description
The frexp functions break the floating-point number (value) into
a normalized fraction and an integral power of 2, as follows:
value = fraction * (2exp)
The fractional part is returned as the return value. The exponent
is placed in the integer variable pointed to by eptr.
179.3 – Example
#include <math.h>
main ()
{
double val = 16.0, fraction;
int exp;
fraction = frexp(val, &exp);
printf("fraction = %f\n",fraction);
printf("exp = %d\n",exp);
}
In this example, frexp converts the value 16 to .5 * 2 . The
example produces the following output:
fraction = 0.500000
exp = 5
|value| = Infinity or NaN is an invalid argument.
179.4 – Return Values
x The fractional part of value.
0 Both parts of the result are 0.
NaN If value is NaN, NaN is returned, errno
is set to EDOM, and the value of *eptr is
unspecified.
value If |value| = Infinity, value is returned,
errno is set to EDOM, and the value of *eptr
is unspecified.
180 – fscanf
Performs formatted input from a specified file, interpreting it
according to the format specification.
Format
#include <stdio.h>
int fscanf (FILE *file_ptr, const char *format_spec, . . . );
180.1 – Arguments
file_ptr
A pointer to the file that provides input text.
format_spec
A pointer to a character string that contains the format
specification.
. . .
Optional expressions whose results correspond to conversion
specifications given in the format specification.
If no conversion specifications are given, you can omit the input
pointers. Otherwise, the function calls must have exactly as
many input pointers as there are conversion specifications, and
the conversion specifications must match the types of the input
pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
180.2 – Description
An example of a conversion specification follows:
#include <stdio.h>
main ()
{
int temp, temp2;
fscanf(stdin, "%d %d", &temp, &temp2);
printf("The answers are %d, and %d.", temp, temp2);
}
Consider a file, designated by stdin, with the following
contents:
4 17
The example conversion specification produces the following
result:
The answers are 4, and 17.
180.3 – Return Values
x The number of successfully matched and
assigned input items.
EOF Indicates that the end-of-file was encountered
or a read error occurred. If a read error
occurs, the function sets errno to one of the
following:
o EILSEQ - Invalid character detected.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This can indicate that conversion to a
numeric value failed due to overflow.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
181 – fseek
Positions the file to the specified byte offset in the file.
Format
#include <stdio.h>
int fseek (FILE *file_ptr, long int offset, int direction);
181.1 – Arguments
file_ptr
A file pointer.
offset
The offset, specified in bytes.
direction
An integer indicating the position to which the offset is added
to calculate the new position. The new position is the beginning
of the file if direction is SEEK_SET, the current value of the
file position indicator if direction is SEEK_CUR, or end-of-file
if direction is SEEK_END.
181.2 – Description
The fseek function can position a fixed-length record-access
file with no carriage control or a stream-access file on any
byte offset, but can position all other files only on record
boundaries.
The available Standard I/O functions position a variable-length
or VFC record file at its first byte, at the end-of-file, or on
a record boundary. Therefore, the arguments given to fseek must
specify any of the following:
o The beginning or end of the file
o A 0 offset from the current position (an arbitrary record
boundary)
o The position returned by a previous, valid ftell call
See the fgetpos and fsetpos functions for a portable way to seek
to arbitrary locations with these types of record files.
CAUTION
If, while accessing a stream file, you seek beyond the
end-of-file and then write to the file, the fseek function
creates a hole by filling the skipped bytes with zeros.
In general, for record files, fseek should only be directed
to an absolute position that was returned by a previous
valid call to ftell, or to the beginning or end of a file.
If a call to fseek does not satisfy these conditions, the
results are unpredictable.
See also open, creat, dup, dup2, and lseek.
181.3 – Return Values
0 Indicates successful seeks.
-1 Indicates improper seeks.
182 – fseeko
Positions the file to the specified byte offset in the file.
Equivalent to fseek.
Format
#include <stdio.h>
int fseeko (FILE *file_ptr, off_t offset, int direction);
182.1 – Arguments
file_ptr
A file pointer.
offset
The offset, specified in bytes. The off_t data type is either a
32-bit or 64-bit integer. The 64-bit interface allows for file
sizes greater than 2 GB, and can be selected at compile time by
defining the _LARGEFILE feature-test macro as follows:
CC/DEFINE=_LARGEFILE
direction
An integer indicating the position to which the offset is added
to calculate the new position. The new position is the beginning
of the file if direction is SEEK_SET, the current value of the
file position indicator if direction is SEEK_CUR, or end-of-file
if direction is SEEK_END.
182.2 – Description
The fseeko function is identical to the fseek function, except
that the offset argument is of type off_t instead of long int.
183 – fsetpos
Sets the file position indicator for a given file.
Format
#include <stdio.h>
int fsetpos (FILE *stream, const fpos_t *pos);
183.1 – Arguments
stream
A file pointer.
pos
A pointer to an implementation-defined structure. The fgetpos
function fills this structure with information that can be used
on subsequent calls to fsetpos.
183.2 – Description
Call the fgetpos function before using the fsetpos function.
183.3 – Return Values
0 Indicates success.
-1 Indicates an error.
184 – fstat
Accesses information about the file specified by the file
descriptor.
Format
#include <stat.h>
int fstat (int file_desc, struct stat *buffer);
184.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to the
fstat function that is equivalent to the behavior before OpenVMS
Version 7.0.
184.2 – Arguments
file_desc
A file descriptor.
buffer
A pointer to a structure of type stat_t, which is defined in the
<stat.h> header file. The argument receives information about
that particular file. The members of the structure pointed to by
buffer are:
Member Type Definition
st_dev dev_t Pointer to a physical device name
st_ino[3] ino_t Three words to receive the file ID
st_mode mode_t File "mode" (prot, dir, . . . )
st_nlink nlink_t For UNIX system compatibility only
st_uid uid_t Owner user ID
st_gid gid_t Group member: from st_uid
st_rdev dev_t UNIX system compatibility - always 0
st_size off_t File size, in bytes. For st_size to
report a correct value, you need to
flush both the C RTL and RMS buffers.
st_atime time_t File access time; always the same as
st_mtime
st_mtime time_t Last modification time
st_ctime time_t File creation time
st_fab_rfm char Record format
st_fab_rat char Record attributes
st_fab_fsz char Fixed header size
st_fab_mrs unsigned Record size
The types dev_t, ino_t, off_t, mode_t, nlink_t, uid_t, gid_t, and
time_t, are defined in the <stat.h> header file. However, when
compiling for compatibility (/DEFINE=_DECC_V4_SOURCE), only dev_
t, ino_t, and off_t are defined.
The off_t data type is either a 32-bit or 64-bit integer. The 64-
bit interface allows for file sizes greater than 2 GB, and can be
selected at compile time by defining the _LARGEFILE feature-test
macro as follows:
CC/DEFINE=_LARGEFILE
As of OpenVMS Version 7.0, times are given in seconds since the
Epoch (00:00:00 GMT, January 1, 1970).
The st_mode structure member is the status information mode and
is defined in the <stat.h> header file. The st_mode bits follow:
Bits Constant Definition
0170000 S_IFMT Type of file
0040000 S_IFDIR Directory
0020000 S_IFCHR Character special
0060000 S_IFBLK Block special
0100000 S_IFREG Regular
0030000 S_IFMPC Multiplexed char special
0070000 S_IFMPB Multiplexed block special
0004000 S_ISUID Set user ID on execution
0002000 S_ISGID Set group ID on execution
0001000 S_ISVTX Save swapped text even after use
0000400 S_IREAD Read permission, owner
0000200 S_IWRITE Write permission, owner
0000100 S_IEXEC Execute/search permission, owner
184.3 – Description
The fstat function does not work on remote network files.
Be aware that for the stat_t structure member st_size to report a
correct value, you need to flush both the C RTL and RMS buffers.
NOTE (Integrity servers, Alpha)
On OpenVMS Alpha and Integrity server systems, the stat,
fstat, utime, and utimes functions have been enhanced to
take advantage of the new file-system support for POSIX
compliant file timestamps.
This support is available only on ODS-5 devices on OpenVMS
Alpha and Integrity servers systems beginning with a version
of OpenVMS Alpha after Version 7.3.
Before this change, the stat and fstat functions were
setting the values of the st_ctime, st_mtime, and st_atime
fields based on the following file attributes:
st_ctime - ATR$C_CREDATE (file creation time)
st_mtime - ATR$C_REVDATE (file revision time)
st_atime - was always set to st_mtime because no support
for file access time was available
Also, for the file-modification time, utime and utimes were
modifying the ATR$C_REVDATE file attribute, and ignoring the
file-access-time argument.
After the change, for a file on an ODS-5 device, the stat
and fstat functions set the values of the st_ctime, st_
mtime, and st_atime fields based on the following new file
attributes:
st_ctime - ATR$C_ATTDATE (last attribute modification
time)
st_mtime - ATR$C_MODDATE (last data modification time)
st_atime - ATR$C_ACCDATE (last access time)
If ATR$C_ACCDATE is zero, as on an ODS-2 device, the stat
and fstat functions set st_atime to st_mtime.
For the file-modification time, the utime and utimes
functions modify both the ATR$C_REVDATE and ATR$C_MODDATE
file attributes. For the file-access time, these functions
modify the ATR$C_ACCDATE file attribute. Setting the ATR$C_
MODDATE and ATR$C_ACCDATE file attributes on an ODS-2 device
has no effect.
For compatibility, the old behavior of stat, fstat, utime,
and utimes remains the default, regardless of the kind of
device.
The new behavior must be explicitly enabled at run time
by defining the DECC$EFS_FILE_TIMESTAMPS logical name to
"ENABLE" before invoking the application. Setting this
logical does not affect the behavior of stat, fstat, utime
and utimes for files on an ODS-2 device.
184.4 – Return Values
0 Indicates successful completion.
-1 Indicates an error other than a protection
violation.
-2 Indicates a protection violation.
185 – fstatvfs
Gets information about a device containing the specified file.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <statvfs.h>
int fstatvfs (int filedes, struct statvfs *buffer);
185.1 – Arguments
filedes
File descriptor obtained from a successful open or fcntl function
call.
buffer
Pointer to a statvfs structure to hold the returned information.
185.2 – Description
The fstatvfs function returns descriptive information about the
device containing the specified file. Read, write, or execute
permission of the specified file is not required. The returned
information is in the format of a statvfs structure, which is
defined in the <statvfs.h> header file and contains the following
members:
unsigned long f_bsize - Preferred block size.
unsigned long f_frsize - Fundamental block size.
fsblkcnt_t f_blocks - Total number of blocks in units of f_
frsize.
fsblkcnt_t f_bfree - Total number of free blocks. If f_bfree
would assume a meaningless value due to the misreporting of
free block count by $GETDVI for a DFS disk, then f_bfree is
set to the maximum block count.
fsblkcnt_t f_bavail - Number of free blocks available. Set to
the unused portion of the caller's disk quota.
fsfilcnt_t f_files - Total file (inode) count.
fsfilcnt_t f_ffree - Free file (inode) count. For OpenVMS
systems, this value is calculated as freeblocks/clustersize.
fsfilcnt_t f_favail - Free file (inode) count nonprivileged.
Set to f_ffree.
unsigned long f_fsid - File system identifier. This identifier
is based on the allocation-class device name. This gives a
unique value based on device, as long as the device is locally
mounted.
unsigned long f_flag - Bit mask representing one or more of
the following flags:
ST_RONLY - The volume is read-only.
ST_NOSUID - The volume has protected subsystems enabled.
unsigned long f_namemax - Maximum length of a filename.
char f_basetype[64] - Device-type name.
char f_fstr[64] - Logical volume name.
char __reserved[64] - Media type name.
Upon successful completion, fstatvfs returns 0 (zero). Otherwise,
it returns -1 and sets errno to indicate the error.
See also statvfs.
185.3 – Return Value
0 Successful completion.
-1 Indicates an error. errno is set to one of the
following:
o EBADF - The file descriptor parameter
contains an invalid value.
o EIO - An I/O error occurred while reading
the device.
o EINTR - A signal was intercepted during
execution of the function.
o EOVERFLOW - One of the values to be
returned cannot be represented correctly
in the structure pointed to by buffer.
186 – fsync
Flushes data all the way to the disk.
Format
#include <unistd.h>
int fsync (int fd);
186.1 – Argument
fd
A file descriptor corresponding to an open file.
186.2 – Description
The fsync function behaves much like the fflush function. The
primary difference between the two is that fsync flushes data
all the way to the disk while fflush flushes data only as far as
the underlying RMS buffers. Also, with fflush, you can flush all
buffers at once; with fsync you cannot.
186.3 – Return Values
0 Indicates successful completion.
-1 Indicates an error.
187 – ftell
Returns the current byte offset to the specified stream file.
Format
#include <stdio.h>
long int ftell (FILE *file_ptr);
187.1 – Argument
file_ptr
A file pointer.
187.2 – Description
The ftell function measures the byte offset from the beginning of
the file.
For variable-length files, VFC files, or any file with carriage-
control attributes, if the file is opened in record mode, then
ftell returns the starting position of the current record, not
the current byte offset.
When using record files, the ftell function ignores any
characters that have been pushed back using either ungetc or
ungetwc. This behavior does not occur if stream files are being
used.
For a portable way to measure the exact offset for any type of
file, see the fgetpos function.
187.3 – Return Values
n The current offset.
EOF Indicates an error.
188 – ftello
Returns the current byte offset to the specified stream file.
This function is equivalent to ftell.
Format
#include <stdio.h>
off_t ftello (FILE *file_ptr);
188.1 – Argument
file_ptr
A file pointer.
188.2 – Description
The ftello function is identical to the ftell function, except
that the return value is of type off_t instead of long int.
The off_t data type is either a 64-bit or 32-bit integer. The 64-
bit interface allows for file sizes greater than 2 GB, and can be
selected at compile time by defining the _LARGEFILE feature-test
macro as follows:
CC/DEFINE=_LARGEFILE
189 – ftime
Returns the elapsed time since 00:00:00, January 1, 1970, in the
structure pointed at by timeptr.
Format
#include <timeb.h>
int ftime (struct timeb *timeptr);
189.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to the
ftime function that is equivalent to the behavior before OpenVMS
Version 7.0.
189.2 – Argument
timeptr
A pointer to the structure timeb_t.
189.3 – Description
The typedef timeb_t refers to the following structure defined in
the <timeb.h> header file:
typedef struct timeb
{
time_t time;
unsigned short millitm;
short timezone;
short dstflag;
};
The member time gives the time in seconds.
The member millitm gives the fractional time in milliseconds.
After a call to ftime, the timezone and dstflag members of the
timeb structure have the values of the global variables timezone
and dstflag, respectively. See the description of the tzset
function for timezone and dstflag global variables.
189.4 – Return Values
0 Successful execution. The timeb_t structure is
filled in.
-1 Indicates an error. Failure might indicate
that the system's time-differential factor
(that is, the difference between the system
time and UTC time) is not set correctly.
If the value of the SYS$TIMEZONE_DIFFERENTIAL
logical is wrong, the function fails with
errno set to EINVAL.
190 – ftok
Generates a standard interprocess communication key that is
usable in subsequent calls to semget.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <ipc.h>
key_t ftok (const char *path_name, int project_id);
190.1 – Argument
path_name
the pathname of an existing file that is accessible to the
process.
project_id
a value that uniquely identifies a project.
190.2 – Description
The ftok function returns a key, based on the path_name and
project_id parameters, that is usable in subsequent calls to the
semget function. The ftok function returns the same key for all
paths that name the same file, when called with the same project_
id parameter. Different keys are returned for the same file if
different project_id parameters are used, or if paths are used
that name different files existing on the same file system at the
same time. If a file named by path_name is removed and recreated
with the same name, the ftok function may return a different key
than the original one.
Only the low order 8 bits of project_id are significant. The
behavior of ftok is unspecified if these bits are 0.
For maximum portability, project_id must be a single-byte
character.
Upon successful completion, the ftok function returns a key.
Otherwise, it returns the value (key_t)-1 and sets errno to
indicate the error.
190.3 – Return Values
n Upon successful completion, the ftok function
returns a key.
(key_t)-1 Indicates an error. The function sets errno
to:
o EACCESS - Search permission is denied for a
component of the path_name parameter.
191 – ftruncate
Truncates a file to a specified length.
Format
#include <unistd.h>
int ftruncate (int filedes, off_t length);
191.1 – Arguments
filedes
The descriptor of a file that must be open for writing.
length
The new length of the file, in bytes. The off_t data type is
either a 32-bit or 64-bit integer. The 64-bit interface allows
for file sizes greater than 2 GB, and can be selected at compile
time by defining the _LARGEFILE feature-test macro as follows:
CC/DEFINE=_LARGEFILE
191.2 – Description
The ftruncate function truncates a file at the specified
position. For record files, the position must be a record
boundary. Also, the files must be local, regular files.
If the file was previously larger than length, extra data is
lost. If the file was previously shorter than length, bytes
between the old and new lengths are read as zeros.
191.3 – Return Values
0 Indicates success.
-1 An error occurred; errno is set to indicate
the error.
192 – ftrylockfile
Acquires ownership of a stdio (FILE*) object.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int ftrylockfile (FILE *file_ptr);
192.1 – Argument
file_ptr
A file pointer.
192.2 – Description
The ftrylockfile function is used by a thread to acquire
ownership of a stdio (FILE*) object, if the object is available.
The ftrylockfile function is a non-blocking version of flockfile.
The ftrylockfile function returns zero for success and nonzero to
indicate that the lock cannot be acquired.
See also flockfile and funlockfile.
192.3 – Return Values
0 Indicates success.
nonzero Indicates the lock cannot be acquired.
193 – ftw
Walks a file tree.
Format
#include <ftw.h>
int ftw (const char *path, int(*function)(const char *, const
struct stat *, int), int depth);
193.1 – Arguments
path
The directory hierarchy to be searched.
function
The function to be invoked for each file in the directory
hierarchy.
depth
The maximum number of directory streams or file descriptors, or
both, available for use by ftw. This argument should be in the
range of 1 to OPEN_MAX.
193.2 – Description
The ftw function recursively searches the directory hierarchy
that descends from the directory specified by the path argument.
The path argument can be specified in OpenVMS style or UNIX
style.
For each file in the hierarchy, ftw calls the function specified
by the function argument, passes it a pointer to a null-
terminated character string containing the name of the file, a
pointer to a stat structure containing information about the
file, and an integer.
The integer identifies the file type. Possible values, defined in
<ftw.h> are:
FTW_F Regular file.
FTW_D Directory.
FTW_DNR Directory that cannot be read.
FTW_NS A file on which stat could not successfully be
executed.
If the integer is FTW_DNR, then the files and subdirectories
contained in that directory are not processed.
If the integer is FTW_NS, then the stat structure contents are
meaningless. For example, a file in a directory for which you
have read permission but not execute (search) permission can
cause the function argument to pass FTW_NS.
The ftw function finishes processing a directory before
processing any of its files or subdirectories.
The ftw function continues the search until:
o The directory hierarchy specified by the path argument is
completed.
o An invocation of the function specified by the function
argument returns a nonzero value.
o An error (such as an I/O error) is detected within the ftw
function.
Because the ftw function is recursive, it is possible for it
to terminate with a memory fault because of stack overflow when
applied to very deep file structures.
The ftw function uses the malloc function to allocate dynamic
storage during its operation. If ftw is forcibly terminated,
as with a call to longjmp from the function pointed to by the
function argument, ftw has no chance to free that storage. It
remains allocated.
A safe way to handle interrupts is to store the fact that
an interrupt has occurred, and arrange to have the function
specified by the function argument return a nonzero value the
next time it is called.
NOTES
o The ftw function is reentrant; make sure that the
function supplied as argument function is also reentrant.
o The C RTL supports a standard-compliant definition of the
stat structure and associated definitions. To use them,
compile your application with the _USE_STD_STAT feature-
test macro defined. See the <stat.h> header file on your
system for more information.
o The ftw function supports UNIX style path name
specifications.
See also malloc, longjump, and stat.
193.3 – Return Values
0 Indicates success.
x Indicates that the function specified by
the function argument stops its search, and
returns the value that was returned by the
function.
-1 Indicates an error; errno is set to one of the
following values:
o EACCES - Search permission is denied for
any component of the path argument or read
permission is denied for the path argument.
o ENAMETOOLONG - The length of the path
string exceeds PATH_MAX, or a pathname
component is longer than NAME_MAX while
[_POSIX_NO_TRUNC] is in effect.
o ENOENT - The path argument points to the
name of a file that does not exist or
points to an empty string.
o ENOMEM - There is insufficient memory for
this operation.
Also, if the function pointed to by the
function argument encounters an error, errno
can be set accordingly.
194 – funlockfile
Unlocks a stdio stream.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
void funlockfile (FILE *file_ptr);
194.1 – Argument
file_ptr
A file pointer.
194.2 – Description
The funlockfile function unlocks a stdio stream, causing the
thread that had been holding the lock to relinquish exclusive use
of the stream.
File pointers passed are assumed to be valid; flockfile will
perform locking even on invalid file pointers. Also, the
funlockfile function will not fail if the calling thread does
not own a lock on the file pointer passed.
Matching flockfile and funlockfile calls can be nested. If the
stream has been locked recursively, it will remain locked until
the last matching funlockfile is called.
All C RTL file-pointer I/O functions lock their file pointers as
if calling flockfile and funlockfile.
See also flockfile and ftrylockfile.
195 – fwait
Waits for I/O on a specific file to complete.
Format
#include <stdio.h>
int fwait (FILE *fp);
195.1 – Argument
fp
A file pointer corresponding to an open file.
195.2 – Description
The fwait function is used primarily to wait for completion of
pending asynchronous I/O.
195.3 – Return Values
0 Indicates successful completion.
-1 Indicates an error.
196 – fwide
Determines and sets the orientation of a stream.
Format
#include <wchar.h>
int fwide (FILE *stream, int mode);
196.1 – Arguments
stream
A file pointer.
mode
A value that specifies the desired orientation of the stream.
196.2 – Description
The fwide function determines the orientation of the stream
pointed to by stream and sets the orientation of a nonoriented
stream according to the mode argument in the following way:
If the mode
argument is: Then the fwide function:
greater than makes the stream wide-oriented.
zero
less than zero makes the stream byte-oriented.
zero does not alter the orientation of the stream.
If the orientation of the stream has already been set, fwide does
not alter it. Because no error status is defined for fwide, the
calling application should check errno if fwide returns a 0.
196.3 – Return Values
> 0 After the call, the stream is wide-oriented.
< 0 After the call, the stream is byte-oriented.
0 After the call, the stream has no orientation
or a stream argument is invalid; the function
sets errno.
197 – fwprintf
Writes output to the stream under control of the wide-character
format string.
Format
#include <wchar.h>
int fwprintf (FILE *stream, const wchar_t *format, . . . );
197.1 – Arguments
stream
A file pointer.
format
A pointer to a wide-character string containing the format
specifications.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, the output sources can
be omitted. Otherwise, the function calls must have exactly as
many output sources as there are conversion specifications, and
the conversion specifications must match the types of the output
sources.
Conversion specifications are matched to output sources in left-
to-right order. Any excess output sources are ignored.
197.2 – Description
The fwprintf function writes output to the stream pointed to by
stream under control of the wide-character string pointed to by
format, which specifies how to convert subsequent arguments to
output. If there are insufficient arguments for the format, the
behavior is undefined. If the format is exhausted while arguments
remain, the excess arguments are evaluated, but are otherwise
ignored. The fwprintf function returns when it encounters the end
of the format string.
The format argument is composed of zero or more directives that
include:
o Ordinary wide characters (not the percent sign (%))
o Conversion specifications
197.3 – Return Values
n The number of wide characters written.
Negative value Indicates an error. The function sets errno to
one of the following:
o EILSEQ - Invalid character detected.
o EINVAL - Insufficient arguments.
o ENOMEM - Not enough memory available for
conversion.
o ERANGE - Floating-point calculations
overflow.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This might indicate that conversion to a
numeric value failed because of overflow.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENOSPC - No free space on the device
containing the file.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o ESPIPE - Illegal seek in a file opened for
append.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
197.4 – Example
The following example shows how to print a date and time in the
form "Sunday, July 3, 10:02", followed by pi to five decimal
places:
#include <math.h>
#include <stdio.h>
#include <wchar.h>
/* . . . */
wchar_t *weekday, *month; /* pointers to wide-character strings */
int day, hours, min;
fwprintf(stdout, L"%ls, %ls %d, %.2d:%.2d\n",
weekday, month, day, hour, min);
fwprintf(stdout, L"pi = %.5f\n", 4 * atan(1.0));
198 – fwrite
Writes a specified number of items to the file.
Format
#include <stdio.h>
size_t fwrite (const void *ptr, size_t size_of_item, size_t
number_items, FILE *file_ptr);
198.1 – Arguments
ptr
A pointer to the memory location from which information is being
written. The type of the object pointed to is determined by the
type of the item being written.
size_of_item
The size, in bytes, of the items being written.
number_items
The number of items to be written.
file_ptr
A file pointer that indicates the file to which the items are
being written.
198.2 – Description
The type size_t is defined in the header file <stdio.h> as
follows:
typedef unsigned int size_t
The writing begins at the current location in the file. The items
are written from storage beginning at the location given by the
first argument. You must also specify the size of an item, in
bytes.
If the file pointed to by file_ptr is a record file, the fwrite
function outputs at least number_items records, each of length
size_of_item.
198.3 – Return Value
x The number of items written. The number of
records written depends upon the maximum
record size of the file.
199 – fwscanf
Reads input from the stream under control of the wide-character
format string.
Format
#include <wchar.h>
int fwscanf (FILE *stream, const wchar_t *format, . . . );
199.1 – Arguments
stream
A file pointer.
format
A pointer to a wide-character string containing the format
specification.
. . .
Optional expressions whose results correspond to conversion
specifications given in the format specification.
If no conversion specifications are given, you can omit the input
pointers. Otherwise, the function calls must have exactly as
many input pointers as there are conversion specifications, and
the conversion specifications must match the types of the input
pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
199.2 – Description
The fwscanf function reads input from the stream pointed to by
stream under the control of the wide-character string pointed
to by format. If there are insufficient arguments for the
format, the behavior is undefined. If the format is exhausted
while arguments remain, the excess arguments are evaluated, but
otherwise ignored.
The format is composed of zero or more directives that include:
o One or more white-space wide characters.
o An ordinary wide character (neither a percent (%)) nor a
white-space wide character).
o Conversion specifications.
Each conversion specification is introduced by the wide character
%.
If the stream pointed to by the stream argument has no
orientation, fwscanf makes the stream wide-oriented.
199.3 – Return Values
n The number of input items assigned, sometimes
fewer than provided for, or even zero, in the
event of an early matching failure.
EOF Indicates an error; input failure occurs
before any conversion.
200 – gcvt
Converts its argument to a null-terminated string of ASCII digits
and returns the address of the string.
Format
#include <stdlib.h>
char *gcvt (double value, int ndigit, char *buffer);
200.1 – Function Variants
The gcvt function has variants named _gcvt32 and _gcvt64 for use
with 32-bit and 64-bit pointer sizes, respectively.
200.2 – Arguments
value
An object of type double that is converted to a null-terminated
string of ASCII digits.
ndigit
The number of ASCII digits to use in the converted string. If
ndigit is less than 6, the value of 6 is used.
buffer
A storage location to hold the converted string.
200.3 – Description
The gcvt function places the converted string in a buffer and
returns the address of the buffer. If possible, gcvt produces
ndigit significant digits in F-format, or if not possible, in
E-format. Trailing zeros are suppressed.
The ecvt, fcvt, and gcvt functions represent the following
special values specified in the IEEE Standard for floating-point
arithmetic:
Value Representation
Quiet NaN NaNQ
Signalling NaNS
NaN
+Infinity Infinity
-Infinity -Infinity
The sign associated with each of these values is stored into the
sign argument. In IEEE floating-point representation, a value
of 0 (zero) can be positive or negative, as set by the sign
argument.
See also fcvt and ecvt.
200.4 – Return Value
x The address of the buffer.
201 – getc
Returns the next character from a specified file.
Format
#include <stdio.h>
int getc (FILE *file_ptr);
201.1 – Argument
file_ptr
A pointer to the file to be accessed.
201.2 – Description
The getc macro returns the next byte from the input stream
specified by the file_ptr parameter and moves the file pointer,
if defined, ahead one byte in the input stream.
Since getc is a macro, a file pointer argument with side effects
(for example, getc (*f++)) might be evaluated incorrectly.
In such a case, use the fgetc function instead. See the fgetc
function.
See also getc_unlocked.
201.3 – Return Values
n The returned character.
EOF Indicates the end-of-file or an error.
202 – getc_unlocked
Same as getc, except used only within a scope protected by
flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int getc_unlocked (FILE *file_ptr);
202.1 – Argument
file_ptr
A file pointer.
202.2 – Description
The reentrant version of the getc macro is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the stream. The unlocked version of this
call, getc_unlocked can be used to avoid the overhead. The getc_
unlocked macro is functionally identical to the getc macro,
except that it is not required to be implemented in a thread-
safe manner. The getc_unlocked macro can be safely used only
within a scope that is protected by the flockfile and funlockfile
functions used as a pair. The caller must ensure that the stream
is locked before getc_unlocked is used.
Since getc_unlocked is a macro, a file pointer argument with side
effects might be evaluated incorrectly. In such a case, use the
fgetc_unlocked function instead.
See also flockfile, ftrylockfile, and funlockfile.
202.3 – Return Values
n The returned character.
EOF Indicates the end-of-file or an error.
203 – [w]getch
Get a character from the terminal screen and echo it on the
specified window. The getch function echoes the character on
the stdscr window.
Format
#include <curses.h>
char getch();
char wgetch (WINDOW *win);
203.1 – Argument
win
A pointer to the window.
203.2 – Description
The getch and wgetch functions refresh the specified window
before fetching a character. For more information, see the
scrollok function.
203.3 – Return Values
x The returned character.
ERR Indicates that the function makes the screen
scroll illegally.
204 – getchar
Reads a single character from the standard input (stdin).
Format
#include <stdio.h>
int getchar (void);
204.1 – Description
The getchar function is identical to fgetc(stdin).
See also getchar_unlocked.
204.2 – Return Values
x The next character from stdin, converted to
int.
EOF Indicates the end-of-file or an error.
205 – getchar_unlocked
Same as getchar, except used only within a scope protected by
flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int getchar_unlocked (void);
205.1 – Description
The reentrant version of the getchar function is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the input stream. The unlocked version of
this call, getchar_unlocked can be used to avoid the overhead.
The getchar_unlocked function is functionally identical to
the getchar function, except that it is not required to be
implemented in a thread-safe manner. The getchar_unlocked
function can be safely used only within a scope that is protected
by the flockfile and funlockfile functions used as a pair. The
caller must ensure that the stream is locked before getchar_
unlocked is used.
See also flockfile, ftrylockfile, and funlockfile.
205.2 – Return Values
x The next character from stdin, converted to
int.
EOF Indicates the end-of-file or an error.
206 – getclock
Gets the current value of the systemwide clock.
Format
#include <timers.h>
int getclock (int clktyp, struct timespec *tp);
206.1 – Arguments
clktyp
The type of systemwide clock.
tp
Pointer to a timespec structure space where the current value of
the systemwide clock is stored.
206.2 – Description
The getclock function sets the current value of the clock
specified by clktyp into the location pointed to by tp.
The clktyp argument is given as a symbolic constant name,
as defined in the <timers.h> header file. Only the TIMEOFDAY
symbolic constant, which specifies the normal time-of-day clock
to access for systemwide time, is supported.
For the clock specified by TIMEOFDAY, the value returned by
this function is the elapsed time since the Epoch. The Epoch
is referenced to 00:00:00 UTC (Coordinated Universal Time) 1 Jan
1970.
The getclock function returns a timespec structure, which is
defined in the <timers.h> header file as follows:
struct timespec {
unsigned long tv_sec /* Elapsed time in seconds since the Epoch*/
long tv_nsec /* Elapsed time as a fraction of a second */
/* since the Epoch (in nanoseconds) */
};
206.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to one of the
following values:
o EINVAL - The clktyp argument does not
specify a known systemwide clock.
Or, the value of SYS$TIMEZONE_DIFFERENTIAL
logical is wrong.
o EIO - An error occurred when the systemwide
clock specified by the clktyp argument was
accessed.
207 – getcwd
Returns a pointer to the file specification for the current
working directory.
Format
#include <unistd.h>
char *getcwd (char *buffer, size_t size); (ISO POSIX-1)
char *getcwd (char *buffer, unsigned int size, . . . );
(DEC C Extension)
207.1 – Function Variants
The getcwd function has variants named _getcwd32 and _getcwd64
for use with 32-bit and 64-bit pointer sizes, respectively.
207.2 – Arguments
buffer
Pointer to a character string large enough to hold the directory
specification.
If buffer is a NULL pointer, getcwd obtains size bytes of space
using malloc. In this case, you can use the pointer returned by
getcwd as the argument in a subsequent call to free.
size
The length of the directory specification to be returned.
. . .
An optional argument that can be either 1 or 0. If you specify 1,
the directory specification is returned in OpenVMS format. If you
specify 0, the directory specification (pathname) is returned in
UNIX style format. If you omit this argument, getcwd returns the
filename according to your current command-language interpreter
(CLI).
207.3 – Return Values
x A pointer to the file specification.
NULL Indicates an error.
208 – getdtablesize
Gets the total number of file descriptors that a process can have
open simultaneously.
Format
#include <unistd.h>
int getdtablesize (void);
208.1 – Description
The getdtablesize function returns the total number of file
descriptors that a process can have open simultaneously. Each
process is limited to a fixed number of open file descriptors.
The number of file descriptors that a process can have open is
the minumum of the following:
o C RTL open file limit-65535 on OpenVMS Alpha and
Integrity servers.
o SYSGEN CHANNELCNT parameter-permanent I/O channel count.
o Process open file quota FILLM parameter-number of open files
that can be opened by a process at one time.
208.2 – Return Values
x The number of file descriptors that a process
can have open simultaneously.
-1 Indicates an error.
209 – getegid
With POSIX IDs disabled, this function is equivalent to getgid
and returns the group number from the user identification code
(UIC).
With POSIX IDs enabled, this function returns the effective group
ID of the calling process.
Format
#include <unistd.h>
gid_t getegid (void);
209.1 – Description
The getegid function can be used with POSIX style identifiers
(IDs) or with UIC-based identifiers.
POSIX style IDs are supported on OpenVMS Version 7.3-2 and
higher.
With POSIX style IDs disabled, the getegid and getgid functions
are equivalent and return the group number from the current UIC.
For example, if the UIC is [313,031], 313 is the group number.
With POSIX style IDs enabled, getegid returns the effective group
ID of the calling process, and getgid returns the real group ID
of the calling process. The real group ID is specified at login
time. The effective group ID is more transient, and determines
additional access permission during execution of a set-group-ID
process. It is for such processes that the getgid function is
most useful.
The getegid function is always successful; no return value is
reserved to indicate an error.
See also geteuid and getuid.
209.2 – Return Value
x The effective group ID (POSIX IDs enabled),
or the group number from the UIC (POSIX IDs
disabled).
210 – getenv
Searches the environment array for the current process and
returns the value associated with a specified environment name.
Format
#include <stdlib.h>
char *getenv (const char *name);
210.1 – Argument
name
One of the following values:
o HOME-Your login directory
o TERM-The type of terminal being used
o PATH-The default device and directory
o USER-The name of the user who initiated the process
o Logical name or command-language interpreter (CLI) symbolic
name
o An environment variable set with setenv or putenv
The case of the specified name is important.
210.2 – Description
In certain situations, the getenv function attempts to perform a
logical name translation on the user-specified argument:
1. If the argument to getenv does not match any of the
environment strings present in your environment array, getenv
attempts to translate your argument as a logical name by
searching the logical name tables indicated by the LNM$FILE_
DEV logical, as is done for file processing.
getenv first does a case-sensitive lookup. If that fails, it
does a case-insensitive lookup. In most instances, logical
names are defined in uppercase, but getenv can also find
logical names that include lowercase letters.
getenv does not perform iterative logical name translation.
2. If the logical name is a search list with multiple equivalence
values, the returned value points to the first equivalence
value. For example:
$ DEFINE A B,C
ptr = getenv("A");
A returns a pointer to "B".
3. If no logical name exists, getenv attempts to translate the
argument string as a CLI symbol. If it succeeds, it returns
the translated symbol text. If it fails, the return value is
NULL.
getenv does not perform iterative CLI translation.
If your CLI is the DEC/Shell, the function does not attempt a
logical name translation since Shell environment symbols are
implemented as DCL symbols.
NOTES
o In OpenVMS Version 7.1, a cache of OpenVMS environment
variables (that is, logical names and DCL symbols)
was added to the getenv function to avoid the library
making repeated calls to translate a logical name or
to obtain the value of a DCL symbol. By default, the
cache is disabled. If your application does not need to
track changes in OpenVMS environment variables that can
occur during its execution, the cache can be enabled
by enabling the DECC$ENABLE_GETENV_CACHE logical before
invoking the application.
o Do not use the setenv, getenv, and putenv functions
to manipulate symbols and logicals. Instead use the
OpenVMS library calls lib$set_logical, lib$get_logical,
lib$set_symbol, and lib$get_symbol. The *env functions
deliberately provide UNIX behavior, and are not a
substitute for these OpenVMS runtime library calls.
OpenVMS DCL symbols, not logical names, are the closest
analog to environment variables on UNIX systems. While
getenv is a mechanism to retrieve either a logical name
or a symbol, it maintains an internal cache of values for
use with setenv and subsequent getenv calls. The setenv
function does not write or create DCL symbols or OpenVMS
logical names.
This is consistent with UNIX behavior. On UNIX systems,
setenv does not change or create any symbols that will be
visible in the shell after the program exits.
210.3 – Return Values
x Pointer to an array containing the translated
symbol. An equivalence name is returned at
index zero.
NULL Indicates that the translation failed.
211 – geteuid
With POSIX IDs disabled, this function is equivalent to getuid
and returns the member number (in OpenVMS terms) from the user
identification code (UIC).
With POSIX IDs enabled, this function returns the effective user
ID.
Format
#include <unistd.h>
uid_t geteuid (void);
211.1 – Description
The geteuid function can be used with POSIX style identifiers
(IDs) or with UIC-based identifiers.
POSIX style IDs are supported on OpenVMS Version 7.3-2 and
higher.
With POSIX style IDs disabled (the default), the geteuid and
getuid functions are equivalent and return the member number from
the current UIC as follows:
o For programs compiled with the _VMS_V6_SOURCE feature-
test macro or programs that do not include the <unistd.h>
header file, the getuid and geteuid functions return the
member number of the OpenVMS UIC. For example, if the UIC
is [313,31], then the member number, 31, is returned.
o For programs compiled without the _VMS_V6_SOURCE feature-
test macro that do include the <unistd.h> header file, the
full UIC is returned in decimal after converting the octal
representation to decimal. For example, if the UIC is [313,
31] then 13303833 is returned. (13303833 = 25 + 203 * 65536;
Octal 31 = 25 decimal; Octal 313 = 203 decimal.)
With POSIX style IDs enabled, geteuid returns the effective user
ID of the calling process, and getuid returns the real user ID of
the calling process.
See also getegid and getgid.
211.2 – Return Value
x The effective user ID (POSIX IDs enabled), or
the member number from the current UIC or the
full UIC (POSIX IDs disabled).
212 – getgid
With POSIX IDs disabled, this function is equivalent to getegid
and returns the group number from the user identification code
(UIC).
With POSIX IDs enabled, this function returns the real group ID.
Format
#include <unistd.h>
gid_t getgid (void);
212.1 – Description
The getgid function can be used with POSIX style identifiers or
with UIC-based identifiers.
POSIX style IDs are supported on OpenVMS Version 7.3-2 and
higher.
With POSIX style IDs disabled (the default), the getegid and
getgid functions are equivalent and return the group number from
the current UIC. For example, if the UIC is [313,031], 313 is the
group number.
With POSIX style IDs enabled, getegid returns the effective group
ID of the calling process, and getgid returns the real group ID
of the calling process. The real group ID is specified at login
time. The effective group ID is more transient, and determines
additional access permission during execution of a set-group-ID
process. It is for such processes that the getgid function is
most useful.
See also geteuid and getuid.
212.2 – Return Value
x The real group ID (POSIX IDs enabled), or the
group number from the current UIC (POSIX IDs
disabled).
Gets a group database entry.
213 – getgrent
Gets a group database entry.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <grp.h>
struct group *getgrent (void);
213.1 – Description
The getgrent function returns the next group in the sequential
search, returning a pointer to a structure containing the broken-
out fields of an entry in the group database.
When first called, getgrent returns a pointer to a group
structure containing the first entry in the group database.
Thereafter, it returns a pointer to the next group structure
in the group database, so successive calls can be used to search
the entire database.
If an end-of-file or an error is encountered on reading, getgrent
returns a NULL pointer and sets errno.
213.2 – Return Values
x Pointer to a group structure, if successful.
NULL Indicates that an error occurred. The function
sets errno to one of the following values:
o EACCES - The user process does not have
appropriate privileges enabled to access
the user authorization file.
o EINTR - A signal was intercepted during the
operation.
o EIO - Indicates that an I/O error occurred.
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
214 – getgrgid
Gets a group database entry for a group ID.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <types.h>
#include <grp.h>
struct group *getgrgid (gid_t gid);
214.1 – Argument
gid
The group ID of the group for which the group database entry is
to be retrieved.
214.2 – Description
The getgrgid function searches the group database for an entry
with a matching gid and returns a pointer to the group structure
containing the matching entry.
214.3 – Return Values
x Pointer to a valid group structure containing
a matching entry.
NULL An error occurred.
Note: The return value points to a static area
that is overwritten by subsequent calls to
getgrent, getgrgid, or getgrnam.
On error, the function sets errno to one of
the following values:
o EACCES - The user process does not have
appropriate privileges enabled to access
the user authorization file.
o EIO - An I/O error has occurred.
o EINTR - A signal was intercepted during
getgrgid.
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
Applications checking for error situations
must set errno to 0 before calling getgrgid.
If errno is set on return, an error has
occurred.
215 – getgrgid_r
Gets a group database entry for a group ID.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <types.h>
#include <grp.h>
int getgrgid_r (gid_t gid, struct group *grp, char *buffer,
size_t bufsize, struct group **result);
215.1 – Arguments
gid
The group ID of the group for which the group database entry is
to be retrieved.
grp
Storage area to hold the retrieved group structure.
buffer
The working buffer that is able to hold the longest group entry
in the database.
bufsize
The length, in characters, of buffer.
result
Upon successful return, result points to the retrieved group
structure.
Upon unsuccessful return, result is set to NULL.
215.2 – Description
The getgrgid_r function updates the group structure pointed to
by grp and stores a pointer to that structure at the location
pointed to by result. The structure contains an entry from the
group database with a matching gid. Storage referenced by the
group structure is allocated from the memory provided with the
buffer argument, which is bufsize characters in size. The maximum
size needed for this buffer can be determined with the _SC_GETGR_
R_SIZE_MAX parameter of the sysconf function. On error or if the
requested entry is not found, a NULL pointer is returned at the
location pointed to by result.
215.3 – Return Values
0 Successful completion.
x On error, the function sets the return value
to one of the following:
o EACCES - The user process does not have
appropriate privileges enabled to access
the user authorization file.
o EIO - An I/O error has occurred.
o EINTR - A signal was intercepted during
getgrgid.
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
o ERANGE - Insufficient storage was supplied
through the buffer and bufsize arguments
to contain the data to be referenced by the
resulting group structure.
216 – getgrnam
Gets a group database entry for a name.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <types.h>
#include <grp.h>
struct group *getgrnam (const char *name);
216.1 – Argument
name
The group name of the group for which the group database entry is
to be retrieved.
216.2 – Description
The getgrnam function searches the group database for an
entry with a matching name, and returns a pointer to the group
structure containing the matching entry.
216.3 – Return Values
x Pointer to a valid group structure containing
a matching entry.
NULL Indicates an error.
Note: The return value points to a static area
which is overwritten by subsequent calls to
getgrent, getgrgid, or getgrnam.
On error, the function sets the return value
to one of the following:
o EACCES - The user process does not have
appropriate privileges enabled to access
the user authorization file.
o EIO - An I/O error has occurred.
o EINTR - A signal was intercepted during
getgrnam.
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
Applications wishing to check for error
situations should set errno to 0 before
calling getgrnam. If errno is set on return,
an error occurred.
217 – getgrnam_r
Gets a group database entry for a name.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <types.h>
#include <grp.h>
int getgrnam_r (const char *name, struct group *grp,
char *buffer, size_t bufsize, struct group
**result);
217.1 – Arguments
name
The group name of the group for which the group database entry is
to be retrieved.
grp
Storage area to hold the retrieved group structure.
buffer
The working buffer that is able to hold the longest group entry
in the database.
bufsize
The length, in characters, of buffer.
result
Upon successful return, result points to the retrieved group
structure.
Upon unsuccessful return, result is set to NULL.
217.2 – Description
The getgrnam_r function updates the group structure pointed to
by grp and stores a pointer to that structure at the location
pointed to by result. The structure contains an entry from the
group database with a matching name. Storage referenced by the
group structure is allocated from the memory provided with the
buffer argument, which is bufsize characters in size. The maximum
size needed for this buffer can be determined with the _SC_GETGR_
R_SIZE_MAX parameter of the sysconf function. On error or if the
requested entry is not found, a NULL pointer is returned at the
location pointed to by result.
217.3 – Return Values
0 Successful completion.
x On error, the function sets the return value
to one of the following:
o EACCES - The user process does not have
appropriate privileges enabled to access
the user authorization file.
o EIO - An I/O error has occurred.
o EINTR - A signal was intercepted during
getgrnam.
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
o ERANGE - Insufficient storage was supplied
through the buffer and bufsize arguments
to contain the data to be referenced by the
resulting group structure.
218 – getgroups
Gets the current supplementary group IDs of the calling process.
Format
#include <unistd.h>
int getgroups (int gidsetsize, gid_t grouplist[]);
218.1 – Arguments
gidsetsize
Indicates the number of entries that can be stored in the array
pointed to by the grouplist parameter.
grouplist
Points to the array in which the supplementary group IDs of
the process are stored. The effective group ID of the process
is not returned by the getgroups function if it is not also a
supplementary group ID of the calling process.
218.2 – Description
The getgroups function gets the current supplementary group IDs
of the calling process. The list is stored in the array pointed
to by the grouplist parameter. The gidsetsize parameter indicates
the number of entries that can be stored in this array.
The getgroups function never returns more IDs than the value
indicated by the sysconf parameter _SC_NGROUPS_MAX.
See also getgid and setsid.
218.3 – Return Value
n The number of elements stored in the array
pointed to by the grouplist parameter.
-1 Indicates failure. errno might be set to one
of the following values:
o EFAULT - The gidsetsize and grouplist
parameters specify an array that is
partially or completely outside of the
allocated address space of the process.
o EINVAL - The gidsetsize parameter is
nonzero and smaller than the number of
supplementary group IDs.
219 – getitimer
Returns the value of interval timers.
Format
#include <time.h>
int getitimer (int which, struct itimerval *value);
219.1 – Arguments
which
The type of interval timer. The C RTL supports only
ITIMER_REAL.
value
Pointer to an itimerval structure whose members specify a timer
interval and the time left to the end of the interval.
219.2 – Description
The getitimer function returns the current value for the timer
specified by the which argument in the structure pointed to by
value.
A timer value is defined by the itimerval structure:
struct itimerval {
struct timeval it_interval;
struct timeval it_value;
};
The following table lists the values for the itimerval structure
members:
itimerval Member
Value Meaning
it_interval = 0 Disables a timer after its next expiration and
assumes it_value is nonzero.
it_interval = Specifies a value used in reloading it_value
nonzero when the timer expires.
it_value = 0 Disables a timer.
it_value = Indicates the time to the next timer
nonzero expiration.
Time values smaller than the resolution of the system clock are
rounded up to this resolution.
The C RTL provides each process with one interval timer,
defined in the <time.h> header file as ITIMER_REAL. This timer
decrements in real time and delivers a SIGALRM signal when the
timer expires.
219.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to EINVAL
(The value argument specified a time that was
too large to handle.)
220 – getlogin
Gets the login name.
Format
#include <unistd.h>
char *getlogin (void);
int *getlogin_r (char *name, size_t namesize);
220.1 – Description
The getlogin function returns the login name of the user
associated with the current session. If getlogin returns a non-
null pointer, then that pointer points to the name that the user
logged in under, even if there are several login names with the
same user ID.
The getlogin_r function is the reentrant version of getlogin.
Upon successful completion, getlogin_r returns 0 and puts the
name associated by the login activity with the controlling
terminal of the current process in the character array pointed
to by name. The array is namesize characters long and should
have space for the name and the terminating null character. The
maximum size of the login name is LOGIN_NAME_MAX.
If getlogin_r is successful, name points to the name the user
used at login, even if there are several login names with the
same user ID.
220.2 – Return Values
x Upon successful completion, getlogin returns
a pointer to a null-terminated string in a
static buffer.
0 Indicates successful completion of getlogin_r.
NULL Indicates an error; errno is set.
221 – getname
Returns the file specification associated with a file descriptor.
Format
#include <unixio.h>
char *getname (int file_desc, char *buffer, . . . );
221.1 – Function Variants
The getname function has variants named _getname32 and _getname64
for use with 32-bit and 64-bit pointer sizes, respectively.
221.2 – Arguments
file_desc
A file descriptor.
buffer
A pointer to a character string that is large enough to hold the
file specification.
. . .
An optional argument that can be either 1 or 0. If you specify
1, the getname function returns the file specification in OpenVMS
format. If you specify 0, the getname function returns the file
specification in UNIX style format. If you omit this argument,
the getname function returns the filename according to your
current command-language interpreter (CLI).
221.3 – Description
The getname function places the file specification into the
area pointed to by buffer and returns that address. The area
pointed to by buffer should be an array large enough to contain
a fully qualified file specification (the maximum length is 256
characters).
221.4 – Return Values
x The address passed in the buffer argument.
0 Indicates an error.
222 – getopt
A command-line parser that can be used by applications that
follow UNIX command-line conventions.
Format
#include <unistd.h> (X/Open, POSIX-1)
#include <stdio.h> (X/Open, POSIX-2)
int getopt (int argc, char * const argv[], const char *optstring);
extern char *optarg;
extern int optind, opterr, optopt;
222.1 – Arguments
argc
The argument count as passed to main.
argv
The argument array as passed to main.
optstring
A string of recognized option characters. If a character is
followed by a colon, the option takes an argument.
222.2 – Description
The variable optind is the index of the next element of the
argv vector to be processed. It is initialized to 1 by the
system, and it is updated by getopt when it finishes with each
element of argv. When an element of argv contains multiple option
characters, it is unspecified how getopt determines which options
have already been processed.
The getopt function returns the next option character (if one is
found) from argv that matches a character in optstring, if there
is one that matches. If the option takes an argument, getopt sets
the variable optarg to point to the option-argument as follows:
o If the option was the last character in the string pointed to
by an element of argv, then optarg contains the next element
of argv, and optind is incremented by 2. If the resulting
value of optind is not less than argc, getopt returns an
error, indicating a missing option-argument.
o Otherwise, optarg points to the string following the option
character in that element of argv, and optind is incremented
by 1.
If one of the following is true, getopt returns -1 without
changing optind:
argv[optind] is a NULL pointer
*argv[optind] is not the character -
argv[optind] points to the string "-"
If argv[optind] points to the string "- -" getopt returns -1
after incrementing optind.
If getopt encounters an option character not contained in
optstring, the question-mark character (?) is returned.
If getopt detects a missing argument, the colon character (:)
is returned if the first character of optstring is a colon;
otherwise, a question-mark character is returned.
In either of the previous two cases, getopt sets the variable
optopt to the option character that caused the error. If the
application has not set the variable opterr to 0 and the first
character of optstring is not a colon, getopt also prints a
diagnostic message to stderr.
222.3 – Return Values
x The next option character specified on the
command line.
A colon is returned if getopt detects a
missing argument and the first character of
optstring is a colon.
A question mark is returned if getopt
encounters an option character not in
optstring or detects a missing argument and
the first character of optstring is not a
colon.
-1 When all command-line options are parsed.
222.4 – Example
The following example shows how you might process the arguments
for a utility that can take the mutually exclusive options a
and b and the options f and o, both of which require arguments:
#include <unistd.h>
int main (int argc, char *argv[ ])
{
int c;
int bflg, aflg, errflg;
char *ifile;
char *ofile;
extern char *optarg;
extern int optind, optopt;
.
.
.
while ((c = getopt(argc, argv, ":abf:o:)) != -1) {
switch (c) {
case 'a':
if (bflg)
errflg++;
else
aflg++;
break;
case 'b':
if (aflg)
errflg++;
else {
bflg++;
bproc();
}
break;
case 'f':
ifile = optarg;
break;
case 'o':
ofile = optarg;
break;
case ':': /* -f or -o without operand */
fprintf (stderr,
"Option -%c requires an operand\n"' optopt);
errflg++;
break;
case '?':
fprintf (stderr,
"Unrecognized option -%c\n"' optopt);
errflg++;
}
}
if (errflg) {
fprintf (stderr, "usage: ...");
exit(2);
}
for ( ; optind < argc; optind++) {
if (access(argv[optind], R_OK)) {
.
.
.
}
This sample code accepts any of the following as equivalent:
cmd -ao arg path path
cmd -a -o arg path path
cmd -o arg -a path path
cmd -a -o arg -- path path
cmd -a -oarg path path
cmd -aoarg path path
223 – getpagesize
Gets the system page size.
Format
#include <unistd.h>
int getpagesize (void);
223.1 – Description
The getpagesize function returns the number of bytes in a page.
The system page size is useful for specifying arguments to memory
management system calls.
The page size is a system page size and is not necessarily the
same as the underlying hardware page size.
223.2 – Return Value
x Always indicates success. Returns the number
of bytes in a page.
224 – getpgid
Gets the process group ID for a process.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
pid_t getpgid (pid_t pid);
224.1 – Argument
pid
The process ID for which the group ID is being requested.
224.2 – Description
The getpgid function returns the process group ID of the process
specified by pid. If pid is 0, the getpgid function returns the
process group ID of the calling process.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
224.3 – Return Values
x The process group ID of the session leader of
the specified process.
(pid_t)-1 Indicates an error. The function sets errno to
one of the following values:
o EPERM - The process specified by pid is
not in the same session as the calling
process, and the implementation does not
allow access to the process group ID of
that process from the calling process.
o ESRCH - There is no process with a process
ID of pid.
o EINVAL - The value of pid is invalid.
225 – getpgrp
Gets the process group ID of the calling process.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
pid_t getpgrp (void);
225.1 – Description
The getpgrp function returns the process group ID of the calling
process.
The getpgrp function is always successful, and no return value is
reserved to indicate an error.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
225.2 – Return Values
x The process group ID of the calling process.
226 – getpid
Returns the process ID of the current process.
Format
#include <unistd.h>
pid_t getpid (void);
226.1 – Return Value
x The process ID of the current process.
227 – getppid
Returns the parent process ID of the calling process.
Format
#include <unistd.h>
pid_t getppid (void);
227.1 – Return Values
x The parent process ID.
0 Indicates that the calling process does not
have a parent process.
228 – getpwent
Accesses user entry information in the user database, returning a
pointer to a passwd structure.
Format
#include <pwd.h>
struct passwd *getpwent (void);
228.1 – Function Variants
The getpwent function has variants named __32_getpwent and
__64_getpwent for use with 32-bit and 64-bit pointer sizes,
respectively.
228.2 – Description
The getpwent function returns a pointer to a structure containing
fields whose values are derived from an entry in the user
database. Entries in the database are accessed sequentially by
getpwent. When first called, getpwent returns a pointer to a
passwd structure containing the first entry in the user database.
Thereafter, it returns a pointer to a passwd structure containing
the next entry in the user database. Successive calls can be used
to search the entire user database.
The passwd structure is defined in the <pwd.h> header file as
follows:
pw_name The name of the user.
pw_uid The ID of the user.
pw_gid The group ID of the principle group of the user.
pw_dir The home directory of the user.
pw_shell The initial program for the user.
If an end-of-file or an error is encountered on reading, getpwent
returns a NULL pointer.
Because getpwent accesses the user authorization file (SYSUAF)
directly, the process must have appropriate privileges enabled or
the function will fail.
NOTES
All information generated by the getpwent function is stored
in a per-thread static area and is overwritten on subsequent
calls to the function.
Password file entries that are too long are ignored.
228.3 – Return Values
x Pointer to a passwd structure, if successful.
NULL Indicates an end-of-file or error occurred.
The function sets errno to one of the
following values:
o EIO - Indicates that an I/O error occurred
or the user does not have appropriate
privileges enabled to access the user
authorization file (SYSUAF).
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
229 – getpwnam
The getpwnam function returns information about a user database
entry for the specified name.
The getpwnam_r function is a reentrant version of getpwnam.
Format
#include <pwd.h>
struct passwd *getpwnam (const char *name); (ISO POSIX-1)
struct passwd *getpwnam (const char *name, . . . );
(DEC C Extension)
int getpwnam_r (const char *name, struct passwd *pwd,
char *buffer, size_t bufsize, struct
passwd **result); (ISO POSIX-1),
(Integrity servers, Alpha)
int getpwnam_r (const char *name, struct passwd *pwd,
char *buffer, size_t bufsize, struct
passwd **result, . . . ); (DEC C Extension),
(Integrity servers, Alpha)
229.1 – Function Variants
The getpwnam and getpwnam_r functions have variants named __32_
getpwnam, _getpwnam_r32 and __64_getpwnam, _getpwnam_r64 for use
with 32-bit and 64-bit pointer sizes, respectively.
229.2 – Arguments
name
The name of the user for which the attributes are to be read.
pwd
The address of a passwd structure into which the function writes
its results.
buffer
A working buffer for the result argument that is able to hold the
largest entry in the passwd structure. Storage referenced by the
passwd structure is allocated from the memory provided with the
buffer argument, which is bufsize characters in length.
bufsize
The length of the character array that buffer points to.
result
Upon successful return, is set to pwd. Upon unsuccessful return,
the result is set to NULL.
. . .
An optional argument that can be either 1 or 0. If you specify
1, the directory specification is returned in OpenVMS format. If
you specify 0, the directory specification (pathname) is returned
in UNIX style format. If you omit this argument, the function
returns the directory specification according to your current
command-language interpreter.
229.3 – Description
The getpwnam function searches the user database for an entry
with the specified name. The function returns the first user
entry in the database with the pw_name member of the passwd
structure that matches the name argument.
The passwd structure is defined in the <pwd.h> header file as
follows:
pw_name The user's login name.
pw_uid The numerical user ID.
pw_gid The numerical group ID.
pw_dir The home directory of the user.
pw_shell The initial program for the user.
NOTE
All information generated by the getpwnam function is stored
in a per-thread static area and is overwritten on subsequent
calls to the function.
The getpwnam_r function is the reentrant version of getpwnam.
The getpwnam_r function updates the passwd structure pointed to
by pwd and stores a pointer to that structure at the location
pointed to by result. The structure will contain an entry from
the user database that matches the specified name. Storage
referenced by the structure is allocated from the memory provided
with the buffer argument, which is bufsize characters in length.
The maximum size needed for this buffer can be determined with
the _SC_GETPW_R_SIZE_MAX parameter of the sysconf function. On
error or if the requested entry is not found, a NULL pointer is
returned at the location pointed to by result.
Applications wishing to check for error situations should set
errno to 0 before calling getpwnam. If getpwnam returns a NULL
pointer and errno is nonzero, an error occurred.
229.4 – Return Values
x getpwnam returns a pointer to a valid passwd
structure, if a matching entry is found.
NULL getpwnam returns NULL if an error occurred
or a the specified entry was not found. errno
is set to indicate the error. The getpwnam
function may fail if:
o EIO - An I/O error has occurred.
o EINTR - A signal was intercepted during
getpwnam.
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
0 When successful, getpwnam_r returns 0 and
stores a pointer to the updated passwd
structure at the location pointed to by
result.
0 When unsuccessful (on error or if the
requested entry is not found), getpwnam_r
returns 0 and stores a NULL pointer at the
location pointed to by result. The getpwnam_r
function may fail if:
o ERANGE - Insufficient storage was supplied
through buffer and bufsize to contain the
data to be referenced by the resulting
passwd structure.
229.5 – Example
When building a sample program with /def=_USE_STD_STAT, you can
observe the following:
o When the DECC$POSIX_STYLE_UID logical is enabled:
- For a system, that supports POSIX style identifiers:
- getpwnam_r API reads information from the TCP/IP proxy
database and fills UID and GID with values from the
TCP/IP proxy database.
- getgrgid_r API returns gr_name and gr_mem from
the right's database associated with GID returned by
getpwnam_r API.
- System with no support for POSIX style identifiers,
getpwnam_r fills GID and UID with SYSGEN parameters as
"DEFUID" and "DEFGID".
o When the DECC$POSIX_STYLE_UID logical is not defined:
getpwnam function returns information about a user database
entry for the specified name, which is specified in
SYSUAF.DAT
#include <unistd> // getuid()
#include <pwd> // getpwuid_r()
#include <grp>
#include <errno.h>
#include <stdio.h>
#include <string.h>
main()
{
struct passwd pwd2;
const unsigned int PWD_BUFF_SIZE = 1024;
const unsigned int GRP_BUFF_SIZE = 1024;
struct passwd *p_passwd;
struct passwd *result;
struct group *grpresult;
struct group grp;
char pwdBuffer[PWD_BUFF_SIZE],*name;
char grpBuffer[GRP_BUFF_SIZE];
char buf[PWD_BUFF_SIZE];
gid_t gid;
uid_t uid;
int status;
p_passwd = getpwnam("user1");
uid=p_passwd->pw_uid;
gid=p_passwd->pw_gid;
printf("User id is %u\n", uid);
printf("Group id is %u\n", gid);
status = getpwnam_r("user1", &pwd2, pwdBuffer, PWD_BUFF_SIZE, &result);
gid = pwd2.pw_gid;
status = getgrgid_r(gid, &grp, grpBuffer, GRP_BUFF_SIZE, &grpresult);
gid=grp.gr_gid; name=grp.gr_name;
strcpy(name,grp.gr_name);
printf("Group id is %u\n", gid);
printf("Group name is %s\n", name);
}
Running the example program with /def=_USE_STD_STAT produces
the following result:
o When the DECC$POSIX_STYLE_UID logical is NOT enabled, prints
uid as 11010118 (result of 65536*168+ 70) and gid as 168
with group name as RTL.
o When the DECC$POSIX_STYLE_UID logical is enabled and POSIX
style identifiers are supported, prints uid as 70, gid as
168 with group name as FOR_POSIX_TEST (retrieved from TCP/IP
proxy database).
o When the DECC$POSIX_STYLE_UID logical is enabled, but POSIX
style identifiers are not supported, prints uid as DEFUID,
gid as DEFGID with group name as invalid buffer.
230 – getpwuid
The getpwuid function returns information about a user database
entry for the specified uid.
The getpwuid_r function is a reentrant version of getpwuid.
These functions are OpenVMS Alpha only.
Format
#include <pwd.h>
struct passwd *getpwuid (uid_t uid); (ISO POSIX-1)
struct passwd *getpwuid (uid_t uid, . . . ); (DEC C Extension)
int getpwuid_r (uid_t uid, struct passwd *pwd, char *buffer,
size_t bufsize, struct passwd **result);
(ISO POSIX-1)
int getpwuid_r (uid_t uid, struct passwd *pwd, char *buffer,
size_t bufsize, struct passwd **result, . . . );
(DEC C Extension)
230.1 – Function Variants
The getpwuid and getpwuid_r functions have variants named __32_
getpwuid, _getpwuid_r32 and __64_getpwuid, _getpwuid_r64 for use
with 32-bit and 64-bit pointer sizes, respectively.
230.2 – Arguments
uid
The user ID (UID) for which the attributes are to be read.
pwd
The location where the retrieved passwd structure is to be
placed.
buffer
A working buffer for the result argument that is able to hold the
entry in the passwd structure. Storage referenced by the passwd
structure is allocated from the memory provided with the buffer
argument, which is bufsize characters in size.
bufsize
The length of the character array that buffer points to.
result
Upon successful return, result is set to pwd. Upon unsuccessful
return, result is set to NULL.
. . .
An optional argument that can be either 1 or 0. If you specify
1, the directory specification is returned in OpenVMS format. If
you specify 0, the directory specification (pathname) is returned
in UNIX style format. If you omit this argument, the function
returns the directory specification according to your current
command-language interpreter.
230.3 – Description
The getpwuid function searches the user database for an entry
with the specified uid. The function returns the first user entry
in the database with a pw_uid member of the passwd structure that
matches the uid argument.
The passwd structure is defined in the <pwd.h> header file as
follows:
pw_name The user's login name.
pw_uid The numerical user ID.
pw_gid The numerical group ID.
pw_dir The home directory of the user.
pw_shell The initial program for the user.
NOTE
All information generated by the getpwuid function is stored
in a per-thread static area and is overwritten on subsequent
calls to the function.
The getpwuid_r function is the reentrant version of getpwuid.
The getpwuid_r function updates the passwd structure pointed to
by pwd and stores a pointer to that structure at the location
pointed to by result. The structure will contain an entry from
the user database with a matching uid. Storage referenced by the
structure is allocated from the memory provided with the buffer
argument, which is bufsize characters in size. The maximum size
needed for this buffer can be determined with the _SC_GETPW_R_
SIZE_MAX parameter of the sysconf function. On error or if the
requested entry is not found, a NULL pointer is returned at the
location pointed to by result.
Applications wishing to check for error situations should set
errno to 0 before calling getpwuid. If getpwuid returns a NULL
pointer and errno is nonzero, an error occurred.
See also getuid to know how UIC is represented.
230.4 – Return Values
x getpwuid returns a pointer to a valid passwd
structure, if a matching entry is found.
NULL getpwuid returns NULL if an error occurred or
a matching entry was not found. errno is set
to indicate the error. The getpwuid function
may fail if:
o EIO - An I/O error has occurred.
o EINTR - A signal was intercepted during
getpwnam.
o EMFILE - OPEN_MAX file descriptors are
currently open in the calling process.
o ENFILE - The maximum allowable number of
files is currently open in the system.
0 When successful, getpwuid_r returns 0 and
stores a pointer to the updated passwd
structure at the location pointed to by
result.
0 When unsuccessful (on error or if the
requested entry is not found), getpwuid_r
returns 0 and stores a NULL pointer at the
location pointed to by result. The getpwuid_r
function may fail if:
o ERANGE - Insufficient storage was supplied
through buffer and bufsize to contain the
data to be referenced by the resulting
passwd structure.
231 – gets
Reads a line from the standard input (stdin).
Format
#include <stdio.h>
char *gets (char *str);
231.1 – Function Variants
The gets function has variants named _gets32 and _gets64 for use
with 32-bit and 64-bit pointer sizes, respectively.
231.2 – Argument
str
A pointer to a character string that is large enough to hold the
information fetched from stdin.
231.3 – Description
The new-line character (\n) that ends the line is replaced by
the function with an ASCII null character (\0).
When stdin is opened in record mode, gets treats the end of a
record the same as a new-line character and, therefore, reads
up to and including a new-line character or to the end of the
record.
231.4 – Return Values
x A pointer to the str argument.
NULL Indicates that an error has occurred or that
the end-of-file was encountered before a new-
line character was encountered. The contents
of str are undefined if a read error occurs.
232 – getsid
Gets the process group ID of the session leader.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
pid_t getsid (pid_t pid);
232.1 – Argument
pid
The process ID of the process whose session leader process group
ID is being requested.
232.2 – Description
The getsid function obtains the process group ID of the process
that is the session leader of the process specified by pid. If
pid is (pid_t)0, it specifies the calling process.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
232.3 – Return Values
x The process group ID of the session leader of
the specified process.
(pid_t)-1 Indicates an error. The function sets errno to
one of the following values:
o EPERM - The process specified by pid is
not in the same session as the calling
process, and the implementation does not
allow access to the process group ID of
the session leader of that process from the
calling process.
o ESRCH - There is no process with a process
ID of pid.
233 – [w]getstr
Get a string from the terminal screen, store it in the variable
str, and echo it on the specified window. The getstr function
works on the stdscr window.
Format
#include <curses.h>
int getstr (char *str);
int wgetstr (WINDOW *win, char *str);
233.1 – Arguments
win
A pointer to the window.
str
Must be large enough to hold the character string fetched from
the window.
233.2 – Description
The getstr and wgetstr functions refresh the specified window
before fetching a string. The new-line terminator is stripped
from the fetched string. For more information, see the scrollok
function.
233.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the screen
scroll illegally.
234 – gettimeofday
Gets the date and time.
Format
#include <time.h>
int gettimeofday (struct timeval *tp, void *tzp);
234.1 – Arguments
tp
Pointer to a timeval structure, defined in the <time.h> header
file.
tzp
A NULL pointer. If this argument is not a NULL pointer, it is
ignored.
234.2 – Description
The gettimeofday function gets the current time (expressed as
seconds and microseconds) since 00::00 Coordinated Universal
Time, January 1, 1970. The current time is stored in the timeval
structure pointed to by the tp argument.
The tzp argument is intended to hold time-zone information set
by the kernel. However, because the OpenVMS kernel does not
set time-zone information, the tzp argument should be NULL. If
it is not NULL, it is ignored. This function is supported for
compatibility with BSD programs.
If the value of the SYS$TIMEZONE_DIFFERENTIAL logical is wrong,
the function fails with errno set to EINVAL.
234.3 – Return Values
0 Indicates success.
-1 An error occurred. errno is set to indicate
the error.
235 – getuid
With POSIX IDs disabled, this function is equivalent to geteuid
and returns the member number (in OpenVMS terms) from the user
identification code (UIC).
With POSIX IDs enabled, returns the real user ID.
Format
#include <unistd.h>
uid_t getuid (void);
235.1 – Description
The getuid function can be used with POSIX style identifiers or
with UIC-based identifiers.
POSIX style IDs are supported on OpenVMS Version 7.3-2 and
higher.
With POSIX style IDs disabled (the default), the geteuid and
getuid functions are equivalent and return the member number from
the current UIC as follows:
o For programs compiled with the _VMS_V6_SOURCE feature-
test macro or programs that do not include the <unistd.h>
header file, the getuid and geteuid functions return the
member number of the OpenVMS UIC. For example, if the UIC
is [313,31], then the member number, 31, is returned.
o For programs compiled without the _VMS_V6_SOURCE feature-
test macro that do include the <unistd.h> header file, the
full UIC is returned in decimal after converting the octal
representation to decimal. For example, if the UIC is [313,
31] then 13303833 is returned. (13303833 = 25 + 203 * 65536;
Octal 31 = 25 decimal; Octal 313 = 203 decimal.)
With POSIX style IDs enabled, geteuid returns the effective user
ID of the calling process, and getuid returns the real user ID of
the calling process.
See also getegid and getgid.
235.2 – Return Value
x The real user ID (POSIX IDs enabled), or the
member number from the current UIC or the full
UIC (POSIX IDs disabled).
236 – getw
Returns characters from a specified file.
Format
#include <stdio.h>
int getw (FILE *file_ptr);
236.1 – Argument
file_ptr
A pointer to the file to be accessed.
236.2 – Description
The getw function returns the next four characters from the
specified input file as an int.
236.3 – Return Values
x The next four characters, in an int.
EOF Indicates that the end-of-file was encountered
during the retrieval of any of the four
characters and all four characters were
lost. Since EOF is an acceptable integer,
use feof and ferror to check the success of
the function.
237 – getwc
Reads the next character from a specified file, and converts it
to a wide-character code.
Format
#include <wchar.h>
wint_t getwc (FILE *file_ptr);
237.1 – Argument
file_ptr
A pointer to the file to be accessed.
237.2 – Description
Since getwc is implemented as a macro, a file pointer argument
with side effects (for example getwc (*f++)) might be evaluated
incorrectly. In such a case, use the fgetwc function instead. See
the fgetwc function.
237.3 – Return Values
n The returned character.
WEOF Indicates the end-of-file or an error. If an
error occurs, the function sets errno. For a
list of the values set by this function, see
fgetwc.
238 – getwchar
Reads a single wide character from the standard input (stdin).
Format
#include <wchar.h>
wint_t getwchar (void);
238.1 – Description
The getwchar function is identical to fgetwc(stdin).
238.2 – Return Values
x The next character from stdin, converted to
wint_t.
WEOF Indicates the end-of-file or an error. If an
error occurs, the function sets errno. For a
list of the values set by this function, see
fgetwc.
239 – getyx
Puts the (y,x) coordinates of the current cursor position on win
in the variables y and x.
Format
#include <curses.h>
getyx (WINDOW *win, int y, int x);
239.1 – Arguments
win
Must be a pointer to the window.
y
Must be a valid lvalue.
x
Must be a valid lvalue.
240 – glob
Returns a list of existing files for a user supplied pathname
(with optional wildcards).
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <glob.h>
int glob (const char *pattern, int flags, int (*errfunc)(const
char *epath, int eerrno), glob_t *pglob);
240.1 – Function Variants
The glob function has variants named _glob32 and _glob64 for use
with 32-bit and 64-bit pointer sizes, respectively.
240.2 – Arguments
pattern
The pattern string to match with accessible files and pathnames.
This pattern can have wildcards.
flags
Controls the customizable behavior of the glob function.
errfunc
An optional function that, if specified, is called when the glob
function detects an error condition, or if not specified, is
NULL.
epath
First argument of the optional errfunc function, epath is the
pathname that failed because a directory could not be opened or
read.
eerrno
Second argument of the optional errfunc function, eerrno is the
errno value from a failure specified by the epath argument as set
by the opendir, readdir, or stat functions.
pglob
Pointer to a glob_t structure that returns the matching
accessible existing filenames. The structure is allocated by the
caller. The array of structures containing the located filenames
that match the pattern argument are stored by the glob function
into the structure. The last entry is a NULL pointer.
The structure type glob_t is defined in the <glob.h> header file
and includes at least the following members:
size_t gl_pathc //Count of paths matched by pattern.
char ** gl_pathv //Pointer to a list of matched pathnames.
size_t gl_offs //Slots to reserve at the beginning of gl_pathv.
240.3 – Description
The glob function constructs a list of accessible files that
match the pattern argument.
The glob function operates in one of two modes: UNIX mode or
OpenVMS mode.
You can select UNIX mode explicitly by enabling the feature
logical DECC$GLOB_UNIX_STYLE, which is disabled by default.
The glob function defaults to OpenVMS mode unless one of the
following conditions is met (in which case glob uses UNIX mode):
o The DECC$GLOB_UNIX_STYLE is enabled.
o The DECC$FILENAME_UNIX_ONLY feature logical is enabled.
o The glob function checks the specified pattern for pathname
indications, such as directory delimiters, and determines it
to be a UNIX style pathname.
OpenVMS mode
This mode allows an OpenVMS programmer to give an OpenVMS style
pattern to the glob function and get expected OpenVMS style
output. The OpenVMS style pattern is what a user would expect
from DCL commands or as input to the SYS$PARSE and SYS$SEARCH
system routines.
In this mode, you can use any of the expected OpenVMS wildcards
(see the OpenVMS documentation for additional information).
OpenVMS mode does not support the UNIX wildcard ?, or [] pattern
matching. OpenVMS users expect [] to be available as directory
delimiters.
Some additional behavior differences between OpenVMS mode and
UNIX mode:
o OpenVMS mode outputs full file specifications, not relative
ones, as in UNIX mode.
o The GLOB_MARK flag is ignored in OpenVMS mode because it
is not meaningful to append a slash (/) to a directory on
OpenVMS.
For example:
Sample pattern input Sample output
[.SUBDIR1]A.TXT DEV:[DIR.SUBDIR1]A.TXT;1
[.SUB*]%.* DEV:[DIR.SUBDIR1]A.TXT;1
UNIX mode
You can enable this mode explicitly with:
$ DEFINE DECC$GLOB_UNIX_STYLE ENABLE
UNIX mode is also enabled if the DECC$FILENAME_UNIX_ONLY feature
logical is set, or if the glob function determines that the
specified pattern looks like a UNIX style pathname.
In UNIX mode, the glob function follows the X/Open specification
where possible.
For example:
Sample pattern input Sample output
./a/b/c ./a/b/c
./?/b/* ./a/b/c
[a-c] c
Standard Description
The glob function matches all accessible pathnames against this
pattern and develops a list of all pathnames that match. To
have access to a pathname, the glob function requires search
permission on every component of a pathname except the last, and
read permission on each directory of any filename component of
the pattern argument.
The glob function stores the number of matched pathnames and a
pointer to a list of pointers to pathnames in the pglob argument.
The pathnames are sorted, based on the setting of the LC_COLLATE
category in the current locale. The first pointer after the last
pathname is NULL. If the pattern does not match any pathnames,
the returned number of matched pathnames is 0.
It is the caller's responsibility to create the structure pointed
to by the pglob argument. The glob function allocates other space
as needed. The globfree function frees any space associated with
the pglob argument as a result of a previous call to the glob
function.
The flags argument is used to control the behavior of the glob
function. The flags value is the bitwise inclusive OR (|) of any
of the following constants, which are defined in the <glob.h>
header file:
GLOB_APPEND Appends pathnames located with this call to any
pathnames previously located.
GLOB_DOOFFS Uses the gl_offs structure to specify the number
of NULL pointers to add to the beginning of the gl_
pathv component of the pglob argument.
GLOB_ERR Causes the glob function to return when it
encounters a directory that it cannot open or
read. If the GLOB_ERR flag is not set, the glob
function continues to find matches if it encounters
a directory that it cannot open or read.
GLOB_MARK Specifies that each pathname that is a directory
should have a slash (/) appended. GLOB_MARK is
ignored in OpenVMS mode because it is not meaningful
to append a slash to a directory on OpenVMS systems.
GLOB_ If the pattern argument does not match any pathname,
NOCHECK then the glob function returns a list consisting
only of the pattern argument, and the number of
matched pathnames is 1.
GLOB_ If the GLOB_NOESCAPE flag is set, a backslash (\)
NOESCAPE cannot be used to escape metacharacters.
The GLOB_APPEND flag can be used to append a new set of pathnames
to those found in a previous call to the glob function. The
following rules apply when two or more calls to the glob function
are made with the same value of the pglob argument, and without
intervening calls to the globfree function:
o If the application sets the GLOB_DOOFFS flag in the first call
to the glob function, then it is also set in the second call,
and the value of the gl_offs field of the pglob argument is
not modified between the calls.
o If the application did not set the GLOB_DOOFFS flag in the
first call to the glob function, then it is not set in the
second call.
o After the second call, pglob->gl_pathv points to a list
containing the following:
- Zero or more NULLs, as specified by the GLOB_DOOFFS flag
and pglob->gl_offs.
- Pointers to the pathnames that were in the pglob->gl_pathv
list before the call, in the same order as after the first
call to the glob function.
- Pointers to the new pathnames generated by the second call,
in the specified order.
o The count returned in the pglob->gl_offs argument is the total
number of pathnames from the two calls.
o The application should not modify the pglob->gl_pathc or
pglob->gl_pathv fields between the two calls.
On successful completion, the glob function returns a value of 0
(zero). The pglob->gl_pathc field returns the number of matched
pathnames and the pglob->gl_pathv field contains a pointer to
a NULL-terminated list of matched and sorted pathnames. If the
number of matched pathnames in the pglob->gl_pathc argument is 0
(zero), the pointer in the pglob->gl_pathv argument is undefined.
If the glob function terminates because of an error, the function
returns one of the nonzero constants GLOB_ABORTED, GLOB_NOMATCH,
or GLOB_NOSPACE, defined in the <glob.h> header file. In this
case, the pglob argument values are still set as defined above.
If, during the search, a directory is encountered that cannot
be opened or read and the errfunc argument value is not NULL,
the glob function calls errfunc with the two arguments epath and
eerno:
epath-The pathname that failed because a directory could not
be opened or read.
eerno-The errno value from a failure specified by the epath
argument as set by the opendir, readdir, or stat functions.
If errfunc is called and returns nonzero, or if the GLOB_ERR flag
is set in flags, the glob function stops the scan and returns
GLOB_ABORTED after setting the pglob argument to reflect the
pathnames already scanned. If GLOB_ERR is not set and either
errfunc is NULL or errfunc returns zero, the error is ignored.
No errno values are returned.
See also globfree, readdir, and stat.
240.4 – Return Values
0 Successful completion.
GLOB_ABORTED The scan was stopped because GLOB_ERROR was
set or errfunc returned a nonzero value.
GLOB_NOMATCH The pattern does not match any existing
pathname, and GLOB_NOCHECK was not set in
flags.
GLOB_NOSPACE An attempt to allocate memory failed.
241 – globfree
Frees any space associated with the pglob argument resulting from
a previous call to the glob function.
Format
#include <glob.h>
void globfree (glob_t *pglob);
241.1 – Function Variants
The globfree function has variants named _globfree32 and _
globfree64 for use with 32-bit and 64-bit pointer sizes,
respectively.
241.2 – Argument
pglob
Pointer to a previously allocated glob_t structure.
241.3 – Description
The globfree function frees any space associated with the pglob
argument resulting from a previous call to the glob function. The
globfree function returns no value.
242 – gmtime
Converts time units to the broken-down UTC time.
Format
#include <time.h>
struct tm *gmtime (const time_t *timer);
struct tm *gmtime_r (const time_t *timer, struct tm *result);
(ISO POSIX-1)
242.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to
the gmtime_r function that is equivalent to the behavior before
OpenVMS Version 7.0.
242.2 – Arguments
timer
Points to a variable that specifies a time value in seconds since
the Epoch.
result
A pointer to a tm structure where the result is stored.
The tm structure is defined in the <time.h> header, and is also
shown in tm Structure in the description of localtime.
242.3 – Description
The gmtime and gmtime_r functions convert the time (in seconds
since the Epoch) pointed to by timer into a broken-down time,
expressed as Coordinated Universal Time (UTC), and store it in a
tm structure.
The difference between the gmtime_r and gmtime functions is that
the former puts the result into a user-specified tm structure
where the result is stored. The latter puts the result into
thread-specific static memory allocated by the C RTL,
and which is overwritten by subsequent calls to gmtime; you must
make a copy if you want to save it.
On success, gmtime returns a pointer to the tm structure; gmtime_
r returns its second argument. On failure, these functions return
the NULL pointer.
NOTE
Generally speaking, UTC-based time functions can affect in-
memory time-zone information, which is processwide data.
However, if the system time zone remains the same during
the execution of the application (which is the common case)
and the cache of timezone files is enabled (which is the
default), then the _r variant of the time functions asctime_
r, ctime_r, gmtime_r and localtime_r, is both thread-safe
and AST-reentrant.
If, however, the system time zone can change during the
execution of the application or the cache of timezone files
is not enabled, then both variants of the UTC-based time
functions belong to the third class of functions, which are
neither thread-safe nor AST-reentrant.
242.4 – Return Values
x Pointer to a tm structure.
NULL Indicates an error; errno is set to the
following value:
o EINVAL - The timer argument is NULL.
243 – gsignal
Generates a specified software signal, which invokes the action
routine established by a signal, ssignal, or sigvec function.
Format
#include <signal.h>
int gsignal (int sig [, int sigcode]);
243.1 – Arguments
sig
The signal to be generated.
sigcode
An optional signal code. For example, signal SIGFPE-the
arithmetic trap signal-has 10 different codes, each representing
a different type of arithmetic trap.
The signal codes can be represented by mnemonics or numbers. The
arithmetic trap codes are represented by the numbers 1 to 10, but
the SIGILL codes are represented by the numbers 0 to 2. The code
values are defined in the <signal.h> header file.
243.2 – Description
Calling the gsignal function has one of the following results:
o If gsignal specifies a sig argument that is outside the range
defined in the <signal.h> header file, then gsignal returns 0
and sets errno to EINVAL.
o If signal, ssignal, or sigvec establishes SIG_DFL (default
action) for the signal, then gsignal does not return. The
image is exited with the OpenVMS error code corresponding to
the signal.
o If signal, ssignal, or sigvec establishes SIG_IGN (ignore
signal) as the action for the signal, then gsignal returns its
argument, sig.
o signal, ssignal, or sigvec must be used to establish an action
routine for the signal. That function is called and its return
value is returned by gsignal.
See the Error and Signal Handling chapter of the C RTL Reference
Manual for more information.
See also raise, signal, ssignal, and sigvec.
243.3 – Return Values
0 Indicates a sig argument that is outside the
range defined in the <signal.h> header file;
errno is set to EINVAL.
sig Indicates that SIG_IGN (ignore signal) has
been established as the action for the signal.
x Indicates that signal, ssignal, or sigvec has
established an action function for the signal.
That function is called, and its return value
is returned by gsignal.
244 – hypot
Returns the length of the hypotenuse of a right triangle.
Format
#include <math.h>
double hypot (double x, double y);
float hypotf (float x, float y); (Integrity servers, Alpha)
long double hypotl (long double x, long double y);
(Integrity servers, Alpha)
244.1 – Arguments
x
A real value.
y
A real value.
244.2 – Description
The hypot functions return the length of the hypotenuse of a
right triangle, where x and y represent the perpendicular sides
of the triangle. The length is calculated as:
sqrt(x2 + y2)
On overflow, the return value is undefined, and errno is set to
ERANGE.
244.3 – Return Values
x The length of the hypotenuse.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
0 Underflow occurred; errno is set to ERANGE.
NaN x or y is NaN; errno is set to EDOM.
245 – iconv
Converts characters coded in one codeset to characters coded in
another codeset.
Format
#include <iconv.h>
size_t iconv (iconv_t cd, const char **inbuf, size_t
*inbytesleft, char **outbuf, size_t
*outbytesleft);
245.1 – Arguments
cd
A conversion descriptor. This is returned by a successful call to
iconv_open.
inbuf
A pointer to a variable that points to the first character in the
input buffer.
inbytesleft
Initially, this argument is a pointer to a variable that
indicates the number of bytes to the end of the input buffer
(inbuf). When the conversion is completed, the variable indicates
the number of bytes in inbuf not converted.
outbuf
A pointer to a variable that points to the first available byte
in the output buffer. The output buffer contains the converted
characters.
outbytesleft
Initially, this argument is a pointer to a variable that
indicates the number of bytes to the end of the output buffer
(outbuf). When the conversion is completed, the variable
indicates the number of bytes left in outbuf.
245.2 – Description
The iconv function converts characters in the buffer pointed
to by inbuf to characters in another code set. The resulting
characters are stored in the buffer pointed to by outbuf. The
conversion type is specified by the conversion descriptor cd.
This descriptor is returned from a successful call to iconv_open.
If an invalid character is found in the input buffer, the
conversion stops after the last successful conversion. The
variable pointed to by inbytesleft is updated to reflect the
number of bytes in the input buffer that are not converted. The
variable pointed to by outbytesleft is updated to reflect the
number of bytes remaining in the output buffer.
245.3 – Return Values
x Number of nonidentical conversions performed.
Indicates successful conversion. In most
cases, 0 is returned.
(size_t) -1 Indicates an error condition. The function
sets errno to one of the following:
o EBADF - The cd argument is not a valid
conversion descriptor.
o EILSEQ - The conversion stops when an
invalid character detected.
o E2BIG - The conversion stops because of
insufficient space in the output buffer.
o EINVAL - The conversion stops because of
an incomplete character at the end of the
input buffer.
246 – iconv_close
Deallocates a specified conversion descriptor and the resources
allocated to the descriptor.
Format
#include <iconv.h>
int iconv_close (iconv_t cd);
246.1 – Argument
cd
The conversion descriptor to be deallocated. A conversion
descriptor is returned by a successful call to iconv_open.
246.2 – Return Values
0 Indicates that the conversion descriptor was
successfully deallocated.
-1 Indicates an error occurred. The function sets
errno to one of the following:
o EBADF - The cd argument is not a valid
conversion descriptor.
o EVMSERR - Nontranslatable OpenVMS error
occur. vaxc$errno contains the VMS error
code.
247 – iconv_open
Allocates a conversion descriptor for a specified codeset
conversion.
Format
#include <iconv.h>
iconv_t iconv_open (const char *tocode, const char *fromcode);
247.1 – Arguments
tocode
The name of the codeset to which characters are converted.
fromcode
The name of the source codeset. See the "Developing International
Software" chapter of the VSI C RTL Reference Manual for
information on obtaining a list of currently available codesets
or for details on adding new codesets.
247.2 – Return Values
x A conversion descriptor. Indicates the call
was successful. This descriptor is used in
subsequent calls to iconv
(iconv_t) -1 Indicates an error occurred. The function sets
errno to one of the following:
o EMFILE - The process does not have enough
I/O channels to open a file.
o ENOMEM - Insufficient space is available.
o EINVAL - The conversion specified by
fromcode and tocode is not supported.
o EVMSERR - Nontranslatable OpenVMS error
occur. vaxc$errno contains the OpenVMS
error code. A value of SS$_BADCHKSUM in
vaxc$errno indicates that a conversion
table file was found, but its contents is
corrupted. A value of SS$_IDMISMATCH in
vaxc$errno indicates that the conversion
table file version does not match the
version of the C Run-Time Library.
247.3 – Example
#include <stdio.h>
#include <iconv.h>
#include <errno.h>
int main()
{
/* Declare variables to be used */
char fromcodeset[30];
char tocodeset[30];
int iconv_opened;
iconv_t iconv_struct; /* Iconv descriptor */
/* Initialize variables */
sprintf(fromcodeset, "DECHANYU");
sprintf(tocodeset, "EUCTW");
iconv_opened = FALSE;
/* Attempt to create a conversion descriptor for the */
/* codesets specified. If the return value from */
/* iconv_open is -1 then an error has occurred. */
/* Check the value of errno. */
if ((iconv_struct = iconv_open(tocodeset, fromcodeset))
/* Check the value of errno */
switch (errno) {
case EMFILE:
case ENFILE:
printf("Too many iconv conversion files open\n");
break;
case ENOMEM:
printf("Not enough memory\n");
break;
case EINVAL:
printf("Unsupported conversion\n");
break;
default:
printf("Unexpected error from iconv_open\n");
break;
}
}
else
/* Successfully allocated a conversion descriptor */
iconv_opened = TRUE;
/* Was a conversion descriptor allocated */
if (iconv_opened) {
/* Attempt to deallocate the conversion descriptor. */
/* If iconv_close returns -1 then an error has */
/* occurred. */
if (iconv_close(iconv_struct) == -1) {
/* An error occurred. Check the value of errno */
switch (errno) {
case EBADF:
printf("Conversion descriptor is invalid\n");
break;
default:
printf("Unexpected error from iconv_close\n");
break;
}
}
}
return (EXIT_FAILURE);
}
248 – ilogb
Returns the exponent part of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
int ilogb (double x);
int ilogbf (float x);
int ilogbl (long double x);
248.1 – Argument
x
A real value.
248.2 – Description
The ilogb functions return the exponent part of their argument
x. Formally, the return value is the integral part of logr|x| as
a signed integral value, for nonzero x, where r is the radix of
the machine's floating-point arithmetic, which is the value of
FLT_RADIX defined in <float.h>.
248.3 – Return Values
n Upon success, the exponent part of x as a
signed integer value. These functions are
equivalent to calling the corresponding logb
function and casting the returned value to
type int.
249 – [w]inch
Return the character at the current cursor position on the
specified window without making changes to the window. The inch
function acts on the stdscr window.
Format
#include <curses.h>
char inch();
char winch (WINDOW *win);
249.1 – Argument
win
A pointer to the window.
249.2 – Return Values
x The returned character.
ERR Indicates an input error.
250 – index
Searches for a character in a string.
Format
#include <strings.h>
char *index (const char *s, int c);
250.1 – Function Variants
The index function has variants named _index32 and _index64 for
use with 32-bit and 64-bit pointer sizes, respectively.
250.2 – Arguments
s
The string to search.
c
The character to search for.
250.3 – Description
The index function is identical to the strchr function, and is
provided for compatibility with some UNIX implementations.
251 – initscr
Initializes the terminal-type data and all screen functions. You
must call initscr before using any of the curses functions.
Format
#include <curses.h>
void initscr (void);
251.1 – Description
The OpenVMS Curses version of the initscr function clears the
screen before doing the initialization. The BSD-based Curses
version does not.
252 – initstate
Initializes random-number generators.
Format
#include <stdlib.h>
char *initstate (unsigned int seed, char *state, int size);
252.1 – Arguments
seed
An initial seed value.
state
Pointer to an array of state information.
size
The size of the state information array.
252.2 – Description
The initstate function initializes random-number generators. It
lets you initialize, for future use, a state array passed as an
argument. The size, in bytes, of the state array is used by the
initstate function to decide how sophisticated a random-number
generator to use; the larger the state array, the more random the
numbers.
Values for the amount of state information are 8, 32, 64, 128,
and 256 bytes. Amounts less than 8 bytes generate an error, while
other amounts are rounded down to the nearest known value.
The seed argument specifies a starting point for the random-
number sequence and provides for restarting at the same point.
The initstate function returns a pointer to the previous state
information array.
Once you initialize a state, the setstate function allows rapid
switching between states. The array defined by the state argument
is used for further random-number generation until the initstate
function is called or the setstate function is called again. The
setstate function returns a pointer to the previous state array.
After initialization, you can restart a state array at a
different point in one of two ways:
o Use the initstate function with the desired seed argument,
state array, and size of the array.
o Use the setstate function with the desired state, followed by
the srandom function with the desired seed. The advantage of
using both functions is that you do not have to save the state
array size once you initialize it.
See also setstate, srandom, and random.
252.3 – Return Values
x A pointer to the previous state array
information.
0 Indicates an error. Call made with less than 8
bytes of state information. Further specified
in the global errno.
253 – [w]insch
Insert a character at the current cursor position in the
specified window. The insch function acts on the stdscr window.
Format
#include <curses.h>
int insch (char ch);
int winsch (WINDOW *win, char ch);
253.1 – Arguments
win
A pointer to the window.
ch
The character to be inserted.
253.2 – Description
After the character is inserted, each character on the line
shifts to the right, and the last character in the line is
deleted. For more information, see the scrollok function.
253.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the screen
scroll illegally.
254 – [w]insertln
Insert a line above the line containing the current cursor
position. The insertln function acts on the stdscr window.
Format
#include <curses.h>
int insertln();
int winsertln (WINDOW *win);
254.1 – Argument
win
A pointer to the window.
254.2 – Description
The current line and every line below it shifts down, and the
bottom line disappears. The inserted line is blank and the
current (y,x) coordinates remain the same. For more information,
see the scrollok function.
254.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the screen
scroll illegally.
255 – [w]insstr
Insert a string at the current cursor position in the specified
window. The insstr function acts on the stdscr window.
Format
#include <curses.h>
int insstr (char *str);
int winsstr (WINDOW *win, char *str);
255.1 – Arguments
win
A pointer to the window.
str
A pointer to the string to be inserted.
255.2 – Description
Each character after the string shifts to the right, and the last
character disappears. These functions are specific to VSI C
for OpenVMS Systems and are not portable.
255.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the screen
scroll illegally. For more information, see
the scrollok function.
256 – isalnum
Indicates if a character is classed either as alphabetic or as a
digit in the program's current locale.
Format
#include <ctype.h>
int isalnum (int character);
256.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
256.2 – Return Values
nonzero If alphanumeric.
0 If not alphanumeric.
257 – isalpha
Indicates if a character is classed as an alphabetic character in
the program's current locale.
Format
#include <ctype.h>
int isalpha (int character);
257.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
257.2 – Return Values
nonzero If alphabetic.
0 If not alphabetic.
258 – isapipe
Indicates if a specified file descriptor is associated with a
pipe.
Format
#include <unixio.h>
int isapipe (int file_desc);
258.1 – Argument
file_desc
A file descriptor.
258.2 – Description
For more information about pipes, see the "Subprocess Functions"
chapter of the VSI C RTL Reference Manual.
258.3 – Return Values
1 Indicates an association with a pipe.
0 Indicates no association with a pipe.
-1 Indicates an error (for example, if the file
descriptor is not associated with an open
file).
259 – isascii
Indicates if a character is an ASCII character.
Format
#include <ctype.h>
int isascii (int character);
259.1 – Argument
character
An object of type char.
259.2 – Return Values
nonzero If ASCII.
0 If not ASCII.
260 – isatty
Indicates if a specified file descriptor is associated with a
terminal.
Format
#include <unistd.h>
int isatty (int file_desc);
260.1 – Argument
file_desc
A file descriptor.
260.2 – Return Values
1 If the file descriptor is associated with a
terminal.
0 If the file descriptor is not associated with
a terminal.
-1 Indicates an error (for example, if the file
descriptor is not associated with an open
file).
261 – iscntrl
Indicates if a character is classed as a control character in the
program's current locale.
Format
#include <ctype.h>
int iscntrl (int character);
261.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
261.2 – Return Values
nonzero If a control character.
0 If not a control character.
262 – isdigit
Indicates if a character is classed as a digit in the program's
current locale.
Format
#include <ctype.h>
int isdigit (int character);
262.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
262.2 – Return Values
nonzero If a decimal digit.
0 If not a decimal digit.
263 – isgraph
Indicates if a character is classed as a graphic character in the
program's current locale.
Format
#include <ctype.h>
int isgraph (int character);
263.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
263.2 – Return Values
nonzero If a graphic character.
0 If not a graphic character.
264 – islower
Indicates if a character is classed as a lowercase character in
the program's current locale.
Format
#include <ctype.h>
int islower (int character);
264.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
264.2 – Return Values
nonzero If a lowercase alphabetic character.
0 If not a lowercase alphabetic character.
265 – isnan
Test for a NaN. Returns 1 if the argument is NaN; 0 if not.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
int isnan (double x);
int isnanf (float x);
int isnanl (long double x);
265.1 – Argument
x
A real value.
265.2 – Description
The isnan functions return the integer value 1 (TRUE) if x is NaN
(the IEEE floating point reserved not-a-number value); otherwise,
they return the value 0 (FALSE).
266 – isprint
Indicates if a character is classed as a printing character in
the program's current locale.
Format
#include <ctype.h>
int isprint (int character);
266.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
266.2 – Return Values
nonzero If a printing character.
0 If not a printing character.
267 – ispunct
Indicates if a character is classed as a punctuation character in
the program's current locale.
Format
#include <ctype.h>
int ispunct (int character);
267.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
267.2 – Return Values
nonzero If a punctuation character.
0 If not a punctuation character.
268 – isspace
Indicates if a character is classed as white space in the
program's current locale; that is, if it is an ASCII space, tab
(horizontal or vertical), carriage-return, form-feed, or new-line
character.
Format
#include <ctype.h>
int isspace (int character);
268.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
268.2 – Return Values
nonzero If a white-space character.
0 If not a white-space character.
269 – isupper
Indicates if a character is classed as an uppercase character in
the program's current locale.
Format
#include <ctype.h>
int isupper (int character);
269.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char or must equal the value of the
macro EOF. If it has any other value, the behavior is undefined.
269.2 – Return Values
nonzero If an uppercase alphabetic character.
0 If not an uppercase alphabetic character.
270 – iswalnum
Indicates if a wide character is classed either as alphabetic or
as a digit in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswalnum (wint_t wc);
270.1 – Argument
wc
An object of type wint_t. The value of character must be
representable as a wchar_t in the current locale, or must equal
the value of the macro WEOF. If it has any other value, the
behavior is undefined.
270.2 – Return Values
nonzero If alphanumeric.
0 If not alphanumeric.
271 – iswalpha
Indicates if a wide character is classed as an alphabetic
character in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswalpha (wint_t wc);
271.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
271.2 – Return Values
nonzero If alphabetic.
0 If not alphabetic.
272 – iswcntrl
Indicates if a wide character is classed as a control character
in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswcntrl (wint_t wc);
272.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
272.2 – Return Values
nonzero If a control character.
0 If not a control character.
273 – iswctype
Indicates if a wide character has a specified property.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswctype (wint_t wc, wctype_t wc_prop);
273.1 – Arguments
wc
An object of type wint_t. The value of wc must be representable
as a valid wide-character code in the current locale, or must
equal the value of the macro WEOF. If it has any other value, the
behavior is undefined.
wc_prop
A valid property name in the current locale. This is set up by
calling the wctype function.
273.2 – Description
The iswctype function tests whether wc has the character-class
property wc_prop. Set wc_prop by calling the wctype function.
See also wctype.
273.3 – Return Values
nonzero If the character has the property wc_prop.
0 If the character does not have the property
wc_prop.
273.4 – Example
#include <locale.h>
#include <wchar.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
/* This test will set up the "upper" character class using */
/* wctype() and then verify whether the characters 'a' and 'A' */
/* are members of this class */
#include <stdlib.h>
main()
{
wchar_t w_char1,
w_char2;
wctype_t ret_val;
char *char1 = "a";
char *char2 = "A";
ret_val = wctype("upper");
/* Convert char1 to wide-character format - w_char1 */
if (mbtowc(&w_char1, char1, 1) == -1) {
perror("mbtowc");
exit(EXIT_FAILURE);
}
if (iswctype((wint_t) w_char1, ret_val))
printf("[%C] is a member of the character class upper\n",
w_char1);
else
printf("[%C] is not a member of the character class upper\n",
w_char1);
/* Convert char2 to wide-character format - w_char2 */
if (mbtowc(&w_char2, char2, 1) == -1) {
perror("mbtowc");
exit(EXIT_FAILURE);
}
if (iswctype((wint_t) w_char2, ret_val))
printf("[%C] is a member of the character class upper\n",
w_char2);
else
printf("[%C] is not a member of the character class upper\n",
w_char2);
}
Running the example program produces the following result:
[a] is not a member of the character class upper
[A] is a member of the character class upper
274 – iswdigit
Indicates if a wide character is classed as a digit in the
program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswdigit (wint_t wc);
274.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
274.2 – Return Values
nonzero If a decimal digit.
0 If not a decimal digit.
275 – iswgraph
Indicates if a wide character is classed as a graphic character
in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswgraph (wint_t wc);
275.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
275.2 – Return Values
nonzero If a graphic character.
0 If not a graphic character.
276 – iswlower
Indicates if a wide character is classed as a lowercase character
in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswlower (wint_t wc);
276.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
276.2 – Return Values
nonzero If a lowercase character.
0 If not a lowercase character.
277 – iswprint
Indicates if a wide character is classed as a printing character
in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswprint (wint_t wc);
277.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
277.2 – Return Values
nonzero If a printing character.
0 If not a printing character.
278 – iswpunct
Indicates if a wide character is classed as a punctuation
character in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswpunct (wint_t wc);
278.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
278.2 – Return Values
nonzero If a punctuation character.
0 If not a punctuation character.
279 – iswspace
Indicates if a wide character is classed as a space character in
the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswspace (wint_t wc);
279.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
279.2 – Return Values
nonzero If a white-space character.
0 If not a white-space character.
280 – iswupper
Indicates if a wide character is classed as an uppercase
character in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswupper (wint_t wc);
280.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
280.2 – Return Values
nonzero If an uppercase character.
0 If not an uppercase character.
281 – iswxdigit
Indicates if a wide character is a hexadecimal digit (0 to 9, A
to F, or a to f) in the program's current locale.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int iswxdigit (wint_t wc);
281.1 – Argument
wc
An object of type wint_t. The value of wc must be representable
as a wchar_t in the current locale, or must equal the value
of the macro WEOF. If it has any other value, the behavior is
undefined.
281.2 – Return Values
nonzero If a hexadecimal digit.
0 If not a hexadecimal digit.
282 – isxdigit
Indicates if a character is a hexadecimal digit (0 to 9, A to F,
or a to f) in the program's current locale.
Format
#include <ctype.h>
int isxdigit (int character);
282.1 – Argument
character
An object of type int. The value of character must be
representable as an unsigned char in the current locale, or must
equal the value of the macro EOF. If it has any other value, the
behavior is undefined.
282.2 – Return Values
nonzero If a hexadecimal digit.
0 If not a hexadecimal digit.
283 – j0,j1,jn
Compute Bessel functions of the first kind.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double j0 (double x);
float j0f (float x);
long double j0l (long double x);
double j1 (double x);
float j1f (float x);
long double j1l (long double x);
double jn (int n, double x);
float jnf (int n, float x);
long double jnl (int n, long double x);
283.1 – Arguments
x
A real value.
n
An integer.
283.2 – Description
The j0 functions return the value of the Bessel function of the
first kind of order 0.
The j1 functions return the value of the Bessel function of the
first kind of order 1.
The jn functions return the value of the Bessel function of the
first kind of order n.
The j1 and jn functions can result in an underflow as x gets
small. The largest value of x for which this occurs is a function
of n.
283.3 – Return Values
x The relevant Bessel value of x of the first
kind.
0 The value of the x argument is too large, or
underflow occurred; errno is set to ERANGE.
NaN x is NaN; errno is set to EDOM.
284 – jrand48
Generates uniformly distributed pseudorandom-number sequences.
Returns 48-bit signed, long integers.
Format
#include <stdlib.h>
long int jrand48 (unsigned short int xsubi[3]);
284.1 – Argument
xsubi
An array of three short ints that form a 48-bit integer when
concatenated together.
284.2 – Description
The jrand48 function generates pseudorandom numbers using the
linear congruential algorithm and 48-bit integer arithmetic.
The function returns signed long integers uniformly distributed
over the range of y values, such that -231
The function works by generating a sequence of 48-bit integer
values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n >= 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke the lcong48 function, the multiplier
value a and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The jrand48 function requires that the calling program pass an
array as the xsubi argument, which for the first call must be
initialized to the initial value of the pseudorandom-number
sequence. Unlike the drand48 function, it is not necessary to
call an initialization function prior to the first call.
By using different arguments, jrand48 allows separate modules
of a large program to generate several independent sequences of
pseudorandom numbers. For example, the sequence of numbers that
one module generates does not depend upon how many times the
function is called by other modules.
284.3 – Return Value
n Signed, long integers uniformly distributed
over the range -231
285 – kill
Sends a signal to the process specified by a process ID.
Format
#include <signal.h>
int kill (int pid, int sig);
285.1 – Arguments
pid
The process ID.
sig
The signal code.
285.2 – Description
The kill function is restricted to C and C++ programs that
include the main function.
The kill function sends a signal to a process, as if the process
had called raise. If the signal is not trapped or ignored by the
target program, the program exits.
OpenVMS VAX and Alpha implement different rules about what
process you are allowed to send signals to. A program always has
privileges to send a signal to a child started with vfork/exec.
For other processes, the results are determined by the OpenVMS
security model for your system.
Because of an OpenVMS restriction, the kill function cannot
deliver a signal to a target process that runs an image installed
with privileges.
Unless you have system privileges, the sending and receiving
processes must have the same user identification code (UIC).
On OpenVMS systems before Version 7.0, kill treats a signal value
of 0 as if SIGKILL were specified.
For OpenVMS Version 7.0 and higher systems, if you include
<stdlib.h> and compile with the _POSIX_EXIT feature-test macro
set, then:
o If the signal value is 0, kill validates the process ID but
does not send any signals.
o If the process ID is not valid, kill returns -1 and sets errno
to ESRCH.
285.3 – Return Values
0 Indicates that kill was successfully queued.
-1 Indicates errors. The receiving process may
have a different UIC and you are not a system
user, or the receiving process does not exist.
286 – l64a
Converts a long integer to a character string.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdlib.h>
char *l64a (long l);
286.1 – Argument
l
A long integer that is to be converted to a character string.
286.2 – Description
The a64l and l64a functions are used to maintain numbers stored
in base-64 ASCII characters:
o a64l converts a character string to a long integer.
o l64a converts a long integer to a character string.
Each character used to store a long integer represents a numeric
value from 0 through 63. Up to six characters can be used to
represent a long integer.
The characters are translated as follows:
o A period (.) represents 0.
o A slash (/) represents 1.
o The numbers 0 through 9 represent 2 through 11.
o Uppercase letters A through Z represent 12 through 37.
o Lowercase letters a through z represent 38 through 63.
The l64a function takes a long integer and returns a pointer to a
corresponding base-64 notation of the least significant 32 bits.
The value returned by l64a is a pointer to a thread-specific
buffer whose contents are overwritten on subsequent calls from
the same
See also a64l.
286.3 – Return Value
x Upon successful completion, a pointer to
the corresponding base-64 ASCII character-
string notation. If the l parameter is 0, l64a
returns a pointer to an empty string.
287 – labs
Returns the absolute value of an integer as a long int.
Format
#include <stdlib.h>
long int labs (long int j);
287.1 – Argument
j
A value of type long int.
288 – lchown
Changes the user and group ownership of the specified file.
Format
#include <unistd.h>
int lchown (const char *file_path, uid_t file_owner, gid_t
file_group);
288.1 – Arguments
file_path
The name of the file for which you want to change the owner and
group IDs.
file_owner
The new user ID for the file.
file_group
The new group ID for the file.
288.2 – Description
The lchown function changes the owner and/or group of the
specified file (file_path). If the file is a symbolic link, the
owner of the symbolic link is modified (in contrast to chown
which would modify the file that the symbolic link points to).
See also symlink, unlink, readlink, realpath, and lstat.
288.3 – Return Values
0 Successful completion.
-1 Indicates an error. errno is set to any errno
value returned by chown.
289 – lcong48
Initializes a 48-bit uniformly distributed pseudorandom-number
sequence.
Format
#include <stdlib.h>
void lcong48 (unsigned short int param[7]);
289.1 – Argument
param
An array that in turn specifies the initial Xi, the multiplier
value a, and the addend value c.
289.2 – Description
The lcong48 function generates pseudorandom numbers using the
linear congruential algorithm and 48-bit integer arithmetic.
You can use lcong48 to initialize the random number generator
before you call any of the following functions:
drand48
lrand48
mrand48
The lcong48 function specifies the initial Xi value, the
multiplier value a, and the addend value c. The param array
elements specify the following:
param[0- Xi
2]
param[3- Multiplier a value
5]
param[6] 16-bit addend c value
After lcong48 has been called, a subsequent call to either
srand48 or seed48 restores the standard a and c as specified
previously.
The lcong48 function does not return a value.
See also drand48, lrand48, mrand48, srand48, and seed48.
290 – ldexp
Returns its first argument multiplied by 2 raised to the power of
its second argument; that is, x(2n).
Format
#include <math.h>
double ldexp (double x, int n);
float ldexp (float x, int n); (Integrity servers, Alpha)
long double ldexp (long double x, int n);
(Integrity servers, Alpha)
290.1 – Arguments
x
A base value of type double, float, or long double that is to be
multiplied by 2n.
n
The integer exponent value to which 2 is raised.
290.2 – Return Values
x(2n) The first argument multiplied by 2 raised to
the power of the second argument.
0 Underflow occurred; errno is set to ERANGE.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
NaN x is NaN; errno is set to EDOM.
291 – ldiv
Returns the quotient and the remainder after the division of its
arguments.
Format
#include <stdlib.h>
ldiv_t ldiv (long int numer, long int denom);
291.1 – Arguments
numer
A numerator of type long int.
denom
A denominator of type long int.
291.2 – Description
The type ldiv_t is defined in the <stdlib.h> header file as
follows:
typedef struct
{
long quot, rem;
} ldiv_t;
See also div.
292 – leaveok
Signals Curses to leave the cursor at the current coordinates
after an update to the window.
Format
#include <curses.h>
leaveok (WINDOW *win, bool boolf);
292.1 – Arguments
win
A pointer to the window.
boolf
A Boolean TRUE or FALSE value. If boolf is TRUE, the cursor
remains in place after the last update and the coordinate setting
on win changes accordingly. If boolf is FALSE, the cursor moves
to the currently specified (y,x) coordinates of win.
292.2 – Description
The leaveok function defaults to moving the cursor to the current
coordinates of win. The bool type is defined in the <curses.h>
header file as follows:
#define bool int
293 – lgamma
Computes the logarithm of the gamma function.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double lgamma (double x);
float lgammaf (float x);
long double lgammal (long double x);
293.1 – Argument
x
A real number. x cannot be 0, a negative integer, or Infinity.
293.2 – Description
The lgamma functions return the logarithm of the absolute value
of gamma of x, or ln(|G(x)|), where G is the gamma function.
The sign of gamma of x is returned in the external integer
variable signgam. The x argument cannot be 0, a negative integer,
or Infinity.
293.3 – Return Values
x The logarithmic gamma of the x argument.
-HUGE_VAL The x argument is a negative integer; errno is
set to ERANGE.
NaN The x argument is NaN; errno is set to EDOM.
0 Underflow occurred; errno is set to ERANGE.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
294 – link
Creates a new link (directory entry) for an existing file. This
function is supported only on volumes that have hard link counts
enabled.
Format
#include <unistd.h>
link (const char *path1, const char *path2);
294.1 – Arguments
path1
Pointer to a pathname naming an existing file.
path2
Pointer to a pathname naming the new directory entry to be
created.
294.2 – Description
The link function atomically creates a new link for the existing
file, and the link count of the file is incremented by one.
The link function can be used on directory files.
If link fails, no link is created and the link count of the file
remains unchanged.
294.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EEXIST - The link named by path2 exists.
o EFTYPE - Wildcards appear in either path1
or path2.
o EINVAL - One or both arguments specify a
syntactically invalid pathname.
o ENAMETOOLONG - The length of path1 or path2
exceeds PATH_MAX, or a pathname component
is longer than NAME_MAX.
o EXDEV - The link named by path2 and
the filenamed by path1 are on different
devices.
295 – localeconv
Sets the members of a structure of type struct lconv with values
appropriate for formatting numeric quantities according to the
rules of the current locale.
Format
#include <locale.h>
struct lconv *localeconv (void);
295.1 – Description
The localeconv function returns a pointer to the lconv structure
defined in the <locale.h> header file. This structure should
not be modified by the program. It is overwritten by calls to
localeconv, or by calls to the setlocale function that change the
LC_NUMERIC, LC_MONETARY, or LC_ALL categories.
The members of the structure are:
Member Description
char *decimal_point The radix character.
char *thousands_sep The character used to separate groups of
digits.
char *grouping The string that defines how digits are
grouped in nonmonetary values.
char *int_curr_symbol The international currency symbol.
char *currency_symbol The local currency symbol.
char *mon_decimal_ The radix character used to format
point monetary values.
char *mon_thousands_ The character used to separate groups of
sep digits in monetary values.
char *mon_grouping The string that defines how digits are
grouped in a monetary value.
char *positive_sign The string used to indicate a nonnegative
monetary value.
char *negative_sign The string used to indicate a negative
monetary value.
char int_frac_digits The number of digits displayed after
the radix character in a monetary value
formatted with the international currency
symbol.
char frac_digits The number of digits displayed after the
radix character in a monetary value.
char p_cs_precedes For positive monetary values, this is
set to 1 if the local or international
currency symbol precedes the number, and
it is set to 0 if the symbol succeeds the
number.
char p_sep_by_space For positive monetary values, this is
set to 0 if there is no space between the
currency symbol and the number. It is set
to 1 if there is a space, and it is set to
2 if there is a space between the symbol
and the sign string.
char n_cs_precedes For negative monetary values, this is
set to 1 if the local or international
currency symbol precedes the number, and
it is set to 0 if the symbol succeeds the
number.
char n_sep_by_space For negative monetary values, this is
set to 0 if there is no space between the
currency symbol and the number. It is set
to 1 if there is a space, and it is set to
2 if there is a space between the symbol
and the sign string.
char p_sign_posn An integer used to indicate where the
positive_sign string should be placed for
a nonnegative monetary quantity.
char n_sign_posn An integer used to indicate where the
negative_sign string should be placed for
a negative monetary quantity.
Members of the structure of type char* are pointers to strings,
any of which (except decimal_point) can point to "", indicating
that the associated value is not available in the current locale
or is zero length. Members of the structure of type char are
positive numbers, any of which can be CHAR_MAX, indicating that
the associated value is not available in the current locale.
CHAR_MAX is defined in the <limits.h> header file.
Be aware that the value of the CHAR_MAX macro in the <limits.h>
header depends on whether the program is compiled with the
/UNSIGNED_CHAR qualifier:
o Use the CHAR_MAX macro as an indicator of a nonavailable value
in the current locale only if the program is compiled without
/UNSIGNED_CHAR (/NOUNSIGNED_CHAR is the default).
o If the program is compiled with /UNSIGNED_CHAR, use the SCHAR_
MAX macro instead of the CHAR_MAX macro.
In /NOUNSIGNED_CHAR mode, the values of CHAR_MAX and SCHAR_MAX
are the same; therefore, comparison with SCHAR_MAX gives correct
results regardless of the /[NO]UNSIGNED_CHAR mode used.
The members grouping and mon_grouping point to a string that
defines the size of each group of digits when formatting a
number. Each group size is separated by a semicolon (;). For
example, if grouping points to the string 5;3 and the thousands_
sep character is a comma (,), the number 123450000 would be
formatted as 1,234,50000.
The elements of grouping and mon_grouping are interpreted as
follows:
Value Interpretation
CHAR_MAX No further grouping is performed.
0 The previous element is to be used repeatedly for the
remainder of the digits.
other The integer value is the number of digits that comprise
the current group. The next element is examined to
determine the size of the next group of digits before
the current group.
The values of p_sign_posn and n_sign_posn are interpreted as
follows:
Value Interpretation
0 Parentheses surround the number and currency symbol.
1 The sign string precedes the number and currency symbol.
2 The sign string succeeds the number and currency symbol.
3 The sign string immediately precedes the number and
currency symbol.
4 The sign string immediately succeeds the number and
currency symbol.
295.2 – Return Value
x Pointer to the lconv structure.
295.3 – Example
#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <locale.h>
#include <string.h>
/* The following test program will set up the British English */
/* locale, and then extract the International Currency symbol */
/* and the International Fractional Digits fields for this */
/* locale and print them. */
int main()
{
/* Declare variables */
char *return_val;
struct lconv *lconv_ptr;
/* Load a locale */
return_val = (char *) setlocale(LC_ALL, "en_GB.iso8859-1");
/* Did the locale load successfully? */
if (return_val == NULL) {
/* It failed to load the locale */
printf("ERROR : The locale is unknown");
exit(EXIT_FAILURE);
}
/* Get the lconv structure from the locale */
lconv_ptr = (struct lconv *) localeconv();
/* Compare the international currency symbol string with an */
/* empty string. If they are equal, then the international */
/* currency symbol is not defined in the locale. */
if (strcmp(lconv_ptr->int_curr_symbol, "")) {
printf("International Currency Symbol = %s\n",
lconv_ptr->int_curr_symbol);
}
else {
printf("International Currency Symbol =");
printf("[Not available in this locale]\n");
}
/* Compare International Fractional Digits with CHAR_MAX. */
/* If they are equal, then International Fractional Digits */
/* are not defined in this locale. */
if ((unsigned char) (lconv_ptr->int_frac_digits) != CHAR_MAX) {
printf("International Fractional Digits = %d\n",
lconv_ptr->int_frac_digits);
}
else {
printf("International Fractional Digits =");
printf("[Not available in this locale]\n");
}
}
Running the example program produces the following result:
International Currency Symbol = GBP
International Fractional Digits = 2
296 – localtime
Convert a time value to broken-down local time.
Format
#include <time.h>
struct tm *localtime (const time_t *timer);
struct tm *localtime_r (const time_t *timer, struct tm *result);
(ISO POSIX-1)
296.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to the
localtime_r function that is equivalent to the behavior before
OpenVMS Version 7.0.
296.2 – Arguments
timer
A pointer to a time in seconds since the Epoch. You can generate
this time by using the time function or you can supply a time.
result
A pointer to a tm structure where the result is stored. The tm
structure is defined in the <time.h> header file, and is also
shown in tm Structure.
296.3 – Description
The localtime and localtime_r functions convert the time (in
seconds since the Epoch) pointed to by timer into a broken-down
time, expressed as a local time, and store it in a tm structure.
The difference between the localtime_r and localtime functions
is that the former stores the result into a user-specified tm
structure. The latter stores the result into thread-specific
static memory allocated by the C RTL, and which is
overwritten by subsequent calls to localtime; you must make a
copy if you want to save it.
On success, localtime returns a pointer to the tm structure;
localtime_r returns its second argument. On failure, these
functions return the NULL pointer.
The tm structure is defined in the <time.h> header file and
described in tm Structure.
Table REF-4 tm Structure
int tm_sec; Seconds after the minute (0-60)
int tm_min; Minutes after the hour (0-59)
int tm_hour; Hours since midnight (0-23)
int tm_mday; Day of the month (1-31)
int tm_mon; Months since January (1-11)
int tm_year; Years since 1900
int tm_wday; Days since Sunday (0-6)
int tm_yday; Days since January 1 (0-365)
int tm_isdst; Daylight Savings Time flag
o tm_isdst = 0 for Standard Time
o tm_isdst = 1 for Daylight Time
long tm_gmtoff; Seconds east of Greenwich (negative values
indicate seconds west of Greenwich)
char *tm_zone; Time zone string, for example "GMT"
The type time_t is defined in the <time.h> header file as
follows:
typedef long int time_t
NOTE
Generally speaking, UTC-based time functions can affect in-
memory time-zone information, which is processwide data.
However, if the system time zone remains the same during
the execution of the application (which is the common case)
and the cache of timezone files is enabled (which is the
default), then the _r variant of the time functions asctime_
r, ctime_r, gmtime_r and localtime_r, is both thread-safe
and AST-reentrant.
If, however, the system time zone can change during the
execution of the application or the cache of timezone files
is not enabled, then both variants of the UTC-based time
functions belong to the third class of functions, which are
neither thread-safe nor AST-reentrant.
296.4 – Return Values
x Pointer to a tm structure.
NULL Indicates failure.
297 – log,log2,log10
Return the logarithm of their arguments.
Format
#include <math.h>
double log (double x);
float logf (float x); (Integrity servers, Alpha)
long double logl (long double x); (Integrity servers, Alpha)
double log2 (double x); (Integrity servers, Alpha)
float log2f (float x); (Integrity servers, Alpha)
long double log2l (long double x); (Integrity servers, Alpha)
double log10 (double x);
float log10f (float x); (Integrity servers, Alpha)
long double log10l (long double x);
(Integrity servers, Alpha)
297.1 – Argument
x
A real number.
297.2 – Description
The log functions compute the natural (base e) logarithm of x.
The log2 functions compute the base 2 logarithm of x.
The log10 functions compute the common (base 10) logarithm of x.
297.3 – Return Values
x The logarithm of the argument (in the
appropriate base).
-HUGE_VAL x is 0 (errno is set to ERANGE), or x is
negative (errno is set to EDOM).
NaN x is NaN; errno is set to EDOM.
298 – log1p
Computes ln(1+y) accurately.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double log1p (double y);
float log1pf (float y);
long double log1pl (long double y);
298.1 – Argument
y
A real number greater than -1.
298.2 – Description
The log1p functions compute ln(1+y) accurately, even for tiny y.
298.3 – Return Values
x The natural logarithm of (1+y).
-HUGE_VAL y is less than -1 (errno is set to EDOM), or y
NaN y is NaN; errno is set to EDOM.
299 – logb
Returns the radix-independent exponent of the argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double logb (double x);
float logbf (float x);
long double logbl (long double x);
299.1 – Argument
x
A nonzero, real number.
299.2 – Description
The logb functions return the exponent of x, which is the
integral part of log(2)|x|, as a signed floating-point value,
for nonzero x.
299.3 – Return Values
x The exponent of x.
-HUGE_VAL x = 0.0; errno is set to EDOM.
+Infinity x is +Infinity or -Infinity.
NaN y is NaN; errno is set to EDOM.
300 – longjmp
Provides a way to transfer control from a nested series of
function invocations back to a predefined point without returning
normally; that is, by not using a series of return statements.
The longjmp function restores the context of the environment
buffer.
Format
#include <setjmp.h>
void longjmp (jmp_buf env, int value);
300.1 – Arguments
env
The environment buffer, which must be an array of integers long
enough to hold the register context of the calling function.
The type jmp_buf is defined in the <setjmp.h> header file. The
contents of the general-purpose registers, including the program
counter (PC), are stored in the buffer.
value
Passed from longjmp to setjmp, and then becomes the subsequent
return value of the setjmp call. If value is passed as 0, it is
converted to 1.
300.2 – Description
When setjmp is first called, it returns the value 0. If longjmp
is then called, naming the same environment as the call to
setjmp, control is returned to the setjmp call as if it had
returned normally a second time. The return value of setjmp in
this second return is the value you supply in the longjmp call.
To preserve the true value of setjmp, the function calling setjmp
must not be called again until the associated longjmp is called.
The setjmp function preserves the hardware general-purpose
registers, and the longjmp function restores them. After a
longjmp, all variables have their values as of the time of the
longjmp except for local automatic variables not marked volatile.
These variables have indeterminate values.
The setjmp and longjmp functions rely on the OpenVMS condition-
handling facility to effect a nonlocal goto with a signal
handler. The longjmp function is implemented by generating a
C RTL specified signal and allowing the OpenVMS condition-
handling facility to unwind back to the desired destination.
The C RTL must be in control of signal handling for any
VSI C image.
For VSI C to be in control of signal handling, you must
establish all exception handlers through a call to the
VAXC$ESTABLISH function (rather than LIB$ESTABLISH).
NOTE
The C RTL provides nonstandard decc$setjmp and decc$fast_
longjmp functions for Alpha and Integrity server systems.
To use these nonstandard functions instead of the standard
ones, a program must be compiled with the __FAST_SETJMP or
__UNIX_SETJMP macros defined.
Unlike the standard longjmp function, the decc$fast_longjmp
function does not convert its second argument from 0 to 1.
After a call to decc$fast_longjmp, a corresponding setjmp
function returns with the exact value of the second argument
specified in the decc$fast_longjmp call.
300.3 – Restrictions
You cannot invoke the longjmp function from an OpenVMS condition
handler. However, you may invoke longjmp from a signal handler
that has been established for any signal supported by the
C RTL, subject to the following nesting restrictions:
o The longjmp function will not work if invoked from nested
signal handlers. The result of the longjmp function, when
invoked from a signal handler that has been entered as a
result of an exception generated in another signal handler,
is undefined.
o Do not invoke the setjmp function from a signal handler unless
the associated longjmp is to be issued before the handling of
that signal is completed.
o Do not invoke the longjmp function from within an exit handler
(established with atexit or SYS$DCLEXH). Exit handlers are
invoked after image tear-down, so the destination address of
the longjmp no longer exists.
o Invoking longjmp from within a signal handler to return to
the main thread of execution might leave your program in
an inconsistent state. Possible side effects include the
inability to perform I/O or to receive any more UNIX signals.
301 – longname
Returns the full name of the terminal.
Format
#include <curses.h>
void longname (char *termbuf, char *name);
301.1 – Function Variants
The longname function has variants named _longname32 and
_longname64 for use with 32-bit and 64-bit pointer sizes,
respectively.
301.2 – Arguments
termbuf
A string containing the name of the terminal.
name
A character-string buffer with a minimum length of 64 characters.
301.3 – Description
The terminal name is in a readable format so that you can
double-check to be sure that Curses has correctly identified
your terminal. The dummy argument termbuf is required for UNIX
software compatibility and serves no function in the OpenVMS
environment. If portability is a concern, you must write a set
of dummy routines to perform the functionality provided by the
database termcap in the UNIX system environment.
302 – lrand48
Generates uniformly distributed pseudorandom-number sequences.
Returns 48-bit signed long integers.
Format
#include <stdlib.h>
long int lrand48 (void);
302.1 – Description
The lrand48 function generates pseudorandom numbers using the
linear congruential algorithm and 48-bit integer arithmetic.
It returns nonnegative, long integers uniformly distributed over
the range of y values such that 0
Before you call the lrand48 function use either srand48, seed48,
or lcong48 to initialize the random-number generator. You must
initialize prior to invoking the lrand48 function, because it
stores the last 48-bit Xi generated into an internal buffer.
(Although it is not recommended, constant default initializer
values are supplied automatically if the drand48, lrand48,
or mrand48 functions are called without first calling an
initialization function.)
The function works by generating a sequence of 48-bit integer
values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n >= 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke the lcong48 function, the multiplier
value a and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The value returned by the lrand48 function is computed by
first generating the next 48-bit Xi in the sequence. Then the
appropriate bits, according to the type of data item to be
returned, are copied from the high-order (most significant) bits
of Xi and transformed into the returned value.
See also drand48, lcong48, mrand48, seed48, and srand48.
302.2 – Return Value
n Signed nonnegative long integers uniformly
distributed over the range 0
303 – lrint
Rounds to the nearest integer value, rounding according to the
current rounding direction.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
long lrint (double x);
long lrintf (float x);
long lrintl (long double x);
303.1 – Argument
x
A real value.
303.2 – Description
The lrint functions return the rounded integer value of x,
rounded according to the current rounding direction.
303.3 – Return Values
n Upon success, the rounded integer value.
304 – lround
Rounds to the nearest integer value, rounding halfway cases away
from zero regardless of the current rounding direction.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
long lround (double x);
long lroundf (float x);
long lroundl (long double x);
304.1 – Argument
x
A real value.
304.2 – Description
The lround functions return the rounded integer value of x, with
halfway cases rounded away from zero regardless of the current
rounding direction.
304.3 – Return Values
n Upon success, the rounded integer value.
305 – lseek
Positions a file to an arbitrary byte position and returns the
new position.
Format
#include <unistd.h>
off_t lseek (int file_desc, off_t offset, int direction);
305.1 – Arguments
file_desc
An integer returned by open, creat, dup, or dup2.
offset
The offset, specified in bytes. The off_t data type is either a
32-bit or a 64-bit integer. The 64-bit interface allows for file
sizes greater than 2 GB, and can be selected at compile time by
defining the _LARGEFILE feature-test macro as follows:
CC/DEFINE=_LARGEFILE
direction
An integer indicating whether the offset is to be measured
forward from the beginning of the file (direction=SEEK_SET),
forward from the current position (direction=SEEK_CUR), or
backward from the end of the file (direction=SEEK_END).
305.2 – Description
The lseek function can position a fixed-length record-access
file with no carriage control or a stream-access file on any
byte offset, but can position all other files only on record
boundaries.
The available Standard I/O functions position a record file at
its first byte, at the end-of-file, or on a record boundary.
Therefore, the arguments given to lseek must specify either
the beginning or end of the file, a 0 offset from the current
position (an arbitrary record boundary), or the position returned
by a previous, valid lseek call.
This function returns the new file position as an integer of type
off_t which, like the offset argument, is either a 64-bit integer
if _LARGEFILE is defined, or a 32-bit integer if not.
For a portable way to position an arbitrary byte location with
any type of file, see the fgetpos and fsetpos functions.
CAUTION
If, while accessing a stream file, you seek beyond the
end-of-file and then write to the file, the lseek function
creates a hole by filling the skipped bytes with zeros.
In general, for record files, lseek should only be directed
to an absolute position that was returned by a previous
valid call to lseek or to the beginning or end of a file.
If a call to lseek does not satisfy these conditions, the
results are unpredictable.
See also open, creat, dup, dup2, and fseek.
305.3 – Return Values
x The new file position.
-1 Indicates that the file descriptor is
undefined, or a seek was attempted before
the beginning of the file.
306 – lstat
Retrieves information about the specified file.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <sys/stat.h>
int lstat (const char *restrict file_path, struct stat
*restrict user_buffer);
306.1 – Arguments
file_path
The name of the file for which you want to retrieve information.
user_buffer
The stat structure in which information is returned.
306.2 – Description
The lstat function retrieves information about the specified file
(file_path). If the file is a symbolic link, information about
the link itself is returned (in contrast to stat, which returns
information about the file that the symbolic link points to).
See also symlink, unlink, readlink, realpath, and lchown.
306.3 – Return Values
0 Successful completion.
-1 Indicates an error. errno is set to any errno
value returned by stat.
307 – lwait
Waits for I/O on a specific file to complete.
Format
#include <stdio.h>
int lwait (int fd);
307.1 – Argument
fd
A file descriptor corresponding to an open file.
307.2 – Description
The lwait function is used primarily to wait for completion of
pending asynchronous I/O.
307.3 – Return Values
0 Indicates successful completion.
-1 Indicates an error.
308 – malloc
Allocates an area of memory. These functions are AST-reentrant.
Format
#include <stdlib.h>
void *malloc (size_t size);
308.1 – Function Variants
The malloc function has variants named _malloc32 and _malloc64
for use with 32-bit and 64-bit pointer sizes, respectively.
308.2 – Argument
size
The total number of bytes to be allocated.
308.3 – Description
The malloc function allocates a contiguous area of memory whose
size, in bytes, is supplied as an argument. The space is not
initialized.
NOTE
The malloc routines call the system routine LIB$VM_MALLOC.
Because LIB$VM_MALLOC is designed as a general-purpose
routine to allocate memory, it is called upon in a wide
array of scenarios to allocate and reallocate blocks
efficiently. The most common usage is the management of
smaller blocks of memory, and the most important aspect of
memory allocation under these circumstances is efficiency.
LIB$VM_MALLOC makes use of its own free space to satisfy
requests, once the heap storage is consumed by splitting
large blocks and merging adjacent blocks. Memory can still
become fragmented, leaving unused blocks. Once heap storage
is consumed, LIB$VM_MALLOC manages its own free space and
merged blocks to satisfy requests, but varying sizes of
memory allocations can cause blocks to be left unused.
Because LIB$VM_MALLOC cannot be made to satisfy all
situations in the best possible manner, perform your own
memory management if you have special memory usage needs.
This assures the best use of memory for your particular
application.
The OpenVMS Programming Concepts Manual explains the several
memory allocation routines that are available. They are
grouped into three levels of hierarchy:
1. At the highest level are the RTL Heap Management Routines
LIB$GET_VM and LIB$FREE_VM, which provide a mechanism
for allocating and freeing blocks of memory of arbitrary
size. Also at this level are the routines based on the
concept of zones, such as LIB$CREATE_VM_ZONE, and so on.
2. At the next level are the RTL Page Management routines
LIB$GET_VM_PAGE and LIB$FREE_VM_PAGE, which allocate a
specified number of contiguous pages.
3. At the lowest level are the Memory Management System
Services, such as $CRETVA and $EXPREG, that provide
extensive control over address space allocation. At this
level, you must manage the allocation precisely.
The maximum amount of memory allocated at once is limited to
0xFFFFD000.
308.4 – Return Values
x The address of the first byte, which
is aligned on a quadword boundary
(Alpha only) or an octaword boundary
(Integrity servers(ONLY)) .
NULL Indicates that the function is unable to
allocate enough memory. errno is set to
ENOMEM.
309 – mblen
Determines the number of bytes comprising a multibyte character.
Format
#include <stdlib.h>
int mblen (const char *s, size_t n);
309.1 – Arguments
s
A pointer to the multibyte character.
n
The maximum number of bytes that comprise the multibyte
character.
309.2 – Description
If the character is n bytes or less, the mblen function returns
the number of bytes comprising the multibyte character pointed
to by s. If the character is greater than n bytes, the function
returns -1 to indicate an error.
This function is affected by the LC_CTYPE category of the
program's current locale.
309.3 – Return Values
x The number of bytes that comprise the
multibyte character, if the next n or fewer
bytes form a valid character.
0 If s is NULL or a pointer to the NULL
character.
-1 Indicates an error. The function sets errno to
EILSEQ - Invalid character detected.
310 – mbrlen
Determines the number of bytes comprising a multibyte character.
Format
#include <wchar.h>
size_t mbrlen (const char *s, size_t n, mbstate_t *ps);
310.1 – Arguments
s
A pointer to a multibyte character.
n
The maximum number of bytes that comprise the multibyte
character.
ps
A pointer to the mbstate_t object. If a NULL pointer is
specified, the function uses its internal mbstate_t object.
mbstate_t is an opaque datatype intended to keep the conversion
state for the state-dependent codesets.
310.2 – Description
The mbrlen function is equivalent to the call:
mbrtowc(NULL, s, n, ps != NULL ? ps : &internal)
Where internal is the mbstate_t object for the mbrlen function.
If the multibyte character pointed to by s is of n bytes or less,
the function returns the number of bytes comprising the character
(including any shift sequences).
If either an encoding error occurs or the next n bytes contribute
to an incomplete but potentially valid multibyte character, the
function returns -1 or -2, respectively.
See also mbrtowc.
310.3 – Return Values
x The number of bytes comprising the multibyte
character.
0 Indicates that s is a NULL pointer or a
pointer to a null byte.
-1 Indicates an encoding error, in which case
the next n or fewer bytes do not contribute
to a complete and valid multibyte character.
errno is set to EILSEQ; the conversion state
is undefined.
-2 Indicates an incomplete but potentially valid
multibyte character (all n bytes have been
processed).
311 – mbrtowc
Converts a multibyte character to its wide-character
representation.
Format
#include <wchar.h>
size_t mbrtowc (wchar_t *pwc, const char *s, size_t n,
mbstate_t *ps);
311.1 – Arguments
pwc
A pointer to the resulting wide-character code.
s
A pointer to a multibyte character.
n
The maximum number of bytes that comprise the multibyte
character.
ps
A pointer to the mbstate_t object. If a NULL pointer is
specified, the function uses its internal mbstate_t object.
mbstate_t is an opaque datatype intended to keep the conversion
state for the state-dependent codesets.
311.2 – Description
If s is a NULL pointer, mbrtowc is equivalent to the call:
mbrtowc(NULL, "", 1, ps)
In this case, the values of pwc and n are ignored.
If s is not a NULL pointer, mbrtowc inspects at most n bytes
beginning with the byte pointed to by s to determine the
number of bytes needed to complete the next multibyte character
(including any shift sequences).
If the function determines that the next multibyte character
is completed, it determines the value of the corresponding wide
character and then, if pwc is not a NULL pointer, stores that
value in the object pointed to by pwc. If the corresponding
wide character is the null wide character, the resulting state
described is the initial conversion state.
If mbrtowc is called as a counting function, which means that pwc
is a NULL pointer and s is neither a NULL pointer nor a pointer
to a null byte, the value of the internal mbstate_t object will
remain unchanged.
311.3 – Return Values
x The number of bytes comprising the multibyte
character.
0 The next n or fewer bytes complete the
multibyte character that corresponds to the
null wide character (which is the value stored
if pwc is not a NULL pointer). The wide-
character code corresponding to a null byte
is zero.
-1 Indicates an encoding error. The next n or
fewer bytes do not contribute to a complete
and valid multibyte character. errno is set to
EILSEQ. The conversion state is undefined.
-2 Indicates an incomplete but potentially valid
multibyte character (all n bytes have been
processed).
312 – mbstowcs
Converts a sequence of multibyte characters into a sequence of
corresponding wide-character codes.
Format
#include <stdlib.h>
size_t mbstowcs (wchar_t *pwcs, const char *s, size_t n);
312.1 – Arguments
pwcs
A pointer to the array containing the resulting sequence of wide-
character codes.
s
A pointer to the array of multibyte characters.
n
The maximum number of wide-character codes that can be stored in
the array pointed to by pwcs.
312.2 – Description
The mbstowcs function converts a sequence of multibyte characters
from the array pointed to by s to a sequence of wide-character
codes that are stored into the array pointed to by pwcs, up to a
maximum of n codes.
This function is affected by the LC_CTYPE category of the
program's current locale. If copying takes place between objects
that overlap, the behavior is undefined.
312.3 – Return Values
x The number of array elements modified or
required, not included any terminating zero
code. The array will not be zero-terminated
if the value returned is n. If pwcs is the
NULL pointer, mbstowcs returns the number
of elements required for the wide-character
array.
(size_t) -1 Indicates that an error occurred. The function
sets errno to EILSEQ - Invalid character
detected.
313 – mbtowc
Converts a multibyte character to its wide-character equivalent.
Format
#include <stdlib.h>
int mbtowc (wchar_t *pwc, const char *s, size_t n);
313.1 – Arguments
pwc
A pointer to the resulting wide-character code.
s
A pointer to the multibyte character.
n
The maximum number of bytes that comprise the next multibyte
character.
313.2 – Description
If the character is n or fewer bytes, the mbtowc function
converts the multibyte character pointed to by s to its wide-
character equivalent. If the character is invalid or greater than
n bytes, the function returns -1 to indicate an error.
If pwc is a NULL pointer and s is not a null pointer, the
function determines the number of bytes that constitute the
multibyte character pointed to by s (regardless of the value
of n).
This function is affected by the LC_CTYPE category of the
program's current locale.
313.3 – Return Values
x The number of bytes that comprise the valid
character pointed to by s.
0 If s is either a NULL pointer or a pointer to
the null byte.
-1 Indicates an error. The function sets errno to
EILSEQ - Invalid character detected.
314 – mbsinit
Determines whether an mbstate_t object decribes an initial
conversion state.
Format
#include <wchar.h>
int mbsinit (const mbstate_t *ps);
314.1 – Argument
ps
A pointer to the mbstate_t object. mbstate_t is an opaque
datatype intended to keep the conversion state for the state-
dependent codesets.
314.2 – Description
If ps is not a NULL pointer, the mbsinit function determines
whether the mbstate_t object pointed to by ps describes an
initial conversion state. A zero mbstate_t object always
describes an initial conversion state.
314.3 – Return Values
nonzero The ps argument is a NULL pointer, or the
mbstate_t object pointed to by ps describes an
initial conversion state.
0 The mbstate_t object pointed to by ps does not
describe an initial conversion state.
315 – mbsrtowcs
Converts a sequence of multibyte characters to a sequence of
corresponding wide-character codes.
Format
#include <wchar.h>
size_t mbsrtowcs (wchar_t *dst, const char **src, size_t len,
mbstate_t *ps);
315.1 – Function Variants
The mbsrtowcs function has variants named _mbsrtowcs32 and
_mbsrtowcs64 for use with 32-bit and 64-bit pointer sizes,
respectively.
315.2 – Arguments
dst
A pointer to the destination array containing the resulting
sequence of wide-character codes.
src
An address of the pointer to an array containing a sequence of
multibyte characters to be converted.
len
The maximum number of wide character codes that can be stored in
the array pointed to by dst.
ps
A pointer to the mbstate_t object. If a NULL pointer is
specified, the function uses its internal mbstate_t object.
mbstate_t is an opaque datatype intended to keep the conversion
state for the state-dependent codesets.
315.3 – Description
The mbsrtowcs function converts a sequence of multibyte
characters, beginning in the conversion state described by the
object pointed to by ps, from the array indirectly pointed to by
src, into a sequence of corresponding wide characters.
If dst is not a NULL pointer, the converted characters are stored
into the array pointed to by dst. Conversion continues up to and
including a terminating null character, which is also stored.
Conversion stops earlier for one of the following reasons:
o A sequence of bytes is encountered that does not form a valid
multibyte character.
o If dst is not a NULL pointer, when len codes have been stored
into the array pointed to by dst.
If dst is not a NULL pointer, the pointer object pointed to by
src is assigned either a NULL pointer (if the conversion stopped
because of reaching a terminating null wide character), or the
address just beyond the last multibyte character converted (if
any). If conversion stopped because of reaching a terminating
null wide character, the resulting state described is the initial
conversion state.
315.4 – Return Values
n The number of multibyte characters
successfully converted, sequence, not
including the terminating null (if any).
-1 Indicates an error. A sequence of bytes that
do not form valid multibyte character was
encountered. errno is set to EILSEQ; the
conversion state is undefined.
316 – memccpy
Copies characters sequentially between strings in memory areas.
Format
#include <string.h>
void *memccpy (void *dest, void *source, int c, size_t n);
316.1 – Function Variants
The memccpy function has variants named _memccpy32 and _memccpy64
for use with 32-bit and 64-bit pointer sizes, respectively.
316.2 – Arguments
dest
A pointer to the location of a destination string.
source
A pointer to the location of a source string.
c
A character that you want to search for.
n
The number of charcter you want to copy.
316.3 – Description
The memccpy function operates on strings in memory areas. A
memory area is a group of contiguous characters bound by a count
and not terminated by a null character. The function does not
check for overflow of the receiving memory area. The memccpy
function is defined in the <string.h> header file.
The memccpy function sequentially copies characters from the
location pointed to by source into the location pointed to by
dest until one of the following occurs:
o The character specified by c (converted to an unsigned char)
is copied.
o The number of characters specified by n is copied.
316.4 – Return Values
x A pointer to the character following the
character specified by c in the string pointed
to by dest.
NULL Indicates an error. The character c is not
found after scanning n characters in the
string.
317 – memchr
Locates the first occurrence of the specified byte within the
initial size bytes of a given object.
Format
#include <string.h>
void *memchr (const void *s1, int c, size_t size);
317.1 – Function Variants
The memchr function has variants named _memchr32 and _memchr64
for use with 32-bit and 64-bit pointer sizes, respectively.
317.2 – Arguments
s1
A pointer to the object to be searched.
c
The byte value to be located.
size
The length of the object to be searched.
If size is zero, memchr returns NULL.
317.3 – Description
Unlike strchr, the memchr function does not stop when it
encounters a null character.
317.4 – Return Values
pointer A pointer to the first occurrence of the byte.
NULL Indicates that the specified byte does not
occur in the object.
318 – memcmp
Compares two objects, byte by byte. The compare operation starts
with the first byte in each object.
Format
#include <string.h>
int memcmp (const void *s1, const void *s2, size_t size);
318.1 – Arguments
s1
A pointer to the first object.
s2
A pointer to the second object.
size
The length of the objects to be compared.
If size is zero, the two objects are considered equal.
318.2 – Description
The memcmp function uses native byte comparison. The sign of
the value returned is determined by the sign of the difference
between the values of the first pair of unlike bytes in the
objects being compared. Unlike the strcmp function, the memcmp
function does not stop when a null character is encountered.
318.3 – Return Value
x An integer less than, equal to, or greater
than 0, depending on whether the lexical value
of the first object is less than, equal to, or
greater than that of the second object.
319 – memcpy
Copies a specified number of bytes from one object to another.
Format
#include <string.h>
void *memcpy (void *dest, const void *source, size_t size);
319.1 – Function Variants
The memcpy function has variants named _memcpy32 and _memcpy64
for use with 32-bit and 64-bit pointer sizes, respectively.
319.2 – Arguments
dest
A pointer to the destination object.
source
A pointer to the source object.
size
The length of the object to be copied.
319.3 – Description
The memcpy function copies size bytes from the object pointed
to by source to the object pointed to by dest; it does not check
for the overflow of the receiving memory area (dest). Unlike the
strcpy function, the memcpy function does not stop when a null
character is encountered.
319.4 – Return Value
x The value of dest.
320 – memmove
Copies a specified number of bytes from one object to another.
Format
#include <string.h>
void *memmove (void *dest, const void *source, size_t size);
320.1 – Function Variants
The memmove function has variants named _memmove32 and _memmove64
for use with 32-bit and 64-bit pointer sizes, respectively.
320.2 – Arguments
dest
A pointer to the destination object.
source
A pointer to the source object.
size
The length of the object to be copied.
320.3 – Description
In VSI C for OpenVMS Systems, memmove and memcpy perform the
same function. Programs that require portability should use
memmove if the area pointed at by dest could overlap the area
pointed at by source.
320.4 – Return Value
x The value of dest.
320.5 – Example
#include <string.h>
#include <stdio.h>
main()
{
char pdest[14] = "hello there";
char *psource = "you are there";
memmove(pdest, psource, 7);
printf("%s\n", pdest);
}
This example produces the following output:
you are there
321 – memset
Sets a specified number of bytes in a given object to a given
value.
Format
#include <string.h>
void *memset (void *s, int value, size_t size);
321.1 – Function Variants
The memset function has variants named _memset32 and _memset64
for use with 32-bit and 64-bit pointer sizes, respectively.
321.2 – Arguments
s
An array pointer.
value
The value to be placed in s.
size
The number of bytes to be placed in s.
321.3 – Description
The memset function copies value (converted to an unsigned char)
into each of the first size characters of the object pointed to
by s.
This function returns s. It does not check for the overflow of
the receiving memory area pointed to by s.
321.4 – Return Value
x The value of s.
322 – mkdir
Creates a directory.
Format
#include <stat.h>
int mkdir (const char *dir_spec, mode_t mode); (ISO POSIX-1)
int mkdir (const char *dir_spec, mode_t mode, . . . );
(DEC C Extension)
322.1 – Arguments
dir_spec
A valid OpenVMS or UNIX style directory specification that may
contain a device name. For example:
DBA0:[BAY.WINDOWS] /* OpenVMS */
/dba0/bay/windows /* UNIX style */
This specification cannot contain a node name, filename, file
extension, file version, or a wildcard character. The same
restriction applies to the UNIX style directory specifications.
mode
A file protection. See the chmod function in this section for
information about the specific file protections.
The file protection of the new directory is derived from the
mode argument, the process's file protection mask (see the umask
function), and the parent-directory default protections.
In a manner consistent with the OpenVMS behavior for creating
directories, mkdir never applies delete access to the directory.
An application that needs to set delete access should use an
explicit call to chmod to set write permission.
See the Description section of this function for more information
about how the file protection is set for the newly created
directory.
. . .
Represents the following optional arguments. These arguments have
fixed position in the argument list, and cannot be arbitrarily
placed.
unsigned int uic
The user identification code (UIC) that identifies the
owner of the created directory. If this argument is 0, the
C RTL gives the created directory the UIC of the parent
directory. If this argument is not specified, the C RTL
gives the created directory your UIC. This optional argument
is specific to the C RTL and is not portable.
unsigned short max_versions
The maximum number of file versions to be retained in the
created directory. The system automatically purges the
directory keeping, at most, max_versions number of every file.
If this argument is 0, the C RTL does not place a limit
on the maximum number of file versions.
If this argument is not specified, the C RTL gives
the created directory the default version limit of the parent
directory.
This optional argument is specific to the C RTL and is
not portable.
unsigned short r_v_number
The volume (device) on which to place the created directory
if the device is part of a volume set. If this argument is
not specified, the C RTL arbitrarily places the created
directory within the volume set. This optional argument is
specific to the C RTL and is not portable.
322.2 – Description
If dir_spec specifies a path that includes directories, which
do not exist, intermediate directories are also created.
This differs from the behavior of the UNIX system where these
intermediate directories must exist and will not be created.
If you do not specify any optional arguments, the C RTL
gives the directory your UIC and the default version limit of the
parent directory, and arbitrarily places the directory within the
volume set. You cannot get the default behavior for the uic or
max_versions arguments if you specify any arguments after them.
NOTE
The way to create files with OpenVMS RMS default protections
using the UNIX system-call functions umask, mkdir, creat,
and open is to call mkdir, creat, and open with a file-
protection mode argument of 0777 in a program that never
specifically calls umask. These default protections include
correctly establishing protections based on ACLs, previous
versions of files, and so on.
In programs that do vfork/exec calls, the new process image
inherits whether umask has ever been called or not from
the calling process image. The umask setting and whether
the umask function has ever been called are both inherited
attributes.
The file protection supplied by the mode argument is modified by
the process's file protection mask in such a way that the file
protection for the new directory is set to the bitwise AND of the
mode argument and the complement of the file protection mask.
Default file protections are supplied to the new directory
from the parent-directory such that if a protection value bit
in the new directory is zero, then the value of this bit is
inherited from the parent directory. However, bits in the parent
directory's file protection that indicate delete access do not
cause corresponding bits to be set in the new directory's file
protection.
322.3 – Return Values
0 Indicates success.
-1 Indicates failure.
322.4 – Examples
1.umask (0002); /* turn world write access off */
mkdir ("sys$disk:[.parentdir.childdir]", 0222);
/* turn write access on */
Parent directory file protection: System:RWD, Owner:RWD,
Group:R, World:R
The file protection derived from the combination of the mode
argument and the file protection mask set by umask is (0222)
& ~(0002), which is 0220. When the parent directory defaults
are applied to this protection, the protection for the new
directory becomes:
File protection: System:RWD, Owner:RWD, Group:RWD, World:R
2.umask (0000);
mkdir ("sys$disk:[.parentdir.childdir]", 0444);
/* turn read access on */
Parent directory file protection: System:RWD, Owner:RWD,
Group:RWD, World:RWD
The file protection derived from the combination of the mode
argument and the file protection mask set by umask is (0444)
& ~(0000), which is 0444. When the parent directory defaults
are applied to this protection, the protection for the new
directory is:
File protection: System:RW, Owner:RW, Group:RW, World:RW
Note that delete access is not inherited.
323 – mkstemp
Constructs a unique filename.
Format
#include <stdlib.h>
int mkstemp (char *template);
323.1 – Argument
template
A pointer to a string that is replaced with a unique filename.
The string in the template argument must be a filename with six
trailing Xs.
323.2 – Description
The mkstemp function replaces the six trailing Xs of the string
pointed to by template with a unique set of characters, and
returns a file descriptor for the file open for reading and
writing.
The string pointed to by template should look like a filename
with six trailing X's. The mkstemp function replaces each X with
a character from the portable file-name character set, making
sure not to duplicate an existing filename.
If the string pointed to by template does not contain six
trailing Xs, -1 is returned.
323.3 – Return Values
x An open file descriptor.
-1 Indicates an error. (The string pointed to by
template does not contain six trailing Xs.)
324 – mktemp
Creates a unique filename from a template.
Format
#include <stdlib.h>
char *mktemp (char *template);
324.1 – Function Variants
The mktemp function has variants named _mktemp32 and _mktemp64
for use with 32-bit and 64-bit pointer sizes, respectively.
324.2 – Argument
template
A pointer to a buffer containing a user-defined template. You
supply the template in the form, namXXXXXX. The six trailing Xs
are replaced by a unique series of characters. You may supply
the first three characters. Because the template argument is
overwritten, do not specify a string literal (const object).
324.3 – Description
The use of mktemp is not recommended for new applications. See
the tmpnam and mkstemp functions for the preferable alternatives.
324.4 – Return Value
x A pointer to the template, with the template
modified to contain the created filename. If
this value is a pointer to a null string, it
indicates that a unique filename cannot be
created.
325 – mktime
Converts a local-time structure to a time, in seconds, since the
Epoch.
Format
#include <time.h>
time_t mktime (struct tm *timeptr);
325.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to the
mktime function that is equivalent to the behavior before OpenVMS
Version 7.0.
325.2 – Argument
timeptr
A pointer to the local-time structure.
325.3 – Description
The mktime function converts a local-time structure (struct tm)
pointed to by timeptr, to a time in seconds since the Epoch (a
time_t variable), in the same manner as the values returned by
the time function.
The original values of the tm_wday and tm_yday components of
the structure are ignored, and the original values of the other
components are not restricted to the ranges defined in <time.h>.
Upon successful completion, the tm_wday and tm_yday components of
the structure are set appropriately, and the other components are
set to represent the specified time, with their values forced to
the normal range.
If the local time cannot be encoded, then mktime returns the
value (time_t)(-1).
The time_t type is defined in the <time.h> header file as
follows:
typedef unsigned long int time_t;
Local time-zone information is set as if mktime called tzset.
If the tm_isdst field in the local-time structure pointed to
by timeptr is positive, mktime initially presumes that Daylight
Savings Time (DST) is in effect for the specified time.
If tm_isdst is 0, mktime initially presumes that DST is not in
effect.
If tm_isdst is negative, mktime attempts to determine whether or
not DST is in effect for the specified time.
325.4 – Return Values
x The specified calendar time encoded as a value
of type time_t.
(time_t)(-1) If the local time cannot be encoded.
Be aware that a return value of (time_t)(-1)
can also represent the valid date: Sun Feb 7
06:28:15 2106.
326 – mmap
Maps file system object into virtual memory. This function is
reentrant.
Format
#include <types.h>
#include <mman.h>
void mmap (void *addr, size_t len, int prot, int flags, int
filedes, off_t off); (X/Open, POSIX-1)
void mmap (void *addr, size_t len, int prot, int flags, int
filedes, off_t off ...); (DEC C Extension)
326.1 – Function Variants
The mmap function has variants named _mmap32 and _mmap64 for use
with 32-bit and 64-bit pointer sizes, respectively.
326.2 – Arguments
addr
The starting address of the new region (must be the page
boundary).
len
The length, in bytes, of the new region.
prot
Access permission, as defined in the <mman.h> header file.
Specify either PROT_NONE, PROT_READ, or PROT_WRITE.
flags
Attributes of the mapped region as the results of a bitwise-
inclusive OR operation on any combination of the following:
o MAP_FILE or MAP_ANONYMOUS
o MAP_VARIABLE or MAP_FIXED
o MAP_SHARED or MAP_PRIVATE
filedes
The file that you want to map to the new mapped file region
returned by the open function.
off
The offset, specified in bytes. The off_t data type is either a
64-bit or 32-bit integer. The 64-bit interface allows for file
sizes greater than 2 GB, and can be selected at compile time by
defining the _LARGEFILE feature-test macro as follows:
CC/DEFINE=_LARGEFILE
. . .
An optional integer specifying additional flags for the
SYS$CRMPSC system service for MAP_SHARED. This optional argument
(VSI C Extension) of the mmap function was introduced in
OpenVMS Version 7.2.
326.3 – Description
The mmap function creates a new mapped file region, a new private
region, or a new shared memory region.
Your application must ensure correct synchronization when using
mmap in conjunction with any other file access method, such as
read and write, and standard input/output.
Before calling mmap, the calling application must also ensure
that all bytes in the range [off, off+len] are written to the
file (using the fsync function, for example). If this requirement
is not met, mmap fails with errno set to ENXIO (No such device or
address).
The addr and len arguments specify the requested starting address
and length, in bytes, for the new region. The address is a
multiple of the page size returned by sysconf(_SC_PAGE_SIZE).
If the len argument is not a multiple of the page size returned
by sysconf(_SC_PAGE_SIZE), then the result of any reference to
an address between the end of the region and the end of the page
containing the end of the region is undefined.
The flags argument specifies attributes of the mapped region.
Values for flags are constructed by a bitwise-inclusive OR
operation on the flags from the following list of symbolic names
defined in the <mman.h> header file:
MAP_FILE Create a mapped file region.
MAP_ANONYMOUS Create an unnamed memory region.
MAP_VARIABLE Place region at the computed address.
MAP_FIXED Place region at fixed address.
MAP_SHARED Share changes.
MAP_PRIVATE Changes are private.
The MAP_FILE and MAP_ANONYMOUS flags control whether the region
you want to map is a mapped file region or an anonymous shared
memory region. One of these flags must be selected.
If MAP_FILE is set in the flags argument:
o A new mapped file region is created, mapping the file
associated with the filedes argument.
o The off argument specifies the file byte offset where the
mapping starts. This offset must be a multiple of the page
size returned by sysconf(_SC_PAGE_SIZE).
o If the end of the mapped file region is beyond the end of the
file, the result of any reference to an address in the mapped
file region corresponding to an offset beyond the end of the
file is unspecified.
If MAP_ANONYMOUS is set in the flags argument:
o A new memory region is created and initialized to all zeros.
o The filedes argument is ignored.
The new region is placed at the requested address if the
requested address is not null and it is possible to place the
region at this address. When the requested address is null or
the region cannot be placed at the requested address, the MAP_
VARIABLE and MAP_FIXED flags control the placement of the region.
One of these flags must be selected.
If MAP_VARIABLE is set in the flags argument:
o If the requested address is null or if it is not possible for
the system to place the region at the requested address, the
region is placed at an address selected by the system.
If MAP_FIXED is set in the flags argument:
o If the requested address is not null, the mmap function
succeeds even if the requested address is already part of
another region. (If the address is within an existing region,
the effect on the pages within that region and within the area
of the overlap produced by the two regions is the same as if
they were unmapped. In other words, whatever is mapped between
addr and addr + len is unmapped.)
o If the requested address is null and MAP_FIXED is specified,
the results are undefined.
The MAP_PRIVATE and MAP_SHARED flags control the visibility of
modifications to the mapped file or shared memory region. One of
these flags must be selected.
If MAP_SHARED is set in the flags argument:
o If the region is a mapped region, modifications to the region
are visible to other processes that mapped the same region
using MAP_SHARED.
o If the region is a mapped file region, modifications to the
region are written to the file. (Note that the modifications
are not immediately written to the file because of buffer
cache delay; that is, the write to the file does not occur
until there is a need to reuse the buffer cache. If the
modifications must be written to the file immediately, use
the msync function to ensure that this is done.)
If MAP_PRIVATE is set in the flags argument:
o Modifications to the mapped region by the calling process are
not visible to other processes that mapped the same region
using either MAP_PRIVATE or MAP_SHARED.
o Modifications to the mapped region by the calling process are
not written to the file.
It is unspecified whether modifications by processes that mapped
the region using MAP_SHARED are visible to other processes that
mapped the same region using MAP_PRIVATE.
The prot argument specifies access permissions for the mapped
region. Specify one of the following:
PROT_NONE No access
PROT_READ Read-only
PROT_WRITE Read/Write access
After the successful completion of the mmap function, you can
close the filedes argument without effect on the mapped region or
on the contents of the mapped file. Each mapped region creates a
file reference, similar to an open file descriptor, that prevents
the file data from being deallocated.
NOTE
The following rules apply to OpenVMS specific file
references:
o Because of the additional file reference, if filedes is
not opened for file sharing, mmap reopens it with file
sharing enabled.
o The additional file reference that remains for mapped
regions implies that a later open, fopen, or create call
to the file that is mapped must specify file sharing.
Modifications made to the file using the write function are
visible to mapped regions, and modifications to a mapped region
are visible with the read function.
NOTE
Beginning with OpenVMS Version 7.2, while processing a MAP_
SHARED request, the mmap function constructs the flags
argument of the SYS$CRMPSC service as a bitwise inclusive
OR of those bits it sets by itself to fulfill the MAP_
SHARED request and those bits specified by the caller in
the optional argument.
By default, for MAP_SHARED the mmap function creates a
temporary group global section. The optional mmap argument
provides the caller with direct access to the features of
the SYS$CRMPSC system service.
Using the optional argument, the caller can create, for
example, a system global section (SEC$M_SYSGBL bit) or
permanent global section (SEC$M_PERM bit). For example,
to create a system permanent global section, the caller
can specify (SEC$M_SYSGBL | SEC$M_PERM) in the optional
argument.
The mmap function does not check or set any privileges.
It is the responsibility of the caller to set appropriate
privileges, such as SYSGBL privilege for SEC$M_SYSGBL, and
PRMGBL for SEC$M_PERM, before calling mmap with the optional
argument.
See also read, write, open, fopen, creat, and sysconf.
326.4 – Return Values
x The address where the mapping is placed.
MAP_FAILED Indicates an error; errno is set to one of the
following values:
o EACCES - The file referred to by filedes
is not open for read access, or the file
is not open for write access and PROT_WRITE
was set for a MAP_SHARED mapping operation.
o EBADF - The filedes argument is not a valid
file descriptor.
o EINVAL -The flags or prot argument is
invalid, or the addr argument or off
argument is not a multiple of the page
size returned by sysconf(_SC_PAGE_SIZE).
o ENODEV - The file descriptor filedes refers
to an object that cannot be mapped, such as
a terminal.
o ENOMEM - There is not enough address space
to map len bytes.
o ENXIO - The addresses specified by the
range [off, off + len] are invalid for
filedes.
o EFAULT - The addr argument is an invalid
address.
327 – modf
Decomposes a floating-point number.
Format
#include <math.h>
double modf (double x, double *iptr);
float modff (float x, float *iptr);
(Integrity servers, Alpha)
long double modfl (long double x, long double *iptr);
(Integrity servers, Alpha)
327.1 – Arguments
x
An object of type double, float, or long double.
iptr
A pointer to an object of type double, float, or long double to
match the type of x.
327.2 – Description
The modf functions decompose their first argument x into a
positive fractional part f and an integer part i, each of which
has the same sign as x.
The functions return f and assign i to the object pointed to by
the second argument (iptr).
327.3 – Return Values
x The fractional part of the argument x.
NaN x is NaN; errno is set to EDOM and *iptr is
set to NaN.
0 Underflow occurred; errno is set to ERANGE.
328 – [w]move
Change the current cursor position on the specified window to the
coordinates (y,x). The move function acts on the stdscr window.
Format
#include <curses.h>
int move (int y, int x);
int wmove (WINDOW *win, int y, int x);
328.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
328.2 – Description
For more information, see the scrollok function in this section.
328.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the screen
scroll illegally.
329 – mprotect
Modifies access protections of memory mapping. This function is
reentrant.
Format
#include <mman.h>
int mprotect (void *addr, size_t len, int prot);
329.1 – Arguments
addr
The address of the region that you want to modify.
len
The length, in bytes, of the region that you want to modify.
prot
Access permission, as defined in the <mman.h> header file.
Specify either PROT_NONE, PROT_READ, or PROT_WRITE.
329.2 – Description
The mprotect function modifies the access protection of a mapped
file or shared memory region.
The addr and len arguments specify the address and length, in
bytes, of the region that you want to modify. The len argument
must be a multiple of the page size as returned by sysconf(_SC_
PAGE_SIZE). If len is not a multiple of the page size as returned
by sysconf(_SC_PAGE_SIZE), the length of the region is rounded up
to the next multiple of the page size.
The prot argument specifies access permissions for the mapped
region. Specify one of the following:
PROT_NONE No access
PROT_READ Read-only
PROT_WRITE Read/Write access
The mprotect function does not modify the access permission of
any region that lies outside of the specified region, except that
the effect on addresses between the end of the region, and the
end of the page containing the end of the region, is unspecified.
If the mprotect function fails under a condition other than that
specified by EINVAL, the access protection of some of the pages
in the range [addr, addr + len] can change. Suppose the error
occurs on some page at an addr2; mprotect can modify protections
of all whole pages in the range [addr, addr2].
See also sysconf.
329.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to one of the
following values:
o EACCESS - The prot argument specifies a
protection that conflicts with the access
permission set for the underlying file.
o EINVAL - The prot argument is invalid, or
the addr argument is not a multiple of the
page size as returned by sysconf(_SC_PAGE_
SIZE).
o EFAULT - The range [addr, addr + len]
includes an invalid address.
330 – mrand48
Generates uniformly distributed pseudorandom-number sequences.
Returns 48-bit signed long integers.
Format
#include <stdlib.h>
long int mrand48 (void);
330.1 – Description
The mrand48 function generates pseudorandom numbers using the
linear congruential algorithm and 48-bit integer arithmetic.
It returns signed long integers uniformly distributed over the
range of y values such that -231
Before you call the mrand48 function, use either srand48,
seed48, or lcong48 to initialize the random-number generator.
You must initialize the mrand48 function prior to invoking it,
because it stores the last 48-bit Xi generated into an internal
buffer. (Although it is not recommended, constant default
initializer values are supplied automatically if the drand48,
lrand48, or mrand48 functions are called without first calling an
initialization function.)
The function works by generating a sequence of 48-bit integer
values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n >= 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke the lcong48 function, the multiplier
value a and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The values returned by the mrand48 function is computed by
first generating the next 48-bit Xi in the sequence. Then the
appropriate bits, according to the type of returned data item,
are copied from the high-order (most significant) bits of Xi and
transformed into the returned value.
See also drand48, lrand48, lcong48, seed48, and srand48.
330.2 – Return Value
n Returns signed long integers uniformly
distributed over the range -231
331 – msync
Synchronizes a mapped file.
Format
#include <mman.h>
int msync (void *addr, size_t len, int flags);
331.1 – Arguments
addr
The address of the region that you want to synchronize.
len
The length, in bytes, of the region that you want to synchronize.
flags
One of the following symbolic constants defined in the <mman.h>
header file:
MS_SYNC Synchronous cache flush
MS_ASYNC Asynchronous cache flush
MS_ Invalidate cashed pages
INVALIDATE
331.2 – Description
The msync function controls the caching operations of a mapped
file region. Use msync to:
o Ensure that modified pages in the region transfer to the
underlying storage device of the file.
o Control the visibility of modifications with respect to file
system operations.
The addr and len arguments specify the region to be synchronized.
The len argument must be a multiple of the page size as returned
by sysconf(_SC_PAGE_SIZE); otherwise, the length of the region is
rounded up to the next multiple of the page size.
If the flags argument is set to:
flags Argument Then the msync Function...
MS_SYNC Does not return until the system completes all
I/O operations.
MS_ASYNC Returns after the system schedules all I/O
operations.
MS_INVALIDATE Invalidates all cached copies of the pages. The
operating system must obtain new copies of the
pages from the file system the next time the
application references them.
After a successful call to the msync function with the flags
argument set to:
o MS_SYNC - All previous modifications to the mapped region
are visible to processes using the read argument. Previous
modifications to the file using the write function are lost.
o MS_INVALIDATE - All previous modifications to the file using
the write function are visible to the mapped region. Previous
direct modifications to the mapped region are lost.
See also read, write, and sysconf.
331.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to one of the
following values:
o EIO - An I/O error occurred while reading
from or writing to the file system.
o ENOMEM - The range specified by
[addr, addr + len] is invalid for a
process's address space, or the range
specifies one or more unmapped pages.
o EINVAL - The addr argument is not a
multiple of the page size as returned by
sysconf(_SC_PAGE_SIZE).
o EFAULT - The range [addr, addr + len]
includes an invalid address.
332 – munmap
Unmaps a mapped region. This function is reentrant.
Format
#include <mman.h>
int munmap (void *addr, size_t len);
332.1 – Arguments
addr
The address of the region that you want to unmap.
len
The length, in bytes, of that region the you want to unmap.
332.2 – Description
The munmap function unmaps a mapped file or shared memory region.
The addr and len arguments specify the address and length, in
bytes, respectively, of the region to be unmapped.
The len argument must be a multiple of the page size as returned
by sysconf(_SC_PAGE_SIZE); otherwise, the length of the region is
rounded up to the next multiple of the page size.
The result of using an address that lies in an unmapped region
and not in any subsequently mapped region is undefined.
See also sysconf.
332.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to one of the
following values:
o ENIVAL - The addr argument is not a
multiple of the page size as returned by
sysconf(_SC_PAGE_SIZE).
o EFAULT - The range [addr, addr + len]
includes an invalid address.
333 – mv[w]addch
Move the cursor to coordinates (y,x) and add a character to the
specified window.
Format
#include <curses.h>
int mvaddch (int y, int x, char ch);
int mvwaddch (WINDOW *win, int y, int x, char ch);
333.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
ch
If this argument is a new-line character (\n), the mvaddch and
mvwaddch functions clear the line to the end, and move the cursor
to the next line at the same x coordinate. A carriage return (\r)
moves the cursor to the beginning of the specified line. A tab
(\t) moves the cursor to the next tabstop within the window.
333.2 – Description
This routine performs the same function as mvwaddch, but on the
stdscr window.
When mvwaddch is used on a subwindow, it writes the character
onto the underlying window as well.
333.3 – Return Values
OK Indicates success.
ERR Indicates that writing the character would
cause the screen to scroll illegally. For more
information, see the scrollok function.
334 – mv[w]addstr
Move the cursor to coordinates (y,x) and add the specified
string, to which str points, to the specified window.
Format
#include <curses.h>
int mvaddstr (int y, int x, char *str);
int mvwaddstr (WINDOW *win, int y, int x, char *str);
334.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
str
A pointer to the character string.
334.2 – Description
This routine performs the same function as mvwaddstr, but on the
stdscr window.
When mvwaddstr is used on a subwindow, the string is written onto
the underlying window as well.
334.3 – Return Values
OK Indicates success.
ERR Indicates that the function causes the screen
to scroll illegally, but it places as much of
the string onto the window as possible. For
more information, see the scrollok function.
335 – mvcur
Moves the terminal's cursor from (lasty,lastx) to (newy,newx).
Format
#include <curses.h>
int mvcur (int lasty, int lastx, int newy, int newx);
335.1 – Arguments
lasty
The cursor position.
lastx
The cursor position.
newy
The resulting cursor position.
newx
The resulting cursor position.
335.2 – Description
In VSI C for OpenVMS Systems, mvcur and move perform the same
function.
See also move.
335.3 – Return Values
OK Indicates success.
ERR Indicates that moving the window placed part
or all of the window off the edge of the
terminal screen. The terminal screen remains
unaltered.
336 – mv[w]delch
Move the cursor to coordinates (y,x) and delete the character
on the specified window. The mvdelch function acts on the stdscr
window.
Format
#include <curses.h>
int mvdelch (int y, int x);
int mvwdelch (WINDOW *win, int y, int x);
336.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
336.2 – Description
Each of the following characters on the same line shifts to the
left, and the last character becomes blank.
336.3 – Return Values
OK Indicates success.
ERR Indicates that deleting the character would
cause the screen to scroll illegally. For more
information, see the scrollok function.
337 – mv[w]getch
Move the cursor to coordinates (y,x), get a character from the
terminal screen, and echo it on the specified window. The mvgetch
function acts on the stdscr window.
Format
#include <curses.h>
int mvgetch (int y, int x);
int mvwgetch (WINDOW *win, int y, int x);
337.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
337.2 – Description
The mvgetch and mvwgetch functions refresh the specified window
before fetching the character.
337.3 – Return Values
x The returned character.
ERR Indicates that the function causes the screen
to scroll illegally. For more information, see
the scrollok function in this section.
338 – mv[w]getstr
Move the cursor to coordinates (y,x), get a string from the
terminal screen, store it in the variable str (which must be
large enough to contain the string), and echo it on the specified
window. The mvgetstr function acts on the stdscr window.
Format
#include <curses.h>
int mvgetstr (int y, int x, char *str);
int mvwgetstr (WINDOW *win, int y, int x, char *str);
338.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
str
The string that is displayed.
338.2 – Description
The mvgetstr and mvwgetstr functions strip the new-line
terminator (\n) from the string.
338.3 – Return Values
OK Indicates success.
ERR Indicates that the function causes the screen
to scroll illegally.
339 – mv[w]inch
Move the cursor to coordinates (y,x) and return the character on
the specified window without making changes to the window. The
mvinch function acts on the stdscr window.
Format
#include <curses.h>
int mvinch (int y, int x);
int mvwinch (WINDOW *win, int y, int x);
339.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
339.2 – Return Values
x The returned character.
ERR Indicates an input error.
340 – mv[w]insch
Move the cursor to coordinates (y,x) and insert the character
ch into the specified window. The mvinsch function acts on the
stdscr window.
Format
#include <curses.h>
int mvinsch (int y, int x, char ch);
int mvwinsch (WINDOW *win, int y, int x, char ch);
340.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
ch
The character to be inserted at the window's coordinates.
340.2 – Description
After the character is inserted, each character on the line
shifts to the right, and the last character on the line is
deleted.
340.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the screen
scroll illegally. For more information, see
the scrollok function in this section.
341 – mv[w]insstr
Move the cursor to coordinates (y,x) and insert the specified
string into the specified window. The mvinsstr function acts on
the stdscr window.
Format
#include <curses.h>
int mvinsstr (int y, int x, char *str);
int mvwinsstr (WINDOW *win, int y, int x, char *str);
341.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
str
The string that is displayed.
341.2 – Description
Each character after the string shifts to the right, and the last
character disappears. The mvinsstr and mvwinsstr functions are
specific to VSI C for OpenVMS Systems and are not portable.
341.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the screen
scroll illegally. For more information, see
the scrollok function.
342 – mvwin
Moves the starting position of the window to the specified (y,x)
coordinates.
Format
#include <curses.h>
mvwin (WINDOW *win, int y, int x);
342.1 – Arguments
win
A pointer to the window.
y
A window coordinate.
x
A window coordinate.
342.2 – Description
When moving subwindows, the mvwin function does not rewrite the
contents of the subwindow on the underlying window at the new
position. If you write anything to the subwindow after the move,
the function also writes to the underlying window.
342.3 – Return Values
OK Indicates success.
ERR Indicates that moving the window put part or
all of the window off the edge of the terminal
screen. The terminal screen remains unaltered.
343 – nanosleep
High-resolution sleep (REALTIME). Suspends a process (or thread
in a threaded program) from execution for the specified timer
interval.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <time.h>
int nanosleep (const struct timespec *rqtp, struct timespec *rmtp);
343.1 – Arguments
rqtp
A pointer to the timespec data structure that defines the time
interval during which the calling process or thread is suspended.
rmtp
A pointer to the timespec data structure that receives the amount
of time remaining in the previously requested interval, or zero
if the full interval has elapsed.
343.2 – Description
The nanosleep function suspends a process or thread until one of
the following conditions is met:
o The time interval specified by the rqtp argument has elapsed.
o A signal is delivered to the calling process and the action
is to invoke a signal-catching function or to terminate the
process.
The suspension time may be longer than requested because the
argument value is rounded up to an integer multiple of the sleep
resolution or because of the scheduling of other activity by the
system. Except when interrupted by a signal, the suspension time
is not less than the time specified by the rqtp argument (as
measured by the system clock, CLOCK_REALTIME).
The use of the nanosleep function has no effect on the action or
blockage of any signal.
If the requested time has elapsed, the call was successful and
the nanosleep function returns zero.
On failure, the nanosleep function returns -1 and sets errno
to indicate the failure. The function fails if it has been
interrupted by a signal, or if the rqtp argument specified
a nanosecond value less than 0 or greater than or equal to 1
billion.
If the rmtp argument is non-NULL, the timespec structure it
references is updated to contain the amount of time remaining in
the interval (the requested time minus the time actually slept).
If the rmtp argument is NULL, the remaining time is not returned.
See also clock_getres, clock_gettime, clock_settime, and sleep.
343.3 – Return Values
0 Indicates success. The requested time has
elapsed.
-1 Indicates failure. The function call was
unsuccessful or was interrupted by a signal;
errno is set to one of the following values:
o EINTR - The nanosleep function was
interrupted by a signal.
o EINVAL - The rqtp argument specified a
nanosecond value less than 0 or greater
than or equal to 1 billion.
344 – newwin
Creates a new window with numlines lines and numcols columns
starting at the coordinates (begin_y,begin_x) on the terminal
screen.
Format
#include <curses.h>
WINDOW *newwin (int numlines, int numcols, int begin_y, int
begin_x);
344.1 – Arguments
numlines
If it is 0, the newwin function sets that dimension to LINES
(begin_y). To get a new window of dimensions LINES by COLS, use
the following line:
newwin (0, 0, 0, 0)
numcols
If it is 0, the newwin function sets that dimension to COLS
(begin_x). Therefore, to get a new window of dimensions LINES
by COLS, use the following line:
newwin (0, 0, 0, 0)
begin_y
A window coordinate.
begin_x
A window coordinate.
344.2 – Return Values
x The address of the allocated window.
ERR Indicates an error.
345 – nextafter
Returns the next machine-representable number following x in the
direction of y.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double nextafter (double x, double y);
float nextafterf (float x, float y);
long double nextafterl (long double x, long double y);
345.1 – Arguments
x
A real number.
y
A real number.
345.2 – Description
The nextafter functions return the next machine-representable
floating-point number following x in the direction of y. If
y is less than x, nextafter returns the largest representable
floating-point number less than x.
345.3 – Return Values
n The next representable floating-point value
following x in the direction of y.
HUGE_VAL Overflow; errno is set to ERANGE.
NaN x or y is NaN; errno is set to EDOM.
346 – nexttoward
Equivalent to the nextafter function, with exceptions noted in
the Description.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double nexttoward (double x, long double y);
float nexttowardf (float x, long double y);
long double nexttowardl (long double x, long double y);
346.1 – Arguments
x
A real number.
y
A real number.
346.2 – Description
The nexttoward functions are equivalent to the corresponding
nextafter functions, except that the second parameter has type
long double and the functions return y converted to the type of
the function if x equals y.
346.3 – Return Values
n The next representable floating-point value
following x in the direction of y.
y (of the type x) If x equals y.
HUGE_VAL Overflow; errno is set to ERANGE.
NaN x or y is NaN; errno is set to EDOM.
347 – nice
Increases or decreases process priority relative to the process
current priority by the amount of the argument. This function is
nonreentrant.
Format
#include <unistd.h>
int nice (int increment);
347.1 – Argument
increment
As a positive argument, decreases priority; as a negative
argument, increases priority. Issuing nice(0) restores the
base priority. The resulting priority cannot be less than 1,
or greater than the process's base priority. If it is, the nice
function quietly does nothing.
347.2 – Description
When a process calls the vfork function, the resulting child
inherits the parent's priority.
With the DECC$ALLOW_UNPRIVILEGED_NICE feature logical enabled,
the nice function exhibits its legacy behavior of not checking
the privilege of the calling process (that is, any user may lower
the nice value to increase process priorities). Also, when the
caller sets a priority above MAX_PRIORITY, the nice value is set
to the base priority.
With DECC$ALLOW_UNPRIVILEGED_NICE disabled, the nice function
conforms to the X/Open standard of checking the privilege of the
calling process (only users with ALTPRI privilege can lower the
nice value to increase process priorities), and when the caller
sets a priority above MAX_PRIORITY, the nice value is set to MAX_
PRIORITY.
See also vfork.
347.3 – Return Values
0 Indicates success.
-1 Indicates failure.
348 – nint
Returns the nearest integral value to the argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double nint (double x);
float nintf (float x,);
long double nintl (long double x);
348.1 – Argument
x
A real number.
348.2 – Description
The nint functions return the nearest integral value to x,
except halfway cases are rounded to the integral value larger
in magnitude. This corresponds to the Fortran generic intrinsic
function nint.
348.3 – Return Values
n The nearest integral value to x.
NaN x is NaN; errno is set to EDOM.
349 – [no]nl
The nl and nonl functions are provided only for UNIX software
compatibility and have no function in the OpenVMS environment.
Format
#include <curses.h>
void nl (void);
void nonl (void);
350 – nl_langinfo
Returns a pointer to a string that contains information obtained
from the program's current locale.
Format
#include <langinfo.h>
char *nl_langinfo (nl_item item);
350.1 – Argument
item
The name of a constant that specifies the information required.
These constants are defined in <langinfo.h>.
The following constants are valid:
Constant Category Description
D_T_FMT LC_TIME String for formatting date and time
D_FMT LC_TIME String for formatting date
T_FMT LC_TIME String for formatting time
T_FMT_AMPM LC_TIME Time format with AM/PM string
AM_STR LC_TIME String that represents AM in 12-hour
clock notation
PM_STR LC_TIME String that represents PM in 12-hour
clock notation
DAY_1 LC_TIME The name of the first day of the week
. . .
DAY_7 LC_TIME The name of the seventh day of the week
ABDAY_1 LC_TIME The abbreviated name of the first day
of the week
. . .
ABDAY_7 LC_TIME The abbreviated name of the seventh day
of the week
MON_1 LC_TIME The name of the first month in the year
. . .
MON_12 LC_TIME The name of the twelfth month in the
year
ABMON_1 LC_TIME The abbreviated name of the first month
in the year
. . .
ABMON_12 LC_TIME The abbreviated name of the twelfth
month in the year
ERA LC_TIME Era description strings
ERA_D_FMT LC_TIME Era date format string
ERA_T_FMT LC_TIME Era time format
ERA_D_T_FMT LC_TIME Era date and time format
ALT_DIGITS LC_TIME Alternative symbols for digits
RADIXCHAR LC_NUMERIC The radix character
THOUSEP LC_NUMERIC The character used to separate groups
of digits in nonmonetary values
YESEXP LC_MESSAGES The expression for affirmative
responses to yes/no questions
NOEXP LC_MESSAGES The expression for negative responses
to yes/no questions
CRNCYSTR LC_MONETARY The currency symbol. It is preceded by
one of the following:
o A minus (-) if the symbol is to
appear before the value
o A plus (+) if the symbol is to
appear after the value
o A period (.) if the symbol replaces
the radix character
CODESET LC_CTYPE Codeset name
350.2 – Description
If the current locale does not have language information defined,
the function returns information from the C locale. The program
should not modify the string returned by the function. This
string might be overwritten by subsequent calls to nl_langinfo.
If the setlocale function is called after a call to nl_langinfo,
then the pointer returned by the previous call to nl_langinfo
will be unspecified. In this case, the nl_langinfo function
should be called again.
350.3 – Return Value
x Pointer to the string containing the requested
information. If item is invalid, the function
returns an empty string.
350.4 – Example
#include <stdio.h>
#include <locale.h>
#include <langinfo.h>
/* This test sets up the British English locale, and then */
/* inquires on the data and time format, first day of the week, */
/* and abbreviated first day of the week. */
#include <stdlib.h>
#include <string.h>
int main()
{
char *return_val;
char *nl_ptr;
/* set the locale, with user supplied locale name */
return_val = setlocale(LC_ALL, "en_gb.iso8859-1");
if (return_val == NULL) {
printf("ERROR : The locale is unknown");
exit(1);
}
printf("+----------------------------------------+\n");
/* Get the date and time format from the locale. */
printf("D_T_FMT = ");
/* Compare the returned string from nl_langinfo with */
/* an empty string. */
if (!strcmp((nl_ptr = (char *) nl_langinfo(D_T_FMT)), "")) {
/* The string returned was empty this could mean that either */
/* 1) The locale does not contain a value for this item */
/* 2) The value for this item is an empty string */
printf("nl_langinfo returned an empty string\n");
}
else {
/* Display the date and time format */
printf("%s\n", nl_ptr);
}
/* Get the full name for the first day of the week from locale */
printf("DAY_1 = ");
/* Compare the returned string from nl_langinfo with */
/* an empty string. */
if (!strcmp((nl_ptr = (char *) nl_langinfo(DAY_1)), "")) {
/* The string returned was empty this could mean that either */
/* 1) The locale does not contain a value for the first */
/* day of the week */
/* 2) The value for the first day of the week is */
/* an empty string */
printf("nl_langinfo returned an empty string\n");
}
else {
/* Display the full name of the first day of the week */
printf("%s\n", nl_ptr);
}
/* Get the abbreviated name for the first day of the week from locale*/
printf("ABDAY_1 = ");
/* Compare the returned string from nl_
langinfo with an empty */
/* string. */
if (!strcmp((nl_ptr = (char *) nl_langinfo(ABDAY_1)), "")) {
/* The string returned was empty this could mean that either */
/* 1) The locale does not contain a value for the first */
/* day of the week */
/* 2) The value for the first day of the week is an */
/* empty string */
printf("nl_langinfo returned an empty string\n");
}
else {
/* Display the abbreviated name of the first day of the week */
printf("%s\n", nl_ptr);
}
}
Running the example program produces the following result:
+----------------------------------------+
D_T_FMT = %a %e %b %H:%M:%S %Y
DAY_1 = Sunday
ABDAY_1 = Sun
351 – nrand48
Generates uniformly distributed pseudorandom-number sequences.
Returns 48-bit signed long integers.
Format
#include <stdlib.h>
long int nrand48 (unsigned short int xsubi[3]);
351.1 – Argument
xsubi
An array of three short ints that, when concatenated together,
form a 48-bit integer.
351.2 – Description
The nrand48 function generates pseudorandom numbers using the
linear congruential algorithm and 48-bit integer arithmetic.
The nrand48 function returns nonnegative, long integers uniformly
distributed over the range of y values, such that 0
The function works by generating a sequence of 48-bit integer
values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n >= 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke the lcong48 function, the multiplier
value a and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The nrand48 function requires that the calling program pass an
array as the xsubi argument, which for the first call must be
initialized to the initial value of the pseudorandom-number
sequence. Unlike the drand48 function, it is not necessary to
call an initialization function prior to the first call.
By using different arguments, the nrand48 function allows
separate modules of a large program to generate several
independent sequences of pseudorandom numbers. For example, the
sequence of numbers that one module generates does not depend
upon how many times the functions are called by other modules.
351.3 – Return Value
n Returns nonnegative, long integers over the
range 0
352 – open
Opens a file for reading, writing, or editing. It positions the
file at its beginning (byte 0).
Format
#include <fcntl.h>
int open (const char *file_spec, int flags, mode_t mode);
(ANSI C)
int open (const char *file_spec, int flags, . . . );
(DEC C Extension)
352.1 – Arguments
file_spec
A null-terminated character string containing a valid file
specification. If you specify a directory in the file_spec and
it is a search list that contains an error, VSI C interprets
it as a file open error.
If the file_spec parameter refers to a symbolic link, the open
function opens the file pointed to by the symbolic link.
flags
The following values are defined in the <fcntl.h> header file:
O_RDONLY Open for reading only
O_WRONLY Open for writing only
O_RDWR Open for reading and writing
O_NDELAY Open for asynchronous input
O_APPEND Append on each write
O_CREAT Create a file if it does not exist
O_TRUNC Create a new version of this file
O_EXCL Error if attempting to create existing file
These flags are set using the bitwise OR operator (|) to
separate specified flags.
Opening a file with O_APPEND causes each write on the file to
be appended to the end. (In contrast, with the VAX C RTL the
behavior of files opened in append mode was to start at EOF and,
thereafter, write at the current file position.)
If O_TRUNC is specified and the file exists, open creates a new
file by incrementing the version number by 1, leaving the old
version in existence.
If O_CREAT is set and the named file does not exist, the C RTL
creates it with any attributes specified in the fourth and
subsequent arguments ( . . . ). If O_EXCL is set with O_CREAT and
the named file exists, the attempted open returns an error.
mode
An unsigned value that specifies the file-protection mode. The
compiler performs a bitwise AND operation on the mode and the
complement of the current protection mode.
You can construct modes by using the bitwise OR operator (|) to
separate specified modes. The modes are:
0400 OWNER:READ
0200 OWNER:WRITE
0100 OWNER:EXECUTE
0040 GROUP:READ
0020 GROUP:WRITE
0010 GROUP:EXECUTE
0004 WORLD:READ
0002 WORLD:WRITE
0001 WORLD:EXECUTE
The system is given the same access privileges as the owner. A
WRITE privilege also implies a DELETE privilege.
. . .
Optional file attribute arguments. The file attribute arguments
are the same as those used in the creat function. For more
information, see the creat function.
352.2 – Description
If a version of the file exists, a new file created with open
inherits certain attributes from the existing file unless
those attributes are specified in the open call. The following
attributes are inherited: record format, maximum record size,
carriage control, and file protection.
NOTES
o If you intend to do random writing to a file, the file
must be opened for update by specifying a flags value of
O_RDWR.
o To create files with OpenVMS RMS default protections
by using the UNIX system-call functions umask, mkdir,
creat, and open, call mkdir, creat, and open with a
file-protection mode argument of 0777 in a program that
never specifically calls umask. These default protections
include correctly establishing protections based on ACLs,
previous versions of files, and so on.
In programs that do vfork/exec calls, the new process
image inherits whether umask has ever been called or not
from the calling process image. The umask setting and
whether the umask function has ever been called are both
inherited attributes.
See also creat, read, write, close, dup, dup2, and lseek.
352.3 – Return Values
x A nonnegative file descriptor number.
-1 Indicates that the file does not exist, that
it is protected against reading or writing, or
that it cannot be opened for another reason.
352.4 – Example
#include <unixio.h>
#include <fcntl.h>
#include <stdlib.h>
main()
{
int file,
stat;
int flags;
flags = O_
RDWR; /* Open for read and write, */
/* with user default file protection, */
/* with max fixed record size of 2048, */
/* and a block size of 2048 bytes. */
file=open("file.dat", flags, 0, "rfm=fix", "mrs=2048", "bls=2048");
if (file == -1)
perror("OPEN error"), exit(1);
close(file);
}
353 – opendir
Opens a specified directory.
Format
#include <dirent.h>
DIR *opendir (const char *dir_name);
353.1 – Argument
dir_name
The name of the directory to be opened.
353.2 – Description
The opendir function opens the directory specified by dir_name
and associates a directory stream with it. The dir_name argument
can be specified in OpenVMS style or UNIX style. The directory
stream is positioned at the first entry. The type DIR, defined
in the <dirent.h> header file, represents a directory stream.
A directory stream is an ordered sequence of all the directory
entries in a particular directory.
The opendir function also returns a pointer to identify the
directory stream in subsequent operations. The NULL pointer is
returned when the directory named by dir_name cannot be accessed,
or when not enough memory is available to hold the entire stream.
NOTES
o An open directory must always be closed with the closedir
function to ensure that the next attempt to open that
directory is successful. The opendir function should be
used with readdir, closedir, and rewinddir to examine the
contents of the directory.
o The opendir function supports UNIX style path name
specifications.
353.3 – Example
See the program example in the description of closedir.
353.4 – Return Values
x A pointer to an object of type DIR.
NULL Indicates an error; errno is set to one of the
following values:
o EACCES - Search permission is denied
for any component of dir_name or read
permission is denied for dir_name.
o ENAMETOOLONG - The length of the dir_name
string exceeds PATH_MAX, or a pathname
component is longer than NAME_MAX.
o ENOENT - The dir_name argument points to
the name of a file that does not exist, or
is an empty string.
354 – overlay
Nondestructively superimposes win1 on win2. The function writes
the contents of win1 that will fit onto win2 beginning at the
starting coordinates of both windows. Blanks on win1 leave
the contents of the corresponding space on win2 unaltered. The
overlay function copies as much of a window's box as possible.
Format
#include <curses.h>
int overlay (WINDOW *win1, WINDOW *win2);
354.1 – Arguments
win1
A pointer to the window.
win2
A pointer to the window.
354.2 – Return Values
OK Indicates success.
ERR Indicates an error.
355 – overwrite
Destructively writes the contents of win1 on win2.
Format
#include <curses.h>
int overwrite (WINDOW *win1, WINDOW *win2);
355.1 – Arguments
win1
A pointer to the window.
win2
A pointer to the window.
355.2 – Description
The overwrite function writes the contents of win1 that will fit
onto win2 beginning at the starting coordinates of both windows.
Blanks on win1 are written on win2 as blanks. This function
copies as much of a window's box as possible.
355.3 – Return Values
OK Indicates success.
ERR Indicates failure.
356 – pathconf
Retrieves file implementation characteristics.
Format
#include <unistd.h>
long int pathconf (const char *path, int name);
356.1 – Arguments
path
The pathname of a file or directory.
name
The configuration attribute to query. If this attribute is
not applicable to the file specified by the path argument, the
pathconf function returns an error.
356.2 – Description
The pathconf function allows an application to determine the
characteristics of operations supported by the file system
underlying the filenamed by path. Read, write, or execute
permission of the named file is not required, but you must be
able to search all directories in the path leading to the file.
Symbolic values for the name argument are defined in the
<unistd.h> header file, as follows:
_PC_LINK_MAX The maximum number of links to the file. If the
path argument refers to a directory, the value
returned applies to the directory itself.
_PC_MAX_CANON The maximum number of bytes in a canonical
input line. This is applicable only to terminal
devices.
_PC_MAX_INPUT The number of types allowed in an input queue.
This is applicable only to terminal devices.
_PC_NAME_MAX Maximum number of bytes in a filename (not
including a terminating null). The byte range
value is between 13 and 255. This is applicable
only to a directory file. The value returned
applies to filenames within the directory.
_PC_PATH_MAX Maximum number of bytes in a pathname (not
including a terminating null). The value is never
larger than 65,535. This is applicable only to a
directory file. The value returned is the maximum
length of a relative pathname when the specified
directory is the working directory.
_PC_PIPE_BUF Maximum number of bytes guaranteed to be written
atomically. This is applicable only to a FIFO.
The value returned applies to the referenced
object. If the path argument refers to a
directory, the value returned applies to any
FIFO that exists or can be created within the
directory.
_PC_CHOWN_ This is applicable only to a directory file. The
RESTRICTED value returned applies to any files (other than
directories) that exist or can be created within
the directory.
_PC_NO_TRUNC Returns 1 if supplying a component name longer
than allowed by NAME_MAX causes an error. Returns
0 (zero) if long component names are truncated.
This is applicable only to a directory file.
_PC_VDISABLE This is always 0 (zero); no disabling character
is defined. This is applicable only to a terminal
device.
356.3 – Return Values
x Resultant value of the configuration attribute
specified in name.
-1 Indicates an error; errno is set to one of the
following values:
o EACCES - Search permission is denied for a
component of the path prefix.
o EINVAL - The name argument specifies an
unknown or inapplicable characteristic.
o EFAULT - The path argument is an invalid
address.
o ENAMETOOLONG - The length of the path
string exceeds PATH_MAX or a pathname
component is longer than NAME_MAX.
o ENOENT - The named file does not exist
or the path argument points to an empty
string.
o ENOTDI - A component of the path prefix is
not a directory.
357 – pause
Suspends the calling process until delivery of a signal whose
action is either to execute a signal-catching function or to
terminate the process.
Format
#include <unistd.h>
int pause (void);
357.1 – Description
The pause function suspends the calling process until delivery
of a signal whose action is either to execute a signal-catching
function or to terminate the process.
If the action is to terminate the process, pause does not return.
If the action is to execute a signal-catching function, pause
returns after the signal-catching function returns.
357.2 – Return Value
Since the pause function suspends process
execution indefinitely unless interrupted by
a signal, there is no successful completion
return value.
-1 In cases where pause returns, the return value
is -1, and errno is set to EINTR.
358 – pclose
Closes a pipe to a process.
Format
#include <stdio.h>
int pclose (FILE *stream);
358.1 – Arguments
stream
A pointer to a FILE structure for an open pipe returned by a
previous call to the popen function.
358.2 – Description
The pclose function closes a pipe between the calling program and
a shell command to be executed. Use pclose to close any stream
you have opened with popen. The pclose function waits for the
associated process to end, and then returns the exit status of
the command. See the description of waitpid for information on
interpreting the exit status.
Beginning with OpenVMS Version 7.3-1, when compiled with the
_VMS_WAIT macro defined, the pclose function returns the OpenVMS
completion code of the child process.
See also popen.
358.3 – Return Values
x Exit status of child.
-1 Indicates an error. The stream argument is not
associated with a popen function. errno is set
to the following:
o ECHILD - cannot obtain the status of the
child process.
359 – perror
Writes a short error message to stderr describing the current
value of errno.
Format
#include <stdio.h>
void perror (const char *str);
359.1 – Argument
str
Usually the name of the program that caused the error.
359.2 – Description
The perror function uses the error number in the external
variable errno to retrieve the appropriate locale-dependent
error message. The function writes out the message as follows:
str (a user-supplied prefix to the error message), followed by a
colon and a space, followed by the message itself, followed by a
new-line character.
See also strerror.
359.3 – Example
#include <stdio.h>
#include <stdlib.h>
main(argc, argv)
int argc;
char *argv[];
{
FILE *fp;
fp = fopen(argv[1], "r"); /* Open an input file. */
if (fp == NULL) {
/* If the fopen call failed, perror prints out a */
/* diagnostic: */
/* */
/* "open: <error message>" */
/* This error message provides a diagnostic explaining */
/* the cause of the failure. */
perror("open");
exit(EXIT_FAILURE);
}
else
fclose(fd) ;
}
360 – pipe
Creates a temporary mailbox that can be used to read and write
data between a parent and child process. The channels through
which the processes communicate are called a pipe.
Format
#include <unistd.h>
int pipe (int array_fdscptr[2]); (ISO POSIX-1)
int pipe (int array_fdscptr[2], . . . ); (DEC C Extension)
360.1 – Arguments
array_fdscptr
An array of file descriptors. A pipe is implemented as an
array of file descriptors associated with a mailbox. These
mailbox descriptors are special in that these are the only file
descriptors which, when passed to the isapipe function, will
return 1.
The file descriptors are allocated in the following way:
o The first available file descriptor is assigned to writing,
and the next available file descriptor is assigned to reading.
o The file descriptors are then placed in the array in reverse
order; element 0 contains the file descriptor for reading, and
element 1 contains the file descriptor for writing.
. . .
Represents three optional, positional arguments, flag, bufsize,
and bufquota:
flag
An optional argument used as a bitmask.
If either the O_NDELAY or O_NONBLOCK bit is set, the I/O
operations to the mailbox through array_fdscptr file descriptors
terminate immediately, rather than waiting for another process.
If, for example, the O_NDELAY bit is set and the child issues
a read request to the mailbox before the parent has put any
data into it, the read terminates immediately with 0 status.
If neither the O_NDELAY nor O_NONBLOCK bit is set, the child
will be waiting on the read until the parent writes any data into
the mailbox. This is the default behavior if no flag argument is
specified.
The values of O_NDELAY and O_NONBLOCK are defined in the
<fcntl.h> header file. Any other bits in the flag argument are
ignored. You must specify this argument if the second optional,
positional argument bufsize is specified. If the flag argument
is needed only to allow specification of the bufsize argument,
specify flag as 0.
bufsize
Optional argument of type int that specifies the size of the
mailbox, in bytes. Specify a value from 512 to 65535.
If you specify 0 or omit this argument, the operating system
creates a mailbox with a default size of 512 bytes.
If you specify a value less than 0 or larger than 65535, the
results are unpredictable.
If you do specify this argument, be sure to precede it with a
flag argument.
The DECC$PIPE_BUFFER_SIZE feature logical can also be used to
specify the size of the mailbox. If bufsize is supplied, it takes
precedence over the value of DECC$PIPE_BUFFER_SIZE. Otherwise,
the value of DECC$PIPE_BUFFER_SIZE is used.
If neither bufsize nor DECC$PIPE_BUFFER_SIZE is specified, the
default buffer size of 512 is used.
bufquota
Optional argument of type int that specifies the buffer quota of
the pipe's mailbox. Specify a value from 512 to 2147483647.
OpenVMS Version 7.3-2 added this argument. In previous OpenVMS
versions, the buffer quota was equal to the buffer size.
The DECC$PIPE_BUFFER_QUOTA feature logical can also be used to
specify the buffer quota. If the optional bufquota argument of
the pipe function is supplied, it takes precedence over the value
of DECC$PIPE_BUFFER_QUOTA. Otherwise, the value of DECC$PIPE_
BUFFER_QUOTA is used.
If neither bufquota nor DECC$PIPE_BUFFER_QUOTA is specified, then
the buffer quota defaults to the buffer size.
360.2 – Description
The mailbox used for the pipe is a temporary mailbox. The mailbox
is not deleted until all processes that have open channels to
that mailbox close those channels. The last process that closes a
pipe writes a message to the mailbox, indicating the end-of-file.
The mailbox is created by using the $CREMBX system service,
specifying the following characteristics:
o A maximum message length of 512 characters
o A buffer quota of 512 characters
o A protection mask granting all privileges to USER and GROUP
and no privileges to SYSTEM or WORLD
The buffer quota of 512 characters implies that you cannot write
more than 512 characters to the mailbox before all or part of the
mailbox is read. Since a mailbox record is slightly larger than
the data part of the message that it contains, not all of the
512 characters can be used for message data. You can increase the
size of the buffer by specifying an alternative size using the
optional, third argument to the pipe function. A pipe under the
OpenVMS system is a stream-oriented file with no carriage-control
attributes. It is fully buffered by default in the C RTL.
A mailbox used as a pipe is different than a mailbox created by
the application. A mailbox created by the application defaults
to a record-oriented file with carriage return, carriage control.
Additionally, writing a zero-length record to a mailbox writes an
EOF, as does each close of the mailbox. For a pipe, only the last
close of a pipe writes an EOF.
The pipe is created by the parent process before vfork and
an exec function are called. By calling pipe first, the child
inherits the open file descriptors for the pipe. You can then use
the getname function to return the name of the mailbox associated
with the pipe, if this information is desired. The mailbox name
returned by getname has the format _MBAnnnn: (Alpha only) or _
MBAnnnnn: (Integrity servers(ONLY)) , where nnnn or nnnnn is a
unique number.
Both the parent and the child need to know in advance which file
descriptors will be allocated for the pipe. This information
cannot be retrieved at run time. Therefore, it is important to
understand how file descriptors are used in any VSI C for
OpenVMS program.
File descriptors 0, 1, and 2 are open in a VSI C for OpenVMS
program for stdin (SYS$INPUT), stdout (SYS$OUTPUT), and stderr
(SYS$ERROR), respectively. Therefore, if no other files are open
when pipe is called, pipe assigns file descriptor 3 for writing
and file descriptor 4 for reading. In the array returned by pipe,
4 is placed in element 0 and 3 is placed in element 1.
If other files have been opened, pipe assigns the first
available file descriptor for writing and the next available
file descriptor for reading. In this case, the pipe does not
necessarily use adjacent file descriptors. For example, assume
that two files have been opened and assigned to file descriptors
3 and 4 and the first file is then closed. If pipe is called at
this point, file descriptor 3 is assigned for writing and file
descriptor 5 is assigned for reading. Element 0 of the array will
contain 5 and element 1 will contain 3.
In large applications that do large amounts of I/O, it gets
more difficult to predict which file descriptors are going to
be assigned to a pipe; and, unless the child knows which file
descriptors are being used, it will not be able to read and write
successfully from and to the pipe.
One way to be sure that the correct file descriptors are being
used is to use the following procedure:
1. Choose two descriptor numbers that will be known to both the
parent and the child. The numbers should be high enough to
account for any I/O that might be done before the pipe is
created.
2. Call pipe in the parent at some point before calling an exec
function.
3. In the parent, use dup2 to assign the file descriptors
returned by pipe to the file descriptors you chose. This now
reserves those file descriptors for the pipe; any subsequent
I/O will not interfere with the pipe.
You can read and write through the pipe using the UNIX I/O
functions read and write, specifying the appropriate file
descriptors. As an alternative, you can issue fdopen calls to
associate file pointers with these file descriptors so that you
can use the Standard I/O functions (fread and fwrite).
Two separate file descriptors are used for reading from and
writing to the pipe, but only one mailbox is used so some I/O
synchronization is required. For example, assume that the parent
writes a message to the pipe. If the parent is the first process
to read from the pipe, then it will read its own message back as
shown in Reading and Writing to a Pipe.
NOTE
For added UNIX portability, you can use the following
feature logicals to control the behavior of the C RTL pipe
implementation:
o Define the DECC$STREAM_PIPE feature logical name to
ENABLE to direct the pipe function to use stream I/O
instead of record I/O.
o Define the DECC$POPEN_NO_CRLF_REC_ATTR feature logical
to ENABLE to prevent CR/LF carriage control from being
added to pipe records for pipes opened with the popen
function. Be aware that enabling this feature might
result in undesired behavior from other functions such
as gets that rely on the carriage-return character.
Figure REF-1 Reading and Writing to a Pipe
360.3 – Return Values
0 Indicates success.
-1 Indicates an error.
361 – poll
Provides users with a mechanism for multiplexing input/output
over a set of file descriptors that reference open streams.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <poll.h>
int poll (struct pollfd filedes [], nfds_t nfds, int timeout);
361.1 – Argument
filedes
Points to an array of pollfd structures, one for each file
descriptor of interest. Each pollfd structure includes the
following members:
int fd - The file descriptor
int events - The requested conditions
int revents - The reported conditions
nfds
The number of pollfd structures in the filedes array.
timeout
The maximum length of time (in milliseconds) to wait for at least
one of the specified events to occur.
361.2 – Description
The poll function provides users with a mechanism for
multiplexing input/output over a set of file descriptors that
reference open streams. For each member of the array pointed
to by filedes, poll examines the given file descriptor for the
event(s) specified in events. The poll function identifies those
streams on which an application can send or receive messages, or
on which certain events have occurred.
The filedes parameter specifies the file descriptor to be
examined and the events of interest for each file descriptor.
It is a pointer to an array of pollfd structures. The fd member
of each pollfd structure specifies an open file descriptor. The
poll function uses the events member to determine what conditions
to report for this file descriptor. If one or more of these
conditions is true, the poll function sets the associated revents
member.
The events and revents members of each pollfd structure are
bitmasks. The calling process sets the events bitmask, and poll
sets the revents bitmasks. These bitmasks contain inclusive
ORed combinations of condition options. The following condition
options are defined:
POLLERR - An error has occurred on the file descriptor. This
option is only valid in the revents bitmask; it is not used in
the events member.
For STREAMS devices, if an error occurs on the file descriptor
and the device is also disconnected, poll returns POLLERR;
POLLERR takes precedence over POLLHUP.
POLLHUP - The device has been disconnected. This event
is mutually exclusive with POLLOUT; a stream can never be
writable if a hangup occurred. However, this event and POLLIN,
POLLRDNORM, POLLRDBAND or POLLPRI are not mutually exclusive.
This option is only valid in the revents bitmask; it is
ignored in the events member.
POLLIN - Data other than high-priority data may be read
without blocking. This option is set in revents even if the
message is of zero length. In revents, this option is mutually
exclusive with POLLPRI.
POLLNVAL - The value specified for fd is invalid. This option
is only valid in the revents member; it is ignored in the
events member.
POLLOUT - Normal (priority band equals 0) data may be written
without blocking.
POLLPRI - High-priority data may be received without blocking.
This option is set in revents even if the message is of zero
length. In revents, this option is mutually exclusive with
POLLIN.
POLLRDBAND - Data from a nonzero priority band may be read
without blocking. This option is set in revents even if the
message is of zero length.
POLLRDNORM - Normal data (priority band equals 0) may be read
without blocking. This option is set in revents even if the
message is of zero length.
POLLWRBAND - Priority data (priority band greater than 0)
may be written. This event only examines bands that have been
written to at least once.
POLLWRNORM - Same as POLLOUT.
The poll function ignores any pollfd structure whose fd member
is less than 0 (zero). If the fd member of all pollfd structures
is less than 0, the poll function will return 0 and have no other
results.
The conditions indicated by POLLNORM and POLLOUT are true if and
only if at least one byte of data can be read or written without
blocking. There are two exceptions: regular files, which always
poll true for POLLNORM and POLLOUT, and pipes, when the rules
for the operation specify to return zero in order to indicate
end-of-file.
The condition options POLLERR, POLLHUP, and POLLNVAL are always
set in revents if the conditions they indicate are true for the
specified file descriptor, whether or not these options are set
in events.
For each call to the poll function, the set of reportable
conditions for each file descriptor consists of those conditions
that are always reported, together with any further conditions
for which options are set in events. If any reportable condition
is true for any file descriptor, the poll function will return
with options set in revents for each true condition for that file
descriptor.
If no reportable condition is true for any of the file
descriptors, the poll function waits up to timeout milliseconds
for a reportable condition to become true. If, in that time
interval, a reportable condition becomes true for any of the file
descriptors, poll reports the condition in the file descriptor's
associated revents member and returns. If no reportable condition
becomes true, poll returns without setting any revents bitmasks.
If the timeout parameter is a value of -1, the poll function does
not return until at least one specified event has occurred. If
the value of the timeout parameter is 0 (zero), the poll function
does not wait for an event to occur but returns immediately, even
if no specified event has occurred.
The behavior of the poll function is not affected by whether
the O_NONBLOCK option is set on any of the specified file
descriptors.
The poll function supports regular files, terminal and pseudo-
terminal devices, STREAMS-based files, FIFOs, and pipes. The
behavior of poll on elements of file descriptors that refer to
other types of files is unspecified.
For sockets, a file descriptor for a socket that is listening for
connections indicates it is ready for reading after connections
are available. A file descriptor for a socket that is connecting
asynchronously indicates it is ready for writing after a
connection is established.
361.3 – Return Values
n Upon successful completion, a nonnegative
value is returned, indicating the number of
file descriptors for which poll has set the
revents bitmask.
0 poll has timed out and has not set any of the
revents bitmasks.
-1 An error occurred. errno is set to indicate
the error:
o EAGAIN - Allocation of internal data
structures failed. A later call to the
poll function might complete successfully.
o EINTR - A signal was intercepted during the
poll function, and the signal handler was
installed with an indication that functions
are not to be restarted.
o EINVAL - The nfds parameter is greater than
OPEN_MAX, or one of the fd members refers
to a stream or multiplexer that is linked
(directly or indirectly) downstream from a
multiplexer.
362 – popen
Initiates a pipe to a process.
Format
#include <stdio.h>
FILE *popen (const char *command, const char *type);
362.1 – Arguments
command
A pointer to a null-terminated string containing a shell command
line.
type
A pointer to a null-terminated string containing an I/O mode.
Because open files are shared, you can use a type r command as
an input filter and a type w command as an output filter. Specify
one of the following values for the type argument:
o r-the calling program can read from the standard output of the
command by reading from the returned file stream.
o w-the calling program can write to the standard input of the
command by writing to the returned file stream.
362.2 – Description
The popen function creates a pipe between the calling program
and a shell command awaiting execution. It returns a pointer to a
FILE structure for the stream.
The popen function uses the value of the DECC$PIPE_BUFFER_SIZE
feature logical to set the buffer size of the mailbox it creates
for the pipe. You can specify a DECC$PIPE_BUFFER_SIZE value of
512 to 65024 bytes. If DECC$PIPE_BUFFER_SIZE is not specified,
the default buffer size of 512 is used.
NOTES
o When you use the popen function to invoke an output
filter, beware of possible deadlock caused by output
data remaining in the program buffer. You can avoid this
by either using the setvbuf function to ensure that the
output stream is unbuffered, or the fflush function to
ensure that all buffered data is flushed before calling
the pclose function.
o For added UNIX portability, you can use the following
feature logicals to control the behavior of the C RTL
pipe implementation:
- Define the DECC$STREAM_PIPE feature logical name to
ENABLE to direct the pipe function to use stream I/O
instead of record I/O.
- Define the DECC$POPEN_NO_CRLF_REC_ATTR feature logical
to ENABLE to prevent CR/LF carriage control from being
added to pipe records for pipes opened with the popen
function. Be aware that enabling this feature might
result in undesired behavior from other functions such
as gets that rely on the carriage-return character.
See also fflush, pclose, and setvbuf.
362.3 – Return Values
x A pointer to the FILE structure for the opened
stream.
NULL Indicates an error. Unable to create files or
processes.
363 – pow
Returns the first argument raised to the power of the second
argument.
Format
#include <math.h>
double pow (double x, double y);
float powf (float x, float y); (Integrity servers, Alpha)
long double powl (long double x, long double y);
(Integrity servers, Alpha)
363.1 – Arguments
x
A floating-point base to be raised to an exponent y.
y
The exponent to which the base x is to be raised.
363.2 – Description
The pow functions raise a floating-point base x to a floating-
point exponent y. The value of pow(x,y) is computed as e**(y
ln(x)) for positive x.
If x is 0 and y is negative, HUGE_VAL is returned and errno is
set to ERANGE or EDOM.
363.3 – Return Values
x The result of the first argument raised to the
power of the second.
1.0 The base is 0 and the exponent is 0.
HUGE_VAL The result overflowed; errno is set to ERANGE.
HUGE_VAL The base is 0 and the exponent is negative;
errno is set to ERANGE or EDOM.
363.4 – Example
#include <stdio.h>
#include <math.h>
#include <errno.h>
main()
{
double x;
errno = 0;
x = pow(-3.0, 2.0);
printf("%d, %f\n", errno, x);
}
This example program outputs the following:
0, 9.000000
364 – pread
Reads bytes from a given position within a file without changing
the file pointer.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
ssize_t pread (int file_desc, void *buffer, size_t nbytes,
off_t offset);
364.1 – Arguments
file_desc
A file descriptor that refers to a file currently opened for
reading.
buffer
The address of contiguous storage in which the input data is
placed.
nbytes
The maximum number of bytes involved in the read operation.
offset
The offset for the desired position inside the file.
364.2 – Description
The pread function performs the same action as read, except that
it reads from a given position in the file without changing the
file pointer. The first three arguments to pread are the same as
for read, with the addition of a fourth argument offset for the
desired position inside the file. An attempt to perform a pread
on a file that is incapable of seeking results in an error.
364.3 – Return Values
n The number of bytes read.
-1 Upon failure, the file pointer remains
unchanged and pread sets errno to one of the
following values:
o EINVAL - The offset argument is invalid.
The value is negative.
o EOVERFLOW - The file is a regular file, and
an attempt was made to read or write at or
beyond the offset maximum associated with
the file.
o ENXIO - A request was outside the
capabilities of the device.
o ESPIPE - fildes is associated with a pipe
or FIFO.
365 – printf
Performs formatted output from the standard output (stdout).
Format
#include <stdio.h>
int printf (const char *format_spec, . . . );
365.1 – Arguments
format_spec
Characters to be written literally to the output or converted as
specified in the . . . arguments.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, you may omit the
output sources. Otherwise, the function call must have exactly
as many output sources as there are conversion specifications,
and the conversion specifications must match the types of the
output sources.
Conversion specifications are matched to output sources in left-
to-right order. Excess output pointers, if any, are ignored.
365.2 – Return Values
x The number of bytes written.
Negative value Indicates that an output error occurred.
The function sets errno. For a list of errno
values set by this function, see fprintf.
366 – [w]printw
Perform a printf in the specified window, starting at the current
position of the cursor. The printw function acts on the stdscr
window.
Format
#include <curses.h>
printw (char *format_spec, . . . );
int wprintw (WINDOW *win, char *format_spec, . . . );
366.1 – Arguments
win
A pointer to the window.
format_spec
A pointer to the format specification string.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, you may omit the
output sources. Otherwise, the function call must have exactly
as many output sources as there are conversion specifications,
and the conversion specifications must match the types of the
output sources.
Conversion specifications are matched to output sources in left-
to-right order. Excess output pointers, if any, are ignored.
366.2 – Description
The formatting specification (format_spec) and the other
arguments are identical to those used with the printf function.
The printw and wprintw functions format and then print the
resultant string to the window using the addstr function. For
more information, see the printf and scrollok functions in this
section.
366.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the window
scroll illegally.
367 – putc
The putc macro writes a single character to a specified file.
Format
#include <stdio.h>
int putc (int character, FILE *file_ptr);
367.1 – Arguments
character
The character to be written.
file_ptr
A file pointer to the output stream.
367.2 – Description
The putc macro writes the byte character (converted to an
unsigned char) to the output specified by the file_ptr parameter.
The byte is written at the position at which the file pointer
is currently pointing (if defined) and advances the indicator
appropriately. If the file cannot support positioning requests,
or if the output stream was opened with append mode, the byte is
appended to the output stream.
Since putc is a macro, a file pointer argument with side effects
(for example, putc (ch, *f++)) might be evaluated incorrectly. In
such a case, use the fputc function instead.
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
See also putc_unlocked.
367.3 – Return Values
x The character written to the file. Indicates
success.
EOF Indicates output errors.
368 – putc_unlocked
Same as putc, except used only within a scope protected by
flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int putc_unlocked (int character, FILE *file_ptr);
368.1 – Argument
character
The character to be written.
file_ptr
A file pointer to the output stream.
368.2 – Description
The reentrant version of the putc macro is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the stream. The unlocked version of this
call, putc_unlocked can be used to avoid the overhead. The putc_
unlocked macro is functionally identical to the putc macro,
except that it is not required to be implemented in a thread-
safe manner. The putc_unlocked macro can be safely used only
within a scope that is protected by the flockfile and funlockfile
functions used as a pair. The caller must ensure that the stream
is locked before putc_unlocked is used.
Since putc_unlocked is a macro, a file pointer argument with side
effects might be evaluated incorrectly. In such a case, use the
fputc_unlocked function instead.
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
See also flockfile, ftrylockfile, and funlockfile.
368.3 – Return Values
x The character written to the file. Indicates
success.
EOF Indicates the end-of-file or an error.
369 – putchar
Writes a single character to the standard output (stdout) and
returns the character.
Format
#include <stdio.h>
int putchar (int character);
369.1 – Argument
character
An object of type int.
369.2 – Description
The putchar function is identical to fputc (character, stdout).
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
369.3 – Return Values
character Indicates success.
EOF Indicates output errors.
370 – putchar_unlocked
Same as putchar, except used only within a scope protected by
flockfile and funlockfile.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int putchar_unlocked (int character);
370.1 – Argument
character
An object of type int.
370.2 – Description
The reentrant version of the putchar function is locked against
multiple threads calling it simultaneously. This incurs overhead
to ensure integrity of the output stream. The unlocked version of
this call, putchar_unlocked can be used to avoid the overhead.
The putchar_unlocked function is functionally identical to
the putchar function, except that it is not required to be
implemented in a thread-safe manner. The putchar_unlocked
function can be safely used only within a scope that is protected
by the flockfile and funlockfile functions used as a pair. The
caller must ensure that the stream is locked before putchar_
unlocked is used.
Compiling with the __UNIX_PUTC macro defined enables an
optimization that uses a faster, inlined version of this
function.
See also flockfile, ftrylockfile, and funlockfile.
370.3 – Return Values
x The next character from stdin, converted to
int.
EOF Indicates the end-of-file or an error.
371 – putenv
Sets an environmental variable.
Format
#include <stdlib.h>
int putenv (const char *string);
371.1 – Argument
string
A pointer to a name=value string.
371.2 – Description
The putenv function sets the value of an environment variable
by altering an existing variable or by creating a new one. The
string argument points to a string of the form name=value, where
name is the environment variable and value is the new value for
it.
The string pointed to by string becomes part of the environment,
so altering the string changes the environment. When a new
string-defining name is passed to putenv, the space used by
string is no longer used.
NOTES
o The putenv function manipulates the environment pointed
to by the environ external variable, and can be used with
getenv. However, the third argument to the main function
(the environment pointer), is not changed.
The putenv function uses the malloc function to enlarge
the environment.
A potential error is to call putenv with an automatic
variable as the argument, then exit the calling function
while string is still part of the environment.
o Do not use the setenv, getenv, and putenv functions
to manipulate symbols and logicals. Instead, use the
OpenVMS library calls lib$set_logical, lib$get_logical,
lib$set_symbol, and lib$get_symbol. The *env functions
deliberately provide UNIX behavior, and are not a
substitute for these OpenVMS runtime library calls.
OpenVMS DCL symbols, not logical names, are the closest
analog to environment variables on UNIX systems. While
getenv is a mechanism to retrieve either a logical name
or a symbol, it maintains an internal cache of values for
use with setenv and subsequent getenv calls. The setenv
function does not write or create DCL symbols or OpenVMS
logical names.
This is consistent with UNIX behavior. On UNIX systems,
setenv does not change or create any symbols that will be
visible in the shell after the program exits.
371.3 – Return Values
0 Indicates success.
-1 Indicates an error. errno is set to ENOMEM-
Not enough memory available to expand the
environment list.
371.4 – Restriction
The putenv function cannot take a 64-bit address.
372 – puts
Writes a character string to the standard output (stdout)
followed by a new-line character.
Format
#include <stdio.h>
int puts (const char *str);
372.1 – Argument
str
A pointer to a character string.
372.2 – Description
The puts function does not copy the terminating null character to
the output stream.
372.3 – Return Values
Nonnegative value Indicates success.
EOF Indicates output errors.
373 – putw
Writes characters to a specified file.
Format
#include <stdio.h>
int putw (int integer, FILE *file_ptr);
373.1 – Arguments
integer
An object of type int or long.
file_ptr
A file pointer.
373.2 – Description
The putw function writes four characters to the output file as an
int. No conversion is performed.
373.3 – Return Values
integer Indicates success.
EOF Indicates output errors.
374 – putwc
Converts a wide character to its corresponding multibyte value,
and writes the result to a specified file.
Format
#include <wchar.h>
wint_t putwc (wint_t wc, FILE *file_ptr);
374.1 – Arguments
wc
An object of type wint_t.
file_ptr
A file pointer.
374.2 – Description
Since putwc might be implemented as a macro, a file pointer
argument with side effects (for example putwc (wc, *f++)) might
be evaluated incorrectly. In such a case, use the fputwc function
instead.
See also fputwc.
374.3 – Return Values
x The character written to the file. Indicates
success.
WEOF Indicates an output error. The function sets
errno. For a list of the errno values set by
this function, see fputwc.
375 – putwchar
Writes a wide character to the standard output (stdout) and
returns the character.
Format
#include <wchar.h>
wint_t putwchar (wint_t wc);
375.1 – Arguments
wc
An object of type wint_t.
375.2 – Description
The putwchar function is identical to fputwc(wc, stdout).
375.3 – Return Values
x The character written to the file. Indicates
success.
WEOF Indicates an output error. The function sets
errno. For a list of the errno values set by
this function, see fputwc.
376 – pwrite
Writes into a given position within a file without changing the
file pointer.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
ssize_t pwrite (int file_desc, const void *buffer, size_t
nbytes, off_t offset);
376.1 – Arguments
file_desc
A file descriptor that refers to a file currently opened for
writing or updating.
buffer
The address of contiguous storage from which the output data is
taken.
nbytes
The maximum number of bytes involved in the write operation.
offset
The offset for the desired position inside the file.
376.2 – Description
The pwrite function performs the same action as write, except
that it writes into a given position in the file without changing
the file pointer. The first three arguments to pwrite are the
same as for write, with the addition of a fourth argument offset
for the desired position inside the file.
376.3 – Return Values
n The number of bytes written.
-1 Upon failure, the file pointer remains
unchanged and pwrite sets errno to one of
the following values:
o EINVAL - The offset argument is invalid.
The value is negative.
o ESPIPE - fildes is associated with a pipe
or FIFO.
377 – qabs,llabs
Returns the absolute value of an integer as an __int64. llabs is
a synonym for qabs.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdlib.h>
__int64 qabs (__int64 j);
__int64 llabs (__int64 j);
377.1 – Argument
j
A value of type __int64.
378 – qdiv,lldiv
Returns the quotient and the remainder after the division of its
arguments. lldiv is a synonym for qdiv.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdlib.h>
qdiv_t qdiv (__int64 numer, __int64 denom);
lldiv_t lldiv (__int64 numer, __int64 denom);
378.1 – Arguments
numer
A numerator of type __int64.
denom
A denominator of type __int64.
378.2 – Description
The types qdiv_t and lldiv_t are defined in the <stdlib.h> header
file as follows:
typedef struct
{
__int64 quot, rem;
} qdiv_t, lldiv_t;
379 – qsort
Sorts an array of objects in place. It implements the quick-sort
algorithm.
Format
#include <stdlib.h>
void qsort (void *base, size_t nmemb, size_t size, int
(*compar) (const void *, const void *));
379.1 – Function Variants
The qsort function has variants named _qsort32 and _qsort64 for
use with 32-bit and 64-bit pointer sizes, respectively.
379.2 – Arguments
base
A pointer to the first member of the array. The pointer should be
of type pointer-to-element and cast to type pointer-to-character.
nmemb
The number of objects in the array.
size
The size of an object, in bytes.
compar
A pointer to the comparison function.
379.3 – Description
Two arguments are passed to the comparison function pointed to
by compar. The two arguments point to the objects being compared.
Depending on whether the first argument is less than, equal to,
or greater than the second argument, the comparison function
returns an integer less then, equal to, or greater than 0.
The comparison function compar need not compare every byte, so
arbitrary data might be contained in the objects in addition to
the values being compared.
The order in the output of two objects that compare as equal is
unpredictable.
380 – raise
Generates a specified software signal. Generating a signal causes
the action routine established by the signal, ssignal, or sigvec
function to be invoked.
Format
#include <signal.h>
int raise (int sig); (ANSI C)
int raise (int sig[, int sigcode]); (DEC C Extension)
380.1 – Arguments
sig
The signal to be generated.
sigcode
An optional signal code, available only when not compiling in
strict ANSI C mode. For example, signal SIGFPE-the arithmetic
trap signal-has 10 different codes, each representing a different
type of arithmetic trap.
The signal codes can be represented by mnemonics or numbers. The
arithmetic trap codes are represented by the numbers 1 to 10;
the SIGILL codes are represented by the numbers 0 to 2. The code
values are defined in the <signal.h> header file.
380.2 – Description
Calling the raise function has one of the following results:
o If raise specifies a sig argument that is outside the range
defined in the <signal.h> header file, then the raise function
returns 0, and the errno variable is set to EINVAL.
o If signal, ssignal, or sigvec establishes SIG_DFL (default
action) for the signal, then the functions do not return. The
image is exited with the OpenVMS error code corresponding to
the signal.
o If signal, ssignal, or sigvec establishes SIG_IGN (ignore
signal) as the action for the signal, then raise returns its
argument, sig.
o signal, ssignal, or sigvec must establish an action function
for the signal. That function is called and its return value
is returned by raise.
See also gsignal, signal, ssignal, and sigvec.
380.3 – Return Values
0 If successful.
nonzero If unsuccessful.
381 – rand
Returns pseudorandom numbers in the range 0 to 2[31] - 1.
Format
#include <stdlib.h>
int rand (void);
int rand_r (unsigned int seed); (Integrity servers, Alpha)
381.1 – Argument
seed
An initial seed value.
381.2 – Description
The rand function computes a sequence of pseudorandom integers in
the range 0 to {RAND_MAX} with a period of at least 2[32].
The rand_r function computes a sequence of pseudorandom integers
in the range 0 to {RAND_MAX}. The value of the {RAND_MAX} macro
will be at least 32767.
If rand_r is called with the same initial value for the object
pointed to by seed and that object is not modified between
successive returns and calls to rand_r, the same sequence is
generated.
See also srand.
For other random-number algorithms, see random and all the *48
functions.
381.3 – Return Value
n A pseudorandom number.
382 – random
Generates pseudorandom numbers in a more random sequence.
Format
#include <stdlib.h>
long int random (void);
382.1 – Description
The random function is a random-number generator that has
virtually the same calling sequence and initialization properties
as the rand function, but produces sequences that are more
random. The low 12 bits generated by rand go through a cyclic
pattern. All bits generated by random are usable. For example,
random() &1 produces a random binary value.
The random function uses a nonlinear, additive-feedback, random-
number generator employing a default state-array size of 31
integers to return successive pseudorandom numbers in the range
from 0 to 231 - 1. The period of this random-number generator is
approximately 16*(231 -1). The size of the state array determines
the period of the random-number generator. Increasing the state
array size increases the period.
With a full 256 bytes of state information, the period of the
random-number generator is greater than 269, and is sufficient
for most purposes.
Like the rand function, the random function produces by default a
sequence of numbers that you can duplicate by calling the srandom
function with a value of 1 as the seed. The srandom function,
unlike the srand function, does not return the old seed because
the amount of state information used is more than a single word.
See also rand, srand, srandom, setstate, and initstate.
382.2 – Return Value
n A random number.
383 – [no]raw
Raw mode only works with the Curses input routines [w]getch
and [w]getstr. Raw mode is not supported with the C RTL
emulation of UNIX I/O, Terminal I/O, or Standard I/O.
Format
#include <curses.h>
raw()
noraw()
383.1 – Description
Raw mode reads are satisfied on one of two conditions: after
a minimum number (5) of characters are input at the terminal
or after waiting a fixed time (10 seconds) from receipt of any
characters from the terminal.
383.2 – Example
/* Example of standard and raw input in Curses package. */
#include <curses.h>
main()
{
WINDOW *win1;
char vert = '.',
hor = '.',
str[80];
/* Initialize standard screen, turn echo off. */
initscr();
noecho();
/* Define a user window. */
win1 = newwin(22, 78, 1, 1);
leaveok(win1, TRUE);
leaveok(stdscr, TRUE);
box(stdscr, vert, hor);
/* Reset the video, refresh(redraw) both windows. */
mvwaddstr(win1, 2, 2, "Test line terminated input");
wrefresh(win1);
/* Do some input and output it. */
nocrmode();
wgetstr(win1, str);
mvwaddstr(win1, 5, 5, str);
mvwaddstr(win1, 7, 7, "Type something to clear screen");
wrefresh(win1);
/* Get another character then delete the window. */
wgetch(win1);
wclear(win1);
mvwaddstr(win1, 2, 2, "Test raw input");
wrefresh(win1);
/* Do some raw input 5 chars or timeout and output it. */
raw();
getstr(str);
noraw();
mvwaddstr(win1, 5, 5, str);
mvwaddstr(win1, 7, 7, "Raw input completed");
wrefresh(win1);
endwin();
}
384 – read
Reads bytes from a file and places them in a buffer.
Format
#include <unistd.h>
ssize_t read (int file_desc, void *buffer, size_t nbytes);
(ISO POSIX-1)
int read (int file_desc, void *buffer, int nbytes);
(Compatibility)
384.1 – Arguments
file_desc
A file descriptor. The specified file descriptor must refer to a
file currently opened for reading.
buffer
The address of contiguous storage in which the input data is
placed.
nbytes
The maximum number of bytes involved in the read operation.
384.2 – Description
The read function returns the number of bytes read. The return
value does not necessarily equal nbytes. For example, if the
input is from a terminal, at most one line of characters is read.
NOTE
The read function does not span record boundaries in a
record file and, therefore, reads at most one record. A
separate read must be done for each record.
384.3 – Return Values
n The number of bytes read.
-1 Indicates a read error, including physical
input errors, illegal buffer addresses,
protection violations, undefined file
descriptors, and so forth.
384.4 – Example
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
main()
{
int fd,
i;
char buf[10];
FILE *fp ; /* Temporary STDIO file */
/* Create a dummy data file */
if ((fp = fopen("test.txt", "w+")) == NULL) {
perror("open");
exit(1);
}
fputs("XYZ\n",fp) ;
fclose(fp) ;
/* And now practice "read" */
if ((fd = open("test.txt", O_RDWR, 0, "shr=upd")) <= 0) {
perror("open");
exit(0);
}
/* Read 2 characters into buf. */
if ((i = read(fd, buf, 2)) < 0) {
perror("read");
exit(0);
}
/* Print out what was read. */
if (i > 0)
printf("buf='%c%c'\n", buf[0], buf[1]);
close(fd);
}
385 – readdir
Finds entries in a directory.
Format
#include <dirent.h>
struct dirent *readdir (DIR *dir_pointer);
int readdir_r (DIR *dir_pointer, struct dirent *entry, struct
dirent **result);
385.1 – Arguments
dir_pointer
A pointer to the dir structure of an open directory.
entry
A pointer to a dirent structure that will be initialized with the
directory entry at the current position of the specified stream.
result
Upon successful completion, the location where a pointer to entry
is stored.
385.2 – Description
The readdir function returns a pointer to a structure
representing the directory entry at the current position in the
directory stream specified by dir_pointer, and positions the
directory stream at the next entry. It returns a NULL pointer
upon reaching the end of the directory stream. The dirent
structure defined in the <dirent.h> header file describes a
directory entry.
The type DIR defined in the <dirent.h> header file represents a
directory stream. A directory stream is an ordered sequence of
all the directory entries in a particular directory. Directory
entries represent files. You can remove files from or add files
to a directory asynchronously to the operation of the readdir
function.
The pointer returned by the readdir function points to data
that you can overwrite by another call to readdir on the same
directory stream. This data is not overwritten by another call to
readdir on a different directory stream.
If a file is removed from or added to the directory after
the most recent call to the opendir or rewinddir function, a
subsequent call to the readdir function might not return an entry
for that file.
When it reaches the end of the directory, or when it detects an
invalid seekdir operation, the readdir function returns the null
value.
An attempt to seek to an invalid location causes the readdir
function to return the null value the next time it is called. A
previous telldir function call returns the position.
The readdir_r function is a reentrant version of readdir. In
addition to dir_pointer, you must specify a pointer to a dirent
structure in which the current directory entry of the specified
stream is returned.
If the operation is successful, readdir_r returns 0 and stores
one of the following two pointers in result:
o Pointer to entry if the entry was found
o NULL pointer if the end of the directory stream was reached
The storage pointed to by entry must be large enough for a dirent
with an array of char d_name member containing at least NAME_MAX
+ 1 elements.
If an error occurred, an error value is returned that indicates
the cause of the error.
Applications wishing to check for error situations should set
errno to 0 before calling readdir. If errno is set to nonzero on
return, then an error occurred.
385.3 – Example
See the description of closedir for an example.
385.4 – Return Values
x On successful completion of readdir, a pointer
to an object of type struct dirent.
0 Successful completion of readdir_r.
x On error, an error value (readdir_r only).
NULL An error occurred or end of the directory
stream (readdir_r only). If an error occurred,
errno is set to a value indicating the cause.
386 – readlink
Reads the contents of the specified symbolic link and places them
into a user-supplied buffer.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
ssize_t readlink (const char *restrict link_name, char
*restrict user_buffer, size_t buffer_size);
386.1 – Arguments
link_name
Pointer to the text string representing the name of the symbolic
link file.
user_buffer
Pointer to the user buffer.
buffer_size
Size of the user buffer.
386.2 – Description
The readlink function reads the contents of the specified
symbolic link (link_name) and places them into a user-supplied
buffer (user_buffer) of size (buffer_size).
See also symlink, unlink, realpath, lchown, and lstat.
386.3 – Return Values
n Upon successful completion, the count of bytes
placed in the user_buffer
-1 Indicates an error. The buffer is unchanged,
and errno is set to indicate the error:
o EACCES - Read permission is denied in the
directory where the symbolic link is being
read, or search permission is denied for a
component of the path prefix of link_name.
o ENAMETOOLONG - The length of the link_name
argument exceeds PATH_MAX, or a pathname
component is longer than NAME_MAX.
o Any errno value from close, open, or read.
387 – readv
Reads from a file.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <sys/uio.h>
ssize_t readv (int file_desc, const struct iovec *iov, int iovcnt);
ssize_t _readv64 (int file_desc, struct __iovec64 *iov, int iovcnt);
387.1 – Function Variants
The readv function has variants named _readv32 and _readv64 for
use with 32-bit and 64-bit pointer sizes, respectively.
387.2 – Arguments
file_desc
A file descriptor. A file descriptor that must refer to a file
currently opened for reading.
iov
Array of iovec structures into which the input data is placed.
iovcnt
The number of buffers specified by the members of the iov array.
387.3 – Description
The readv function is equivalent to read, but places the input
data into the iovcnt buffers specified by the members of the iov
array: iov[0], iov[1], ..., iov[iovcnt-1]. The iovcnt argument is
valid if it is greater than 0 and less than or equal to IOV_MAX.
Each iovec entry specifies the base address and length of an area
in memory where data should be placed. The readv function always
fills an area completely before proceeding to the next.
Upon successful completion, readv marks for update the st_atime
field of the file.
If the Synchronized Input and Output option is supported:
If the O_DSYNC and O_RSYNC bits have been set, read
I/O operations on the file descriptor will complete
as defined by synchronized I/O data integrity
completion.
If the O_SYNC and O_RSYNC bits have been set, read
I/O operations on the file descriptor will complete
as defined by synchronized I/O file integrity
completion.
If the Shared Memory Objects option is supported:
If file_desc refers to a shared memory object, the
result of the read function is unspecified.
For regular files, no data transfer occurs past the offset
maximum established in the open file description associated with
file_desc.
387.4 – Return Values
n The number of bytes read.
-1 Indicates a read error. The function sets
errno to one of the following values:
o EAGAIN - The O_NONBLOCK flag is set for the
file descriptor, and the process would be
delayed.
o EBADF - The file_desc argument is not a
valid file descriptor open for reading.
o EBADMSG - The file is a STREAM file that is
set to control-normal mode, and the message
waiting to be read includes a control part.
o EINTER - The read operation was terminated
because of the receipt of a signal, and no
data was transferred.
o EINVAL - The STREAM or multiplexer
referenced by file_desc is linked
(directly or indirectly) downstream from
a multiplexer.
OR
The sum of the iov_len values in the iov
array overflowed an ssize_t.
o EIO - A physical I/O error has occurred.
OR
The process is a member of a background
process attempting to read from its
controlling terminal, the process is
ignoring or blocking the SIGTTIN signal,
or the process group is orphaned.
o EISDIR - The file_desc argument refers to a
directory, and the implementation does not
allow the directory to be read using read,
pread or readv. Use the readdir function
instead.
o EOVERFLOW - The file is a regular file,
nbyte is greater than 0, and the starting
position is before the end-of-file and is
greater than or equal to the offset maximum
established in the open file description
associated with file_desc.
The readv function may fail if:
o EINVAL - The iovcnt argument was less than
or equal to 0, or greater than IOV_MAX.
388 – realloc
Changes the size of the area pointed to by the first argument to
the number of bytes given by the second argument. These functions
are AST-reentrant.
Format
#include <stdlib.h>
void *realloc (void *ptr, size_t size);
388.1 – Function Variants
The realloc function has variants named _realloc32 and _realloc64
for use with 32-bit and 64-bit pointer sizes, respectively.
388.2 – Arguments
ptr
Points to an allocated area, or can be NULL.
size
The new size of the allocated area.
388.3 – Description
If ptr is the NULL pointer, the behavior of the realloc function
is identical to the malloc function.
The contents of the area are unchanged up to the lesser of the
old and new sizes. The ANSI C Standard states that, "If the
new size is larger than the old size, the value of the newly
allocated portion of memory is indeterminate." For compatibility
with old implementations, VSI C initializes the newly
allocated memory to 0.
For efficiency, the previous actual allocation could have been
larger than the requested size. If it was allocated with malloc,
the value of the portion of memory between the previous requested
allocation and the actual allocation is indeterminate. If it was
allocated with calloc, that same memory was initialized to 0. If
your application relies on realloc initializing memory to 0, then
use calloc instead of malloc to perform the initial allocation.
The maximum amount of memory allocated at once is limited to
0xFFFFD000.
See also free, cfree, calloc, and malloc.
388.4 – Return Values
x The address of the area, quadword-
aligned (Alpha only) or octaword-aligned
(Integrity servers(ONLY)) . The address is
returned because the area may have to be moved
to a new address to reallocate enough space.
If the area was moved, the space previously
occupied is freed.
NULL Indicates that space cannot be reallocated
(for example, if there is not enough room).
389 – realpath
Returns an absolute pathname from the POSIX root.
Format
#include <stdlib.h>
char realpath (const char *restrict file_name, char *restrict
resolved_name);
389.1 – Arguments
file_name
Pointer to the text string representing the name of the file for
which you want the absolute path.
resolved name
Pointer to the generated absolute path stored as a null-
terminated string.
389.2 – Description
The realpath function returns an absolute pathname from the
POSIX root. The generated pathname is stored as a null-terminated
string, up to a maximum of PATH_MAX bytes, in the buffer pointed
to by resolved_name.
The realpath function is supported only in POSIX-compliant modes
(that is, with DECC$POSIX_COMPLIANT_PATHNAMES defined to one of
the allowed values).
See also symlink, unlink, readlink, lchown, and lstat.
389.3 – Return Values
x Upon successful completion, a pointer to the
resolved_name.
NULL Indicates an error. A null pointer is
returned, the contents of the buffer pointed
to by resolved_name are undefined, and errno
is set to indicate the error:
o ENAMETOOLONG - The length of the file_name
argument exceeds PATH_MAX, or a pathname
component is longer than NAME_MAX.
o ENOENT - A component of file_name does not
name an existing file, or file_name points
to an empty string.
o Any errno value from chdir or stat.
390 – [w]refresh
Repaint the specified window on the terminal screen. The refresh
function acts on the stdscr window.
Format
#include <curses.h>
int refresh();
int wrefresh (WINDOW *win);
390.1 – Argument
win
A pointer to the window.
390.2 – Description
The result of this process is that the portion of the window not
occluded by subwindows or other windows appears on the terminal
screen. To see the entire occluded window on the terminal screen,
call the touchwin function instead of the refresh or wrefresh
function.
See also touchwin.
390.3 – Return Values
OK Indicates success.
ERR Indicates an error.
391 – remainder
Returns the floating-point remainder r = x - n*y) when y is
nonzero.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double remainder (double x, double y);
float remainderf (float x, float y);
long double remainderl (long double x, long double y);
391.1 – Argument
x
A real number.
y
A real number.
391.2 – Description
These functions return the floating-point remainder r = x - n*y)
when y is nonzero. The value n is the integral value nearest the
exact value x/y. That is, n = rint(x/y).
When |n - x/y| = 1/2, the value n is chosen to be even.
The behavior of the remainder function is independent of the
rounding mode.
The remainder functions are functionally equivalent to the remquo
functions.
391.3 – Return Values
r Upon successful completion, these functions
return the floating-point remainder r = x - ny
when y is nonzero.
Nan If x or y is Nan.
392 – remquo
Returns the floating-point remainder r = x - n*y) when y is
nonzero.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double remquo (double x, double y, int * quo);
float remquof (float x, float y, int * quo);
long double remquol (long double x, long double y, int * quo);
392.1 – Argument
x
A real number.
y
A real number.
quo
392.2 – Description
The remquo(), remquof(), and remquol() functions compute
the same remainder as the remainder(), remainderf(), and
remainderl() functions, respectively. In the object pointed to
by quo, they store a value whose sign is the sign of x/y and
whose magnitude is congruent modulo 2n to the magnitude of the
integral quotient of x/y, where n is an implementation-defined
integer greater than or equal to 3.
The remquo functions are functionally equivalent to the remainder
functions.
392.3 – Return Values
r Upon successful completion, these functions
return the floating-point remainder r = x - ny
when y is nonzero.
Nan If x or y is Nan.
393 – remove
Deletes a file.
Format
#include <stdio.h>
int remove (const char *file_spec);
393.1 – Argument
file_spec
A pointer to the string that is an OpenVMS or a UNIX style file
specification. The file specification can include a wildcard
in its version number. So, for example, files of the form
filename.txt;* can be deleted.
393.2 – Description
If you specify a directory in the filename and it is a search
list that contains an error, VSI C for OpenVMS Systems
interprets it as a file error.
NOTE
The DECC$ALLOW_REMOVE_OPEN_FILES feature logical controls
the behavior of the remove function on open files.
Ordinarily, the operation fails. However, POSIX conformance
dictates that the operation succeed.
With DECC$ALLOW_REMOVE_OPEN_FILES enabled, this POSIX
conformant behavior is achieved.
When remove is used to delete a symbolic link, the link itself is
deleted, not the file to which it refers.
The remove and delete functions are functionally equivalent in
the C RTL.
See also delete.
393.3 – Return Values
0 Indicates success.
nonzero value Indicates failure.
394 – rename
Gives a new name to an existing file.
Format
#include <stdio.h>
int rename (const char *old_file_spec, const char
*new_file_spec);
394.1 – Arguments
old_file_spec
A pointer to a string that is the existing name of the file to be
renamed.
new_file_spec
A pointer to a string that is to be the new name of the file.
394.2 – Description
If you try to rename a file that is currently open, the behavior
is undefined. You cannot rename a file from one physical device
to another. Both the old and new file specifications must reside
on the same device.
If the new_file_spec does not contain a file extension, the
file extension of old_file_spec is used. To rename a file to
have no file extension, new_file_spec must contain a period
(.) For example, the following renames SYS$DISK:[]FILE.DAT to
SYS$DISK:[]FILE1.DAT:
rename("file.dat", "file1");
However, the following renames SYS$DISK:[]FILE.DAT to
SYS$DISK:[]FILE1:
rename("file.dat", "file1.");
NOTE
Because the rename function does special processing of the
file extension, the caller must be careful when specifying
the name of the renamed file in a call to a C Run-Time
Library function that accepts a file-name argument. For
example, after the following call to the rename function,
the new file should be opened as fopen("bar.dat",...):
rename("foo.dat", "bar");
The rename function is affected by the setting of the
DECC$RENAME_NO_INHERIT and DECC$RENAME_ALLOW_DIR feature logicals
as follows:
o DECC$RENAME_NO_INHERIT provides more UNIX compliant behavior
in rename, and affects whether or not the new name for the
file inherits anything (like file type) from the old name or
must be specified completely.
o DECC$RENAME_ALLOW_DIR lets you choose between the previous
OpenVMS behavior of allowing the renaming of a file from one
directory to another, or the more UNIX compliant behavior of
not allowing the renaming of a file to a directory.
Also see the C RTL help for feature logicals DECC$RENAME_NO_
INHERIT and DECC$RENAME_ALLOW_DIR.
394.3 – Return Values
0 Indicates success.
-1 Indicates failure. The function sets errno to
one of the following values:
o EISDIR - The new argument points to a
directory, and the old argument points
to a file that is not a directory.
o EEXIST - The new argument points to a
directory that already exists.
o ENOTDIR - The old argument names a
directory, and new argument names a non-
directory file.
o ENOENT - The old argument points to a file,
directory, or device that does not exist.
Or the new argument points to a nonexisting
directory path or device.
395 – rewind
Sets the file to its beginning.
Format
#include <stdio.h>
void rewind (FILE *file_ptr); (ISO POSIX-1)
int rewind (FILE *file_ptr); (DEC C Extension)
395.1 – Argument
file_ptr
A file pointer.
395.2 – Description
The rewind function is equivalent to fseek (file_ptr, 0, SEEK_
SET). You can use the rewind function with either record or
stream files.
A successful call to rewind clears the error indicator for the
file.
The ANSI C standard defines rewind as not returning a value;
therefore, the function prototype for rewind is declared with a
return type of void. However, since a rewind can fail, and since
previous versions of the C RTL have declared rewind to
return an int, the code for rewind does return 0 on success and
-1 on failure.
See also fseek.
396 – rewinddir
Resets the position of the specified directory stream to the
beginning of a directory.
Format
#include <dirent.h>
void rewinddir (DIR *dir_pointer);
396.1 – Argument
dir_pointer
A pointer to the dir structure of an open directory.
396.2 – Description
The rewinddir function resets the position of the specified
directory stream to the beginning of the directory. It also
causes the directory stream to refer to the current state of the
corresponding directory, the same as using the opendir function.
If the dir_pointer argument does not refer to a directory stream,
the effect is undefined.
The type DIR, defined in the <dirent.h> header file, represents
a directory stream. A directory stream is an ordered sequence of
all the directory entries in a particular directory. Directory
entries represent files.
See also opendir.
397 – rindex
Searches for a character in a string.
Format
#include <strings.h>
char *rindex (const char *s, int c);
397.1 – Function Variants
The rindex function has variants named _rindex32 and _rindex64
for use with 32-bit and 64-bit pointer sizes, respectively.
397.2 – Arguments
s
The string to search.
c
The character to search for.
397.3 – Description
The rindex function is identical to the strchr function, and is
provided for compatibility with some UNIX implementations.
398 – rint
Rounds its argument to an integral value according to the current
IEEE rounding direction specified by the user.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double rint (double x);
float rintf (float x,);
long double rintl (long double x);
398.1 – Argument
x
A real number.
398.2 – Description
The rint functions return the nearest integral value to x in
the direction of the current IEEE rounding mode specified on the
/ROUNDING_MODE command-line qualifier.
If the current rounding mode rounds toward negative Infinity,
then rint is identical to floor. If the current rounding mode
rounds toward positive Infinity, then rint is identical to ceil.
If |x| = Infinity, rint returns x.
398.3 – Return Values
n The nearest integral value to x in the
direction of the current IEEE rounding mode.
NaN x is NaN; errno is set to EDOM.
399 – rmdir
Removes a directory file.
Format
#include <unistd.h>
int rmdir (const char *path);
399.1 – Argument
path
A directory pathname.
399.2 – Description
The rmdir function removes a directory file whose name is
specified in the path argument. The directory is removed only
if it is empty.
If path names a symbolic link, then rmdir fails and sets errno to
ENOTDIR.
399.3 – Restriction
When using OpenVMS format names, the path argument must be in the
form directory.dir.
399.4 – Return Values
0 Indicates success.
-1 An error occurred; errno is set to indicate
the error.
400 – sbrk
Determines the lowest virtual address that is not used with the
program.
Format
#include <unistd.h>
void *sbrk (long int incr);
400.1 – Argument
incr
The number of bytes to add to the current break address.
400.2 – Description
The sbrk function adds the number of bytes specified by its
argument to the current break address and returns the old break
address.
When a program is executed, the break address is set to the
highest location defined by the program and data storage areas.
Consequently, sbrk is needed only by programs that have growing
data areas.
sbrk(0) returns the current break address.
400.3 – Return Values
x The old break address.
(void *)(-1) Indicates that the program is requesting too
much memory.
400.4 – Restriction
Unlike other C library implementations, the C RTL memory
allocation functions (such as malloc) do not rely on brk or
sbrk to manage the program heap space. Consequently, on OpenVMS
systems, calling brk or sbrk can interfere with memory allocation
routines. The brk and sbrk functions are provided only for
compatibility purposes.
401 – scalb
Returns the exponent of a floating-point number.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double scalb (double x, double n);
float scalbf (float x, float n);
long double scalbl (long double x, long double n);
401.1 – Arguments
x
A nonzero floating-point number.
n
An integer.
401.2 – Description
The scalb functions return x*(2**n) for integer n.
401.3 – Return Values
x On successful completion, x*(2**n) is
returned.
HUGE_VAL On overflow, scalb returns HUGE_VAL (according
to the sign of x) and sets errno to ERANGE.
0 Underflow occurred; errno is set to ERANGE.
x x is Infinity.
NaN x or n is NaN; errno is set to EDOM.
402 – scanf
Performs formatted input from the standard input (stdin),
interpreting it according to the format specification.
Format
#include <stdio.h>
int scanf (const char *format_spec, . . . );
402.1 – Arguments
format_spec
Pointer to a string containing the format specification. The
format specification consists of characters to be taken literally
from the input or converted and placed in memory at the specified
input sources.
. . .
Optional expressions that are pointers to objects whose resultant
types correspond to conversion specifications given in the format
specification.
If no conversion specifications are given, you can omit these
input pointers. Otherwise, the function call must have at least
as many input pointers as there are conversion specifications,
and the conversion specifications must match the types of the
input pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
402.2 – Return Values
x The number of successfully matched and
assigned input items.
EOF Indicates that a read error occurred prior to
any successful conversions. The function sets
errno. For a list of errno values set by this
function, see fscanf.
403 – [w]scanw
Perform a scanf on the window. The scanw function acts on the
stdscr window.
Format
#include <curses.h>
int scanw (char *format_spec, . . . );
int wscanw (WINDOW *win, char *format_spec, . . . );
403.1 – Arguments
win
A pointer to the window.
format_spec
A pointer to the format specification string.
. . .
Optional expressions that are pointers to objects whose resultant
types correspond to conversion specifications given in the format
specification. If no conversion specifications are given, you may
omit these input pointers.
Otherwise, the function call must have at least as many input
pointers as there are conversion specifications, and the
conversion specifications must match the types of the input
pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
403.2 – Description
The formatting specification (format_spec) and the other
arguments are identical to those used with the scanf function.
The scanw and wscanw functions accept, format, and return a line
of text from the terminal screen. For more information, see the
scrollok and scanf functions.
403.3 – Return Values
OK Indicates success.
ERR Indicates that the function makes the
screen scroll illegally or that the scan was
unsuccessful.
404 – scroll
Moves all the lines on the window up one line. The top line
scrolls off the window and the bottom line becomes blank.
Format
#include <curses.h>
int scroll (WINDOW *win);
404.1 – Argument
win
A pointer to the window.
404.2 – Return Values
OK Indicates success.
ERR Indicates an error.
405 – scrollok
Sets the scroll flag for the specified window.
Format
#include <curses.h>
scrollok (WINDOW *win, bool boolf);
405.1 – Arguments
win
A pointer to the window.
boolf
A Boolean TRUE or FALSE value. If boolf is FALSE, scrolling
is not allowed. This is the default setting. The bool type is
defined in the <curses.h> header file as follows:
#define bool int
406 – seed48
Initializes a 48-bit random-number generator.
Format
#include <stdlib.h>
unsigned short *seed48 (unsigned short seed_16v[3]);
406.1 – Argument
seed_16v
An array of three unsigned short ints that form a 48-bit seed
value.
406.2 – Description
The seed48 function initializes the random-number generator.
You can use this function in your program before calling the
drand48, lrand48, or mrand48 functions. (Although it is not
recommended practice, constant default initializer values are
supplied automatically if you call drand48, lrand48, or mrand48
without calling an initialization function).
The seed48 function works by generating a sequence of 48-bit
integer values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n > 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke the lcong48 function, the multiplier
value a and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The initializer function seed48:
o Sets the value of Xi to the 48-bit value specified in the
array pointed to by seed_16v.
o Returns a pointer to a 48-bit internal buffer that contains
the previous value of Xi, used only by seed48.
The returned pointer allows you to restart the pseudorandom
sequence at a given point. Use the pointer to copy the previous
Xi value into a temporary array. To resume where the original
sequence left off, you can call seed48 with a pointer to this
array.
See also drand48, lrand48, and mrand48.
406.3 – Return Value
x A pointer to a 48-bit internal buffer.
407 – seekdir
Sets the position of a directory stream.
Format
#include <dirent.h>
void seekdir (DIR *dir_pointer, long int location);
407.1 – Arguments
dir_pointer
A pointer to the dir structure of an open directory.
location
The number of an entry relative to the start of the directory.
407.2 – Description
The seekdir function sets the position of the next readdir
operation on the directory stream specified by dir_pointer to
the position specified by location. The value of location should
be returned from an earlier call to telldir.
If the value of location was not returned by a call to the
telldir function, or if there was an intervening call to the
rewinddir function on this directory stream, the effect is
unspecified.
The type DIR, defined in the <dirent.h> header file, represents
a directory stream. A directory stream is an ordered sequence of
all the directory entries in a particular directory. Directory
entries represent files. You can remove files from or add files
to a directory asynchronously to the operation of the readdir
function.
See readdir, rewinddir, and telldir.
408 – sem_close
Deallocates the specified named semaphore.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_close (sem_t *sem);
408.1 – Argument
sem
The semaphore to be closed. Use the sem argument returned by the
previous call to sem_open.
408.2 – Description
The sem_close function makes a semaphore available for reuse
by deallocating any system resources allocated for use by the
current process for the named semaphore indicated by sem.
If the semaphore has not been removed with a call to sem_unlink,
sem_close does not change the current state of the semaphore.
If the semaphore has been removed with a call to sem_unlink after
the most recent call to sem_open with O_CREAT, the semaphore is
no longer available after all processes that opened the semaphore
close it.
408.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The sem argument is not a valid
semaphore descriptor.
o ENOSYS - The function is not implemented.
o EVMSERR - OpenVMS specific nontranslatable
error code.
409 – semctl
Semaphore control operations
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <sem.h>
int semctl (int semid, int semnum, int cmd, . . . );
409.1 – Argument
semid
A semaphore set identifier, a positive integer. It is created
by the semget function and used to identify the semaphore set on
which to perform the control operation.
semnum
Semaphore number, a non-negative integer. It identifies a
semaphore within the semaphore set on which to perform the
control operation.
cmd
The control operation to perform on the semaphore.
. . .
Optional fourth argument of type union semun, which depends on
the control operation requested in cmd.
409.2 – Description
The semctl function provides a variety of semaphore control
operations as specified by cmd. The fourth argument is optional
and depends upon the operation requested. If required, it is of
type union semun, which is explicitly declared as:
union semun {
int val;
struct semid_ds *buf;
unsigned short *array;
} arg;
The following semaphore control operations as specified by cmd
are executed with respect to the semaphore specified by semid and
semnum. The level of permission required for each operation is
shown with each command. The symbolic names for the values of cmd
are defined in the <sem.h> header:
o GETVAL
Returns the value of semval. Requires read permission.
o SETVAL
Sets the value of semval to arg.val, where arg is the value
of the fourth argument to semctl. When this command is
successfully executed, the semadj value corresponding to the
specified semaphore in all processes is cleared. Requires
alter permission.
o GETPID
Returns the value of sempid; requires read permission.
o GETNCNT
Returns the value of semncnt; requires read permission.
o GETZCNT
Returns the value of semzcnt; requires read permission.
The following values of cmd operate on each semval in the set of
semaphores:
o GETALL
Returns the value of semval for each semaphore in the
semaphore set and places it into the array pointed to by
arg.array, where arg is the fourth argument to semctl;
requires read permission.
o SETALL
Sets the value of semval for each semaphore in the semaphore
set according to the array pointed to by arg.array, where
arg is the fourth argument to semctl. When this command is
successfully executed, the semadj values corresponding to each
specified semaphore in all processes are cleared. Requires
alter permission.
The following values of cmd are also available:
o IPC_STAT
Places the current value of each member of the semid_ds data
structure associated with semid into the structure pointed to
by arg.buf, where arg is the fourth argument to semctl. The
contents of this structure are defined in <sem.h>. Requires
read permission.
o IPC_SET
Sets the value of the following members of the semid_ds data
structure associated with semid to the corresponding value
found in the structure pointed to by arg.buf, where arg is the
fourth argument to semctl:
sem_perm.uid
sem_perm.gid
sem_perm.mode
The mode bits specified in The Open Group Base Specifications
IPC General Description section are copied into the
corresponding bits of the sem_perm.mode associated with semid.
The stored values of any other bits are unspecified.
This command can only be executed by a process that has an
effective user ID equal to either that of a process with
appropriate privileges or to the value of sem_perm.cuid or
sem_perm.uid in the semid_ds data structure associated with
semid.
o IPC_RMID
Removes the semaphore identifier specified by semid from
the system and destroys the set of semaphores and semid_ds
data structure associated with it. This command can only be
executed by a process that has an effective user ID equal to
either that of a process with appropriate privileges or to the
value of sem_perm.cuid or sem_perm.uid in the semid_ds data
structure associated with semid.
409.3 – Return Values
n or 0 Upon successful completion, the value returned
by the function depends on cmd as follows:
o GETVAL - The value of semval
o GETPID - The value of sempid
o GETNCNT - The value of semncnt
o GETZCNT - The value of semzcnt
o All others - 0
-1 Indicates an error. The function sets errno to
one of the following values:
o EACCES - Operation permission is denied to
the calling process.
o EFAULT - The arguments passed to the
function are not accessible.
o EINVAL - The value of semid is not a valid
semaphore identifier, or the value of
semnum is less than zero or greater than
or equal to sem_nsems, or the value of cmd
is not a valid command.
o EPERM - The argument cmd is equal to IPC_
RMID or IPC_SET and the effective user ID
of the calling process is not equal to that
of a process with appropriate privileges
and it is not equal to the value of sem_
perm.cuid or sem_perm.uid in the data
structure associated with semid.
o EVMSERR - OpenVMS specific nontranslatable
error code.
410 – sem_destroy
Destroys an unnamed semaphore.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_destroy (sem_t *sem);
410.1 – Argument
sem
The unnamed semaphore to be destroyed. Use the sem argument that
was supplied to, and filled in by, the previous call to sem_init.
410.2 – Description
The sem_destroy function destroys an unnamed semaphore indicated
by sem. Only a semaphore created using sem_init may be destroyed
using sem_destroy.
The potential for deadlock exists if a process calls sem_destroy
for a semaphore while there is a pending sem_wait, because a
process may be waiting for a poster that has not yet opened the
semaphore.
410.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno
to one of the following values, without
destroying the semaphore indicated by the
sem argument:
o EINVAL - The sem argument is not a valid
semaphore.
o ENOSYS - The function is not implemented.
o EVMSERR - OpenVMS specific nontranslatable
error code.
o EBUSY - The processes are blocked on the
semaphore.
411 – semget
Gets a set of semaphores.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <sem.h>
int semget (key_t key, int nsems, int semflg);
411.1 – Argument
key
The key for which the associated semaphore identifier is
returned.
nsems
Value used to initialize the sem_nsems member of the semid_ds
data structure. See the description.
semflg
Flag used to initialize the low-order 9 bits of the sem_perm.mode
member of the semid_ds data structure associated with the new
semaphore. See the description.
value
The initial value to be given to the semaphore. This argument is
used only when the semaphore is being created.
411.2 – Description
The semget function returns the semaphore identifier associated
with key.
A semaphore identifier with its associated semid_ds data
structure and its associated set of nsems semaphores (see
the <sys/sem.h> header file) is created for key if one of the
following is true:
o The key argument is equal to IPC_PRIVATE.
o The key argument does not already have a semaphore identifier
associated with it and (semflg &IPC_CREAT) is nonzero.
When it is created, the semid_ds data structure associated with
the new semaphore identifier is initialized as follows:
o In the operation permissions structure sem_perm.cuid, sem_
perm.uid, sem_perm.cgid, and sem_perm.gid are set equal to the
effective user ID and effective group ID, respectively, of the
calling process.
o The low-order 9 bits of sem_perm.mode are set equal to the
low-order 9 bits of the semflg argument.
o The variable sem_nsems is set equal to the value of the nsems
argument.
o The variable sem_otime is set equal to 0 and the variable sem_
ctime is set equal to the current time.
o The data structure associated with each semaphore in the
set does not need to be initialized. You can use the semctl
function with the command SETVAL or SETALL to initialize each
semaphore.
411.3 – Return Values
n Successful completion. The function returns a
non-negative integer semaphore identifier.
-1 Indicates an error. The function sets errno to
one of the following values:
o EACCES - A semaphore identifier exists for
key, but operation permission as specified
by the low-order 9 bits of semflg was not
granted.
o EEXIST - A semaphore identifier exists
for key but ((semflg &IPC_CREAT) &&(semflg
&IPC_EXCL)) is nonzero.
o EFAULT - The arguments passed to the
function are not accessible.
o EINVAL - The value of nsems is either
less than or equal to 0 or greater than
the system-imposed limit, or a semaphore
identifier exists for key, but the number
of semaphores in the set associated with it
is less than nsems and nsems is not equal
to 0.
o ENOENT - A semaphore identifier does not
exist for key and (semflg &IPC_CREAT) is
equal to 0.
o ENOSPC - A semaphore identifier is to be
created but the system-imposed limit on
the maximum number of allowed semaphores
system-wide will be exceeded.
o EVMSERR - OpenVMS specific nontranslatable
error code.
412 – sem_getvalue
Gets the value of a specified semaphore.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_getvalue (sem_t *sem, int *sval);
412.1 – Argument
sem
The semaphore for which a value is to be returned.
sval
The location to be updated with the value of the semaphore
indicated by the sem argument.
412.2 – Description
The sem_getvalue function updates a location referenced by the
sval argument with the value of semaphore sem. The updated value
represents an actual semaphore value that occurred during the
call, but may not be the actual value of the semaphore at the
time that the value is returned to the calling process.
If the semaphore is locked, the value returned will either be
zero or a negative number indicating the number of processes
waiting for the semaphore at some time during the call.
412.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The sem argument is not a valid
semaphore.
o EVMSERR - OpenVMS specific nontranslatable
error code.
413 – sem_init
Initializes an unnamed semaphore.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_init (sem_t *sem, int pshared, unsigned int value );
413.1 – Argument
sem
The location to receive the descriptor of the initialized
semaphore.
pshared
A value indicating whether the semaphore should be sharable
between the creating process and its descendants (nonzero value)
or not (zero).
NOTE
The value for pshared must be zero between threads because
this release does not support unnamed semaphores to be
shared across processes.
value
The initial value to be given to the semaphore.
413.2 – Description
The sem_init function creates a new counting semaphore with a
specific value. A semaphore is used to limit access to a critical
resource. When a process requires access to the resource without
interference from other processes, it attempts to establish
a connection with the associated semaphore. If the semaphore
value is greater than zero, the connection is established and the
semaphore value is decremented by one. If the semaphore value is
less than or equal to zero, the process attempting to access the
resource is blocked and must wait for another process to release
the semaphore and increment the semaphore value.
The sem_init function establishes a connection between an
unnamed semaphore and a process; the sem_wait and sem_trywait
functions lock the semaphore; and the sem_post function unlocks
the semaphore. Use the sem_destroy function to deallocate system
resources allocated to the process for use with the semaphore.
You can use the sem_getvalue function to obtain the value of a
semaphore.
A semaphore created by a call to the sem_init function remains
valid until the semaphore is removed by a call to the sem_destroy
function.
413.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The value argument exceeds {SEM_
VALUE_MAX}.
o ENOSYS - The function is not implemented.
o EVMSERR - OpenVMS specific nontranslatable
error code.
414 – sem_open
Opens/creates a named semaphore for use by a process.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
sem_t *sem_open (const char *name, int ooption...) ;
414.1 – Argument
name
a string naming the semaphore object.
ooption
Specifies whether the semaphore is to be created (O_CREAT option
bit set) or only opened (O_CREAT option bit clear). If O_CREAT is
set, the O_EXCL option bit may additionally be set to specify
that the call should fail if a semaphore of the same name
already exists. The O_CREAT and O_EXCL options are defined in
the <fcntl.h> header file.
mode
The semaphore's permission bits. This argument is used only when
the semaphore is being created.
value
The initial value to be given to the semaphore. This argument is
used only when the semaphore is being created.
414.2 – Description
Use the sem_open function to establish the connection between a
named semaphore and a process. Subsequently, the calling process
can reference the semaphore by using the address returned from
the call. The semaphore is available in subsequent calls to sem_
wait, sem_trywait, sem_post, and sem_getvalue functions. The
semaphore remains usable by the process until the semaphore is
closed by a successful call to the sem_close function.
The O_CREAT option bit in the ooption parameter controls whether
the semaphore is created or only opened by the call to sem_open.
A created semaphore's user ID is set to the user ID of the
calling process and its group ID is set to a system default group
or to the group ID of the process. The semaphore's permission
bits are set to the value of the mode argument, except for those
set in the file mode creation mask of the process.
After a semaphore is created, other processes can open the
semaphore by calling sem_open with the same value for the name
argument.
414.3 – Return Values
sem Successful completion. The function opens
the semaphore and returns the semaphore's
descriptor.
sem_failed Indicates an error. The function sets errno to
one of the following values:
o EACCES-The named semaphore exists and
the permissions specified by ooption are
denied, or the named semaphore does not
exist and the permissions specified by
ooption are denied.
o EEXIST-O_CREAT and O_EXCL are set, and the
named semaphore already exists.
o EINVAL-The sem_open operation is not
supported for the given name. Or, O_CREAT
was specified in ooption and value was
greater than {SEM_VALUE_MAX}.
o EMFILE-Too many semaphore descriptors or
file descriptors are currently in use by
this process.
o ENAMETOOLONG-The length of the name string
exceeds {PATH_MAX}, or a pathname component
is longer than {NAME_MAX} while {_POSIX_NO_
TRUNC} is in effect.
o ENFILE-Too many semaphores are currently
open in the system. ENOENT O_CREAT is
not set, and the named semaphore does not
exist.
o ENOSPC-Insufficient space exists for the
creation of a new named semaphore.
o EVMSERR-OpenVMS specific nontranslatable
error code.
415 – semop
Performs operations on semaphores in a semaphore set.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <sem.h>
int semop (int semid, struct sembuf *sops, size_t nsops);
415.1 – Argument
semid
Semaphore set identifier.
sops
Pointer to a user-defined array of semaphore operation (sembuf)
structures.
nsops
Number of sembuf structures in the sops array.
415.2 – Description
The semop function performs operations on semaphores in the
semaphore set specified by semid. These operations are supplied
in a user-defined array of semaphore operation sembuf structures
specified by sops. Each sembuf structure includes the following
member variables:
struct sembuf { /* semaphore operation structure */
unsigned short sem_num; /* semaphore number */
short sem_op; /* semaphore operation */
short sem_flg; /* operation flags SEM_UNDO and IPC_NOWAIT */
Each semaphore operation specified by the sem_op variable is
performed on the corresponding semaphore specified by the semid
function argument and the sem_num variable.
The sem_op variable specifies one of three semaphore operations:
1. If sem_op is a negative integer and the calling process has
change permission, one of the following occurs:
o If semval (see <sem.h>) is greater than or equal to the
absolute value of sem_op, the absolute value of sem_op
is subtracted from semval. Also, if (sem_flg &SEM_UNDO)
is non-zero, the absolute value of sem_op is added to the
calling process' semadj value for the specified semaphore.
o If semval is less than the absolute value of sem_op
and (sem_flg &IPC_NOWAIT) is nonzero, semop returns
immediately.
o If semval is less than the absolute value of sem_op and
(sem_flg &IPC_NOWAIT) is 0, semop increments the semncnt
associated with the specified semaphore and suspends
execution of the calling thread until one of the following
conditions occurs:
- The value of semval becomes greater than or equal to the
absolute value of sem_op. When this occurs, the value
of semncnt associated with the specified semaphore is
decremented, the absolute value of sem_op is subtracted
from semval and, if (sem_flg &SEM_UNDO) is nonzero,
the absolute value of sem_op is added to the calling
process' semadj value for the specified semaphore.
- The semid for which the calling thread is awaiting
action is removed from the system. When this occurs,
errno is set equal to EIDRM and -1 is returned.
- The calling thread receives a signal that is to be
intercepted. When this occurs, the value of semncnt
associated with the specified semaphore is decremented,
and the calling thread is resumes execution in the
manner prescribed in sigaction.
2. If sem_op is a positive integer and the calling process has
change permission, the value of sem_op is added to semval
and, if (sem_flg &SEM_UNDO) is nonzero, the value of sem_op
is subtracted from the calling process' semadj value for the
specified semaphore.
3. If sem_op is 0 and the calling process has read permission,
one of the following occurs:
o If semval is 0, semop returns immediately.
o If semval is nonzero and (sem_flg &IPC_NOWAIT) is nonzero,
semop returns immediately.
o If semval is nonzero and (sem_flg &IPC_NOWAIT) is 0, semop
increments the semzcnt associated with the specified
semaphore and suspends execution of the calling thread
until one of the following occurs:
- The value of semval becomes 0, at which time the value
of semzcnt associated with the specified semaphore is
decremented.
- The semid for which the calling thread is awaiting
action is removed from the system. When this occurs,
errno is set equal to EIDRM and -1 is returned.
- The calling thread receives a signal that is to be
intercepted. When this occurs, the value of semzcnt
associated with the specified semaphore is decremented,
and the calling thread resumes execution in the manner
prescribed in sigaction.
On successful completion, the value of sempid for each semaphore
specified in the array pointed to by sops is set equal to the
process ID of the calling process.
415.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o E2BIG - The value of nsops is greater than
the system-imposed maximum.
o EACCES - Operation permission is denied to
the calling process.
o EAGAIN - The operation would result in
suspension of the calling process but (sem_
flg &IPC_NOWAIT) is nonzero.
o EFAULT - The arguments passed to the
function are not accessible.
o EFBIG - The value of sem_num is less than
0 or greater than or equal to the number
of semaphores in the set associated with
semid.
o EIDRM - The semaphore identifier semid is
removed from the system.
o EINVAL - The value of semid is not a valid
semaphore identifier, or the number of
individual semaphores for which the calling
process requests a SEM_UNDO would exceed
the system-imposed limit.
o EVMSERR - OpenVMS specific nontranslatable
error code.
416 – sem_post
Unlocks a semaphore.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_post (sem_t *sem);
416.1 – Argument
sem
The semaphore to be unlocked.
416.2 – Description
The sem_post function unlocks the specified semaphore by
performing the semaphore unlock operation on that semaphore. The
appropriate function (sem_open for named semaphores or sem_init
for unnamed semaphores) must be called for a semaphore before
you can call the locking and unlocking functions, sem_wait, sem_
trywait, and sem_post.
If the semaphore value after a sem_post function is positive, no
processes were blocked waiting for the semaphore to be unlocked;
the semaphore value is incremented. If the semaphore value after
a sem_post function is zero, one of the processes blocked waiting
for the semaphore is allowed to return successfully from its call
to sem_wait.
If more than one process is blocked while waiting for the
semaphore, only one process is unblocked and the state of
the semaphore remains unchanged when the sem_post function
returns. The process to be unblocked is selected according to
the scheduling policies and priorities of all blocked processes.
If the scheduling policy is SCHED_FIFO or SCHED_RR, the highest-
priority waiting process is unblocked. If more than one process
of that priority is blocked, then the process that has waited the
longest is unblocked.
The sem_post function can be called from a signal-catching
function.
416.3 – Return Values
0 Successful completion. The sem_post function
performs a semaphore unlock operation,
unblocking a process.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The sem argument is not a valid
semaphore.
o EVMSERR - OpenVMS specific nontranslatable
error code.
417 – sem_timedwait
Performs a semaphore lock.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
#include <time.h>
int sem_timedwait (sem_t *sem, const struct timespec
*abs_timeout);
417.1 – Argument
sem
The semaphore to be locked.
abs_timeout
The absolute time after which the timeout expires.
417.2 – Description
The sem_timedwait function locks the semaphore referenced by
sem as in the sem_wait function. But if the semaphore cannot be
locked without waiting for another process or thread to unlock
the semaphore by performing a sem_post function, this wait
terminates when the specified timeout expires.
The timeout expires when the absolute time specified by abs_
timeout passes, as measured by the clock on which timeouts are
based (that is, when the value of that clock equals or exceeds
abs_timeout, or if the absolute time specified by abs_timeout has
already been passed at the time of the call.
The function will not fail with a timeout if the semaphore can be
locked immediately. The validity of abs_timeout does not need to
be checked if the semaphore can be locked immediately.
417.3 – Return Values
0 Successful completion. The function executes
the semaphore lock operation.
-1 Indicates an error. The function sets errno to
one of the following values:
o ETIMEDOUT - The semaphore could not
be locked before the specified timeout
expired.
o EINVAL - The sem argument does not refer to
a valid semaphore. Or the process or thread
would have blocked, and the abs_timeout
parameter specified a nanoseconds field
value less than zero or greater than or
equal to 1000 million.
o EVMSERR - OpenVMS specific nontranslatable
error code.
418 – sem_trywait
Conditionally performs a semaphore lock.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_trywait (sem_t *sem);
418.1 – Argument
sem
The semaphore to be locked.
418.2 – Description
The sem_trywait function locks a semaphore only if the semaphore
is currently not locked. If the semaphore value is zero, the sem_
trywait function returns without locking the semaphore.
The sem_wait and sem_trywait functions help ensure that the
resource associated with the semaphore cannot be accessed by
other processes. The semaphore remains locked until the process
unlocks it with a call to the sem_post function.
Use the sem_wait function instead of the sem_trywait function if
the process should wait for access to the semaphore.
418.3 – Return Values
0 Successful completion. The function executes
the semaphore lock operation.
-1 Indicates an error. The function sets errno to
one of the following values:
o EAGAIN - The semaphore was already locked
and cannot be locked by the sem_trywait
operation.
o EINVAL - The sem argument does not refer to
a valid semaphore.
o EVMSERR - OpenVMS specific nontranslatable
error code.
419 – sem_unlink
Removes the specified named semaphore.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_unlink (const char *name);
419.1 – Argument
name
The name of the semaphore to remove.
419.2 – Description
The sem_unlink function removes a semaphore named by the name
string. If the semaphore is referenced by other processes, sem_
unlink does not change the state of the semaphore.
If other processes have the semaphore open when sem_unlink is
called, the semaphore is not destroyed until all references to
the semaphore have been destroyed by calls to sem_close. The sem_
unlink function returns immediately; it does not wait until all
references have been destroyed.
Calls to sem_open to recreate or reconnect to the semaphore refer
to a new semaphore after sem_unlink is called.
419.3 – Return Values
0 Successful completion. The function executes
the semaphore unlink operation.
-1 Indicates an error. The function sets errno to
one of the following values:
o EACCESS - Permission is denied to unlink
the named semaphore.
o ENAMETOOLONG - The length of the path
name exceeds PSEM_MAX_PATHNAME defined
in semaphore.h.
o ENOENT - The named semaphore does not
exist.
o EVMSERR - OpenVMS specific nontranslatable
error code.
420 – sem_wait
Performs a semaphore lock.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <semaphore.h>
int sem_wait (sem_t *sem);
420.1 – Argument
sem
The semaphore to be locked.
420.2 – Description
The sem_wait function locks the semaphore referenced by sem by
performing a semaphore lock operation on it. If the semaphore
value is zero, the sem_wait function blocks until it either locks
the semaphore or is interrupted by a signal.
The sem_wait and sem_trywait functions help ensure that the
resource associated with the semaphore cannot be accessed by
other processes. The semaphore remains locked until the process
unlocks it with a call to the sem_post function.
Use the sem_wait function instead of the sem_trywait function if
the process should wait for access to the semaphore.
420.3 – Return Values
0 Successful completion. The function executes
the semaphore lock operation.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINTR - A signal interrupted this function.
o EVMSERR - OpenVMS specific nontranslatable
error code.
421 – [w]setattr
Activate the video display attribute attr within the window. The
setattr function acts on the stdscr window.
Format
#include <curses.h>
int setattr (int attr);
int wsetattr (WINDOW *win, int attr);
421.1 – Arguments
win
A pointer to the window.
attr
One of a set of video display attributes, which are blinking,
boldface, reverse video, and underlining, and are represented by
the defined constants _BLINK, _BOLD, _REVERSE, and _UNDERLINE,
respectively. You can set multiple attributes by separating them
with a bitwise OR operator (|) as follows:
setattr(_BLINK | _UNDERLINE);
421.2 – Description
The setattr and wsetattr functions are specific to VSI C for
OpenVMS Systems and are not portable.
421.3 – Return Values
OK Indicates success.
ERR Indicates an error.
422 – setbuf
Associates a new buffer with an input or output file and
potentially modifies the buffering behavior.
Format
#include <stdio.h>
void setbuf (FILE *file_ptr, char *buffer);
422.1 – Arguments
file_ptr
A file pointer.
buffer
A pointer to a character array or a NULL pointer.
422.2 – Description
You can use the setbuf function after the specified file is
opened but before any I/O operations are performed.
If buffer is a NULL pointer, then the call is equivalent to a
call to setvbuf with the same file_ptr, a NULL buffer pointer, a
buffering type of _IONBF (no buffering), and a buffer size of 0.
If buffer is not a NULL pointer, then the call is equivalent to a
call to setvbuf with the same file_ptr, the same buffer pointer,
a buffering type of _IOFBF, and a buffer size given by the value
BUFSIZ (defined in <stdio.h>). Therefore, use BUFSIZ to allocate
the buffer argument used in the call to setbuf. For example:
#include <stdio.h>
.
.
.
char my_buf[BUFSIZ];
.
.
.
setbuf(stdout, my_buf);
.
.
.
User programs must not depend on the contents of buffer once I/O
has been performed on the stream. The C RTL might or might
not use buffer for any given I/O operation.
The setbuf function originally allowed programmers to substitute
larger buffers in place of the system default buffers in obsolete
versions of UNIX. The large default buffer sizes in modern
implementations of C make the use of this function unnecessary
most of the time. The setbuf function is retained in the ANSI C
standard for compatibility with old programs. New programs should
use setvbuf instead, because it allows the programmer to bind the
buffer size at run time instead of compile time, and it returns a
result value that can be tested.
423 – setenv
Inserts or resets the environment variable specified by name in
the current environment list.
Format
#include <stdlib.h>
int setenv (const char *name, const char *value, int
overwrite);
423.1 – Arguments
name
A variable name in the environment variable list.
value
The value for the environment variable.
overwrite
A value of 0 or 1 indicating whether to reset the environment
variable, if it exists.
423.2 – Description
The setenv function inserts or resets the environment variable
name in the current environment list. If the variable name does
not exist in the list, it is inserted with the value argument. If
the variable does exist, the overwrite argument is tested. When
the overwrite argument value is:
o 0 then the variable is not reset.
o 1 then the variable is reset to value.
NOTE
Do not use the setenv, getenv, and putenv functions to
manipulate symbols and logicals. Instead, use the OpenVMS
library calls lib$set_logical, lib$get_logical, lib$set_
symbol, and lib$get_symbol. The *env functions deliberately
provide UNIX behavior, and are not a substitute for these
OpenVMS runtime library calls.
OpenVMS DCL symbols, not logical names, are the closest
analog to environment variables on UNIX systems. While
getenv is a mechanism to retrieve either a logical name
or a symbol, it maintains an internal cache of values for
use with setenv and subsequent getenv calls. The setenv
function does not write or create DCL symbols or OpenVMS
logical names.
This is consistent with UNIX behavior. On UNIX systems,
setenv does not change or create any symbols that will be
visible in the shell after the program exits.
423.3 – Return Values
0 Indicates success.
-1 Indicates an error. errno is set to ENOMEM-
Not enough memory available to expand the
environment list.
424 – seteuid
Sets the process's effective user ID.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
int seteuid (uid_t euid);
424.1 – Argument
euid
The value to which you want the effective user ID set.
424.2 – Description
If the process has the IMPERSONATE privilege, the seteuid
function sets the process's effective user ID.
An unprivileged process can set the effective user ID only if the
euid argument is equal to either the real, effective, or saved
user ID of the process.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
See also getuid to know how UIC is represented.
424.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The value of the euid argument is
invalid and not supported.
o EPERM - The process does not have the
IMPERSONATE privilege, and euid does not
match the real user ID or the saved set-
user-ID.
425 – setgid
With POSIX IDs disabled, setgid is implemented for program
portability and serves no function. It returns 0 (to indicate
success).
With POSIX IDs enabled, setgid sets the group IDs.
Format
#include <types.h>
#include <unistd.h>
int setgid (__gid_t gid); (_DECC_V4_SOURCE)
int setgid (gid_t gid); (not _DECC_V4_SOURCE)
425.1 – Argument
gid
The value to which you want the group IDs set.
425.2 – Description
The setgid function can be used with POSIX style identifiers
enabled or disabled.
POSIX style IDs are supported on OpenVMS Version 7.3-2 and
higher.
With POSIX IDs disabled, the setgid function is implemented for
program portability and serves no function. It returns 0 (to
indicate success).
With POSIX style IDs enabled:
o If the process has the IMPERSONATE privilege, the setgid
function sets the real group ID, effective group ID, and the
saved set-group-ID to gid.
o If the process does not have appropriate privileges but gid is
equal to the real group ID or to the saved set-group-ID, then
the setgid function sets the effective group ID to gid. The
real group ID and saved set-group-ID remain unchanged.
o Any supplementary group IDs of the calling process remain
unchanged.
425.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The value of the gid argument
is invalid and not supported by the
implementation.
o EPERM - The process does not have
appropriate privileges and gid does not
match the real group ID or the saved set-
group-ID.
426 – setgrent
Rewinds the group database.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <grp.h>
void setgrent (void);
426.1 – Description
The setgrent function effectively rewinds the group database to
allow repeated searches.
This function is always successful. No value is returned, and
errno is not set.
427 – setitimer
Sets the value of interval timers.
Format
#include <time.h>
int setitimer (int which, struct itimerval *value, struct
itimerval *ovalue);
427.1 – Arguments
which
The type of interval timer. The C RTL only supports
ITIMER_REAL.
value
A pointer to an itimerval structure whose members specify a timer
interval and the time left to the end of the interval.
ovalue
A pointer to an itimerval structure whose members specify a
current timer interval and the time left to the end of the
interval.
427.2 – Description
The setitimer function sets the timer specified by which to the
value specified by value, returning the previous value of the
timer if ovalue is nonzero.
A timer value is defined by the itimerval structure:
struct itimerval {
struct timeval it_interval;
struct timeval it_value;
};
The value of the itimerval structure members are: as follows
itimerval Member
Value Meaning
it_interval = 0 Disables a timer after its next expiration
(assumes it_value is nonzero).
it_interval = Specifies a value used in reloading it_value
nonzero when the timer expires.
it_value = 0 Disables a timer.
it_value = Indicates the time to the next timer
nonzero expiration.
Time values smaller than the resolution of the system clock are
rounded up to this resolution.
The getitimer function provides one interval timer, defined in
the <time.h> header file as ITIMER_REAL. This timer decrements in
real time. When the timer expires, it delivers a SIGALARM signal.
NOTE
The interaction between setitimer and any of alarm, sleep,
or usleep is unspecified.
427.3 – Return Values
0 Indicates success.
-1 An error occurred; errno is set to indicate
the error.
428 – setjmp
Provides a way to transfer control from a nested series of
function invocations back to a predefined point without returning
normally. It does not use a series of return statements. The
setjmp function saves the context of the calling function in an
environment buffer.
Format
#include <setjmp.h>
int setjmp (jmp_buf env);
428.1 – Argument
env
The environment buffer, which must be an array of integers long
enough to hold the register context of the calling function.
The type jmp_buf is defined in the <setjmp.h> header file. The
contents of the general-purpose registers, including the program
counter (PC), are stored in the buffer.
428.2 – Description
When setjmp is first called, it returns the value 0. If longjmp
is then called, naming the same environment as the call to
setjmp, control is returned to the setjmp call as if it had
returned normally a second time. The return value of setjmp in
this second return is the value supplied by you in the longjmp
call. To preserve the true value of setjmp, the function calling
setjmp must not be called again until the associated longjmp is
called.
The setjmp function preserves the hardware general-purpose
registers, and the longjmp function restores them. After a
longjmp, all variables have their values as of the time of the
longjmp except for local automatic variables not marked volatile.
These variables have indeterminate values.
The setjmp and longjmp functions rely on the OpenVMS
condition-handling facility to effect a nonlocal goto with
a signal handler. The longjmp function is implemented by
generating a C RTL specified signal that allows the
OpenVMS condition-handling facility to unwind back to the desired
destination.
The C RTL must be in control of signal handling for any
VSI C image. For VSI C to be in control of signal handling,
you must establish all exception handlers through a call to the
VAXC$ESTABLISH function.
NOTE
The C RTL provides nonstandard decc$setjmp and decc$fast_
longjmp functions for Alpha and Integrity server systems. To
use these nonstandard functions instead of the standard
ones, a program must be compiled with __FAST_SETJMP or
__UNIX_SETJMP macros defined.
Unlike the standard longjmp function, the decc$fast_longjmp
function does not convert its second argument from 0 to 1.
After a call to decc$fast_longjmp, a corresponding setjmp
function returns with the exact value of the second argument
specified in the decc$fast_longjmp call.
428.3 – Restrictions
You cannot invoke the longjmp function from an OpenVMS condition
handler. However, you may invoke longjmp from a signal handler
that has been established for any signal supported by the
C RTL, subject to the following nesting restrictions:
o The longjmp function will not work if you invoke it from
nested signal handlers. The result of the longjmp function,
when invoked from a signal handler that has been entered as a
result of an exception generated in another signal handler, is
undefined.
o Do not invoke the setjmp function from a signal handler unless
the associated longjmp is to be issued before the handling of
that signal is completed.
o Do not invoke the longjmp function from within an exit handler
(established with atexit or SYS$DCLEXH). Exit handlers are
invoked after image tear-down, so the destination address of
the longjmp no longer exists.
o Invoking longjmp from within a signal handler to return to
the main thread of execution might leave your program in
an inconsistent state. Possible side effects include the
inability to perform I/O or to receive any more UNIX signals.
Use siglongjmp instead.
428.4 – Return Values
See the
Description
section.
429 – setkey
Sets an encoding key for use by the encrypt function.
Format
#include <unistd.h>
#include <stdlib.h>
void setkey (const char *key;)
429.1 – Argument
key
A character array of length 64 containing 0s and 1s.
429.2 – Description
The argument of setkey is a character array of length 64
containing only the characters with numerical value 0 and 1.
If this string is divided into groups of 8, the low-order bit in
each group is ignored, leading to a 56-bit key which is set into
the machine.
No value is returned.
See also crypt and encrypt.
430 – setlocale
Selects the appropriate portion of the program's locale as
specified by the category and locale arguments. You can use this
function to change or query one category or the program's entire
current locale.
Format
#include <locale.h>
char *setlocale (int category, const char *locale);
430.1 – Arguments
category
The name of the category. Specify LC_ALL to change or query the
entire locale. Other valid category names are:
o LC_COLLATE
o LC_CTYPE
o LC_MESSAGES
o LC_MONETARY
o LC_NUMERIC
o LC_TIME
locale
Pointer to a string that specifies the locale.
430.2 – Description
The setlocale function sets or queries the appropriate portion
of the program's locale as specified by the category and locale
arguments. Specifying LC_ALL for the category argument names the
entire locale; specifying the other values name only a portion of
the program's locale.
The locale argument points to a character string that identifies
the locale to be used. This argument can be one of the following:
o Name of the public locale
Specifies the public locale in the following format:
language_country.codeset[@modifier]
The function searches for the public locale binary file in
the location defined by the logical name SYS$I18N_LOCALE. The
file type defaults to .LOCALE. The period (.) and at-sign (@)
characters in the name are replaced by an underscore (_).
For example, if the specified name is
"zh_CN.dechanzi@radical", the function searches for the
SYS$I18N_LOCALE:ZH_CN_DECHANZI_RADICAL.LOCALE binary locale
file.
o A file specification
Specifies the binary locale file. It can be any valid file
specification. If either the device or directory is omitted,
the function first applies the current caller's device and
directory as defaults for any missing component. If the file
is not found, the function applies the device and directory
defined by the SYS$I18N_LOCALE logical name as defaults. The
file type defaults to .LOCALE.
No wildcards are allowed. The binary locale file cannot reside
on a remote node.
o "C"
Specifies the C locale. If a program does not call setlocale,
the C locale is the default.
o "POSIX"
This is the same as the C locale.
o ""
Specifies that the locale is initialized from the setting
of the international environment logical names. The function
checks the following logical names in the order shown until it
finds a logical that is defined:
1. LC_ALL
2. Logical names corresponding to the category. For example,
if LC_NUMERIC is specified as the category, then the first
logical name that setlocale checks is LC_NUMERIC.
3. LANG
4. SYS$LC_ALL
5. The system default for the category, which is defined by
the SYS$LC_* logical names. For example, the default for
the LC_NUMERIC category is defined by the SYS$LC_NUMERIC
logical name.
6. SYS$LANG
If none of the logical names is defined, the C locale is
used as the default. The SYS$LC_* logical names are set up
at the system startup time.
Like the locale argument, the equivalence name of the
international environment logical name can be either the name
of the public locale or the file specification. The setlocale
function treats this equivalence name as if it were specified
as the locale argument.
o NULL
Causes setlocale to query the current locale. The function
returns a pointer to a string describing the portion of the
program's locale associated with category. Specifying the LC_
ALL category returns the string describing the entire locale.
The locale is not changed.
o The string returned from the previous call to setlocale
Causes the function to restore the portion of the program's
locale associated with category. If the string contains the
description of the entire locale, the part of the string
corresponding to category is used. If the string describes the
portion of the program's locale for a single category, this
locale is used. For example, this means that you can use the
string returned from the call setlocale with the LC_COLLATE
category to set the same locale for the LC_MESSAGES category.
If the specified locale is available, then setlocale returns
a pointer to the string that describes the portion of the
program's locale associated with category. For the LC_ALL
category, the returned string describes the entire program's
locale. If an error occurs, a NULL pointer is returned and the
program's locale is not changed.
Subsequent calls to setlocale overwrite the returned string.
If that part of the locale needs to be restored, the program
should save the string. The calling program should make no
assumptions about the format or length of the returned string.
430.3 – Return Values
x Pointer to a string describing the locale.
NULL Indicates an error occurred; errno is set.
430.4 – Example
#include <errno.h>
#include <stdio.h>
#include <locale.h>
/* This program calls setlocale() three times. The second call */
/* is for a nonexistent locale. The third call is for an */
/* existing file that is not a locale file. */
main()
{
char *ret_str;
errno = 0;
printf("setlocale (LC_ALL, \"POSIX\")");
ret_str = (char *) setlocale(LC_ALL, "POSIX");
if (ret_str == NULL)
perror("setlocale error");
else
printf(" call was successful\n");
errno = 0;
printf("\n\nsetlocale (LC_ALL, \"junk.junk_codeset\")");
ret_str = (char *) setlocale(LC_ALL, "junk.junk_codeset");
if (ret_str == NULL)
perror(" returned error");
else
printf(" call was successful\n");
errno = 0;
printf("\n\nsetlocale (LC_
ALL, \"sys$login:login.com\")");
ret_str = (char *) setlocale(LC_
ALL, "sys$login:login.com");
if (ret_str == NULL)
perror(" returned error");
else
printf(" call was successful\n");
}
Running the example program produces the following result:
setlocale (LC_ALL, "POSIX") call was successful
setlocale (LC_ALL, "junk.junk_codeset")
returned error: no such file or directory
setlocale (LC_ALL, "sys$login:login.com")
returned error: nontranslatable vms error code: 0x35C07C
%c-f-localebad, not a locale file
431 – setpgid
Sets the process group ID for job control.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
int setpgid (pid_t pid, pid_t pgid);
431.1 – Arguments
pid
The process ID for which the process group ID is to be set.
pgid
The value to which the process group ID is set.
431.2 – Description
The setpgid function is used either to join an existing process
group or create a new process group within the session of the
calling process. The process group ID of a session leader will
not change.
Upon successful completion, the process group ID of the process
with a process ID of pid is set to pgid. As a special case, if
pid is 0, the process ID of the calling process is used. Also, if
pgid is 0, the process group ID of the indicated process is used.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
431.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EACCES - The value of the pid argument
matches the process ID of a child process
of the calling process and the child
process has successfully executed one of
the exec functions.
o EINVAL - The value of the pgid argument is
less than 0, or is not a value supported by
the implementation.
o EPERM - The process indicated by the pid
argument is a session leader. The value
of the pid argument matches the process ID
of a child process of the calling process,
and the child process is not in the same
session as the calling process. The value
of the pgid argument is valid but does
not match the process ID of the process
indicated by the pid argument, and there
is no process with a process group ID that
matches the value of the pgid argument in
the same session as the calling process.
o ESRCH - The value of the pid argument does
not match the process ID of the calling
process or of a child process of the
calling process.
432 – setpgrp
Sets the process group ID.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
pid_t setpgrp (void);
432.1 – Description
If the calling process is not already a session leader, setpgrp
sets the process group ID of the calling process to the process
ID of the calling process. If setpgrp creates a new session, then
the new session has no controlling terminal.
The setpgrp function has no effect when the calling process is a
session leader.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
432.2 – Return Value
x The process group ID of the calling process.
433 – setpwent
Rewinds the user database.
Format
#include <pwd.h>
void setpwent (void);
433.1 – Description
The setpwent function effectively rewinds the user database to
allow repeated searches.
No value is returned, but errno is set to EIO if an I/O error
occurred.
See also getpwent.
434 – setregid
Sets the real and effective group IDs.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
int setregid (gid_t rgid, gid_t egid);
434.1 – Arguments
rgid
The value to which you want the real group ID set.
egid
The value to which you want the effective group ID set.
434.2 – Description
The setregid function is used to set the real and effective group
IDs of the calling process. If rgid is -1, the real group ID
is not changed; if egid is -1, the effective group ID is not
changed. The real and effective group IDs can be set to different
values in the same call.
Only a process with the IMPERSONATE privilege can set the real
group ID and the effective group ID to any valid value.
A nonprivileged process can set either the real group ID to the
saved set-group-ID from an exec function, or the effective group
ID to the saved set-group-ID or the real group ID.
Any supplementary group IDs of the calling process remain
unchanged.
If a set-group-ID process sets its effective group ID to its real
group ID, it can still set its effective group ID back to the
saved set-group-ID.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
434.3 – Return Values
0 Successful completion.
-1 Indicates an error. Neither of the group IDs
is changed, and errno is set to one of the
following values:
o EINVAL - The value of the rgid or egid
argument is invalid or out-of-range.
o EPERM - The process does not have the
IMPERSONATE privilege, and a change
other than changing the real group ID to
the saved set-group-ID, or changing the
effective group ID to the real group ID or
the saved group ID, was requested.
435 – setreuid
Sets the user IDs.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
int setreuid (uid_t ruid, uid_t euid);
435.1 – Arguments
ruid
The value to which you want the real user ID set.
euid
The value to which you want the effective user ID set.
435.2 – Description
The setreuid function sets the real and effective user IDs of
the current process to the values specified by the ruid and euid
arguments. If ruid or euid is -1, the corresponding effective or
real user ID of the current process is left unchanged.
A process with the IMPERSONATE privilege can set either ID to any
value. An unprivileged process can set the effective user ID only
if the euid argument is equal to either the real, effective, or
saved user ID of the process.
It is unspecified whether a process without the IMPERSONATE
privilege is permitted to change the real user ID to match the
current real, effective, or saved user ID of the process.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
See also getuid to know how UIC is represented.
435.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The value of the ruid or euid
argument is invalid or out of range.
o EPERM - The current process does not have
the IMPERSONATE privilege, and either an
attempt was made to change the effective
user ID to a value other than the real user
ID or the saved set-user-ID, or an attempt
was made to change the real user ID to a
value not permitted by the implementation.
436 – setsid
Creates a session and sets the process group ID.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
pid_t setsid (void);
436.1 – Description
The setsid function creates a new session if the calling process
is not a process group leader. Upon return, the calling process
is the session leader of this new session and the process
group leader of a new process group, and it has no controlling
terminal. The process group ID of the calling process is set
equal to the process ID of the calling process. The calling
process is the only process in the new process group and the
only process in the new session.
This function requires that long (32-bit) UID/GID support be
enabled. See 32-Bit UID and GID Macro (Integrity servers, Alpha)
for more information.
436.2 – Return Values
x The process group ID of the calling process.
(pid_t)-1 Indicates an error. The function sets errno to
the following value:
o EPERM - The calling process is already a
process group leader, or the process group
ID of a process other than the calling
process matches the process ID of the
calling process.
437 – setstate
Restarts and changes random-number generators.
Format
char *setstate (char *state;)
437.1 – Argument
state
Points to the array of state information.
437.2 – Description
The setstate function handles restarting and changing random-
number generators.
Once you initialize a state, the setstate function allows rapid
switching between state arrays. The array defined by state is
used for further random-number generation until the initstate
function is called or the setstate function is called again. The
setstate function returns a pointer to the previous state array.
After initialization, you can restart a state array at a
different point in one of two ways:
o Use the initstate function, with the desired seed, state
array, and size of the array.
o Use the setstate function, with the desired state, followed by
the srandom function with the desired seed. The advantage of
using both functions is that you do not have to save the state
array size once you initialize it.
See also initstate, srandom, and random.
437.3 – Return Values
x A pointer to the previous state array
information.
0 Indicates an error. The state information is
damaged, and errno is set to the following
value:
o EINVAL-The state argument is invalid.
438 – setuid
With POSIX IDs disabled, implemented for program portability and
serves no function. It returns 0 (to indicate success).
With POSIX IDs enabled, sets the user IDs.
Format
#include <types.h>
#include <unistd.h>
int setuid (__uid_t uid); (_DECC_V4_SOURCE)
uid_t setuid (uid_t uid); (not _DECC_V4_SOURCE)
438.1 – Argument
uid
The value to which you want the user IDs set.
438.2 – Description
The setuid function can be used with POSIX style identifiers
enabled or disabled.
POSIX style IDs are supported on OpenVMS Version 7.3-2 and
higher.
With POSIX IDs disabled (the default), the setuid function is
implemented for program portability and serves no function. It
returns 0 (to indicate success).
With POSIX style IDs enabled:
o If the process has the IMPERSONATE privilege, the setuid
function sets the real user ID, effective user ID, and the
saved set-user-ID to uid.
o If the process does not have appropriate privileges but uid
is equal to the real user ID or to the saved set-user-ID, then
the setuid function sets the effective user ID to uid. The
real user ID and saved set-user-ID remain unchanged.
See also getuid to know how UIC is represented.
438.3 – Return Values
0 Successful completion.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - The value of the uid argument
is invalid and not supported by the
implementation.
o EPERM - The process does not have
appropriate privileges and uid does not
match the real user ID or the saved set-
user-ID.
439 – setvbuf
Associates a buffer with an input or output file and potentially
modifies the buffering behavior.
Format
#include <stdio.h>
int setvbuf (FILE *file_ptr, char *buffer, int type, size_t size);
439.1 – Arguments
file_ptr
A pointer to a file.
buffer
A pointer to a character array, or a NULL pointer.
type
The buffering type. Use one of the following values defined in
<stdio.h>: _IOFBF or _IOLBF.
size
The number of bytes to be used in buffer by the C RTL for
buffering this file. The buffer size must be a minimum of 8192
bytes and a maximum of 32767 bytes.
439.2 – Description
You can use the setvbuf function after the file is opened but
before any I/O operations are performed.
The C RTL provides the following types of ANSI-conforming file
buffering:
In line-buffered I/O, characters are buffered in an area of
memory until a new-line character is seen, at which point the
appropriate RMS routine is called to transmit the entire buffer.
Line buffering is more efficient than unbuffered I/O since it
reduces the system overhead, but it delays the availability of
the data to the user or disk on output.
In fully buffered I/O, characters are buffered in an area of
memory until the buffer is full, regardless of the presence of
break characters. Full buffering is more efficient than line
buffering or unbuffered I/O, but it delays the availability of
output data even longer than line buffering.
Use the values _IOLBF and _IOFBF defined in <stdio.h> for the
type argument to specify line-buffered and fully buffered I/O,
respectively.
If file_ptr specifies a terminal device, the C RTL uses
line-buffered I/O; otherwise, it uses fully buffered I/O.
Please note that the previously documented value _IONBF is not
supported.
The C RTL automatically allocates a buffer to use for each
I/O stream, so there are several buffer allocation possibilities:
o If buffer is not a NULL pointer and size is not smaller than
the automatically allocated buffer, then setvbuf uses buffer
as the file buffer.
o If buffer is a NULL pointer or size is smaller than the
automatically allocated buffer, the automatically allocated
buffer is used as the buffer area.
o If buffer is a NULL pointer and size is larger than the
automatically allocated buffer, then setvbuf allocates a new
buffer equal to the specified size and uses that as the file
buffer.
User programs must not depend on the contents of buffer once I/O
has been performed on the stream. The C RTL might or might
not use buffer for any given I/O operation.
Generally, it is unnecessary to use setvbuf or setbuf to control
the buffer size used by the C RTL. The automatically
allocated buffer sizes are chosen for efficiency based on the
kind of I/O operations performed and the device characteristics
(such as terminal, disk, or socket).
The setvbuf and setbuf functions are useful to introduce
buffering for improved performance when writing a large amount of
text to the stdout stream. This stream is unbuffered by default
when bound to a terminal device (the normal case), and therefore
incurs a large number of OpenVMS buffered I/O operations unless
C RTL buffering is introduced by a call to setvbuf or
setbuf.
The setvbuf function is used only to control the buffering used
by the C RTL, not the buffering used by the underlying RMS
I/O operations. You can modify RMS default buffering behavior by
specifying various values for the ctx, fop, rat, gbc, mbc, mbf,
rfm, and rop RMS keywords when the file is opened by the creat,
freopen or open functions.
439.3 – Return Values
0 Indicates success.
nonzero value Indicates that an invalid input value was
specified for type or file_ptr, or because
file_ptr is being used by another thread.
440 – shm_open
Opens a shared memory object.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <sys/mman.h>
int shm_open (const char *name, int oflag, mode_t mode);
440.1 – Argument
name
Pointer to a string naming a shared memory object.
oflag
Specifies options that define file status and file access modes.
This argument is constructed from the bitwise inclusive OR of
zero or more of the options defined in the <fcntl.h> header file.
mode
The shared memory object's permission bits. This argument is used
only when the shared memory object is being created.
440.2 – Description
The shm_open function establishes a connection between a shared
memory object and a file descriptor. It creates an open file
description that refers to the shared memory object and a file
descriptor that refers to that open file description. The file
descriptor is used by other functions to refer to that shared
memory object. The name argument points to a string naming a
shared memory object. The name can be a pathname, in which case
other processes referring to the same pathname refer to the same
shared memory object.
When a shared memory object is created, its state and all data
associated with it persist until the shared memory is unlinked.
The shm_open function returns a file descriptor for the shared
memory object that is the lowest numbered file descriptor not
currently open for that process.
The file status flags and file access modes of the open file
description are set according to the value of oflag, and can have
zero or more of the following values:
O_RDONLY - Open for read access only.
O_RDWR - Open for read or write access.
O_CREAT - Create the shared memory if the memory object does
not exist already. The user ID and group ID of the shared
memory object are identical to those of the calling process.
The shared memory object's permission bits are set to the
value of mode, except those set in the file mode creation mask
of the process.
O_EXCL - Prevent the opening of a shared memory object if O_
CREAT is set and the shared memory object already exists. Use
this option only in combination with O_CREAT.
O_TRUNC - Truncate the shared memory object to zero length if
it is successfully opened for read or write access (O_RDWR).
The initial contents of the shared memory object are binary
zeros.
440.3 – Return Values
n Upon success, a nonnegative integer
representing the lowest numbered unused file
descriptor. The file descriptor points to the
shared memory object.
-1 Indicates failure. errno is set to indicate
the error:
o EACCES - Permission to create the shared
memory object is denied, or the shared
memory object exists and the permissions
specified by oflag are denied, or O_TRUNC
is specified and write permission is
denied.
o EEXIST - O_CREAT and O_EXCL are set, but
the named shared memory object already
exists.
o EINTR - A signal has interrupted the shm_
open operation.
o EINVAL - The shm_open operation is not
supported for the given name.
o EMFILE - Too many file descriptors are
currently in use by this process.
o ENAMETOOLONG - The length of the name
argument exceeds PATH_MAX or a pathname
component is longer than NAME_MAX.
o ENFILE - Too many shared memory objects are
currently open in the system.
o ENOENT - O_CREAT is not set and the named
shared memory object does not exist.
o ENOSPC - Memory space for creation of the
new shared memory object is insufficient.
441 – shm_unlink
Removes a shared memory object.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <sys/mman.h>
int shm_unlink (const char *name);
441.1 – Argument
name
Pointer to a string naming the shared memory object to remove.
441.2 – Description
The shm_unlink function removes the name of the shared memory
object named by the string pointed to by name.
If one or more references to the shared memory object exist
when the object is unlinked, the name is removed before shm_
unlink returns, but the removal of the memory object contents is
postponed until all open and map references to the shared memory
object have been removed.
Even if the object continues to exist after the last shm_unlink,
reuse of the name subsequently causes shm_unlink to behave as
if no shared memory object with this name exists (that is, shm_
open will fail if O_CREAT is not set, or will create a new shared
memory object if O_CREAT is set).
441.3 – Return Values
0 Indicates success.
-1 Indicates failure, the named shared memory
object is not changed by the function call,
and errno is set to indicate the error:
o EACCES - Permission is denied to unlink the
named shared memory object.
o ENAMETOOLONG - The length of the name
argument exceeds PATH_MAX or a pathname
component is longer than NAME_MAX.
o ENOENT - The named shared memory object
does not exist.
442 – sigaction
Specifies the action to take upon delivery of a signal.
Format
#include <signal.h>
int sigaction (int sig, const struct sigaction *action, struct
sigaction *o_action);
442.1 – Arguments
sig
The signal for which the action is to be taken.
action
A pointer to a sigaction structure that describes the action to
take when you receive the signal specified by the sig argument.
o_action
A pointer to a sigaction structure. When the sigaction function
returns from a call, the action previously attached to the
specified signal is stored in this structure.
442.2 – Description
When a process requests the sigaction function, the process
can both examine and specify what action to perform when the
specified signal is delivered. The arguments determine the
behavior of the sigaction function as follows:
o Specifying the sig argument identifies the affected signal.
Use any one of the signal values defined in the <signal.h>
header file, except SIGKILL.
If sig is SIGCHLD and the SA_NOCLDSTOP flag is not set in
sa_flags, then a SIGCHLD signal is generated for the calling
process whenever any of its child processes stop. If sig is
SIGCHLD and the SA_NOCLDSTOP flag is set in sa_flags, then
SIGCHLD signal is not generated in this way.
o Specifying the action argument, if not null, points to a
sigaction structure that defines what action to perform when
the signal is received. If the action argument is null, signal
handling remains unchanged, so you can use the call to inquire
about the current handling of the signal.
o Specifying the o_action argument, if not null, points to
a sigaction structure that contains the action previously
attached to the specified signal.
The sigaction structure consists of the following members:
void (*sa_handler)(int);
sigset_t sa_mask;
int sa_flags;
The sigaction structure members are defined as follows:
sa_ This member can contain the following values:
handler
o SIG_DFL - Specifies the default action taken when
the signal is delivered.
o SIG_IGN - Specifies that the signal has no effect on
the receiving process.
o Function pointer - Requests to catch the signal. The
signal causes the function call.
sa_mask This member can request that individual signals, in
addition to those in the process signal mask, are
blocked from delivery while the signal handler function
specified by the sa_handler member is executing.
sa_flags This member can set the flags to enable further control
over the actions taken when a signal is delivered.
The sa_flags member of the sigaction structure has the following
values:
SA_ONSTACK Setting this bit causes the system to run the
signal catching function on the signal stack
specified by the sigstack function. If this bit
is not set, the function runs on the stack of the
process where the signal is delivered.
SA_RESETHAND Setting this bit resets the signal to SIG_DFL. Be
aware that you cannot automatically reset SIGILL
and SIGTRAP.
SA_NODEFER Setting this bit does not automatically block the
signal as it is intercepted.
SA_NOCLDSTOP If this bit is set and the sig argument is equal
to SIGCHLD and a child process of the calling
process stops, then a SIGCHLD signal is sent to
the calling process only if SA_NOCLDSTOP is not
set for SIGCHLD.
When a signal is intercepted by a signal-catching function
installed by sigaction, a new signal mask is calculated and
installed for the duration of the signal-catching function (or
until a call to either sigprocmask or sigsuspend is made. This
mask is formed by taking the union of the current signal mask and
the value of the sa_mask for the signal being delivered unless
SA_NODEFER or SA_RESETHAND is set, and then including the signal
being delivered. If and when the user's signal handler returns
normally, the original signal mask is restored.
Once an action is installed for a specific signal, it remains
installed until another action is explicitly requested (by
another call to sigaction), until the SA_RESETHAND flag causes
resetting of the handler, or until one of the exec functions is
called.
If the previous action for a specified signal had been
established by signal, the values of the fields returned in
the structure pointed to by the o_action argument of sigaction
are unspecified, and in particular o_action->sa_handler is
not necessarily the same value passed to signal. However, if a
pointer to the same structure or a copy thereof is passed to a
subsequent call to sigaction by means of the action argument
of sigaction), the signal is handled as if the original call to
signal were repeated.
If sigaction fails, no new signal handler is installed.
It is unspecified whether an attempt to set the action for a
signal that cannot be intercepted or ignored to SIG_DFL is
ignored or causes an error to be returned with errno set to
EINVAL.
See the "Error and Signal Handling" chapter of the VSI C RTL
Reference Manual for more information on signal handling.
NOTE
The sigvec and signal functions are provided for
compatibility to old UNIX systems; their function is a
subset of that available with the sigaction function.
See also sigvec, signal, wait, read, and write.
442.3 – Return Values
0 Indicates success.
-1 Indicates an error; A new signal handler is
not installed. errno is set to one of the
following values:
o EFAULT - The action or o_action argument
points to a location outside of the
allocated address space of the process.
o EINVAL - The sig argument is not a valid
signal number. Or an attempt was made to
ignore or supply a handler for the SIGKILL,
SIGSTOP, and SIGCONT signals.
443 – sigaddset
Adds the specified individual signal.
Format
#include <signal.h>
int sigaddset (sigset_t *set, int sig_number);
443.1 – Arguments
set
The signal set.
sig_number
The individual signal.
443.2 – Description
The sigaddset function manipulates sets of signals. This function
operates on data objects that you can address by the application,
not on any set of signals known to the system. For example, this
function does not operate on the set blocked from delivery to a
process or the set pending for a process.
The sigaddset function adds the individual signal specified by
sig_number from the signal set specified by set.
443.3 – Example
The following example shows how to generate and use a signal
mask that blocks only the SIGINT signal from delivery:
#include <signal.h>
int return_value;
sigset_t newset;
. . .
sigemptyset(&newset);
sigaddset(&newset, SIGINT);
return_value = sigprocmask (SIG_SETMASK, &newset, NULL);
443.4 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to the
following value:
o EINVAL - The value of sig_number is not a
valid signal number.
444 – sigblock
Adds the signals in mask to the current set of signals being
blocked from delivery.
Format
#include <signal.h>
int sigblock (int mask);
444.1 – Argument
mask
The signals to be blocked.
444.2 – Description
Signal i is blocked if the i - 1 bit in mask is a 1. For example,
to add the protection-violation signal to the set of blocked
signals, use the following line:
sigblock(1 << (SIGBUS - 1));
You can express signals in mnemonics (such as SIGBUS for a
protection violation) or numbers as defined in the <signal.h>
header file, and you can express combinations of signals by using
the bitwise OR operator (|).
444.3 – Return Value
x Indicates the previous set of masked signals.
445 – sigdelset
Deletes a specified individual signal.
Format
#include <signal.h>
int sigdelset (sigset_t *set, int sig_number;)
445.1 – Arguments
set
The signal set.
sig_number
The individual signal.
445.2 – Description
The sigdelset function deletes the individual signal specified by
sig_number from the signal set specified by set.
This function operates on data objects that you can address by
the application, not on any set of signals known to the system.
For example, this function does not operate on the set blocked
from delivery to a process or the set pending for a process.
445.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to the
following value:
o EINVAL - The value of sig_number is not a
valid signal number.
446 – sigemptyset
Initializes the signal set to exclude all signals.
Format
#include <signal.h>
int sigemptyset (sigset_t *set);
446.1 – Argument
set
The signal set.
446.2 – Description
The sigemptyset function initializes the signal set pointed to
by set such that you exclude all signals. A call to sigemptyset
or sigfillset must be made at least once for each object of type
sigset_t prior to any other use of that object.
This function operates on data objects that you can address by
the application, not on any set of signals known to the system.
For example, this function does not operate on the set blocked
from delivery to a process or the set pending for a process.
See also sigfillset.
446.3 – Example
The following example shows how to generate and use a signal
mask that blocks only the SIGINT signal from delivery:
#include <signal.h>
int return_value;
sigset_t newset;
. . .
sigemptyset(&newset);
sigaddset(&newset, SIGINT);
return_value = sigprocmask (SIG_SETMASK, &newset, NULL);
446.4 – Return Values
0 Indicates success.
-1 Indicates an error; the global errno is set to
indicate the error.
447 – sigfillset
Initializes the signal set to include all signals.
Format
#include <signal.h>
int sigfillset (sigset_t *set);
447.1 – Argument
set
The signal set.
447.2 – Description
The sigfillset function initializes the signal set pointed to
by set such that you include all signals. A call to sigemptyset
or sigfillset must be made at least once for each object of type
sigset_t prior to any other use of that object.
This function operates on data objects that you can address by
the application, not on any set of signals known to the system.
For example, this function does not operate on the set blocked
from delivery to a process or the set pending for a process.
See also sigemptyset.
447.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to the
following value:
o EINVAL - The value of the sig_number
argument is not a valid signal number.
448 – sighold
Adds the specified signal to the calling process's signal mask.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <signal.h>
int sighold (int signal);
448.1 – Argument
signal
The specified signal. The signal argument can be assigned any of
the signals defined in the <signal.h> header file, except SIGKILL
and SIGSTOP.
448.2 – Description
The sighold, sigrelse, and sigignore functions provide simplified
signal management:
o The sighold function adds signal to the calling process's
signal mask.
o The sigrelse function removes signal from the calling
process's signal mask.
o The sigignore function sets the disposition of signal to SIG_
IGN.
The sighold function, in conjunction with sigrelse and sigpause,
can be used to establish critical regions of code that require
the delivery of a signal to be temporarily deferred.
Upon success, the sighold function returns a value of 0.
Otherwise, a value of -1 is returned, and errno is set to
indicate the error.
NOTE
These interfaces are provided for compatibility only. New
programs should use sigaction and sigprocmask to control the
disposition of signals.
448.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to the
following value:
o EINVAL - The value of the signal argument
is either an invalid signal number or
SIGKILL.
449 – sigignore
Sets the disposition of the specified signal to SIG_IGN.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <signal.h>
int sigignore (int signal);
449.1 – Argument
signal
The specified signal. The signal argument can be assigned any of
the signals defined in the <signal.h> header file, except SIGKILL
and SIGSTOP.
449.2 – Description
The sighold, sigrelse, and sigignore functions provide simplified
signal management:
o The sighold function adds signal to the calling process's
signal mask.
o The sigrelse function removes signal from the calling
process's signal mask.
o The sigignore function sets the disposition of signal to SIG_
IGN.
The sighold function, in conjunction with sigrelse and sigpause,
can be used to establish critical regions of code that require
the delivery of a signal to be temporarily deferred.
Upon success, the sigignore function returns a value of 0.
Otherwise, a value of -1 is returned, and errno is set to
indicate the error.
NOTE
These interfaces are provided for compatibility only. New
programs should use sigaction and sigprocmask to control the
disposition of signals.
449.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to the
following value:
o EINVAL - The value of the signal argument
is either an invalid signal number or
SIGKILL, or an attempt is made to catch
a signal that cannot be intercepted or to
ignore a signal that cannot be ignored.
450 – sigismember
Tests whether a specified signal is a member of the signal set.
Format
#include <signal.h>
int sigismember (const sigset_t *set, int sig_number);
450.1 – Arguments
set
The signal set.
sig_number
The individual signal.
450.2 – Description
The sigismember function tests whether sig_number is a member of
the signal set pointed to by set.
This function operates on data objects that you can address by
the application, not on any set of signals known to the system.
For example, this function does not operate on the set blocked
from delivery to a process or the set pending for a process.
450.3 – Return Values
1 Indicates success. The specified signal is a
member of the specified set.
0 Indicates an error. The specified signal is
not a member of the specified set.
451 – siglongjmp
Nonlocal goto with signal handling.
Format
#include <setjmp.h>
void siglongjmp (sigjmp_buf env, int value);
451.1 – Arguments
env
An address for a sigjmp_buf structure.
value
A nonzero value.
451.2 – Description
The siglongjmp function restores the environment saved by the
most recent call to sigsetjmp in the same process with the
corresponding sigjmp_buf argument.
All accessible objects have values when siglongjmp is called,
with one exception: values of objects of automatic storage
duration that changed between the sigsetjmp call and siglongjmp
call are indeterminate.
Because it bypasses the usual function call and return
mechanisms, siglongjmp executes correctly during interrupts,
signals, and any of their associated functions. However, if you
invoke siglongjmp from a nested signal handler (for example,
from a function invoked as a result of a signal raised during the
handling of another signal), the behavior is undefined.
The siglongjmp function restores the saved signal mask only if
you initialize the env argument by a call to sigsetjmp with a
nonzero savemask argument.
After siglongjmp is completed, program execution continues
as if the corresponding call of sigsetjmp just returned the
value specified by value. The siglongjmp function cannot cause
sigsetjmp to return 0 (zero); if value is 0, sigsetjmp returns 1
See also sigsetjmp.
452 – sigmask
Constructs the mask for a given signal number.
Format
#include <signal.h>
int sigmask (signum);
452.1 – Argument
signum
The signal number for which the mask is to be constructed.
452.2 – Description
The sigmask function is used to construct the mask for a given
signum. This mask can be used with the sigblock function.
452.3 – Return Value
x The mask constructed for signum
453 – signal
Allows you to specify the way in which the signal sig is to be
handled: use the default handling for the signal, ignore the
signal, or call the signal handler at the address specified.
Format
#include <signal.h>
void (*signal (int sig, void (*func) (int))) (int);
453.1 – Arguments
sig
The number or mnemonic associated with a signal. This argument
is usually one of the mnemonics defined in the <signal.h> header
file.
func
Either the action to take when the signal is raised, or the
address of a function needed to handle the signal.
453.2 – Description
If func is the constant SIG_DFL, the action for the given
signal is reset to the default action, which is to terminate
the receiving process. If the argument is SIG_IGN, the signal is
ignored. Not all signals can be ignored.
If func is neither SIG_DFL nor SIG_IGN, it specifies the address
of a signal-handling function. When the signal is raised, the
addressed function is called with sig as its argument. When the
addressed function returns, the interrupted process continues
at the point of interruption. (This is called catching a signal.
Signals are reset to SIG_DFL after they are intercepted, except
as shown in the Error and Signal Handling chapter of the VSI C RTL
Reference Manual.
You must call the signal function each time you want to catch a
signal.
See the "Error and Signal Handling" chapter of the VSI C RTL
Reference Manual for more information on signal handling.
To cause an OpenVMS exception or a signal to generate a UNIX
style signal, OpenVMS condition handlers must return SS$_RESIGNAL
upon receiving any exception that they do not want to handle.
Returning SS$_CONTINUE prevents the correct generation of a UNIX
style signal.
453.3 – Return Values
x The address of the function previously
established to handle the signal.
SIG_ERR Indicates that the sig argument is out of
range.
454 – sigpause
Assigns mask to the current set of masked signals and then waits
for a signal.
Format
#include <signal.h>
int sigpause (int mask);
454.1 – Argument
mask
The signals to be blocked.
454.2 – Description
See the sigblock function for information about the mask
argument.
When control returns to sigpause, the function restores the
previous set of masked signals, sets errno to EINTR, and returns
-1 to indicate an interrupt. The value EINTR is defined in the
<errno.h> header file.
454.3 – Return Value
-1 Indicates an interrupt. errno is set to EINTR.
455 – sigpending
Examines pending signals.
Format
#include <signal.h>
int sigpending (sigset_t *set);
455.1 – Argument
set
A pointer to a sigset_t structure.
455.2 – Description
The sigpending function stores the set of signals that are
blocked from delivery and pending to the calling process in the
location pointed to by the set argument.
Call either the sigemptyset or the sigfillset function at least
once for each object of type sigset_t prior to any other use of
that object. If you do not initialize an object in this way and
supply an argument to the sigpending function, the result is
undefined.
See also sigemptyset and sigfillset in this section.
455.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to the
following value:
o SIGSEGV - Bad mask argument.
456 – sigprocmask
Sets the current signal mask.
Format
#include <signal.h>
int sigprocmask (int how, const sigset_t *set, sigset_t *o_set);
456.1 – Arguments
how
An integer value that indicates how to change the set of masked
signals. Use one of the following values:
SIG_BLOCK The resulting set is the union of the current set
and the signal set pointed to by the set argument.
SIG_UNBLOCK The resulting set is the intersection of the
current set and the complement of the signal set
pointed to by the set argument.
SIG_SETMASK The resulting set is the signal set pointed to by
the set argument.
set
The signal set. If the value of the set argument is:
o Not NULL - It points to a set of signals used to change the
currently blocked set.
o NULL - The value of the how argument is not significant, and
the process signal mask is unchanged, so you can use the call
to inquire about currently blocked signals.
o_set
A non-NULL pointer to the location where the signal mask in
effect at the time of the call is stored.
456.2 – Description
The sigprocmask function is used to examine or change the signal
mask of the calling process.
Typically, use the sigprocmask SIG_BLOCK value to block signals
during a critical section of code, then use the sigprocmask SIG_
SETMASK value to restore the mask to the previous value returned
by the sigprocmask SIG_BLOCK value.
If there are any unblocked signals pending after the call to the
sigprocmask function, at least one of those signals is delivered
before the sigprocmask function returns.
You cannot block SIGKILL or SIGSTOP signals with the sigprocmask
function. If a program attempts to block one of these signals,
the sigprocmask function gives no indication of the error.
456.3 – Example
The following example shows how to set the signal mask to block
only the SIGINT signal from delivery:
#include <signal.h>
int return_value;
sigset_t newset;
. . .
sigemptyset(&newset);
sigaddset(&newset, SIGINT);
return_value = sigprocmask (SIG_SETMASK, &newset, NULL);
456.4 – Return Values
0 Indicates success.
-1 Indicates an error. The signal mask of the
process is unchanged. errno is set to one of
the following values:
o EINVAL - The value of the how argument is
not equal to one of the defined values.
o EFAULT - The set or o_set argument points
to a location outside the allocated address
space of the process.
457 – sigrelse
Removes the specified signal from the calling process's signal
mask.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <signal.h>
int sigrelse (int signal);
457.1 – Argument
signal
The specified signal. The signal argument can be assigned any of
the signals defined in the <signal.h> header file, except SIGKILL
and SIGSTOP.
457.2 – Description
The sighold, sigrelse, and sigignore functions provide simplified
signal management:
o The sighold function adds signal to the calling process's
signal mask.
o The sigrelse function removes signal from the calling
process's signal mask.
o The sigignore function sets the disposition of signal to SIG_
IGN.
The sighold function, in conjunction with sigrelse and sigpause,
can be used to establish critical regions of code that require
the delivery of a signal to be temporarily deferred.
Upon success, the sigrelse function returns a value of 0.
Otherwise, a value of -1 is returned, and errno is set to
indicate the error.
NOTE
These interfaces are provided for compatibility only. New
programs should use sigaction and sigprocmask to control the
disposition of signals.
457.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno is set to the
following value:
o EINVAL - The value of the signal argument
is either an invalid signal number or
SIGKILL.
458 – sigsetjmp
Sets a jump point for a nonlocal goto.
Format
#include <setjmp.h>
init sigsetjmp (sigjmp_buf env, int savemask);
458.1 – Arguments
env
An address for a sigjmp_buf structure.
savemask
An integer value that specifies whether you need to save the
current signal mask.
458.2 – Description
The sigsetjmp function saves its calling environment in its env
argument for later use by the siglongjmp function.
If the value of savemask is not 0 (zero), sigsetjmp also
saves the process's current signal mask as part of the calling
environment.
See also siglongjmp.
458.3 – Restrictions
You cannot invoke the longjmp function from an OpenVMS condition
handler. However, you may invoke longjmp from a signal handler
that has been established for any signal supported by the
C RTL, subject to the following nesting restrictions:
o The longjmp function will not work if you invoke it from
nested signal handlers. The result of the longjmp function,
when invoked from a signal handler that has been entered as a
result of an exception generated in another signal handler, is
undefined.
o Do not invoke the sigsetjmp function from a signal handler
unless the associated longjmp is to be issued before the
handling of that signal is completed.
o Do not invoke the longjmp function from within an exit handler
(established with atexit or SYS$DCLEXH). Exit handlers are
invoked after image tear-down, so the destination address of
the longjmp no longer exists.
o Invoking longjmp from within a signal handler to return to
the main thread of execution might leave your program in
an inconsistent state. Possible side effects include the
inability to perform I/O or to receive any more UNIX signals.
Use siglongjmp instead.
458.4 – Return Values
0 Indicates success.
nonzero The return is a call to the siglongjmp
function.
459 – sigsetmask
Establishes those signals that are blocked from delivery.
Format
#include <signal.h>
int sigsetmask (int mask);
459.1 – Argument
mask
The signals to be blocked.
459.2 – Description
See the sigblock function for information about the mask
argument.
459.3 – Return Value
x The previous set of masked signals.
460 – sigsuspend
Atomically changes the set of blocked signals and waits for a
signal.
Format
#include <signal.h>
int sigsuspend (const sigset_t *signal_mask);
460.1 – Argument
signal_mask
A pointer to a set of signals.
460.2 – Description
The sigsuspend function replaces the signal mask of the process
with the set of signals pointed to by the signal_mask argument.
Then it suspends execution of the process until delivery of
a signal whose action is either to execute a signal catching
function or to terminate the process. You cannot block the
SIGKILL or SIGSTOP signals with the sigsuspend function. If a
program attempts to block either of these signals, sigsuspend
gives no indication of the error.
If delivery of a signal causes the process to terminate,
sigsuspend does not return. If delivery of a signal causes a
signal catching function to execute, sigsuspend returns after the
signal catching function returns, with the signal mask restored
to the set that existed prior to the call to sigsuspend.
The sigsuspend function sets the signal mask and waits for
an unblocked signal as one atomic operation. This means that
signals cannot occur between the operations of setting the mask
and waiting for a signal. If a program invokes sigprocmask SIG_
SETMASK and sigsuspend separately, a signal that occurs between
these functions is often not noticed by sigsuspend.
In normal usage, a signal is blocked by using the sigprocmask
function at the beginning of a critical section. The process then
determines whether there is work for it to do. If there is no
work, the process waits for work by calling sigsuspend with the
mask previously returned by sigprocmask.
If a signal is intercepted by the calling process and control
is returned from the signal handler, the calling process resumes
execution after sigsuspend, which always returns a value of -1
and sets errno to EINTR.
See also sigpause and sigprocmask.
461 – sigtimedwait
Suspends a calling thread and waits for queued signals to arrive.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <signal.h>
int sigtimedwait (const sigset_t set, siginfo_t *info, const
struct timespec *timeout);
461.1 – Arguments
set
The set of signals to wait for.
info
Pointer to a siginfo structure that is receiving data describing
the signal, including any application-defined data specified when
the signal was posted.
timeout
A timeout for the wait. If timeout is NULL, the argument is
ignored.
461.2 – Description
The sigtimedwait function behaves the same as the sigwaitinfo
function except that if none of the signals specified by set are
pending, sigtimedwait waits for the time interval specified in
the timespec structure referenced by timeout. If the timespec
structure pointed to by timeout is zero-valued and if none of the
signals specified by set are pending, then sigtimedwait returns
immediately with an error.
See also sigwait and sigwaitinfo.
See the "Error and Signal Handling" chapter of the VSI C RTL
Reference Manual for more information on signal handling.
461.3 – Return Values
x Upon successful completion, the signal number
selected is returned.
-1 Indicates that an error occurred; errno is set
to one of the following values:
o EINVAL - The timeout argument specified a
tv_nsec value less than 0 or greater than
or equal to 1 billion.
o EINTR - The wait was interrupted by an
unblocked, intercepted signal.
o EAGAIN - No signal specified by set was
generated within the specified timeout
period.
462 – sigvec
Permanently assigns a handler for a specific signal.
Format
#include <signal.h>
int sigvec (int sigint, struct sigvec *sv, struct sigvec *osv);
462.1 – Arguments
sigint
The signal identifier.
sv
Pointer to a sigvec structure (see the Description section).
osv
If osv is not NULL, the previous handling information for the
signal is returned.
462.2 – Description
If sv is not NULL, it specifies the address of a structure
containing a pointer to a handler routine and mask to be used
when delivering the specified signal, and a flag indicating
whether the signal is to be processed on an alternative stack.
If sv->onstack has a value of 1, the system delivers the signal
to the process on a signal stack specified with sigstack.
The sigvec function establishes a handler that remains
established until explicitly removed or until the image
terminates.
The sigvec structure is defined in the <signal.h> header file:
struct sigvec
{
int (*handler)();
int mask;
int onstack;
};
See the "Error and Signal Handling" chapter of the VSI C RTL
Reference Manual for more information on signal handling.
462.3 – Return Values
0 Indicates that the call succeeded.
-1 Indicates that an error occurred.
463 – sigwait
Suspends a calling thread and waits for queued signals to arrive.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <signal.h>
int sigwait (const sigset_t set, int *sig);
463.1 – Arguments
set
The set of signals to wait for.
sig
Returns the signal number of the selected signal.
463.2 – Description
The sigwait function suspends the calling thread until at least
one of the signals in the set argument is in the caller's set
of pending signals. When this happens, one of those signals
is automatically selected and removed from the set of pending
signals. The signal number identifying that signal is then
returned in the location referenced by sig.
The effect is unspecified if any signals in the set argument are
not blocked when the sigwait function is called.
The set argument is created using the set manipulation functions
sigemptyset, sigfillset, sigaddset, and sigdelset.
If, while the sigwait function is waiting, a signal occurs that
is eligible for delivery (that is, not blocked by the signal
mask), that signal is handled asynchronously and the wait is
interrupted.
See also sigtimedwait and sigwaitinfo.
See the "Error and Signal Handling" chapter of the VSI C RTL
Reference Manual for more information on signal handling.
463.3 – Return Values
0 Upon successful completion, sigwait stores the
signal number of the received signal at the
location referenced by sig and returns 0.
nonzero Indicates that an error occurred; errno is set
to the following value:
o EINVAL - The set argument contains an
invalid or unsupported signal number.
464 – sigwaitinfo
Suspends a calling thread and waits for queued signals to arrive.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <signal.h>
int sigwaitinfo (const sigset_t set, siginfo_t *info);
464.1 – Arguments
set
The set of signals to wait for.
info
Pointer to a siginfo structure that is receiving data describing
the signal, including any application-defined data specified when
the signal was posted.
464.2 – Description
The sigwaitinfo function behaves the same as the sigwait function
if the info argument is NULL.
If the info argument is non-NULL, the sigwaitinfo function
behaves the same as sigwait, except that the selected signal
number is stored in the si_signo member of the siginfo structure,
and the cause of the signal is stored in the si_code member.
If any value is queued to the selected signal, the first such
queued value is dequeued and the value is stored in the si_value
member of info. The system resource used to queue the signal is
released and made available to queue other signals. If no value
is queued, the content of the si_value member is undefined. If no
further signals are queued for the selected signal, the pending
indication for that signal is reset.
See also sigtimedwait and sigwait.
See the "Error and Signal Handling" chapter of the VSI C RTL
Reference Manual for more information on signal handling.
464.3 – Return Values
x Upon successful completion, the signal number
selected is returned.
-1 Indicates that an error occurred; errno is set
to one of the following values:
o EINVAL - The set argument contains an
invalid or unsupported signal number.
o EINTR - The wait was interrupted by an
unblocked, intercepted signal.
465 – sin
Returns the sine of its radian argument.
Format
#include <math.h>
double sin (double x);
float sinf (float x); (Integrity servers, Alpha)
long double sinl (long double x); (Integrity servers, Alpha)
double sind (double x); (Integrity servers, Alpha)
float sindf (float x); (Integrity servers, Alpha)
long double sindl (long double x); (Integrity servers, Alpha)
465.1 – Argument
x
A radian expressed as a floating-point number.
465.2 – Description
The sin functions compute the sine of x measured in radians.
The sind functions compute the sine of x measured in degrees.
465.3 – Return Values
x The sine of the argument.
NaN x = Infinity or NaN; errno is set to EDOM.
0 Underflow occurred; errno is set to ERANGE.
466 – sinh
Returns the hyperbolic sine of its argument.
Format
#include <math.h>
double sinh (double x);
float sinhf (float x); (Integrity servers, Alpha)
long double sinhl (long double x); (Integrity servers, Alpha)
466.1 – Argument
x
A real number.
466.2 – Return Values
n The hyperbolic sine of the argument.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
0 Underflow occurred; errno is set to ERANGE.
NaN x is NaN; errno is set to EDOM.
467 – sleep
Suspends the execution of the current process (or thread in a
threaded program) for at least the number of seconds indicated by
its argument.
Format
#include <unistd.h>
unsigned int sleep (unsigned seconds); (_DECC_V4_SOURCE)
int sleep (unsigned seconds); (not _DECC_V4_SOURCE)
467.1 – Argument
seconds
The number of seconds.
467.2 – Description
The sleep function sleeps for the specified number of seconds, or
until a signal is received, or until the process (or thread in a
threaded program) executes a call to SYS$WAKE.
If a SIGALRM signal is generated, but blocked or ignored, the
sleep function returns. For all other signals, a blocked or
ignored signal does not cause sleep to return.
467.3 – Return Values
x The number of seconds that the process awoke
early.
0 If the process slept the full number of
seconds specified by seconds.
468 – snprintf
Performs formatted output to a string in memory.
Format
#include <stdio.h>
int snprintf (char *str, size_t n, const char
*format_spec, . . . );
468.1 – Arguments
str
The address of the string that will receive the formatted output.
n
The size of the buffer referred to by str.
format_spec
A pointer to a character string that contains the format
specification.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, you may omit the
output sources. Otherwise, the function calls must have at least
as many output sources as there are conversion specifications,
and the conversion specifications must match the types of the
output sources.
Conversion specifications are matched to output sources in left-
to-right order. Excess output pointers, if any, are ignored.
468.2 – Description
The snprintf function is identical to the sprintf function with
the addition of the n argument, which specifies the size of the
buffer referred to by str.
On successful completion, snprintf returns the number of bytes
(excluding the terminating null byte) that would be written to
str if n is sufficiently large.
If n is 0, nothing is written, the number of bytes (excluding the
terminating null) that would be written if n were sufficiently
large are returned, and str might be a NULL pointer. Otherwise,
output bytes beyond the n - 1st are discarded instead of being
written to the array, and a null byte is written at the end of
the bytes actually written into the array.
If an output error is encountered, a negative value is returned.
468.3 – Return Values
x The number of bytes (excluding the terminating
null byte) that would be written to str if n
is sufficiently large.
Negative value Indicates an output error occurred. The
function sets errno. For a list of errno
values set by this function, see fprintf.
469 – sprintf
Performs formatted output to a string in memory.
Format
#include <stdio.h>
int sprintf (char *str, const char *format_spec, . . . );
469.1 – Arguments
str
The address of the string that will receive the formatted output.
It is assumed that this string is large enough to hold the
output.
format_spec
A pointer to a character string that contains the format
specification.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, you may omit the
output sources. Otherwise, the function calls must have at least
as many output sources as there are conversion specifications,
and the conversion specifications must match the types of the
output sources.
Conversion specifications are matched to output sources in left-
to-right order. Excess output pointers, if any, are ignored.
469.2 – Description
The sprintf function places output followed by the null character
(\0) in consecutive bytes starting at *str. The user must ensure
that enough space is available.
Consider the following example of a conversion specification:
#include <stdio.h>
main()
{
int temp = 4, temp2 = 17;
char s[80];
sprintf(s, "The answers are %d, and %d.", temp, temp2);
}
In this example, character string s has the following contents:
The answers are 4, and 17.
469.3 – Return Values
x The number of characters placed in the
output string, not including the final null
character.
Negative value Indicates an output error occurred. The
function sets errno. For a list of errno
values set by this function, see fprintf.
470 – sqrt
Returns the square root of its argument.
Format
#include <math.h>
double sqrt (double x);
float sqrtf (float x); (Integrity servers, Alpha)
long double sqrtl (long double x); (Integrity servers, Alpha)
470.1 – Argument
x
A real number.
470.2 – Return Values
val The square root of x, if x is nonnegative.
0 x is negative; errno is set to EDOM.
NaN x is NaN; errno is set to EDOM.
471 – srand
Initializes the pseudorandom-number generator rand.
Format
#include <stdlib.h>
void srand (unsigned int seed);
471.1 – Argument
seed
An unsigned integer.
471.2 – Description
The srand function uses the argument as a seed for a new sequence
of pseudorandom numbers to be returned by subsequent calls to
rand.
If srand is then called with the same seed value, the sequence of
pseudorandom numbers is repeated.
If rand is called before any calls to srand, the same sequence of
pseudorandom numbers is generated as when srand is first called
with a seed value of 1.
472 – srand48
Initializes a 48-bit random-number generator.
Format
#include <stdlib.h>
void srand48 (long int seed_val);
472.1 – Argument
seed_val
The initialization value to begin randomization. Changing this
value changes the randomization pattern.
472.2 – Description
The srand48 function initializes the random-number generator. You
can use this function in your program before calling the drand48,
lrand48, or mrand48 functions. (Although it is not recommended
practice, constant default initializer values are automatically
supplied if you call drand48, lrand48, or mrand48 without calling
an initialization function).
The function works by generating a sequence of 48-bit integer
values, Xi, according to the linear congruential formula:
Xn+1 = (aXn+c)mod m n >= 0
The argument m equals 248, so 48-bit integer arithmetic is
performed. Unless you invoke the lcong48 function, the multiplier
value a and the addend value c are:
a = 5DEECE66D16 = 2736731631558
c = B16 = 138
The initializer function srand48 sets the high-order 32 bits
of Xi to the low-order 32 bits contained in its argument. The
low-order 16 bits of Xi are set to the arbitrary value 330E16.
See also drand48, lrand48, and mrand48.
473 – srandom
Initializes the pseudorandom-number generator random.
Format
#include <stdlib.h>
int srandom (unsigned seed);
473.1 – Argument
seed
An initial seed value.
473.2 – Description
The srandom function uses the argument as a seed for a new
sequence of pseudorandom numbers to be returned by subsequent
calls to random. This function has virtually the same calling
sequence and initialization properties as the srand function, but
produce sequences that are more random.
The srandom function initializes the current state with the
initial seed value. The srandom function, unlike the srand
function, does not return the old seed because the amount of
state information used is more than a single word.
See also rand, srand, random, setstate, and initstate.
473.3 – Return Values
0 Indicates success. Initializes the state seed.
-1 Indicates an error, further specified in the
global errno.
474 – sscanf
Reads input from a character string in memory, interpreting it
according to the format specification.
Format
#include <stdio.h>
int sscanf (const char *str, const char *format_spec, . . . );
474.1 – Arguments
str
The address of the character string that provides the input text
to sscanf.
format_spec
A pointer to a character string that contains the format
specification.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, you can omit the input
pointers. Otherwise, the function calls must have at least as
many input pointers as there are conversion specifications, and
the conversion specifications must match the types of the input
pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
474.2 – Description
The following is an example of a conversion specification:
main ()
{
char str[] = "4 17";
int temp,
temp2;
sscanf(str, "%d %d", &temp, &temp2);
printf("The answers are %d and %d.", temp, temp2);
}
This example produces the following output:
$ RUN EXAMPLE
The answers are 4 and 17.
474.3 – Return Values
x The number of successfully matched and
assigned input items.
EOF Indicates that a read error occurred before
any conversion. The function sets errno. For a
list of the values set by this function, see
fscanf.
475 – ssignal
Allows you to specify the action to take when a particular signal
is raised.
Format
#include <signal.h>
void (*ssignal (int sig, void (*func) (int, . . . )))
(int, . . . );
475.1 – Arguments
sig
A number or mnemonic associated with a signal. The symbolic
constants for signal values are defined in the <signal.h> header
file. See the Error and Signal Handling chapter of the VSI C RTL
Reference Manual.
func
The action to take when the signal is raised, or the address of a
function that is executed when the signal is raised.
475.2 – Description
The ssignal function is equivalent to the signal function except
for the return value on error conditions.
Since the signal function is defined by the ANSI C standard and
the ssignal function is not, use signal for greater portability.
See the "Error and Signal Handling" chapter of the VSI C RTL
Reference Manual for more information on signal handling.
475.3 – Return Values
x The address of the function previously
established as the action for the signal.
The address may be the value SIG_DFL (0) or
SIG_IGN (1).
0 Indicates errors. For this reason, there is
no way to know whether a return status of 0
indicates failure, or whether it indicates
that a previous action was SIG_DFL (0).
476 – [w]standend
Deactivate the boldface attribute for the specified window. The
standend function operates on the stdscr window.
Format
#include <curses.h>
int standend (void);
int wstandend (WINDOW *win);
476.1 – Argument
win
A pointer to the window.
476.2 – Description
The standend and wstandend functions are equivalent to clrattr
and wclrattr called with the attribute _BOLD.
476.3 – Return Values
OK Indicates success.
ERR Indicates an error.
477 – [w]standout
Activate the boldface attribute of the specified window. The
standout function acts on the stdscr window.
Format
#include <curses.h>
int standout (void);
int wstandout (WINDOW *win);
477.1 – Argument
win
A pointer to the window.
477.2 – Description
The standout and wstandout functions are equivalent to setattr
and wsetattr called with the attribute _BOLD.
477.3 – Return Values
OK Indicates success.
ERR Indicates an error.
478 – stat
Accesses information about the specified file.
Format
#include <stat.h>
int stat (const char *file_spec, struct stat *buffer);
(ISO POSIX-1)
int stat (const char *file_spec, struct stat *buffer, . . . );
(DEC C Extension)
478.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to the
stat function that is equivalent to the behavior before OpenVMS
Version 7.0.
Compiling with the _USE_STD_STAT feature-test macro defined
enables a variant of the stat function that uses an X/Open
standard-compliant definition of the stat structure. The _USE_
STD_STAT feature-test macro is mutually exclusive with the _DECC_
V4_SOURCE and _VMS_V6_SOURCE macros.
478.2 – Arguments
file_spec
A valid OpenVMS or UNIX style file specification (no wildcards).
Read, write, or execute permission of the named file is not
required, but you must be able to reach all directories listed
in the file specification leading to the file.
buffer
A pointer to a structure of type stat. For convenience, a typedef
stat_t is defined as struct stat in the <stat.h> header file.
This argument receives information about the particular file. The
members of the structure pointed to by buffer are described in
the Description section.
. . .
An optional default file-name string.
This is the only optional RMS keyword that can be specified for
the stat function. See the description of the creat function for
the full list of optional RMS keywords and their values.
478.3 – Description
When the _USE_STD_STAT feature-test macro is not enabled, the
legacy stat structure is used. When _USE_STD_STAT is enabled, the
X/Open standard-compliant stat structure is used.
Legacy stat Structure
With the _USE_STD_STAT feature-test macro defined to DISABLE, the
following legacy stat structure is used:
Member Type Definition
st_dev dev_t Pointer to the physical device name
st_ino[3] ino_t Three words to receive the file ID
st_mode mode_t File "mode" (prot, dir, . . . )
st_nlink nlink_t For UNIX system compatibility only
st_uid uid_t Owner user ID
st_gid gid_t Group member: from st_uid
st_rdev dev_t UNIX system compatibility - always 0
st_size off_t File size, in bytes. For st_size to
report a correct value, you need to
flush both the C RTL and RMS buffers.
st_atime time_t File access time; always the same as
st_mtime
st_mtime time_t Last modification time
st_ctime time_t File creation time
st_fab_rfm char Record format
st_fab_rat char Record attributes
st_fab_fsz char Fixed header size
st_fab_mrs unsigned Record size
The types dev_t, ino_t, off_t, mode_t, nlink_t, uid_t, gid_t, and
time_t, are defined in the <stat.h> header file. However, when
compiling for compatibility (/DEFINE=_DECC_V4_SOURCE), only dev_
t, ino_t, and off_t are defined.
The off_t data type is either a 32-bit or 64-bit integer. The 64-
bit interface allows for file sizes greater than 2 GB, and can be
selected at compile time by defining the _LARGEFILE feature-test
macro as follows:
CC/DEFINE=_LARGEFILE
As of OpenVMS Version 7.0, times are given in seconds since the
Epoch (00:00:00 GMT, January 1, 1970).
The st_mode structure member is the status information mode
defined in the <stat.h> header file. The st_mode bits are
described as follows:
Bits Constant Definition
0170000 S_IFMT Type of file
0040000 S_IFDIR Directory
0020000 S_IFCHR Character special
0060000 S_IFBLK Block special
0100000 S_IFREG Regular
0030000 S_IFMPC Multiplexed char special
0070000 S_IFMPB Multiplexed block special
0004000 S_ISUID Set user ID on execution
0002000 S_ISGID Set group ID on execution
0001000 S_ISVTX Save swapped text even after use
0000400 S_IREAD Read permission, owner
0000200 S_IWRITE Write permission, owner
0000100 S_IEXEC Execute/search permission, owner
The stat function does not work on remote network files.
If the file is a record file, the st_size field includes
carriage-control information. Consequently, the st_size value
will not correspond to the number of characters that can be read
from the file.
Also be aware that for st_size to report a correct value, you
need to flush both the C RTL and RMS buffers.
Standard-Compliant stat Structure
With OpenVMS Version 8.2, the _USE_STD_STAT feature-test macro
and standard-compliant stat structure are introduced in support
of UNIX compatibility.
With _USE_STD_STAT defined to ENABLE, you get the following
behavior:
o Old struct stat definitions
Old definitions of struct stat are obsolete. You must
recompile your applications to access the new features.
Existing applications will continue to access the old
definitions and functions unless they are recompiled to use
the new features.
o Function variants
Calls to stat, fstat, lstat, and ftw accept pointers to
structures of the new type. Calls to these functions are
mapped to the new library entries __std_stat, __std_fstat,
__std_lstat, and __std_ftw, respectively.
o Compatibilities with other feature macros
_DECC_V4_SOURCE source-code compatibility is not supported.
You must not enable _DECC_V4_SOURCE and _USE_STD_STAT at the
same time.
_VMS_V6_SOURCE binary compatibility is not supported. You must
not enable _VMS_V6_SOURCE and _USE_STD_STAT at the same time.
As a result, only UTC (rather than local-time) is supported
for the time_t fields.
o Type changes
The following type changes are in effect:
- 32-bit gid type gid_t is used. _DECC_SHORT_GID_T is
unsupported.
- _LARGEFILE offsets are used. off_t is forced to 64 bits.
- Type ino_t, representing the file number, is an unsigned
int quadword (64 bits). Previously, it was an unsigned
short.
- Type dev_t, representing the device id, is an unsigned int
quadword (64 bits). Previously, it was a 32-bit character
pointer. The new type is standard because it is arithmetic.
- Types blksize_t and blkcnt_t are added and defined as
unsigned int quadwords (64 bits).
o Structure member Changes
- Two members are added to struct stat:
blksize_t st_blksize;
blkcnt_t st_blocks;
According to the X/Open standard, st_blksize is the
filesystem-specific preferred I/O blocksize for this file.
On OpenVMS systems, st_blksize is set to the device buffer
size multiplied by the disk cluster size. st_blocks is set
to the allocated size of the file, in blocks. The blocksize
used to calculate st_blocks is not necessarily the same as
st_blksize and, in most cases, will not be the same.
- In struct stat, member st_ino is of type ino_t. In previous
C RTL versions, it was of type ino_t [3] (array of 3 ino_
t). Since ino_t has changed from a word to a quadword,
the size of this member has increased by one word. The
principal significance of this change is that it makes st_
ino a scalar, which is how most open source applications
define it.
- The new definition of ino_t also affects applications
that include the <dirent.h> header file. In struct dirent,
member d_ino changes in the same way as the st_ino member
of struct stat in <stat.h>.
- Several macros that are not part of any standard were
introduced in <stat.h> to facilitate access to the
constituent parts of ino_t values:
S_INO_NUM(ino), S_INO_SEQ(ino), and S_INO_RVN(ino)
return the FILES-11 file number, sequence number, and
relative volume number of ino, respectively, as unsigned
shorts.
S_INO_RVN_RVN(ino) returns the byte of the RVN field
containing the relative volume number;
S_INO_RVN_NMX(ino) returns the byte of the RVN field
containing the file number extension.
Although individual components can be broken out like this,
they are not part of the X/Open standard and should not be
relied on in portable applications.
o Semantic changes
Values of type dev_t are now unique for each device across
clusters. An algorithm based on device name and allocation
class or SCSSYSTEMID (for single-pathed devices) calculates
the device id value having these characteristics, an X/Open
standard requirement. Typically, the combination of file
number and device id uniquely identifies a file in a cluster.
This change affects stat structure members st_dev and st_rdev.
For compatibility with previous releases, st_rdev is set to
either 0 or st_dev.
NOTE (Integrity servers, Alpha)
On OpenVMS Alpha and Integrity server systems, the stat,
fstat, utime, and utimes functions have been enhanced to
take advantage of the new file-system support for POSIX
compliant file timestamps.
This support is available only on ODS-5 devices on OpenVMS
Alpha systems beginning with a version of OpenVMS Alpha
after Version 7.3.
Before this change, the stat and fstat functions were
setting the values of the st_ctime, st_mtime, and st_atime
fields based on the following file attributes:
st_ctime - ATR$C_CREDATE (file creation time)
st_mtime - ATR$C_REVDATE (file revision time)
st_atime - was always set to st_mtime because no support
for file access time was available
Also, for the file-modification time, utime and utimes were
modifying the ATR$C_REVDATE file attribute, and ignoring the
file-access-time argument.
After the change, for a file on an ODS-5 device, the stat
and fstat functions set the values of the st_ctime, st_
mtime, and st_atime fields based on the following new file
attributes:
st_ctime - ATR$C_ATTDATE (last attribute modification
time)
st_mtime - ATR$C_MODDATE (last data modification time)
st_atime - ATR$C_ACCDATE (last access time)
If ATR$C_ACCDATE is zero, as on an ODS-2 device, the stat
and fstat functions set st_atime to st_mtime.
For the file-modification time, the utime and utimes
functions modify both the ATR$C_REVDATE and ATR$C_MODDATE
file attributes. For the file-access time, these functions
modify the ATR$C_ACCDATE file attribute. Setting the ATR$C_
MODDATE and ATR$C_ACCDATE file attributes on an ODS-2 device
has no effect.
For compatibility, the old behavior of stat, fstat, utime,
and utimes remains the default, regardless of the kind of
device.
The new behavior must be explicitly enabled by defining
the DECC$EFS_FILE_TIMESTAMPS logical name to ENABLE before
invoking the application. Setting this logical does not
affect the behavior of stat, fstat, utime, and utimes for
files on an ODS-2 device.
478.4 – Return Values
0 Indicates success.
-1 Indicates an error other than a privilege
violation; errno is set to indicate the error.
-2 Indicates a privilege violation.
479 – statvfs
Gets information about a device containing the specified file.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <statvfs.h>
int statvfs (const char *restrict path, struct statvfs
*restrict buffer);
479.1 – Arguments
path
Any file on a mounted device.
buffer
Pointer to a statvfs structure to hold the returned information.
479.2 – Description
The statvfs function returns descriptive information about the
device containing the specified file. Read, write, or execute
permission of the specified file is not required. The returned
information is in the format of a statvfs structure, which is
defined in the <statvfs.h> header file and contains the following
members:
unsigned long f_bsize - Preferred block size.
unsigned long f_frsize - Fundamental block size.
fsblkcnt_t f_blocks - Total number of blocks in units of f_
frsize.
fsblkcnt_t f_bfree - Total number of free blocks. If f_bfree
would assume a meaningless value due to the misreporting of
free block count by $GETDVI for a DFS disk, then f_bfree is
set to the maximum block count.
fsblkcnt_t f_bavail - Number of free blocks available. Set to
the unused portion of the caller's disk quota.
fsfilcnt_t f_files - Total number of file serial numbers (for
example, inodes).
fsfilcnt_t f_ffree - Total number of free file serial
numbers. For OpenVMS systems, this value is calculated as
freeblocks/clustersize.
fsfilcnt_t f_favail - Number of file serial numbers available
to a non-privileged process (0 for OpenVMS systems).
unsigned long f_fsid - File system identifier. This identifier
is based on the allocation-class device name. This gives a
unique value based on device, as long as the device is locally
mounted.
unsigned long f_flag - Bit mask representing one or more of
the following flags:
ST_RONLY - The volume is read-only.
ST_NOSUID - The volume has protected subsystems enabled.
unsigned long f_namemax - Maximum length of a filename.
char f_basetype[64] - Device-type name.
char f_fstr[64] - Logical volume name.
char __reserved[64] - Media type name.
Upon successful completion, statvfs returns 0 (zero). Otherwise,
it returns -1 and sets errno to indicate the error.
See also fstatvfs.
479.3 – Return Value
0 Successful completion.
-1 Indicates an error. errno is set to one of the
following:
o EACCES - Search permission is denied for a
component of the path prefix.
o EIO - An I/O error occurred while reading
the device.
o EINTR - A signal was intercepted during
execution of the function.
o EOVERFLOW - One of the values to be
returned cannot be represented correctly
in the structure pointed to by buffer.
o ENAMETOOLONG - The length of a component
of the path parameter exceeds NAME_MAX, or
the length of the path parameter exceeds
PATH_MAX.
o ENOENT - A component of path does not
name an existing file, or path is an empty
string.
o ENOTDIR - A component of the path prefix of
the path parameter is not a directory.
480 – strcasecmp
Does a case-insensitive comparison of two 7-bit ASCII strings.
Format
#include <strings.h>
int strcasecmp (const char *s1, const char *s2);
480.1 – Arguments
s1
The first of two strings to compare.
s2
The second of two strings to compare.
480.2 – Description
The strcasecmp function is case-insensitive. The returned
lexicographic difference reflects a conversion to lowercase.
The strcasecmp function works for 7-bit ASCII compares only. Do
not use this function for internationalized applications.
480.3 – Return Value
n An integer value greater than, equal to, or
less than 0 (zero), depending on whether the
s1 string is greater than, equal to, or less
than the s2 string.
481 – strcat
Concatenates str_2, including the terminating null character, to
the end of str_1.
Format
#include <string.h>
char *strcat (char *str_1, const char *str_2);
481.1 – Function Variants
The strcat function has variants named _strcat32 and _strcat64
for use with 32-bit and 64-bit pointer sizes, respectively.
481.2 – Arguments
str_1, str_2
Pointers to null-terminated character strings.
481.3 – Description
See strncat.
481.4 – Return Value
x The address of the first argument, str_1,
which is assumed to be large enough to hold
the concatenated result.
481.5 – Example
#include <string.h>
#include <stdio.h>
/* This program concatenates two strings using the strcat */
/* function, and then manually compares the result of strcat */
/* to the expected result. */
#define S1LENGTH 10
#define S2LENGTH 8
main()
{
static char s1buf[S1LENGTH + S2LENGTH] = "abcmnexyz";
static char s2buf[] = " orthis";
static char test1[] = "abcmnexyz orthis";
int i;
char *status;
/* Take static buffer s1buf, concatenate static buffer */
/* s2buf to it, and compare the answer in s1buf with the */
/* static answer in test1. */
status = strcat(s1buf, s2buf);
for (i = 0; i <= S1LENGTH + S2LENGTH - 2; i++) {
/* Check for correct returned string. */
if (test1[i] != s1buf[i])
printf("error in strcat");
}
}
482 – strchr
Returns the address of the first occurrence of a given character
in a null-terminated string.
Format
#include <string.h>
char *strchr (const char *str, int character);
482.1 – Function Variants
The strchr function has variants named _strchr32 and _strchr64
for use with 32-bit and 64-bit pointer sizes, respectively.
482.2 – Arguments
str
A pointer to a null-terminated character string.
character
An object of type int.
482.3 – Description
This function returns the address of the first occurrence of a
given character in a null-terminated string. The terminating null
character is considered to be part of the string.
Compare with strrchr, which returns the address of the last
occurrence of a given character in a null-terminated string.
482.4 – Return Values
x The address of the first occurrence of the
specified character.
NULL Indicates that the character does not occur in
the string.
482.5 – Example
#include <stdio.h>
#include <string.h>
main()
{
static char s1buf[] = "abcdefghijkl lkjihgfedcba";
int i;
char *status;
/* This program checks the strchr function by incrementally */
/* going through a string that ascends to the middle and then */
/* descends towards the end. */
for (i = 0; s1buf[i] != '\0' && s1buf[i] != ' '; i++) {
status = strchr(s1buf, s1buf[i]);
/* Check for pointer to leftmost character - test 1. */
if (status != &s1buf[i])
printf("error in strchr");
}
}
483 – strcmp
Compares two ASCII character strings and returns a negative,
0, or positive integer, indicating that the ASCII values of the
individual characters in the first string are less than, equal
to, or greater than the values in the second string.
Format
#include <string.h>
int strcmp (const char *str_1, const char *str_2);
483.1 – Arguments
str_1, str_2
Pointers to character strings.
483.2 – Description
The strings are compared until a null character is encountered or
until the strings differ.
483.3 – Return Values
< 0 Indicates that str_1 is less than str_2.
> 0 Indicates that str_1 is greater than str_2.
484 – strcoll
Compares two strings and returns an integer that indicates if
the strings differ and how they differ. The function uses the
collating information in the LC_COLLATE category of the current
locale to determine how the comparison is performed.
Format
#include <string.h>
int strcoll (const char *s1, const char *s2);
484.1 – Arguments
s1, s2
Pointers to character strings.
484.2 – Description
The strcoll function, unlike strcmp, compares two strings in a
locale-dependent manner. Because no value is reserved for error
indication, the application must check for one by setting errno
to 0 before the function call and testing it after the call.
See also strxfrm.
484.3 – Return Values
< 0 Indicates that s1 is less than s2.
> 0 Indicates that s1 is greater than s2.
485 – strcpy
Copies all of source, including the terminating null character,
into dest.
Format
#include <string.h>
char *strcpy (char *dest, const char *source);
485.1 – Function Variants
The strcpy function has variants named _strcpy32 and _strcpy64
for use with 32-bit and 64-bit pointer sizes, respectively.
485.2 – Arguments
dest
Pointer to the destination character string.
source
Pointer to the source character string.
485.3 – Description
The strcpy function copies source into dest, and stops after
copying source's null character.
The behavior of this function is undefined if the area pointed to
by dest overlaps the area pointed to by source.
485.4 – Return Value
x The address of dest.
486 – strcspn
Returns the length of the prefix of a string that consists
entirely of characters not in a specified set of characters.
Format
#include <string.h>
size_t strcspn (const char *str, const char *charset);
486.1 – Arguments
str
A pointer to a character string. If this character string is a
null string, 0 is returned.
charset
A pointer to a character string containing the set of characters.
486.2 – Description
The strcspn function scans the characters in the string, stops
when it encounters a character found in charset, and returns the
length of the string's initial segment formed by characters not
found in charset.
If none of the characters match in the character strings pointed
to by str and charset, strcspn returns the length of string.
486.3 – Return Value
x The length of the segment.
487 – strdup
Duplicates the specified string.
Format
#include <string.h>
char *strdup (const char *s1);
487.1 – Function Variants
The strdup function has variants named _strdup32 and _strdup64
for use with 32-bit and 64-bit pointer sizes, respectively.
487.2 – Argument
s1
The string to be duplicated.
487.3 – Description
The strdup function returns a pointer to a string that is an
exact duplicate of the string pointed to by s1. The malloc
function is used to allocate space for the new string. The strdup
function is provided for compatibility with existing systems.
487.4 – Return Values
x A pointer to the resulting string.
NULL Indicates an error.
488 – strerror
Maps the error number in error_code to a locale-dependent error
message string.
Format
#include <string.h>
char *strerror (int error_code); (ANSI C)
char *strerror (int error_code[, int vms_error_code]);
(DEC C Extension)
488.1 – Arguments
error_code
An error code.
vms_error_code
An OpenVMS error code.
488.2 – Description
The strerror function uses the error number in error_code to
retrieve the appropriate locale-dependent error message. The
contents of the error message strings are determined by the LC_
MESSAGES category of the program's current locale.
When a program is not compiled with any standards-related
feature-test macros, strerror has a second argument (vms_error_
code), which is used in the following way:
o If error_code is EVMSERR and there is a second argument, then
that second argument is used as the vaxc$errno value.
o If error_code is EVMSERR and there is no second argument, look
at vaxc$errno to get the OpenVMS error condition.
See the Example section.
Use of the second argument is not included in the ANSI C
definition of strerror and is, therefore, not portable.
Because no return value is reserved to indicate an error,
applications should set the value of errno to 0, call strerror,
and then test the value of errno; a nonzero value indicates an
error condition.
488.3 – Return Value
x A pointer to a buffer containing the
appropriate error message. Do not modify
this buffer in your programs. Moreover, calls
to the strerror function may overwrite this
buffer with a new message.
488.4 – Example
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <ssdef.h>
main()
{
puts(strerror(EVMSERR));
errno = EVMSERR;
vaxc$errno = SS$_LINKEXIT;
puts(strerror(errno));
puts(strerror(EVMSERR, SS$_ABORT));
exit(1);
}
Running this example produces the following output:
nontranslatable vms error code: <none>
network partner exited
abort
489 – strfmon
Converts a number of monetary values into a string. The
conversion is controlled by a format string.
Format
#include <monetary.h>
ssize_t strfmon (char *s, size_t maxsize, const char
*format, . . . );
489.1 – Arguments
s
A pointer to the resultant string.
maxsize
The maximum number of bytes to be stored in the resultant string.
format
A pointer to a string that controls the format of the output
string.
. . .
The monetary values of type double that are to be formatted for
the output string. There should be as many values as there are
conversion specifications in the format string pointed to by
format. The function fails if there are insufficient values.
Excess arguments are ignored.
489.2 – Description
The strfmon function creates a string pointed to by s, using the
monetary values supplied. A maximum of maxsize bytes is copied to
s.
The format string pointed to by format consists of ordinary
characters and conversion specifications. All ordinary characters
are copied unchanged to the output string. A conversion
specification defines how one of the monetary values supplied
is formatted in the output string.
A conversion specification consists of a percent character
(%), followed by a number of optional characters (see Optional
Characters in strfmon Conversion Specifications), and concluding
with a conversion specifier (see strfmon Conversion Specifiers).
If any of the optional characters listed in Optional Characters
in strfmon Conversion Specifications is included in a conversion
specification, they must appear in the order shown.
Table REF-5 Optional Characters in strfmon Conversion
Specifications
Character Meaning
left precision is specified. The default numeric
fill character is the space character. The fill
character must be representable as a single byte
in order to work with precision and width count.
This conversion specifier is ignored unless a
left precision is specified, and it does not
affect width filling, which always uses the space
character.
^ Do not use separator characters to format the
number. By default, the digits are grouped
according to the mon_grouping field in the LC_
MONETARY category of the current locale.
+ Add the string specified by the positive_sign
or negative_sign fields in the current locale.
If p_sign_posn or n_sign_posn is set to 0, then
parentheses are used by default to indicate
negative values. Otherwise, sign strings are used
to indicate the sign of the value. You cannot use a
+ and a ( in the same conversion specification.
( Enclose negative values within parentheses. The
default is taken from the p_sign_posn and n_sign_
posn fields in the current locale. If p_sign_
posn or n_sign_posn is set to 0, then parentheses
are used by default to indicate negative values.
Otherwise, sign strings are used to indicate the
sign of the value. You cannot use a + and ( in the
same conversion specification.
! Suppress the currency symbol. By default, the
currency symbol is included.
- Left-justify the value within the field. By
default, values are right-justified.
field width A decimal integer that specifies the minimum
field width in which to align the result of the
conversion. The default field width is the smallest
field that can contain the result.
#left_ A # followed by a decimal integer specifies
precision the number of digits to the left of the radix
character. Extra positions are filled by the
fill character. By default the precision is the
smallest required for the argument. If grouping
is not suppressed with the ^ conversion specifier,
and if grouping is defined for the current locale,
grouping separators are inserted before any fill
characters are added. Grouping separators are
not applied to fill characters even if the fill
character is defined as a digit.
.right_ A period (.) followed by a decimal integer
precision specifies the number of digits to the right of
the radix character. Extra positions are filled
with zeros. The amount is rounded to this number
of decimal places. If the right precision is zero,
the radix character is not included in the output.
By default the right precision is defined by the
frac_digits or int_frac_digits field of the current
locale.
Table REF-6 strfmon Conversion Specifiers
SpecifierMeaning
i Use the international currency symbol defined by the
int_currency_symbol field in the current locale, unless
the currency symbol has been suppressed.
n Use the local currency symbol defined by the currency_
symbol field in the current locale, unless the currency
symbol has been suppressed.
% Output a % character. The conversion specification must
be %%; none of the optional characters is valid with
this specifier.
489.3 – Return Values
x The number of bytes written to the string
pointed to by s, not including the null-
terminating character.
-1 Indicates an error. The function sets errno to
one of the following values:
o EINVAL - A conversion specification is
syntactically incorrect.
o E2BIG - Processing the complete format
string would produce more than maxsize
bytes.
489.4 – Example
#include <stdlib.h>
#include <stdio.h>
#include <locale.h>
#include <monetary.h>
#include <errno.h>
#define MAX_BUF_SIZE 124
main()
{
size_t ret;
char buffer[MAX_BUF_SIZE];
double amount = 102593421;
/* Display a monetary amount using the en_US.ISO8859-1 */
/* locale and a range of different display formats. */
if (setlocale(LC_ALL, "en_US.ISO8859-1") == (char *) NULL) {
perror("setlocale");
exit(EXIT_FAILURE);
}
ret = strfmon(buffer, MAX_BUF_
SIZE, "International: %i\n", amount);
printf(buffer);
ret = strfmon(buffer, MAX_BUF_
SIZE, "National: %n\n", amount);
printf(buffer);
ret = strfmon(buffer, MAX_BUF_
SIZE, "National: %=*#10n\n", amount);
printf(buffer);
ret = strfmon(buffer, MAX_BUF_
SIZE, "National: %(n\n", -1 * amount);
printf(buffer);
ret = strfmon(buffer, MAX_BUF_
SIZE, "National: %^!n\n", amount);
printf(buffer);
}
Running the example program produces the following result:
International: USD 102,593,421.00
National: $102,593,421.00
National: $**102,593,421.00
National: ($102,593,421.00)
National: 102593421.00
490 – strftime
Uses date and time information stored in a tm structure to create
an output string. The format of the output string is controlled
by a format string.
Format
#include <time.h>
size_t strftime (char *s, size_t maxsize, const char *format,
const struct tm *timeptr);
490.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to
the strftime function that is equivalent to the behavior before
OpenVMS Version 7.0.
490.2 – Arguments
s
A pointer to the resultant string.
maxsize
The maximum number of bytes to be stored in the resultant string,
including the null terminator.
format
A pointer to a string that controls the format of the output
string.
timeptr
A pointer to the local time (tm) structure. The tm structure is
defined in the <time.h> header file.
490.3 – Description
The strftime function uses data in the structure pointed to
by timeptr to create the string pointed to by s. A maximum of
maxsize bytes is copied to s.
The format string consists of zero or more conversion
specifications and ordinary characters. All ordinary characters
(including the terminating null character) are copied unchanged
into the output string. A conversion specification defines how
data in the tm structure is formatted in the output string.
A conversion specification consists of a percent (%) character
followed by one or more optional characters (see Optional
Elements of strftime Conversion Specifications), and concluding
with a conversion specifier (see strftime Conversion Specifiers).
If any of the optional characters listed in Optional Elements
of strftime Conversion Specifications are specified, they must
appear in the order shown in the table.
The strftime function behaves as if it called tzset.
Table REF-7 Optional Elements of strftime Conversion
Specifications
Element Meaning
- Optional with the field width to specify that the field
is left-justified and padded with spaces. This cannot
be used with the 0 element.
0 Optional with the field width to specify that the field
is right-justified and padded with zeros. This cannot
be used with the - element.
field A decimal integer that specifies the maximum field
width width
.precision A decimal integer that specifies the precision of data
in a field.
For the d, H, I, j, m, M, o, S, U, w, W, y, and Y
conversion specifiers, the precision specifier is the
minimum number of digits to appear in the field. If
the conversion specification has fewer digits than that
specified by the precision, leading zeros are added.
For the a, A, b, B, c, D, E, h, n, N, p, r, t, T,
x, X, Z, and % conversion specifiers, the precision
specifier is the maximum number of characters to appear
in the field. If the conversion specification has
more characters than that specified by the precision,
characters are truncated on the right.
The default precision for the d, H, I, m, M, o, S, U,
w, W, y and Y conversion specifiers is 2; the default
precision for the j conversion specifier is 3.
Note that the list of conversion specifications in Optional
Elements of strftime Conversion Specifications are extensions
to the XPG4 specification.
strftime Conversion Specifiers lists the conversion specifiers.
The strftime function uses fields in the LC_TIME category of
the program's current locale to provide a value. For example, if
%B is specified, the function accesses the mon field in LC_TIME
to find the full month name for the month specified in the tm
structure. The result of using invalid conversion specifiers is
undefined.
Table REF-8 strftime Conversion Specifiers
Specifier Replaced by
a The locale's abbreviated weekday name
A The locale's full weekday name
b The locale's abbreviated month name
B The locale's full month name
c The locale's appropriate date and time representation
C The century number (the year divided by 100 and
truncated to an integer) as a decimal number (00 -
99)
d The day of the month as a decimal number (01 - 31)
D Same as %m/%d/%y
e The day of the month as a decimal number (1 - 31) in a
2-digit field with the leading space character fill
Ec The locale's alternative date and time representation
EC The name of the base year (period) in the locale's
alternative representation
Ex The locale's alternative date representation
EX The locale's alternative time representation
Ey The offset from the base year (%EC) in the locale's
alternative representation
EY The locale's full alternative year representation
h Same as %b
H The hour (24-hour clock) as a decimal number (00 - 23)
I The hour (12-hour clock) as a decimal number (01 - 12)
j The day of the year as a decimal number (001 - 366)
m The month as a decimal number (01 - 12)
M The minute as a decimal number (00 - 59)
n The new-line character
Od The day of the month using the locale's alternative
numeric symbols
Oe The date of the month using the locale's alternative
numeric symbols
OH The hour (24-hour clock) using the locale's alternative
numeric symbols
OI The hour (12-hour clock) using the locale's alternative
numeric symbols
Om The month using the locale's alternative numeric
symbols
OM The minutes using the locale's alternative numeric
symbols
OS The seconds using the locale's alternative numeric
symbols
Ou The weekday as a number in the locale's alternative
representation (Monday=1)
OU The week number of the year (Sunday as the first day
of the week) using the locale's alternative numeric
symbols
OV The week number of the year (Monday as the first day
of the week) as a decimal number (01 - 53) using the
locale's alternative numeric symbols. If the week
containing January 1 has four or more days in the
new year, it is considered as week 1. Otherwise, it
is considered as week 53 of the previous year, and the
next week is week 1.
Ow The weekday as a number (Sunday=0) using the locale's
alternative numeric symbols
OW The week number of the year (Monday as the first day
of the week) using the locale's alternative numeric
symbols
Oy The year without the century using the locale's
alternative numeric symbols
p The locale's equivalent of the AM/PM designations
associated with a 12-hour clock
r The time in AM/PM notation
R The time in 24-hour notation (%H:%M)
S The second as a decimal number (00 - 61)
t The tab character
T The time (%H:%M:%S)
u The weekday as a decimal number between 1 and 7
(Monday=1)
U The week number of the year (the first Sunday as the
first day of week 1) as a decimal number (00 - 53)
V The week number of the year (Monday as the first day
of the week) as a decimal number (00 - 53). If the
week containing January 1 has four or more days in the
new year, it is considered as week 1. Otherwise, it
is considered as week 53 of the previous year, and the
next week is week 1.
w The weekday as a decimal number (0 [Sunday] - 6)
W The week number of the year (the first Monday as the
first day of week 1) as a decimal number (00 - 53)
x The locale's appropriate date representation
X The locale's appropriate time representation
y The year without century as a decimal number (00 - 99)
Y The year with century as a decimal number
Z Time-zone name or abbreviation. If time-zone
information is not available, no character is output.
% Literal % character.
490.4 – Return Values
x The number of characters placed into the array
pointed to by s, not including the terminating
null character.
0 Indicates an error occurred. The contents of
the array are indeterminate.
490.5 – Example
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <locale.h>
#include <errno.h>
#define NUM_OF_DATES 7
#define BUF_SIZE 256
/* This program formats a number of different dates, once */
/* using the C locale and then using the fr_FR.ISO8859-1 */
/* locale. Date and time formatting is done using strftime(). */
main()
{
int count,
i;
char buffer[BUF_SIZE];
struct tm *tm_ptr;
time_t time_list[NUM_OF_DATES] =
{500, 68200000, 694223999, 694224000,
704900000, 705000000, 705900000};
/* Display dates using the C locale */
printf("\nUsing the C locale:\n\n");
setlocale(LC_ALL, "C");
for (i = 0; i < NUM_OF_DATES; i++) {
/* Convert to a tm structure */
tm_ptr = localtime(&time_list[i]);
/* Format the date and time */
count = strftime(buffer, BUF_SIZE,
"Date: %A %d %B %Y%nTime: %T%n%n", tm_ptr);
if (count == 0) {
perror("strftime");
exit(EXIT_FAILURE);
}
/* Print the result */
printf(buffer);
}
/* Display dates using the fr_FR.ISO8859-1 locale */
printf("\nUsing the fr_FR.ISO8859-1 locale:\n\n");
setlocale(LC_ALL, "fr_FR.ISO8859-1");
for (i = 0; i < NUM_OF_DATES; i++) {
/* Convert to a tm structure */
tm_ptr = localtime(&time_list[i]);
/* Format the date and time */
count = strftime(buffer, BUF_SIZE,
"Date: %A %d %B %Y%nTime: %T%n%n", tm_ptr);
if (count == 0) {
perror("strftime");
exit(EXIT_FAILURE);
}
/* Print the result */
printf(buffer);
}
}
Running the example program produces the following result:
Using the C locale:
Date: Thursday 01 January 1970
Time: 00:08:20
Date: Tuesday 29 February 1972
Time: 08:26:40
Date: Tuesday 31 December 1991
Time: 23:59:59
Date: Wednesday 01 January 1992
Time: 00:00:00
Date: Sunday 03 May 1992
Time: 13:33:20
Date: Monday 04 May 1992
Time: 17:20:00
Date: Friday 15 May 1992
Time: 03:20:00
Using the fr_FR.ISO8859-1 locale:
Date: jeudi 01 janvier 1970
Time: 00:08:20
Date: mardi 29 février 1972
Time: 08:26:40
Date: mardi 31 décembre 1991
Time: 23:59:59
Date: mercredi 01 janvier 1992
Time: 00:00:00
Date: dimanche 03 mai 1992
Time: 13:33:20
Date: lundi 04 mai 1992
Time: 17:20:00
Date: vendredi 15 mai 1992
Time: 03:20:00
491 – strlen
Returns the length of a string of ASCII characters. The returned
length does not include the terminating null character (\0).
Format
#include <string.h>
size_t strlen (const char *str);
491.1 – Argument
str
A pointer to the character string.
491.2 – Return Value
x The length of the string.
492 – strncasecmp
Does a case-insensitive comparison between two 7-bit ASCII
strings.
Format
#include <strings.h>
int strncasecmp (const char *s1, const char *s2, size_t n);
492.1 – Arguments
s1
The first of two strings to compare.
s2
The second of two strings to compare.
n
The maximum number of bytes in a string to compare.
492.2 – Description
The strncasecmp function is case-insensitive. The returned
lexicographic difference reflects a conversion to lowercase.
The strncasecmp function is similar to the strcasecmp function,
but also compares size. If the size specified by n is read before
a NULL, the comparison stops.
The strcasecmp function works for 7-bit ASCII compares only. Do
not use this function for internationalized applications.
492.3 – Return Value
n An integer value greater than, equal to, or
less than 0 (zero), depending on whether s1 is
greater than, equal to, or less than s2.
493 – strncat
Appends not more than maxchar characters from str_2 to the end of
str_1.
Format
#include <string.h>
char *strncat (char *str_1, const char *str_2, size_t
maxchar);
493.1 – Function Variants
The strncat function has variants named _strncat32 and _strncat64
for use with 32-bit and 64-bit pointer sizes, respectively.
493.2 – Arguments
str_1, str_2
Pointers to null-terminated character strings.
maxchar
The number of characters to concatenate from str_2, unless
strncat first encounters a null terminator in str_2. If maxchar
is 0, no characters are copied from str_2.
493.3 – Description
A null character is always appended to the result of the strncat
function. If strncat reaches the specified maximum, it sets the
next byte in str_1 to the null character.
493.4 – Return Value
x The address of the first argument, str_1,
which is assumed to be large enough to hold
the concatenated result.
494 – strncmp
Compares not more than maxchar characters of two ASCII character
strings and returns a negative, 0, or positive integer,
indicating that the ASCII values of the individual characters
in the first string are less than, equal to, or greater than the
values in the second string.
Format
#include <string.h>
int strncmp (const char *str_1, const char *str_2, size_t
maxchar);
494.1 – Arguments
str_1, str_2
Pointers to character strings.
maxchar
The maximum number of characters (beginning with the first) to
search in both str_1 and str_2. If maxchar is 0, no comparison is
performed and 0 is returned (the strings are considered equal).
494.2 – Description
The strncmp function compares no more than maxchar characters
from the string pointed to by str_1 to the string pointed
to by str_2. The strings are compared until a null character
is encountered, the strings differ, or maxchar is reached.
Characters that follow a difference or a null character are not
compared.
494.3 – Return Values
< 0 Indicates that str_1 is less than str_2.
> 0 Indicates that str_1 is greater than str_2.
494.4 – Examples
1.#include <string.h>
#include <stdio.h>
main()
{
printf( "%d\n", strncmp("abcde", "abc", 3));
}
When linked and executed, this example returns 0, because the
first 3 characters of the 2 strings are equal:
$ run tmp
0
2.#include <string.h>
#include <stdio.h>
main()
{
printf( "%d\n", strncmp("abcde", "abc", 4));
}
When linked and executed, this example returns a value greater
than 0 because the first 4 characters of the 2 strings are not
equal (The "d" in the first string is not equal to the null
character in the second):
$ run tmp
100
495 – strncpy
Copies not more than maxchar characters from source into dest.
Format
#include <string.h>
char *strncpy (char *dest, const char *source, size_t
maxchar);
495.1 – Function Variants
The strncpy function has variants named _strncpy32 and _strncpy64
for use with 32-bit and 64-bit pointer sizes, respectively.
495.2 – Arguments
dest
Pointer to the destination character string.
source
Pointer to the source character string.
maxchar
The maximum number of characters to copy from source to dest up
to but not including the null terminator of source.
495.3 – Description
The strncpy function copies no more than maxchar characters from
source to dest, up to but not including the null terminator of
source. If source contains less than maxchar characters, dest
is padded with null characters. If source contains greater than
or equal to maxchar characters, as many characters as possible
are copied to dest. Be aware that the dest argument might not be
terminated by a null character after a call to strncpy.
495.4 – Return Value
x The address of dest.
496 – strnlen
Returns the number of bytes in a string.
Format
#include <string.h>
size_t strnlen (const char *s, size_t n);
496.1 – Arguments
s
Pointer to the string.
n
The maximum number of characters to examine.
496.2 – Description
The strnlen function returns the number of bytes in the string
pointed to by s. The string length value does not include the
terminating null character. The strnlen function counts bytes
until the first null byte or until n bytes have been examined.
496.3 – Return Value
n The length of the string.
497 – strpbrk
Searches a string for the occurrence of one of a specified set of
characters.
Format
#include <string.h>
char *strpbrk (const char *str, const char *charset);
497.1 – Function Variants
The strpbrk function has variants named _strpbrk32 and _strpbrk64
for use with 32-bit and 64-bit pointer sizes, respectively.
497.2 – Arguments
str
A pointer to a character string. If this character string is a
null string, 0 is returned.
charset
A pointer to a character string containing the set of characters
for which the function will search.
497.3 – Description
The strpbrk function scans the characters in the string, stops
when it encounters a character found in charset, and returns the
address of the first character in the string that appears in the
character set.
497.4 – Return Values
x The address of the first character in the
string that is in the set.
NULL Indicates that no character is in the set.
498 – strptime
Converts a character string into date and time values that are
stored in a tm structure. Conversion is controlled by a format
string.
Format
#include <time.h>
char *strptime (const char *buf, const char *format, struct tm
*timeptr);
498.1 – Function Variants
The strptime function has variants named _strptime32 and _
strptime64 for use with 32-bit and 64-bit pointer sizes,
respectively.
498.2 – Arguments
buf
A pointer to the character string to convert.
format
A pointer to the string that defines how the input string is
converted.
timeptr
A pointer to the local time structure. The tm structure is
defined in the <time.h> header file.
498.3 – Description
The strptime function converts the string pointed to by buf into
values that are stored in the structure pointed to by timeptr.
The string pointed to by format defines how the conversion is
performed.
The strptime function modifies only those fields in the tm
structure that have corresponding conversion specifications
in the format. In particular, strptime never sets the tm_isdst
member of the tm structure.
The format string consists of zero or more directives. A
directive is composed of one of the following:
o One or more white-space characters (as defined by the isspace
function). This directive causes the function to read input up
to the first character that is not a white-space character.
o Any character other than the percent character (%) or a white-
space character. This directive causes the function to read
the next character. The character read must be the same as the
character that comprises the directive. If the character is
different, the function fails.
o A conversion specification. A conversion specification defines
how characters in the input string are interpreted as values
that are then stored in the tm structure. A conversion
specification consists of a percent (%) character followed
by a conversion specifier. strptime Conversion Specifications
lists the valid conversion specifications.
The strptime function uses fields in the LC_TIME category of the
program's current locale to provide a value.
NOTE
To be compliant with X/Open CAE Specification System
Interfaces and Headers Issue 5 (commonly known as XPG5), the
strptime function processes the "%y" directive differently
than in previous versions of the C RTL.
With Version 6.4 and higher of the C compiler, for a two-
digit year within the century if no century is specified,
"%y" directive values range from:
o 69 to 99 refer to years in the twentieth century (1969 to
1999 inclusive)
o 00 to 68 refer to years in the twenty-first century (2000
to 2068 inclusive)
In previous (XPG4-compliant) versions of the C RTL,
strptime interpreted a two-digit year with no century
specified as a year within the twentieth century.
The XPG5-compliant strptime is now the default version in
the C RTL.
To obtain the old, XPG4-compliant strptime function
behavior, specify one of the following:
o Define the DECC$XPG4_STRPTIME logical name as follows:
$ DEFINE DECC$XPG4_STRPTIME ENABLE
or:
o Call the XPG4 strptime directly as the function
decc$strptime_xpg4.
To return to using the XPG5 strptime version, DEASSIGN the
DECC$XPG4_STRPTIME logical name:
$ DEASSIGN DECC$XPG4_STRPTIME
Table REF-9 strptime Conversion Specifications
SpecificaReplaced by
%a The weekday name. This is either the abbreviated or the
full name.
%A Same as %a.
%b The month name. This is either the abbreviated or the
full name.
%B Same as %b.
%c The date and time using the locale's date format.
%Ec The locale's alternative date and time representation.
%C The century number (the year divided by 100 and
truncated to an integer) as a decimal number (00 - 99).
Leading zeros are permitted.
%EC The name of the base year (period) in the locale's
alternative representation.
%d The day of the month as a decimal number (01 - 31).
Leading zeros are permitted.
%Od The day of the month using the locale's alternative
numeric symbols.
%D Same as %m/%d/%y.
%e Same as %d.
%Oe The date of the month using the locale's alternative
numeric symbols.
%h Same as %b.
%H The hour (24-hour clock) as a decimal number (00 - 23).
Leading zeros are permitted.
%OH The hour (24-hour clock) using the locale's alternative
numeric symbols.
%I The hour (12-hour clock) as a decimal number (01 - 12).
Leading zeros are permitted.
%OI The hour (12-hour clock) using the locale's alternative
numeric symbols.
%j The day of the year as a decimal number (001 - 366).
%m The month as a decimal number (01 - 12). Leading zeros
are permitted.
%Om The month using the locale's alternative numeric
symbols.
%M The minute as a decimal number (00 - 59). Leading zeros
are permitted.
%OM The minutes using the locale's alternative numeric
symbols.
%n Any white-space character.
%p The locale's equivalent of the AM/PM designations
associated with a 12-hour clock.
%r The time in AM/PM notation (%I:%M:%S %p).
%R The time in 24-hour notation (%H:%M).
%S The second as a decimal number (00 - 61). Leading zeros
are permitted.
%OS The seconds using the locale's alternative numeric
symbols.
%t Any white-space character.
%T The time (%H:%M:%S).
%U The week number of the year (the first Sunday as the
first day of week 1) as a decimal number (00 - 53).
Leading zeros are permitted.
%OU The week number of the year (Sunday as the first day
of the week) using the locale's alternative numeric
symbols.
%w The weekday as a decimal number (0 [Sunday] - 6).
Leading zeros are permitted.
%Ow The weekday as a number (Sunday=0) using the locale's
alternative numeric symbols.
%W The week number of the year (the first Monday as the
first day of week 1) as a decimal number (00 - 53).
Leading zeros are permitted.
%OW The week number of the year (Monday as the first day
of the week) using the locale's alternative numeric
symbols.
%x The locale's appropriate date representation.
%Ex The locale's alternative date representation.
%EX The locale's alternative time representation.
%X The locale's appropriate time representation.
%y The year without century as a decimal number (00 - 99).
%Ey The offset from the base year (%EC) in the locale's
alternative representation.
%Oy The year without the century using the locale's
alternative numeric symbols.
%Y The year with century as a decimal number.
%EY The locale's full alternative year representation.
%% Literal % character.
498.4 – Return Values
x A pointer to the character following the last
character parsed.
NULL Indicates that an error occurred. The contents
of the tm structure are undefined.
498.5 – Example
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <locale.h>
#include <errno.h>
#define NUM_OF_DATES 7
#define BUF_SIZE 256
/* This program takes a number of date and time strings and */
/* converts them into tm structs using strptime(). These tm */
/* structs are then passed to strftime() which will reverse the */
/* process. The resulting strings are then compared with the */
/* originals and if a difference is found then an error is */
/* displayed. */
main()
{
int count,
i;
char buffer[BUF_SIZE];
char *ret_val;
struct tm time_struct;
char dates[NUM_OF_DATES][BUF_SIZE] =
{
"Thursday 01 January 1970 00:08:20",
"Tuesday 29 February 1972 08:26:40",
"Tuesday 31 December 1991 23:59:59",
"Wednesday 01 January 1992 00:00:00",
"Sunday 03 May 1992 13:33:20",
"Monday 04 May 1992 17:20:00",
"Friday 15 May 1992 03:20:00"};
for (i = 0; i < NUM_OF_DATES; i++) {
/* Convert to a tm structure */
ret_val = strptime(dates[i], "%A %d %B %Y %T", &time_struct);
/* Check the return value */
if (ret_val == (char *) NULL) {
perror("strptime");
exit(EXIT_FAILURE);
}
/* Convert the time structure back to a formatted string */
count = strftime(buffer, BUF_SIZE, "%A %d %B %Y %T",&time_struct);
/* Check the return value */
if (count == 0) {
perror("strftime");
exit(EXIT_FAILURE);
}
/* Check the result */
if (strcmp(buffer, dates[i]) != 0) {
printf("Error: Converted string differs from the original\n");
}
else {
printf("Successfully converted <%s>\n", dates[i]);
}
}
}
Running the example program produces the following result:
Successfully converted <Thursday 01 January 1970 00:08:20>
Successfully converted <Tuesday 29 February 1972 08:26:40>
Successfully converted <Tuesday 31 December 1991 23:59:59>
Successfully converted <Wednesday 01 January 1992 00:00:00>
Successfully converted <Sunday 03 May 1992 13:33:20>
Successfully converted <Monday 04 May 1992 17:20:00>
Successfully converted <Friday 15 May 1992 03:20:00>
499 – strrchr
Returns the address of the last occurrence of a given character
in a null-terminated string.
Format
#include <string.h>
char *strrchr (const char *str, int character);
499.1 – Function Variants
The strrchr function has variants named _strrchr32 and _strrchr64
for use with 32-bit and 64-bit pointer sizes, respectively.
499.2 – Arguments
str
A pointer to a null-terminated character string.
character
An object of type int.
499.3 – Description
This function returns the address of the last occurrence of a
given character in a null-terminated string. The terminating null
character is considered to be part of the string.
Compare with strchr, which returns the address of the first
occurrence of a given character in a null-terminated string.
499.4 – Return Values
x The address of the last occurrence of the
specified character.
NULL Indicates that the character does not occur in
the string.
500 – strsep
Separates strings.
Format
#include <string.h>
char *strsep (char **stringp, char *delim);
500.1 – Function Variants
The strsep function has variants named _strsep32 and _strsep64
for use with 32-bit and 64-bit pointer sizes, respectively.
500.2 – Arguments
stringp
A pointer to a pointer to a character string.
delim
A pointer to a string containing characters to be used as
delimiters.
500.3 – Description
The strsep function locates in stringp, the first occurrence of
any character in delim (or the terminating '\0' character) and
replaces it with a '\0'. The location of the next character after
the delimiter character (or NULL, if the end of the string is
reached) is stored in the stringp argument. The original value of
the stringp argument is returned.
You can detect an "empty" field; one caused by two adjacent
delimiter characters, by comparing the location referenced by
the pointer returned in the stringp argument to '\0'.
The stringp argument is initially NULL, strsep returns NULL.
500.4 – Return Values
x The address of the string pointed to by
stringp.
NULL Indicates that stringp is NULL.
500.5 – Example
The following example uses strsep to parse a string, containing
token delimited by white space, into an argument vector:
char **ap, **argv[10], *inputstring;
for (ap = argv; (*ap = strsep(&inputstring, " \t")) != NULL;)
if (**ap != '\0')
++ap;
501 – strspn
Returns the length of the prefix of a string that consists
entirely of characters from a set of characters.
Format
#include <string.h>
size_t strspn (const char *str, const char *charset);
501.1 – Arguments
str
A pointer to a character string. If this string is a null string,
0 is returned.
charset
A pointer to a character string containing the characters for
which the function will search.
501.2 – Description
The strspn function scans the characters in the string, stops
when it encounters a character not found in charset, and returns
the length of the string's initial segment formed by characters
found in charset.
501.3 – Return Value
x The length of the segment.
502 – strstr
Locates the first occurrence in the string pointed to by s1 of
the sequence of characters in the string pointed to by s2.
Format
#include <string.h>
char *strstr (const char *s1, const char *s2);
502.1 – Function Variants
The strstr function has variants named _strstr32 and _strstr64
for use with 32-bit and 64-bit pointer sizes, respectively.
502.2 – Arguments
s1, s2
Pointers to character strings.
502.3 – Return Values
Pointer A pointer to the located string.
NULL Indicates that the string was not found.
502.4 – Example
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
main()
{
static char lookin[]="that this is a test was at the end";
putchar('\n');
printf("String: %s\n", &lookin[0] );
putchar('\n');
printf("Addr: %s\n", &lookin[0] );
printf("this: %s\n", strstr( &lookin[0] ,"this") );
printf("that: %s\n", strstr( &lookin[0] , "that" ) );
printf("NULL: %s\n", strstr( &lookin[0], "" ) );
printf("was: %s\n", strstr( &lookin[0], "was" ) );
printf("at: %s\n", strstr( &lookin[0], "at" ) );
printf("the end: %s\n", strstr( &lookin[0], "the end") );
putchar('\n');
exit(0);
}
This example produces the following results:
$ RUN STRSTR_EXAMPLE
String: that this is a test was at the end
Addr: that this is a test was at the end
this: this is a test was at the end
that: that this is a test was at the end
NULL: that this is a test was at the end
was: was at the end
at: at this is a test was at the end
the end: the end
$
503 – strtod
Converts a given string to a double-precision number.
Format
#include <stdlib.h>
double strtod (const char *nptr, char **endptr);
503.1 – Function Variants
The strtod function has variants named _strtod32 and _strtod64
for use with 32-bit and 64-bit pointer sizes, respectively.
503.2 – Arguments
nptr
A pointer to the character string to be converted to a double-
precision number.
endptr
The address of an object where the function can store the address
of the first unrecognized character that terminates the scan. If
endptr is a NULL pointer, the address of the first unrecognized
character is not retained.
503.3 – Description
The strtod function recognizes an optional sequence of white-
space characters (as defined by isspace), then an optional plus
or minus sign, then a sequence of digits optionally containing a
radix character, then an optional letter (e or E) followed by an
optionally signed integer. The first unrecognized character ends
the conversion.
The string is interpreted by the same rules used to interpret
floating constants.
The radix character is defined the program's current locale
(category LC_NUMERIC).
This function returns the converted value. For strtod, overflows
are accounted for in the following manner:
o If the correct value causes an overflow, HUGE_VAL (with a plus
or minus sign according to the sign of the value) is returned
and errno is set to ERANGE.
o If the correct value causes an underflow, 0 is returned and
errno is set to ERANGE.
If the string starts with an unrecognized character, then the
conversion is not performed, *endptr is set to nptr, a 0 value is
returned, and errno is set to EINVAL.)
503.4 – Return Values
x The converted string.
0 Indicates the conversion could not be
performed. errno is set to one of the
following:
o EINVAL - No conversion could be performed.
o ERANGE - The value would cause an
underflow.
o ENOMEM - Not enough memory available for
internal conversion buffer.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
504 – strtok
Split strings into tokens.
Format
#include <string.h>
char *strtok (char *s1, const char *s2);
char *strtok_r (char *s, const char *sep, char **lasts);
504.1 – Function Variants
The strtok function has variants named _strtok32 and _strtok64
for use with 32-bit and 64-bit pointer sizes, respectively.
Likewise, the strtok_r function has variants named _strtok_r32
and _strtok_r64.
504.2 – Arguments
s1
On the first call, a pointer to a string containing zero or more
text tokens. On all subsequent calls for that string, a NULL
pointer.
s2
A pointer to a separator string consisting of one or more
characters. The separator string may differ from call to call.
s
A null-terminated string that is a sequence of zero or more text
tokens separated by spans of one or more characters from the
separator string sep.
sep
A null-terminated string of separator characters. This separator
string can be different from call to call.
lasts
A pointer that points to a user-provided pointer to stored
information needed for strtok_r to continue scanning the same
string.
504.3 – Description
The strtok function locates text tokens in a given string. The
text tokens are delimited by one or more characters from a
separator string that you specify. The function keeps track of
its position in the string between calls and, as successive calls
are made, the function works through the string, identifying the
text token following the one identified by the previous call.
A token in s1 starts at the first character that is not a
character in the separator string s2 and ends either at the end
of the string or at (but not including) a separator character.
The first call to the strtok function returns a pointer to the
first character in the first token and writes a null character
into s1 immediately following the returned token. Each subsequent
call (with the value of the first argument remaining NULL)
returns a pointer to a subsequent token in the string originally
pointed to by s1. When no tokens remain in the string, the strtok
function returns a NULL pointer. (This can occur on the first
call to strtok if the string is empty or contains only separator
characters.)
Since strtok inserts null characters into s1 to delimit tokens,
s1 cannot be a const object.
The strtok_r function is the reentrant version of strtok. The
function strtok_r considers the null-terminated string s as a
sequence of zero or more text tokens separated by spans of one or
more characters from the separator string sep. The lasts argument
points to a user-provided pointer to stored information needed
for strtok_r to continue scanning the same string.
In the first call to strtok_r, s points to a null-terminated
string, sep points to a null-terminated string of separator
characters, and the value pointed to by lasts is ignored. The
strtok_r function returns a pointer to the first character of
the first token, writes a null character into s immediately
following the returned token, and updates the pointer to which
lasts points.
In subsequent calls, s is a NULL pointer and lasts is unchanged
from the previous call so that subsequent calls move through the
string s, returning successive tokens until no tokens remain. The
separator string sep can be different from call to call. When no
token remains in s, a NULL pointer is returned.
504.4 – Return Values
x A pointer to the first character of the parsed
token in the string.
NULL Indicates that there are no tokens remaining
in the string.
504.5 – Examples
1.#include <stdio.h>
#include <string.h>
main()
{
static char str[] = "...ab..cd,,ef.hi";
printf("|%s|\n", strtok(str, "."));
printf("|%s|\n", strtok(NULL, ","));
printf("|%s|\n", strtok(NULL, ",."));
printf("|%s|\n", strtok(NULL, ",."));
}
Running this example program produces the following results:
$ RUN STRTOK_EXAMPLE1
|ab|
|.cd|
|ef|
|hi|
$
2.#include <stdio.h>
#include <string.h>
main()
{
char *ptr,
string[30];
/* The first character not in the string "-" is "A". The */
/* token ends at "C. */
strcpy(string, "ABC");
ptr = strtok(string, "-");
printf("|%s|\n", ptr);
/* Returns NULL because no characters not in separator */
/* string "-" were found (i.e. only separator characters */
/* were found) */
strcpy(string, "-");
ptr = strtok(string, "-");
if (ptr == NULL)
printf("ptr is NULL\n");
}
Running this example program produces the following results:
$ RUN STRTOK_EXAMPLE2
|abc|
ptr is NULL
$
505 – strtol
Converts strings of ASCII characters to the appropriate numeric
values.
Format
#include <stdlib.h>
long int strtol (const char *nptr, char **endptr, int base);
505.1 – Function Variants
The strtol function has variants named _strtol32 and _strtol64
for use with 32-bit and 64-bit pointer sizes, respectively.
505.2 – Arguments
nptr
A pointer to the character string to be converted to a long.
endptr
The address of an object where the function can store a pointer
to the first unrecognized character encountered in the conversion
process (that is, the character that follows the last character
in the string being converted). If endptr is a NULL pointer, the
address of the first unrecognized character is not retained.
base
The value, 2 through 36, to use as the base for the conversion.
505.3 – Description
The strtol function recognizes strings in various formats,
depending on the value of the base. This function ignores
any leading white-space characters (as defined by isspace in
<ctype.h>) in the given string. It recognizes an optional plus
or minus sign, then a sequence of digits or letters that may
represent an integer constant according to the value of the base.
The first unrecognized character ends the conversion.
Leading zeros after the optional sign are ignored, and 0x or 0X
is ignored if the base is 16.
If base is 0, the sequence of characters is interpreted by
the same rules used to interpret an integer constant: after
the optional sign, a leading 0 indicates octal conversion, a
leading 0x or 0X indicates hexadecimal conversion, and any other
combination of leading characters indicates decimal conversion.
Truncation from long to int can take place after assignment or
by an explicit cast (arithmetic exceptions not withstanding).
The function call atol (str) is equivalent to strtol (str,
(char**)NULL, 10).
505.4 – Return Values
x The converted value.
LONG_MAX or LONG_ Indicates that the converted value would cause
MIN an overflow.
0 Indicates that the string starts with an
unrecognized character or that the value for
base is invalid. If the string starts with
an unrecognized character, *endptr is set to
nptr.
506 – strtoq,strtoll
Convert strings of ASCII characters to the appropriate numeric
values. strtoll is a synonym for strtoq.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdlib.h>
__int64 strtoq (const char *nptr, char **endptr, int base);
__int64 strtoll (const char *nptr, char **endptr, int base);
506.1 – Function Variants
These functions have variants named _strtoq32, _strtoll32 and
_strtoq64, _strtoll64 for use with 32-bit and 64-bit pointer
sizes, respectively.
506.2 – Arguments
nptr
A pointer to the character string to be converted to an __int64.
endptr
The address of an object where the function can store a pointer
to the first unrecognized character encountered in the conversion
process (that is, the character that follows the last character
in the string being converted). If endptr is a NULL pointer, the
address of the first unrecognized character is not retained.
base
The value, 2 through 36, to use as the base for the conversion.
506.3 – Description
The strtoq and strtoll functions recognize strings in various
formats, depending on the value of the base. Any leading white-
space characters (as defined by isspace in <ctype.h>) in the
given string are ignored. The functions recognize an optional
plus or minus sign, then a sequence of digits or letters that may
represent an integer constant according to the value of the base.
The first unrecognized character ends the conversion.
Leading zeros after the optional sign are ignored, and 0x or 0X
is ignored if the base is 16.
If base is 0, the sequence of characters is interpreted by
the same rules used to interpret an integer constant: after
the optional sign, a leading 0 indicates octal conversion, a
leading 0x or 0X indicates hexadecimal conversion, and any other
combination of leading characters indicates decimal conversion.
The function call atoq (str) is equivalent to strtoq (str,
(char**)NULL, 10).
506.4 – Return Values
x The converted value.
__INT64_MAX or Indicates that the converted value would cause
__INT64_MIN an overflow.
0 Indicates that the string starts with an
unrecognized character or that the value for
base is invalid. If the string starts with
an unrecognized character, *endptr is set to
nptr.
507 – strtoul
Converts the initial portion of the string pointed to by nptr to
an unsigned long integer.
Format
#include <stdlib.h>
unsigned long int strtoul (const char *nptr, char **endptr, int base);
507.1 – Function Variants
The strtoul function has variants named _strtoul32 and _strtoul64
for use with 32-bit and 64-bit pointer sizes, respectively.
507.2 – Arguments
nptr
A pointer to the character string to be converted to an unsigned
long.
endptr
The address of an object where the function can store a pointer
to a pointer to the first unrecognized character encountered in
the conversion process (that is, the character that follows the
last character in the string being converted). If endptr is a
NULL pointer, the address of the first unrecognized character is
not retained.
base
The value, 2 through 36, to use as the base for the conversion.
Leading zeros after the optional sign are ignored, and 0x or 0X
is ignored if the base is 16.
If the base is 0, the sequence of characters is interpreted by
the same rules used to interpret an integer constant: after
the optional sign, a leading 0 indicates octal conversion, a
leading 0x or 0X indicates hexadecimal conversion, and any other
combination of leading characters indicates decimal conversion.
507.3 – Return Values
x The converted value.
0 Indicates that the string starts with an
unrecognized character or that the value for
base is invalid. If the string starts with
an unrecognized character, *endptr is set to
nptr.
ULONG_MAX Indicates that the converted value would cause
an overflow.
508 – strtouq,strtoull
Convert the initial portion of the string pointed to by nptr to
an unsigned __int64 integer. strtoull is a synonym for strtouq.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdlib.h>
unsigned __int64 strtouq (const char *nptr, char **endptr, int base);
unsigned __int64 strtoull (const char *nptr, char **endptr, int base);
508.1 – Function Variants
These functions have variants named _strtouq32, _strtoull32 and
_strtouq64, _strtoull64 for use with 32-bit and 64-bit pointer
sizes, respectively.
508.2 – Arguments
nptr
A pointer to the character string to be converted to an unsigned
__int64.
endptr
The address of an object where the function can store a pointer
to a pointer to the first unrecognized character encountered in
the conversion process (that is, the character that follows the
last character in the string being converted). If endptr is a
NULL pointer, the address of the first unrecognized character is
not retained.
base
The value, 2 through 36, to use as the base for the conversion.
Leading zeros after the optional sign are ignored, and 0x or 0X
is ignored if the base is 16.
If the base is 0, the sequence of characters is interpreted by
the same rules used to interpret an integer constant: after
the optional sign, a leading 0 indicates octal conversion, a
leading 0x or 0X indicates hexadecimal conversion, and any other
combination of leading characters indicates decimal conversion.
508.3 – Return Values
x The converted value.
0 Indicates that the string starts with an
unrecognized character or that the value for
base is invalid. If the string starts with
an unrecognized character, *endptr is set to
nptr.
__UINT64_MAX Indicates that the converted value would cause
an overflow.
509 – strxfrm
Changes a string such that the changed string can be passed to
the strcmp function, and produce the same result as passing the
unchanged string to the strcoll function.
Format
#include <string.h>
size_t strxfrm (char *s1, const char *s2, size_t maxchar);
509.1 – Arguments
s1, s2
Pointers to character strings.
maxchar
The maximum number of bytes (including the null terminator) to be
stored in s1.
509.2 – Description
The strxfrm function transforms the string pointed to by s2,
and stores the resulting string in the array pointed to by s1.
No more than maxchar bytes, including the null terminator, are
placed into the array pointed to by s1.
If the value of maxchar is less than the required size to store
the transformed string (including the terminating null), the
contents of the array pointed to by s1 is indeterminate. In such
a case, the function returns the size of the transformed string.
If maxchar is 0, then s1 is allowed to be a NULL pointer, and the
function returns the required size of the s1 array before making
the transformation.
The string comparison functions, strcoll and strcmp, can produce
different results given the same two strings to compare. The
reason for this is that strcmp does a straightforward comparison
of the code point values of the characters in the strings,
whereas strcoll uses the locale information to do the comparison.
Depending on the locale, the strcoll comparison can be a
multipass operation, which is slower than strcmp.
The purpose of the strxfrm function is to transform strings in
such a way that if you pass two transformed strings to the strcmp
function, the result is the same as passing the two original
strings to the strcoll function. The strxfrm function is useful
in applications that need to do a large number of comparisons on
the same strings using strcoll. In this case, it might be more
efficient (depending on the locale) to transform the strings once
using strxfrm, and then do comparisons using strcmp.
509.3 – Return Value
x Length of the resulting string pointed to
by s1, not including the terminating null
character.
No return value is reserved for error
indication. However, the function can set
errno to EINVAL - The string pointed to by s2
contains characters outside the domain of the
collating sequence.
509.4 – Example
/* This program verifies that two transformed strings when */
/* passed through strxfrm and then compared, provide the same */
/* result as if passed through strcoll without any */
/* transformation.
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
#define BUFF_SIZE 256
main()
{
char string1[BUFF_SIZE];
char string2[BUFF_SIZE];
int errno;
int coll_result;
int strcmp_result;
size_t strxfrm_result1;
size_t strxfrm_result2;
/* setlocale to French locale */
if (setlocale(LC_ALL, "fr_FR.ISO8859-1") == NULL) {
perror("setlocale");
exit(EXIT_FAILURE);
}
/* collate string 1 and string 2 and store the result */
errno = 0;
coll_result = strcoll("<a`>bcd", "abcz");
if (errno) {
perror("strcoll");
exit(EXIT_FAILURE);
}
else {
/* Transform the strings (using strxfrm) into string1 */
/* and string2 */
strxfrm_result1 = strxfrm(string1, "<a`>bcd", BUFF_SIZE);
if (strxfrm_result1 == ((size_t) - 1)) {
perror("strxfrm");
exit(EXIT_FAILURE);
}
else if (strxfrm_result1 > BUFF_SIZE) {
perror("\n** String is too long **\n");
exit(EXIT_FAILURE);
}
else {
strxfrm_result2 = strxfrm(string2, "abcz", BUFF_SIZE);
if (strxfrm_result2 == ((size_t) - 1)) {
perror("strxfrm");
exit(EXIT_FAILURE);
}
else if (strxfrm_result2 > BUFF_SIZE) {
perror("\n** String is too long **\n");
exit(EXIT_FAILURE);
}
/* Compare the two transformed strings and verify */
/* that the result is the same as the result from */
/* strcoll on the original strings */
else {
strcmp_result = strcmp(string1, string2);
if (strcmp_result == 0 && (coll_result == 0)) {
printf("\nReturn value from strcoll() and "
"return value from strcmp() are both zero.");
printf("\nThe program was successful\n\n");
}
else if ((strcmp_result < 0) && (coll_result < 0)) {
printf("\nReturn value from strcoll() and "
"return value from strcmp() are less than zero.");
printf("\nThe program successful\n\n");
}
else if ((strcmp_result > 0) && (coll_result > 0)) {
printf("\nReturn value from strcoll() and "
"return value from strcmp() are greater than zero.");
printf("\nThe program was successful\n\n");
}
else {
printf("** Error **\n");
printf("\nReturn values are not of the same type");
}
}
}
}
}
Running the example program produces the following result:
Return value from strcoll() and return value
from strcmp() are less than zero.
The program was successful
510 – subwin
Creates a new subwindow with numlines lines and numcols columns
starting at the coordinates (begin_y,begin_x) on the terminal
screen.
Format
#include <curses.h>
WINDOW *subwin (WINDOW *win, int numlines, int numcols, int
begin_y, int begin_x);
510.1 – Arguments
win
A pointer to the parent window.
numlines
The number of lines in the subwindow. If numlines is 0, then
the function sets that dimension to LINES - begin_y. To get a
subwindow of dimensions LINES by COLS, use the following format:
subwin (win, 0, 0, 0, 0)
numcols
The number of columns in the subwindow. If numcols is 0, then
the function sets that dimension to COLS - begin_x. To get a
subwindow of dimensions LINES by COLS, use the following format:
subwin (win, 0, 0, 0, 0)
begin_y
A window coordinate at which the subwindow is to be created.
begin_x
A window coordinate at which the subwindow is to be created.
510.2 – Description
When creating the subwindow, begin_y and begin_x are relative to
the entire terminal screen. If either numlines or numcols is 0,
then the subwin function sets that dimension to (LINES - begin_y)
or (COLS - begin_x), respectively.
The window pointed to by win must be large enough to contain the
entire area of the subwindow. Any changes made to either window
within the coordinates of the subwindow appear on both windows.
510.3 – Return Values
window pointer A pointer to an instance of the structure
window corresponding to the newly created
subwindow.
ERR Indicates an error.
511 – swab
Swaps bytes.
Format
#include <unistd.h>
void swab (const void *src, void *dest, ssize_t nbytes);
511.1 – Arguments
src
A pointer to the location of the string to copy.
dest
A pointer to where you want the results copied.
nbytes
The number of bytes to copy. Make this argument an even value.
When it is an odd value, the swab function uses nbytes -1
instead.
511.2 – Description
The swab function copies the number of bytes specified by nbytes
from the location pointed to by src to the array pointed to by
dest. The function then exchanges adjacent bytes. If a copy takes
place between objects that overlap, the result is undefined.
512 – swprintf
Writes output to an array of wide characters under control of the
wide-character format string.
Format
#include <wchar.h>
int swprintf (wchar_t *s, size_t n, const wchar_t
*format, . . . );
512.1 – Arguments
s
A pointer to the resulting wide-character sequence.
n
The maximum number of wide characters that can be written to
an array pointed to by s, including a terminating null wide
character.
format
A pointer to a wide-character string containing the format
specifications.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, the output sources can
be omitted. Otherwise, the function calls must have exactly as
many output sources as there are conversion specifications, and
the conversion specifications must match the types of the output
sources.
Conversion specifications are matched to output sources in left-
to-right order. Excess output pointers, if any, are ignored.
512.2 – Description
The swprintf function is equivalent to the fwprintf function,
except that the first argument specifies an array of wide
characters instead of a stream.
No more than n wide characters are written, including a
terminating null wide character, which is always added (unless
n is 0).
See also fwprintf.
512.3 – Return Values
x The number of wide characters written, not
counting the terminating null wide character.
Negative value Indicates an error. Either n or more wide
characters were requested to be written, or a
conversion error occurred, in which case errno
is set to EILSEQ.
513 – swscanf
Reads input from a wide-character string under control of the
wide-character format string.
Format
#include <wchar.h>
int swscanf (const wchar_t *s, const wchar_t *format, . . . );
513.1 – Arguments
s
A pointer to a wide-character string from which the input is to
be obtained.
format
A pointer to a wide-character string containing the format
specifications.
. . .
Optional expressions whose results correspond to conversion
specifications given in the format specification.
If no conversion specifications are given, you can omit the input
pointers. Otherwise, the function calls must have exactly as
many input pointers as there are conversion specifications, and
the conversion specifications must match the types of the input
pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
513.2 – Description
The swscanf function is equivalent to the fwscanf function,
except that the first argument specifies a wide-character string
rather than a stream. Reaching the end of the wide-character
string is the same as encountering EOF for the fwscanf function.
See also fwscanf.
513.3 – Return Values
x The number of input items assigned, sometimes
fewer than provided for, or even 0 in the
event of an early matching failure.
EOF Indicates an error. An input failure occurred
before any conversion.
514 – symlink
Creates a symbolic link containing the specified contents.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
int symlink (const char *link_contents, const char *link_name);
514.1 – Arguments
link_contents
Contents of the symbolic link file, specified as a text string
representing the pathname to which the symbolic link will point.
link_name
The text string representing the name of the symbolic link file.
514.2 – Description
A symbolic link is a special kind of file that points to another
file. It is a directory entry that associates a filename with a
text string that is interpreted as a POSIX pathname when accessed
by certain services. A symbolic link is implemented on OpenVMS
systems as a file of organization SPECIAL and type SYMBOLIC_LINK.
The symlink function creates a symbolic link (link_name)
containing the specified contents (link_contents). No attempt
is made at link creation time to interpret the symbolic link
contents.
See also readlink, unlink, realpath, lchown, and lstat.
514.3 – Return Values
0 Successful completion
-1 Indicates an error. errno is set to indicate
the error:
o EACCES - Write permission is denied in the
directory where the symbolic link is being
created, or search permission is denied
for a component of the path prefix of link_
name.
o EEXIST - The link_name argument names an
existing file or symbolic link.
o ENAMETOOLONG - The length of the link_name
argument exceeds PATH_MAX, or a pathname
component is longer than NAME_MAX, or the
length of the link_contents argument is
longer than SYMLINK_MAX.
o ENOSPC - The directory in which the entry
for the new symbolic link is being placed
cannot be extended because no space is
left on the file system containing the
directory, or the new symbolic link cannot
be created because no space is left on the
file system that would contain the link, or
the file system is out of file-allocation
resources.
o Any errno value from creat, fsync, lstat,
or write.
515 – sysconf
Gets configurable system variables.
Format
#include <unistd.h>
long int sysconf (int name);
515.1 – Argument
name
Specifies the system variable to be queried.
515.2 – Description
The sysconf function provides a method for determining the
current value of a configurable system limit or whether optional
features are supported.
You supply a symbolic constant in the name argument, and sysconf
returns a value for the corresponding system variable:
o The symbolic constants defined in the <unistd.h> header file.
o The system variables are defined in the <limits.h> and
<unistd.h> header files.
sysconf Argument and Return Values lists the system variables
returned by the sysconf function, and the symbolic constants that
you can supply as the name value.
Table REF-10 sysconf Argument and Return Values
Symbolic
System Variable Constant for
Returned name Meaning
ISO POSIX-1
ARG_MAX _SC_ARG_MAX The maximum length, in bytes,
of the arguments for one of
the exec functions, including
environment data.
CHILD_MAX _SC_CHILD_ The maximum number of
MAX simultaneous processes for each
real user ID.
CLK_TCK _SC_CLK_TCK The number of clock ticks per
second. The value of CLK_TCK
can be variable. Do not assume
that CLK_TCK is a compile-time
constant.
NGROUPS_MAX _SC_NGROUPS_ The maximum number of
MAX simultaneous supplementary group
IDs for each process.
OPEN_MAX _SC_OPEN_MAX The maximum number of files that
one process can have open at one
time.
STREAM_MAX _SC_STREAM_ The number of streams that one
MAX process can have open at one
time.
TZNAME_MAX _SC_TZNAME_ The maximum number of bytes
MAX supported for the name of a time
zone (not the length of the TZ
environmental variable).
_POSIX_JOB_ _SC_JOB_ This variable has a value of
CONTROL CONTROL 1 if the system supports job
control; otherwise, -1 is
returned.
_POSIX_SAVED_IDS _SC_SAVED_ This variable has a value of 1
IDS if each process has a saved set
user ID and a saved set group
ID; otherwise, -1 is returned.
_POSIX_VERSION _SC_VERSION The date of approval of the
most current version of the
POSIX-1 standard that the system
supports. The date is a 6-digit
number, with the first 4 digits
signifying the year and the last
2 digits the month.
If_POSIX_VERSION is not defined,
-1 is returned.
Different versions of the POSIX-
1 standard are periodically
approved by the IEEE Standards
Board, and the date of approval
is used to distinguish between
different versions.
ISO POSIX-2
BC_BASE_MAX _SC_BC_BASE_ The maximum value allowed for
MAX the obase variable with the bc
command.
BC_DIM_MAX _SC_BC_DIM_ The maximum number of elements
MAX permitted in an array by the bc
command.
BC_SCALE_MAX _SC_BC_ The maximum value allowed for
SCALE_MAX the scale variable with the bc
command.
BC_STRING_MAX _SC_BC_ The maximum length of string
STRING_MAX constants accepted by the bc
command.
COLL_WEIGHTS_MAX _SC_COLL_ The maximum number of weights
WEIGHTS_MAX that can be assigned to an
entry in the LC_COLLATE locale-
dependent information in a
locale definition file.
EXPR_NEST_MAX _SC_EXPR_ The maximum number of
NEST_MAX expressions that you can nest
within parentheses by the expr
command.
LINE_MAX _SC_LINE_MAX The maximum length, in bytes,
of a command input line (either
standard input or another file)
when the utility is described
as processing text files. The
length includes room for the
trailing new-line character.
RE_DUP_MAX _SC_RE_DUP_ The maximum number of repeated
MAX occurrences of a regular
expression permitted when using
the interval notation arguments,
such as the m and n arguments
with the ed command.
_POSIX2_CHAR_ _SC_2_CHAR_ This variable has a value of 1
TERM TERM if the system supports at least
one terminal type; otherwise, -1
is returned.
_POSIX2_C_BIND _SC_2_C_BIND This variable has a value of
1 if the system supports the
C language binding option;
otherwise, -1 is returned.
_POSIX2_C_DEV _SC_2_C_DEV This variable has a value of
1 if the system supports the
optional C Language Development
Utilities from the ISO POSIX-
2 standard; otherwise, -1 is
returned.
_POSIX2_C_ _SC_2_C_ Integer value indicating the
VERSION VERSION version of the ISO POSIX-2
standard (C language binding).
It changes with each new version
of the ISO POSIX-2 standard.
_POSIX2_VERSION _SC_2_ Integer value indicating the
VERSION version of the ISO POSIX-2
standard (Commands). It changes
with each new version of the ISO
POSIX-2 standard.
_POSIX2_FORT_DEV _SC_2_FORT_ The variable has a value of 1 if
DEV the system supports the Fortran
Development Utilities Option
from the ISO POSIX-2 standard;
otherwise, -1 is returned.
_POSIX2_FORT_RUN _SC_2_FORT_ The variable has a value of
RUN 1 if the system supports the
Fortran Runtime Utilities Option
from the ISO POSIX-2 standard;
otherwise, -1 is returned.
_POSIX2_ _SC_2_ The variable has a value of
LOCALEDEF LOCALEDEF 1 if the system supports the
creation of new locales with the
localedef command; otherwise, -1
is returned.
_POSIX2_SW_DEV _SC_2_SW_DEV The variable has a value of 1 if
the system supports the Software
Development Utilities Option
from the ISO POSIX-2 standard;
otherwise, -1 is returned.
_POSIX2_UPE _SC_2_UPE The variable has a value of 1
if the system supports the User
Portability Utilities Option;
otherwise, -1 is returned.
POSIX 1003.1c-1995
_POSIX_THREADS _SC_THREADS This variable has a value of 1
if the system supports POSIX
threads; otherwise, -1 is
returned.
_POSIX_THREAD_ _SC_THREAD_ This variable has a value of 1
ATTR_STACKSIZE ATTR_ if the system supports the POSIX
STACKSIZE threads stack size attribute;
otherwise, -1 is returned.
_POSIX_THREAD_ _SC_THREAD_ The 1003.1c implementation
PRIORITY_ PRIORITY_ supports the realtime scheduling
SCHEDULING SCHEDULING functions.
_POSIX_THREAD_ _SC_THREAD_ TRUE if the implementation
SAFE_FUNCTIONS SAFE_ supports the thread-safe ANSI
FUNCTIONS C functions in POSIX 1003.1c.
PTHREAD_ _SC_THREAD_ When a thread terminates,
DESTRUCTOR_ DESTRUCTOR_ DECthreads iterates through
ITERATIONS ITERATIONS all non-NULL thread-specific
data values in the thread, and
calls a registered destructor
routine (if any) for each. It
is possible for a destructor
routine to create new values for
one or more thread-specific data
keys. In that case, DECthreads
goes through the entire process
again.
_SC_THREAD_DESTRUCTOR_ITERATIONS
is the maximum number of times
the implementation loops before
it terminates the thread even if
there are still non-NULL values.
PTHREAD_KEYS_MAX _SC_THREAD_ The maximum number of thread-
KEYS_MAX specific data keys that an
application can create.
PTHREAD_STACK_ _SC_THREAD_ The minimum allowed size of a
MIN STACK_MIN stack for a new thread. Any
lower value specified for the
"stacksize" thread attribute is
rounded up.
UINT_MAX _SC_THREAD_ The maximum number of threads
THREADS_MAX an application is allowed to
create. Since DECthreads does
not enforce any fixed limit,
this value is -1.
X/Open
_XOPEN_VERSION _SC_XOPEN_ An integer indicating the
VERSION most current version of the
X/Open standard that the system
supports.
PASS_MAX _SC_PASS_MAX Maximum number of significant
bytes in a password (not
including terminating null).
XOPEN_CRYPT _SC_XOPEN_ This variable has a value of
CRYPT 1 if the system supports the
X/Open Encryption Feature Group;
otherwise, -1 is returned.
XOPEN_ENH_I18N _SC_XOPEN_ This variable has a value
ENH_I18N of 1 if the system supports
the X/Open enhanced
Internationalization Feature
Group; otherwise, -1 is
returned.
XOPEN_SHM _SC_XOPEN_ This variable has a value
SHM of 1 if the system supports
the X/Open Shared Memory
Feature Group; otherwise, -1
is returned.
X/Open Extended
ATEXIT_MAX _SC_ATEXIT_ The maximum number of functions
MAX that you can register with
atexit per process.
PAGESIZE _SC_PAGESIZE Size, in bytes, of a page.
PAGE_SIZE _SC_PAGE_ Same as PAGESIZE. If either
SIZE PAGESIZE or PAGE_SIZE is
defined, the other is defined
with the same value.
IOV_MAX _SC_IOV_MAX Maximum number of iovec
structures that one process
has available for use with readv
or writev.
XOPEN_UNIX _SC_XOPEN_ This variable has a value of
UNIX 1 if the system supports the
X/Open CAE Specification, August
1994, System Interfaces and
Headers, Issue 4, Version 2,
(ISBN: 1-85912-037-7, C435);
otherwise, -1 is returned.
Other
N/A _SC_CPU_ Returns information for
CHIP_TYPE the processor type. See the
description after this table.
For the _SC_CPU_CHIP_TYPE symbolic constant:
o On Alpha servers, sysconf returns the architecture type (2),
as given by the $GETSYI system service.
o Integrity processor information is stored in CPUID register
3. This register contains a 64-bit integer divided into 1-byte
fields indicating version information related to the processor
implementation. The sysconf function returns the low-order
longword with the following information:
31 24 23 16 15 8 7 0
----------------------------------
| family | model | rev |number|
----------------------------------
These fields are described in the following table:
Field Bits Description
number 7:0 Index of the largest implemented CPUID register
(one less than the number of implemented CPUID
registers). This value will be at least 4.
rev 15:8 Processor revision number. An 8-bit value that
represents the revision or stepping of this
processor implementation within the processor
model.
model 23:16 Processor model number. A unique 8-bit value
representing the processor model within the
processor family.
family 31:24 Processor family number. A unique 8-bit value
representing the processor family.
515.3 – Return Values
x The current variable value on the system. The
value does not change during the lifetime of
the calling process.
-1 Indicates an error.
If the value of the name argument is invalid,
errno is set to indicate the error.
If the value of the name argument is
undefined, errno is unchanged.
516 – system
Passes a given string to the host environment to be executed by a
command processor. This function is nonreentrant.
Format
#include <stdlib.h>
int system (const char *string);
516.1 – Argument
string
A pointer to the string to be executed. If string is NULL, a
nonzero value is returned. The string is a DCL command, not
the name of an image. To execute an image, use one of the exec
routines.
516.2 – Description
The system function spawns a subprocess and executes the command
specified by string in that subprocess. The system function waits
for the subprocess to complete before returning the subprocess
status as the return value of the function.
The subprocess is spawned within the system call by a call to
vfork. Because of this, a call to system should not be made after
a call to vfork and before the corresponding call to an exec
function.
For OpenVMS Version 7.0 and higher systems, if you include
<stdlib.h> and compile with the _POSIX_EXIT feature-test macro
set, then the system function returns the status as if it called
waitpid to wait for the child. Therefore, use the WIFEXITED and
WEXITSTATUS macros (described in the wait* routines) to retrieve
the exit status in the range of 0 to 255.
You set the _POSIX_EXIT feature-test macro by using /DEFINE=_
POSIX_EXIT or #define _POSIX_EXIT at the top of your file, before
any file inclusions.
516.3 – Return Value
nonzero value If string is NULL, a value of 1 is returned,
indicating that the system function is
supported. If string is not NULL, the value
is the subprocess OpenVMS return status.
516.4 – Example
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h> /* write, close */
#include <fcntl.h> /* Creat */
main()
{
int status,
fd;
/* Creat a file we are sure is there */
fd = creat("system.test", 0);
write(fd, "this is an example of using system", 34);
close(fd);
if (system(NULL)) {
status = system("DIR/NOHEAD/NOTRAIL/SIZE SYSTEM.TEST");
printf("system status = %d\n", status);
}
else
printf("system() not supported.\n");
}
Running this example program produces the following result:
DISK3$:[JONES.CRTL.2059.SRC]SYSTEM.TEST;1
1
system status = 1
517 – tan
Returns a double value that is the tangent of its radian
argument.
Format
#include <math.h>
double tan (double x);
float tanf (float x); (Integrity servers, Alpha)
long double tanl (long double x); (Integrity servers, Alpha)
double tand (double x); (Integrity servers, Alpha)
float tandf (float x); (Integrity servers, Alpha)
long double tandl (long double x); (Integrity servers, Alpha)
517.1 – Argument
x
A radian expressed as a real number.
517.2 – Description
The tan functions compute the tangent of x, measured in radians.
The tand functions compute the tangent of x, measured in degrees.
517.3 – Return Values
x The tangent of the argument.
HUGE_VAL x is a singular point ( . . . -3pi/2, -pi/2,
pi/2 . . . ).
NaN x is NaN; errno is set to EDOM.
0 x is Infinity; errno is set to EDOM.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
0 Underflow occurred; errno is set to ERANGE.
518 – tanh
Returns the hyperbolic tangent of its argument.
Format
#include <math.h>
double tanh (double x);
float tanhf (float x); (Integrity servers, Alpha)
long double tanhl (long double x); (Integrity servers, Alpha)
518.1 – Argument
x
A real number.
518.2 – Description
The tanh functions return the hyperbolic tangent their argument,
calculated as (e**x - e**(-x))/(e**x + e**(-x)).
518.3 – Return Values
n The hyperbolic tangent of the argument.
HUGE_VAL The argument is too large; errno is set to
ERANGE.
NaN x is NaN; errno is set to EDOM.
0 Underflow occurred; errno is set to ERANGE.
519 – telldir
Returns the current location associated with a specified
directory stream. Performs operations on directories.
Format
#include <dirent.h>
long int telldir (DIR *dir_pointer);
519.1 – Argument
dir_pointer
A pointer to the DIR structure of an open directory.
519.2 – Description
The telldir function returns the current location associated with
the specified directory stream.
519.3 – Return Values
x The current location.
-1 Indicates an error and is further specified in
the global errno.
520 – tempnam
Constructs the name for a temporary file.
Format
#include <stdio.h>
char *tempnam (const char *directory, const char
*prefix, . . . ;)
520.1 – Arguments
directory
A pointer to the pathname of the directory where you want to
create a file.
prefix
A pointer to an initial character sequence of the filename. The
prefix argument can be null, or it can point to a string of up
to five characters used as the first characters of the temporary
filename.
. . .
An optional argument that can be either 1 or 0. If you specify 1,
tempnam returns the file specification in OpenVMS format. If you
specify 0, tempnam returns the file specification in UNIX style
format.
520.2 – Description
The tempnam function generates filenames for temporary files. It
allows you to control the choice of a directory.
If the directory argument is null or points to a string that is
not a pathname for an appropriate directory, the pathname defined
as P_tmpdir in the <stdio.h> header file is used. For programs
running under a detached process, the directory argument cannot
be null.
You can bypass the selection of a pathname by providing the
TMPDIR environment variable in the user environment. The value
of the TMPDIR variable is a pathname for the desired temporary
file directory.
Use the prefix argument to specify a prefix of up to five
characters for the temporary filename.
The tempnam function returns a pointer to the generated pathname,
suitable for use in a subsequent call to the free function.
See also free.
NOTE
In contrast to tmpnam, tempnam does not have to generate
a different filename on each call. tempnam generates a new
filename only if the file with the specified name exists. If
you need a unique filename on each call, use tmpnam instead
of tempnam.
520.3 – Return Values
x A pointer to the generated pathname, suitable
for use in a subsequent call to the free
function.
NULL An error occurred; errno is set to indicate
the error.
521 – tgamma
Returns the gamma function of its argument.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double tgamma (double x);
float tgammaf (float x);
long double tgammal (long double x);
521.1 – Argument
x
A real value.
521.2 – Description
The tgamma functions compute the gamma function of x.
521.3 – Return Values
n Upon success, the gamma function of x.
-1 If x is negative. errno is set to EDOM.
HUGE_VAL Overflow occurred, or x is 0. errno is set to
ERANGE.
NaN If x is NaN or -Inf. errno is set to EDOM.
x If x is +Inf.
522 – time
Returns the time (expressed as Universal Coordinated Time)
elapsed since 00:00:00, January 1, 1970, in seconds.
Format
#include <time.h>
time_t time (time_t *time_location);
522.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to the
time function that is equivalent to the behavior before OpenVMS
Version 7.0.
522.2 – Argument
time_location
Either NULL or a pointer to the place where the returned time is
also stored. The time_t type is defined in the <time.h> header
file as follows:
typedef unsigned long int time_t;
522.3 – Return Values
x The time elapsed past the Epoch.
(time_t)(-1) Indicates an error. If the value of
SYS$TIMEZONE_DIFFERENTIAL logical is wrong,
the function will fail with errno set to
EINVAL.
523 – times
Passes back the accumulated times of the current process and its
terminated child processes.
Format
#include <times.h>
clock_t times (struct tms *buffer); (OpenVMS V7.0 and higher)
void times (tbuffer_t *buffer); (pre OpenVMS V7.0)
523.1 – Argument
buffer
A pointer to the terminal buffer.
523.2 – Description
For both process and children times, the structure breaks down
the time by user and system time. Since the OpenVMS system does
not differentiate between system and user time, all system times
are returned as 0. Accumulated CPU times are returned in 10-
millisecond units.
Only the accumulated times for child processes running a C main
program or a program that calls VAXC$CRTL_INIT or DECC$CRTL_INIT
are included.
On OpenVMS Version 7.0 and higher systems, the times function
returns the elapsed real time in clock ticks since an arbitrary
reference time in the past (for example, system startup time).
This reference time does not change from one times function call
to another. The return value can overflow the possible range of
type clock_t values. When times fails, it returns a value of -1.
The C RTL uses system-boot time as its reference time.
523.3 – Return Values
x The elapsed real time in clock ticks since
system-boot time.
(clock_t)(-1) Indicates an error.
524 – tmpfile
Creates a temporary file that is opened for update.
Format
#include <stdio.h>
FILE *tmpfile (void);
524.1 – Description
The file exists only for the duration of the process, or until
the file is closed and is preserved across calls to vfork.
524.2 – Return Values
x The address of a file pointer (defined in the
<stdio.h> header file).
NULL Indicates an error.
525 – tmpnam
Generates filenames that can be safely used for a temporary file.
Format
#include <stdio.h>
char *tmpnam (char *name);
525.1 – Function Variants
The tmpnam function has variants named _tmpnam32 and _tmpnam64
for use with 32-bit and 64-bit pointer sizes, respectively.
525.2 – Argument
name
A character string containing a name to use in place of file-name
arguments in functions or macros. Successive calls to tmpnam with
a null argument cause the function to overwrite the current name.
525.3 – Return Value
x If the name argument is the NULL pointer
value NULL, tmpnam returns the address of
an internal storage area. If name is not NULL,
then it is considered the address of an area
of length L_tmpnam (defined in the <stdio.h>
header file). In this case, tmpnam returns the
name argument as the result.
526 – toascii
Converts its argument, an 8-bit ASCII character, to a 7-bit ASCII
character.
Format
#include <ctype.h>
int toascii (char character);
526.1 – Argument
character
An object of type char.
526.2 – Return Value
x A 7-bit ASCII character.
527 – tolower
Converts a character to lowercase.
Format
#include <ctype.h>
int tolower (int character);
527.1 – Argument
character
An object of type int representable as an unsigned char or the
value of EOF. For any other value, the behavior is undefined.
527.2 – Description
If the argument represents an uppercase letter, and there is
a corresponding lowercase letter, as defined by character
type information in the program locale category LC_CTYPE, the
corresponding lowercase letter is returned.
If the argument is not an uppercase character, it is returned
unchanged.
527.3 – Return Value
x The lowercase letter corresponding to the
argument. Or, the unchanged argument, if it is
not an uppercase character.
528 – _tolower
Converts an uppercase character to lowercase.
Format
#include <ctype.h>
int _tolower (int character);
528.1 – Argument
character
This argument must be an uppercase letter.
528.2 – Description
The _tolower macro is equivalent to the tolower function except
that its argument must be an uppercase letter (not lowercase, not
EOF).
As of OpenVMS Version 8.3 and to comply with the C99 ANSI
standard and X/Open Specification, the _tolower macro by default
does not evaluate its parameter more than once. It simply calls
the tolower function. This avoids side effects (such as i++
or function calls) where the user can tell how many times an
expression is evaluated.
To keep the older, optimized _tolower macro behavior, compile
with /DEFINE=_FAST_TOUPPER. Then, as in previous releases, _
tolower optimizes the call to avoid the overhead of a runtime
call. The parameters are checked to determine how to calculate
the result, thereby creating unwanted side effects. Therefore,
when compiling with /DEFINE=_FAST_TOUPPER, do not use the _
tolower macro with arguments that contain side-effect operations.
For instance, the following example will not return the expected
result:
d = _tolower (C++);
528.3 – Return Value
x The lowercase letter corresponding to the
argument.
529 – touchwin
Places the most recently edited version of the specified window
on the terminal screen.
Format
#include <curses.h>
int touchwin (WINDOW *win);
529.1 – Argument
win
A pointer to the window.
529.2 – Description
The touchwin function is normally used only to refresh
overlapping windows.
529.3 – Return Values
OK Indicates success.
ERR Indicates an error.
530 – toupper
Converts a character to uppercase.
Format
#include <ctype.h>
int toupper (int character);
530.1 – Argument
character
An object of type int representable as an unsigned char or the
value of EOF. For any other value, the behavior is undefined.
530.2 – Description
If the argument represents a lowercase letter, and there is
a corresponding uppercase letter, as defined by character
type information in the program locale category LC_CTYPE, the
corresponding uppercase letter is returned.
If the argument is not a lowercase character, it is returned
unchanged.
530.3 – Return Value
x The uppercase letter corresponding to the
argument. Or, the unchanged argument, if the
argument is not a lowercase character.
531 – _toupper
Converts a lowercase character to uppercase.
Format
#include <ctype.h>
int _toupper (int character);
531.1 – Argument
character
This argument must be a lowercase letter.
531.2 – Description
The _toupper macro is equivalent to the toupper function except
that its argument must be a lowercase letter (not uppercase, not
EOF).
As of OpenVMS Version 8.3 and to comply with the C99 ANSI
standard and X/Open Specification, the _toupper macro by default
does not evaluate parameters more than once. It simply calls
the toupper function. This avoids side effects (such as i++
or function calls) where the user can tell how many times an
expression is evaluated.
To keep the older, optimized _toupper macro behavior, compile
with /DEFINE=_FAST_TOUPPER. Then, as in previous releases, _
toupper optimizes the call to avoid the overhead of a runtime
call. The parameters are checked to determine how to calculate
the result, thereby creating unwanted side effects. So when
compiling with /DEFINE=_FAST_TOUPPER, do not use the _toupper
macro with arguments that contain side-effect operations. For
instance, the following example will not return the expected
result:
d = _toupper (c++);
531.3 – Return Value
x The uppercase letter corresponding to the
argument.
532 – towctrans
Maps one wide character to another according to a specified
mapping descriptor.
Format
#include <wctype.h>
wint_t towctrans (wint_t wc, wctrans_t desc);
532.1 – Arguments
wc
The wide character that you want to map.
desc
Description of the mapping obtained through a call to the wctrans
function.
532.2 – Description
The towctrans function maps the wide character specified in wc,
using the mapping described by desc.
The current setting of the LC_CTYPE category must be the same as
during the call to the wctrans function that returned the value
of desc.
532.3 – Return Value
x The mapped value of the wc wide character,
if this character exists in the mapping
described by desc. Otherwise, the value of
wc is returned.
533 – towlower
Converts the argument, a wide-character code, to lowercase.
If the argument is not an uppercase character, it is returned
unchanged.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int towlower (wint_t wc);
533.1 – Argument
wc
An object of type wint_t representable as a valid wide character
in the current locale, or the value of WEOF. For any other value,
the behavior is undefined.
533.2 – Description
If the argument is an uppercase wide character, the corresponding
lowercase wide character (as defined in the LC_CTYPE category of
the locale) is returned, if it exists. If it does not exist, the
function returns the input argument unchanged.
534 – towupper
Converts the argument, a wide character, to uppercase. If the
argument is not a lowercase character, it is returned unchanged.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
int towupper (wint_t wc);
534.1 – Argument
wc
An object of type wint_t representable as a valid wide character
in the current locale, or the value of WEOF. For any other value,
the behavior is undefined.
534.2 – Description
If the argument is a lowercase wide character, the corresponding
uppercase wide character (as defined in the LC_CTYPE category of
the locale) is returned, if it exists. If it does not exist, the
function returns the input argument unchanged.
535 – trunc
Truncates the argument to an integral value.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double trunc (double x);
float truncf (float x,);
long double truncl (long double x);
535.1 – Argument
x
A floating-point number.
535.2 – Return Value
n The truncated, integral value of the argument.
536 – truncate
Changes file length to a specified length, in bytes.
Format
#include <unistd.h>
int truncate (const char *path, off_t length);
536.1 – Arguments
path
The name of a file that is to be truncated. This argument must
point to a pathname that names a regular file for which the
calling process has write permission.
length
The new length of the file, in bytes. The off_t type of length
is either a 64-bit or 32-bit integer. The 64-bit interface allows
for file sizes greater than 2 GB, and can be selected at compile
time by defining the _LARGEFILE feature-test macro as follows:
CC/DEFINE=_LARGEFILE
536.2 – Description
The truncate function changes the length of a file to the size,
in bytes, specified by the length argument.
If the new length is less than the previous length, the function
removes all data beyond length bytes from the specified file. All
file data between the new End-of-File and the previous End-of-
File is discarded.
For stream files, if the new length is greater than the previous
length, new file data between the previous End-of-File and the
new End-of-File is added, consisting of all zeros. (For record
files, it is not possible to extend the file in this manner.)
536.3 – Return Values
0 Indicates success.
-1 An error occurred; errno is set to indicate
the error.
537 – ttyname
Find the pathname of a terminal.
Format
#include <unixio.h> (Compatibility)
char *ttyname (void); (Compatibility)
#include <unistd.h> (OpenVMS V7.3-2 and higher)
char *ttyname (int filedes); (OpenVMS V7.3-2 and higher)
int ttyname_r (int filedes, char name, size_t
namesize); (OpenVMS V7.3-2 and higher),
(Integrity servers, Alpha)
537.1 – Arguments
filedes
An open file descriptor.
name
Pointer to a buffer in which the terminal name is stored.
namesize
The length of the buffer pointed to by the name argument.
537.2 – Description
The implementation of the ttyname function that takes no
argument is provided only for backward compatibility. This
legacy implementation returns a pointer to the null-terminated
name of the terminal device associated with file descriptor 0,
the default input device (stdin). A value of 0 is returned if
SYS$INPUT is not a TTY device.
The ttyname_r function and the implementation of ttyname that
takes a filedes argument are UNIX standard compliant and are
available with only OpenVMS Version 7.3-2 and higher.
The standard compliant ttyname function returns a pointer to a
string containing a null-terminated pathname of the terminal
associated with file descriptor filedes. The return value might
point to static data whose content is overwritten by each call.
The ttyname interface need not be reentrant.
The ttyname_r function returns a pointer to store the null-
terminated pathname of the terminal associated with the file
descriptor filedes in the character array referenced by name. The
array is namesize characters long and should have space for the
name and the terminating null character. The maximum length of
the terminal name is TTY_NAME_MAX.
If successful, ttyname returns a pointer to a string. Otherwise,
a NULL pointer is returned and errno is set to indicate the
error.
If successful, ttyname_r stores the terminal name as a null-
terminated string in the buffer pointed to by name and returns 0.
Otherwise, an error number is returned to indicate the error.
537.3 – Return Values
x Upon successful completion, ttyname returns a
pointer to a null-terminated string.
NULL Upon failure, ttyname returns a NULL pointer
and sets errno to indicate the failure:
o EBADF - The fildes argument is not a valid
file descriptor.
o ENOTTY - The fildes argument does not refer
to a terminal device.
0 Upon successful completion, ttyname_r returns
0.
n Upon failure, ttyname_r sets errno to indicate
the failure, and returns the same errno code:
o EBADF - The fildes argument is not a valid
file descriptor.
o ENOTTY - The fildes argument does not refer
to a TTY device.
o ERANGE - The value of namesize is smaller
than the length of the string to be
returned including the terminating null
character.
0 For the legacy ttyname, indicates that
SYS$INPUT is not a TTY device.
538 – tzset
Sets and accesses time-zone conversion.
Format
#include <time.h>
void tzset (void);
extern char *tzname[];
extern long int timezone;
extern int daylight;
538.1 – Description
The tzset function initializes time-conversion information
used by the ctime, localtime, mktime, strftime, and wcsftime
functions.
The tzset function sets the following external variables:
o tzname is set as follows, where "std" is a 3-byte name for
the standard time zone, and "dst" is a 3-byte name for the
Daylight Savings Time zone:
tzname[0] = "std"
tzname[1] = "dst"
o daylight is set to 0 if Daylight Savings Time should never be
applied to the time zone. Otherwise, daylight is set to 1.
o timezone is set to the difference between UTC and local
standard time.
The environment variable TZ specifies how tzset initializes time
conversion information:
o If TZ is absent from the environment, the implementation-
dependent time-zone information is used, as follows:
The best available approximation to local wall-clock time
is used, as defined by the SYS$LOCALTIME system logical,
which points to a tzfile format file that describes default
time-zone rules.
This system logical is set during the installation
of OpenVMS Version 7.0 or higher to define a
time-zone file based off the root directory
SYS$COMMON:[SYS$ZONEINFO.SYSTEM].
o If TZ appears in the environment but its value is a null
string, Coordinated Universal Time (UTC) is used (without
leap-second correction).
o If TZ appears in the environment and its value is not a null
string, the value has one of three formats, as described in
Time-Zone Initialization Rules.
Table REF-11 Time-Zone Initialization Rules
TZ Format Meaning
: UTC is used.
:pathname The characters following the colon specify the
pathname of a tzfile format file from which to
read the time-conversion information. A pathname
beginning with a slash (/) represents an absolute
pathname; otherwise, the pathname is relative to
the system time-conversion information directory
specified by SYS$TZDIR, which by default is
SYS$COMMON:[SYS$ZONEINFO.SYSTEM].
stdoffset[dstThefset]e is first used as the pathname of a file
(as described for the :pathname format) from which
[,rule]] to read the time-conversion information.
If that file cannot be read, the value is then
interpreted as a direct specification of the time-
conversion information, as follows:
std and dst-Three or more characters that are the
designation for the time zone:
o std-Standard time zone. Required.
o dst-Daylight Savings Time zone. Optional. If dst
is omitted, Daylight Savings Time does not apply.
Uppercase and lowercase letters are explicitly
allowed. Any characters are allowed, except the
following:
o digits
o leading colon (:)
o comma (,)
o minus (-)
o plus (+)
o ASCII null character
offset-The value added to the local time to arrive
at UTC. The offset has the following format:
hh[:mm[:ss]]
In this format:
o hh (hours) is a one-or two-digit value of 0-24.
o mm (minutes) is a value of 0-59. (optional)
o ss (seconds) is a value of 0-59. (optional)
The offset following std is required. If no offset
follows dst, summer time is assumed, one hour ahead
of standard time. You can use one or more digits;
the value is always interpreted as a decimal number.
If the time zone is preceded by a minus sign (-),
the time zone is East of Greenwich; otherwise, it
is West, which can also be indicated by a preceding
plus sign (+).
rule-Indicates when to change to and return from
summer time. The rule has the form:
start[/time], end[/time]
where:
o start is the date when the change from standard
time to summer time occurs.
o end is the date for returning from summer time to
standard time.
If start and end are omitted, the default is the
US Daylight Savings Time start and end dates.
The format for start and end must be one of the
following:
o Jn-The Julian day n (1 < n < 365). Leap days are
not counted. That is, in all years, including
leap years, February 28 is day 59 and March 1 is
day 60. You cannot explicitly refer to February
29.
o n-The zero based Julian day (0 < n < 365). Leap
days are counted, making it possible to refer to
February 29.
o Mm.n.d-The nth d day of month m, where:
0 < n < 5
0 < d < 6
1 < m < 12
When n is 5, it refers to the last d day of month
m. Sunday is day 0.
time-The time when, in current time, the change to
or return from summer time occurs. The time argument
has the same format as offset, except that you
cannot use a leading minus (-) or plus (+) sign.
If time is not specified, the default is 02:00:00.
If no rule is present in the TZ specification, the
rules used are those specified by the tzfile format
file defined by the SYS$POSIXRULES system logical
in the system time-conversion information directory,
with the standard and summer time offsets from UTC
replaced by those specified by the offset values in
TZ.
If TZ does not specify a tzfile format file and
cannot be interpreted as a direct specification, UTC
is used.
NOTE
The UTC-based time functions, introduced in OpenVMS Version
7.0, had degraded performance compared with the non-UTC-
based time functions.
OpenVMS Version 7.1 added a cache for time-zone files to
improve performance. The size of the cache is determined
by the logical name DECC$TZ_CACHE_SIZE. To accommodate most
countries changing the time twice per year, the default
cache size is large enough to hold two time-zone files.
See also ctime, localtime, mktime, strftime, and wcsftime.
538.2 – Sample TZ Specification
EST5EDT4,M4.1.0,M10.5.0
This sample TZ specification describes the rule defined in 1987
for the Eastern time zone in the US:
o EST (Eastern Standard Time) is the designation for standard
time, which is 5 hours behind UTC.
o EDT (Eastern Daylight Time) is the designation for summer
time, which is 4 hours behind UTC. EDT starts on the first
Sunday in April and ends on the last Sunday in October.
Because time was not specified in either case, the changes
occur at the default time, which is 2:00 A.M. The start and
end dates did not need to be specified, because they are the
defaults.
539 – ualarm
Sets or changes the timeout of interval timers.
Format
#include <unistd.h>
useconds_t ualarm (useconds_t mseconds, useconds_t interval);
539.1 – Arguments
mseconds
Specifies a number of real-time microseconds.
interval
Specifies the interval for repeating the timer.
539.2 – Description
The ualarm function causes the SIGALRM signal to be generated for
the calling process after the number of real-time microseconds
specified by useconds has elapsed. When the interval argument is
nonzero, repeated timeout notification occurs with a period in
microseconds specified by interval. If the notification signal
SIGALRM is not intercepted or is ignored, the calling process is
terminated.
If you call a combination of ualarm and setitimer functions, and
the AST status is disabled, the return value is invalid.
If you call a combination of ualarm and setitimer functions, and
the AST status is enabled, the return value is valid.
This is because you cannot invoke an AST handler to clear the
previous value of the timer when ASTs are disabled or invoked
from a handler that was invoked at AST level.
NOTE
Interactions between ualarm and either alarm, or sleep are
unspecified.
See also setitimer.
539.3 – Return Values
n The number of microseconds remaining from the
previous ualarm or setitimer call.
0 No timeouts are pending or ualarm not
previously called.
-1 Indicates an error.
540 – umask
Creates a file protection mask that is used when a new file is
created, and returns the previous mask value.
Format
#include <stat.h>
mode_t umask (mode_t mode_complement);
540.1 – Argument
mode_complement
Shows which bits to turn off when a new file is created. See the
description of chmod to determine what the bits represent.
540.2 – Description
Initially, the file protection mask is set from the current
process's default file protection. This is done when the C main
program starts up or when DECC$CRTL_INIT (or VAXC$CRTL_INIT)
is called. You can change this for all files created by your
program by calling umask or you can use chmod to change the file
protection on individual files. The file protection of a file
created by open or creat is the bitwise AND of the open and creat
mode argument with the complement of the value passed to umask on
the previous call.
NOTE
The way to create files with OpenVMS RMS default protections
using the UNIX system-call functions umask, mkdir, creat,
and open is to call mkdir, creat, and open with a file-
protection mode argument of 0777 in a program that never
specifically calls umask. These default protections include
correctly establishing protections based on ACLs, previous
versions of files, and so on.
In programs that do vfork/exec calls, the new process image
inherits whether umask has ever been called or not from
the calling process image. The umask setting and whether
the umask function has ever been called are both inherited
attributes.
540.3 – Return Value
x The old mask value.
541 – uname
Gets system identification information.
Format
#include <utsname.h>
int uname (struct utsname *name);
541.1 – Argument
name
The current system identifier.
541.2 – Description
The uname function stores null-terminated strings of information
identifying the current system into the structure referenced by
the name argument.
The utsname structure is defined in the <utsname.h> header file
and contains the following members:
sysname Name of the operating system implementation
nodename Network name of this machine
release Release level of the operating system
version Version level of the operating system
machine Machine hardware platform
541.3 – Return Values
0 Indicates success.
-1 Indicates an error; errno or vaxc$errno is set
as appropriate.
542 – ungetc
Pushes a character back into the input stream and leaves the
stream positioned before the character.
Format
#include <stdio.h>
int ungetc (int character, FILE *file_ptr);
542.1 – Arguments
character
A value of type int.
file_ptr
A file pointer.
542.2 – Description
When using the ungetc function, the character is pushed back onto
the file indicated by file_ptr.
One push-back is guaranteed, even if there has been no previous
activity on the file. The fseek function erases all memory of
pushed-back characters. The pushed-back character is not written
to the underlying file. If the character to be pushed back is
EOF, the operation fails, the input stream is left unchanged, and
EOF is returned.
See also fseek and getc.
542.3 – Return Values
x The push-back character.
EOF Indicates it cannot push the character back.
543 – ungetwc
Pushes a wide character back into the input stream.
Format
#include <wchar.h>
wint_t ungetwc (wint_t wc, FILE *file_ptr);
543.1 – Arguments
wc
A value of type wint_t.
file_ptr
A file pointer.
543.2 – Description
When using the ungetwc function, the wide character is pushed
back onto the file indicated by file_ptr.
One push-back is guaranteed, even if there has been no previous
activity on the file. If a file positioning function (such as
fseek) is called before the pushed back character is read, the
bytes representing the pushed back character are lost.
If the character to be pushed back is WEOF, the operation fails,
the input stream is left unchanged, and WEOF is returned.
See also getwc.
543.3 – Return Values
x The push-back character.
WEOF Indicates that the function cannot push the
character back. errno is set to one of the
following:
o EBADF - The file descriptor is not valid.
o EALREADY - Operation is already in progress
on the same file.
o EILSEQ - Invalid wide-character code
detected.
544 – unlink
Deletes the specified symbolic link from the system.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <unistd.h>
int unlink (const char *link_name);
544.1 – Arguments
link_name
The name of the symbolic link to be deleted.
544.2 – Description
The unlink function deletes the specified symbolic link (link_
name) from the system. The contents of the symbolic link are not
examined, and no action is performed on the file specified in the
contents. For other files, the unlink function behaves the same
as the C RTL remove function.
See also symlink, readlink, realpath, lchown, and lstat.
544.3 – Return Values
0 Successful completion.
-1 Indicates an error. The named file (link_name)
is unchanged, and errno is set to any errno
value from remove.
545 – unordered
Returns the value 1 (TRUE) if either or both of the arguments is
a NaN. Otherwise, it returns the value 0 (FALSE).
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double unordered (double x, double y);
float unorderedf (float x, float y);
long double unorderedl (long double x, long double y);
545.1 – Arguments
x
A real number.
y
A real number.
545.2 – Return Values
1 Either or both of the arguments is a NaN.
0 Neither argument is a NaN.
546 – unsetenv
Deletes all instances of the environment variable name from the
environment list.
Format
#include <stdlib.h>
void unsetenv (const char *name);
546.1 – Argument
name
The environment variable to delete from the environment list.
546.2 – Description
The unsetenv function deletes all instances of the variable name
pointed to by the name argument from the environment list.
547 – usleep
Suspends execution for an interval.
Format
#include <unistd.h>
int usleep (unsigned int mseconds);
547.1 – Argument
mseconds
The number of microseconds to suspend execution for.
547.2 – Description
The usleep function suspends the current process from execution
for the number of microseconds specified by the mseconds
argument. This argument must be less than 1,000,000. However,
if its value is 0, then the call has no effect.
Be aware that usleep time specifications are rounded up
approximately to the next millisecond because that is the finest
time interval granularity possible on OpenVMS systems.
There is one real-time interval timer for each process. The
usleep function does not interfere with a previous setting of
this timer. If the process set this timer before calling usleep
and if the time specified by mseconds equals or exceeds the
interval timer's prior setting, then the process is awakened
shortly before the timer was set to expire.
547.3 – Return Values
0 Indicates success.
-1 Indicates an error occurred; errno is set to
EINVAL.
548 – utime
Sets file access and modification times.
Format
#include <utime.h>
int utime (const char *path, const struct utimbuf *times);
548.1 – Arguments
path
A pointer to a file.
times
A NULL pointer or a pointer to a utimbuf structure.
548.2 – Description
The utime function sets the access and modification times of the
filenamed by the path argument. The file must be openable for
write-access to use this function.
If times is a NULL pointer, the access and modification times of
the file are set to the current time. To use utime in this way,
the effective user ID of the process must match the owner of the
file, or the process must have write permission to the file or
have appropriate privileges.
If times is not a NULL pointer, it is interpreted as a pointer
to a utimbuf structure, and the access and modification times
are set to the values in the specified structure. Only a process
with an effective user ID equal to the user ID of the file or a
process with appropriate privileges can use utime this way.
The utimbuf structure is defined by the <utime.h> header. The
times in the utimbuf structure are measured in seconds since the
Epoch.
Upon successful completion, utime marks the time of the last file
status change, st_ctime, to be updated. See the <stat.h> header
file.
NOTE (Integrity servers, Alpha)
On OpenVMS Alpha and Integrity server systems, the stat,
fstat, utime, and utimes functions have been enhanced to
take advantage of the new file-system support for POSIX
compliant file timestamps.
This support is available only on ODS-5 devices on OpenVMS
Alpha systems beginning with a version of OpenVMS Alpha
after Version 7.3.
Before this change, stat and fstat set the values of the st_
ctime, st_mtime, and st_atime fields based on the following
file attributes:
st_ctime - ATR$C_CREDATE (file creation time)
st_mtime - ATR$C_REVDATE (file revision time)
st_atime - was always set to st_mtime because no support
for file access time was available
Also, for the file-modification time, utime and utimes were
modifying the ATR$C_REVDATE file attribute, and ignoring the
file-access-time argument.
After the change, for a file on an ODS-5 device, the stat
and fstat functions set the values of the st_ctime, st_
mtime, and st_atime fields based on the following new file
attributes:
st_ctime - ATR$C_ATTDATE (last attribute modification
time)
st_mtime - ATR$C_MODDATE (last data modification time)
st_atime - ATR$C_ACCDATE (last access time)
If ATR$C_ACCDATE is 0, as on an ODS-2 device, the stat and
fstat functions set st_atime to st_mtime.
For the file-modification time, the utime and utimes
functions modify both the ATR$C_REVDATE and ATR$C_MODDATE
file attributes. For the file-access time, these functions
modify the ATR$C_ACCDATE file attribute. Setting the ATR$C_
MODDATE and ATR$C_ACCDATE file attributes on an ODS-2 device
has no effect.
For compatibility, the old behavior of stat, fstat, utime,
and utimes remains the default, regardless of the kind of
device.
The new behavior must be explicitly enabled by defining the
DECC$EFS_FILE_TIMESTAMPS logical name to "ENABLE" before
invoking the application. Setting this logical does not
affect the behavior of stat, fstat, utime, and utimes for
files on an ODS-2 device.
548.3 – Return Values
0 Successful execution.
-1 Indicates an error. The function sets errno to
one of the following values:
The utime function will fail if:
o EACCES - Search permission is denied by
a component of the path prefix; or the
times argument is a NULL pointer and the
effective user ID of the process does
not match the owner of the file and write
access is denied.
o ELOOP - Too many symbolic links were
encountered in resolving path.
o ENAMETOOLONG - The length of the path
argument exceeds PATH_MAX, a pathname
component is longer than NAME_MAX, or a
pathname resolution of a symbolic link
produced an intermediate result whose
length exceeds PATH_MAX.
o ENOENT - path does not name an existing
file, or path is an empty string.
o ENOTDIR - A component of the path prefix is
not a directory.
o EPERM - times is not a NULL pointer and
the calling process's effective user ID has
write-access to the file but does not match
the owner of the file, and the calling
process does not have the appropriate
privileges.
o EROFS - The file system containing the file
is read-only.
549 – utimes
Sets file access and modification times.
Format
#include <time.h>
int utimes (const char *path, const struct timeval times[2]);
549.1 – Arguments
path
A pointer to a file.
times
an array of timeval structures. The first array member represents
the date and time of last access, and the second member
represents the date and time of last modification. The times
in the timeval structure are measured in seconds and microseconds
since the Epoch, although rounding toward the nearest second may
occur.
549.2 – Description
The utimes function sets the access and modification times of the
file pointed to by the path argument to the value of the times
argument. The utimes function allows time specifications accurate
to the microsecond.
If the times argument is a NULL pointer, the access and
modification times of the file are set to the current time. The
effective user ID of the process must be the same as the owner
of the file, or must have write access to the file or appropriate
privileges to use this call in this manner.
Upon completion, utimes marks the time of the last file status
change, st_ctime, for update.
NOTE (Integrity servers, Alpha)
On OpenVMS Alpha and Integrity server systems, the stat,
fstat, utime, and utimes functions have been enhanced to
take advantage of the new file-system support for POSIX
compliant file timestamps.
This support is available only on ODS-5 devices on OpenVMS
Alpha systems beginning with a version of OpenVMS Alpha
after Version 7.3.
Before this change, the stat and fstat functions were
setting the values of the st_ctime, st_mtime, and st_atime
fields based on the following file attributes:
st_ctime - ATR$C_CREDATE (file creation time)
st_mtime - ATR$C_REVDATE (file revision time)
st_atime - was always set to st_mtime because no support
for file access time was available
Also, for the file-modification time, utime and utimes were
modifying the ATR$C_REVDATE file attribute, and ignoring the
file-access-time argument.
After the change, for a file on an ODS-5 device, the stat
and fstat functions set the values of the st_ctime, st_
mtime, and st_atime fields based on the following new file
attributes:
st_ctime - ATR$C_ATTDATE (last attribute modification
time)
st_mtime - ATR$C_MODDATE (last data modification time)
st_atime - ATR$C_ACCDATE (last access time)
If ATR$C_ACCDATE is 0, as on an ODS-2 device, the stat and
fstat functions set st_atime to st_mtime.
For the file-modification time, the utime and utimes
functions modify both the ATR$C_REVDATE and ATR$C_MODDATE
file attributes. For the file-access time, these functions
modify the ATR$C_ACCDATE file attribute. Setting the ATR$C_
MODDATE and ATR$C_ACCDATE file attributes on an ODS-2 device
has no effect.
For compatibility, the old behavior of stat, fstat, utime,
and utimes remains the default, regardless of the kind of
device.
The new behavior must be explicitly enabled by defining the
DECC$EFS_FILE_TIMESTAMPS logical name to "ENABLE" before
invoking the application. Setting this logical does not
affect the behavior of stat, fstat, utime, and utimes for
files on an ODS-2 device.
549.3 – Return Values
0 Successful execution.
-1 Indicates an error. The file times do not
change and the function sets errno to one of
the following values:
The utimes function will fail if:
o EACCES - Search permission is denied by
a component of the path prefix; or the
times argument is a NULL pointer and the
effective user ID of the process does
not match the owner of the file and write
access is denied.
o ELOOP - Too many symbolic links were
encountered in resolving path.
o ENAMETOOLONG - The length of the path
argument exceeds PATH_MAX, a pathname
component is longer than NAME_MAX, or a
pathname resolution of a symbolic link
produced an intermediate result whose
length exceeds PATH_MAX.
o ENOENT - A component of path does not
name an existing file, or path is an empty
string.
o ENOTDIR - A component of the path prefix is
not a directory.
o EPERM -The times argument is not a NULL
pointer and the calling process's effective
user ID has write-access to the file but
does not match the owner of the file and
the calling process does not have the
appropriate privileges.
o EROFS - The file system containing the file
is read-only.
550 – VAXC$CRTL_INIT
Allows you to call the C RTL from other languages or to
use the C RTL when your main function is not in C. It
initializes the run-time environment and establishes both an exit
and condition handler. VAXC$CRTL_INIT is a synonym for DECC$CRTL_
INIT. Either name invokes the same routine.
Format
#include <signal.h>
void VAXC$CRTL_INIT();
550.1 – Description
The following example shows a Pascal program that calls the
C RTL using the VAXC$CRTL_INIT function:
On OpenVMS Alpha systems:
$ PASCAL EXAMPLE
$ LINK EXAMPLE,SYS$LIBRARY:VAXCRTL/LIB
$ TY EXAMPLE.PAS
PROGRAM TESTC(input, output);
PROCEDURE VAXC$CRTL_INIT; extern;
BEGIN
VAXC$CRTL_INIT;
END
$
A shareable image need only call this function if it contains
an VSI C function for signal handling, environment variables,
I/O, exit handling, a default file protection mask, or if it is a
child process that should inherit context.
Although many of the initialization activities are performed
only once, DECC$CRTL_INIT can safely be called multiple times. On
OpenVMS VAX systems, DECC$CRTL_INIT establishes the C RTL
internal OpenVMS exception handler in the frame of the routine
that calls DECC$CRTL_INIT each time DECC$CRTL_INIT is called.
At least one frame in the current call stack must have that
handler established for OpenVMS exceptions to get mapped to UNIX
signals.
551 – VAXC$ESTABLISH
Used for establishing an OpenVMS exception handler for a
particular routine. This function establishes a special C RTL
exception handler in the routine that called it. This special
handler catches all RTL-related exceptions that occur in later
routines, and passes on all other exceptions to your handler.
Format
#include <signal.h>
void VAXC$ESTABLISH (unsigned int (*exception_handler)(void
*sigarr, void *mecharr));
551.1 – Arguments
exception_handler
The name of the function that you want to establish as an OpenVMS
exception handler. You pass a pointer to this function as the
parameter to VAXC$ESTABLISH.
sigarr
A pointer to the signal array.
mecharr
A pointer to the mechanism array.
551.2 – Description
VAXC$ESTABLISH must be used in place of LIB$ESTABLISH when
programs use the C RTL routines setjmp or longjmp. See
setjmp and longjmp, or sigsetjmp and siglongjmp.
You can only invoke the VAXC$ESTABLISH function from an VSI C
for OpenVMS function, because it relies on the allocation of data
space on the run-time stack by the VSI C compiler. Calling
the OpenVMS system library routine LIB$ESTABLISH directly from an
VSI C function results in undefined behavior from the setjmp
and longjmp functions.
To cause an OpenVMS exception to generate a UNIX style signal,
user exception handlers must return SS$_RESIGNAL upon receiving
any exception that they do not want to handle. Returning SS$_
NORMAL prevents the generation of a UNIX style signal. UNIX
signals are generated as if by an exception handler in the
stack frame of the main C program. Not all OpenVMS exceptions
correspond to UNIX signals. See the "Error and Signal Handling"
chapter of the VSI C RTL Reference Manual. for more information on
the interaction of OpenVMS exceptions and UNIX style signals.
Calling VAXC$ESTABLISH with an argument of NULL cancels an
existing handler in that routine.
NOTES
On OpenVMS Alpha systems, VAXC$ESTABLISH is implemented as a
compiler built-in function, not as an C RTL function.
(Alpha only)
552 – va_arg
Returns the next item in the argument list.
Format
#include <stdarg.h> (ANSI C)
#include <varargs.h> (DEC C Extension)
type va_arg (va_list ap, type);
552.1 – Arguments
ap
A variable list containing the next argument to be obtained.
type
A data type that is used to determine the size of the next item
in the list. An argument list can contain items of varying sizes,
but the calling routine must determine what type of argument is
expected since it cannot be determined at run time.
552.2 – Description
The va_arg function interprets the object at the address
specified by the list incrementor according to type. If there
is no corresponding argument, the behavior is undefined.
When using va_arg to write portable applications, include the
<stdarg.h> header file (defined by the ANSI C standard), not the
<varargs.h> header file, and use va_arg only in conjunction with
other functions and macros defined in <stdarg.h>.
For an example of argument-list processing using the <stdarg.h>
functions and definitions, see the "Character, String, and
Argument-List Functions" chapter of the VSI C RTL Reference
Manual.
553 – va_count
Returns the number of quadwords (Alpha only) in the argument
list.
Format
#include <stdarg.h> (ANSI C)
#include <varargs.h> (DEC C Extension)
void va_count (int count);
553.1 – Argument
count
An integer variable name in which the number of quadwords
(Alpha only) is returned.
553.2 – Description
The va_count macro places the number of quadwords (Alpha only) in
the argument list into count. The value returned in count is the
number of quadwords (Alpha only) in the function argument block
not counting the count field itself.
If the argument list contains items whose storage requirements
are a quadword (Alpha only) of memory or less, the number in
the count argument is also the number of arguments. However, if
the argument list contains items that are longer than a quadword
(Alpha only), count must be interpreted to obtain the number of
arguments. Because a double is 8 bytes, it occupies one argument-
list position on OpenVMS Alpha and Integrity server systems.
The va_count macro is specific to VSI C for OpenVMS Systems
and is not portable.
554 – va_end
Finishes the <varargs.h> or <stdarg.h> session.
Format
#include <stdarg.h> (ANSI C)
#include <varargs.h> (DEC C Extension)
void va_end (va_list ap);
554.1 – Argument
ap
The object used to traverse the argument list length. You must
declare and use the argument ap as shown in this format section.
554.2 – Description
You can execute multiple traversals of the argument list, each
delimited by va_start . . . va_end. The va_end function sets ap
equal to NULL.
When using this function to write portable applications, include
the <stdarg.h> header file (defined by the ANSI C standard), not
the <varargs.h> header file, and use va_end only in conjunction
with other routines defined in <stdarg.h>.
For an example of argument-list processing using the <stdarg.h>
functions and definitions, see the "Character, String, and
Argument-List Functions" chapter of the VSI C RTL Reference
Manual.
555 – va_start[_1]
Used for initializing a variable to the beginning of the argument
list.
Format
#include <varargs.h> (DEC C Extension)
void va_start (va_list ap);
void va_start_1 (va_list ap, int offset);
555.1 – Arguments
ap
An object pointer. You must declare and use the argument ap as
shown in the format section.
offset
The number of bytes by which ap is to be incremented so that
it points to a subsequent argument within the list (that is,
not to the start of the argument list). Using a nonzero offset
can initialize ap to the address of the first of the optional
arguments that follow a number of fixed arguments.
555.2 – Description
The va_start macro initializes the variable ap to the beginning
of the argument list.
The va_start_1 macro initializes ap to the address of an argument
that is preceded by a known number of defined arguments. The
printf function is an example of a C RTL function
that contains a variable-length argument list offset from the
beginning of the entire argument list. The variable-length
argument list is offset by the address of the formatting string.
When determining the value of the offset argument used in va_
start_1, the implications of the OpenVMS calling standard must be
considered.
On OpenVMS Alpha and Integrity server systems, each argument item
is a quadword.
NOTE
When accessing argument lists, especially those passed to a
subroutine (written in C) by a program written in another
programming language, consider the implications of the
OpenVMS calling standard. For more information about the
OpenVMS calling standard, see the VSI C User's Guide for
OpenVMS Systems or the VSI OpenVMS Calling Standard.
The preceding version of va_start and va_start_1 is specific to
the C RTL, and is not portable.
The following syntax describes the va_start macro in the
<stdarg.h> header file, as defined in the ANSI C standard:
Format
#include <stdarg.h> (ANSI C)
void va_start (va_list ap, parmN);
555.3 – Arguments
ap
An object pointer. You must declare and use the argument ap as
shown in the format section.
parmN
The name of the last of the known fixed arguments.
555.4 – Description
The pointer ap is initialized to point to the first of the
optional arguments that follow parmN in the argument list.
Always use this version of va_start in conjunction with functions
that are declared and defined with function prototypes. Also use
this version of va_start to write portable programs.
For an example of argument-list processing using the <stdarg.h>
functions and definitions, see the "Character, String, and
Argument-List Functions" chapter of the VSI C RTL Reference
Manual.
556 – vfork
Creates an independent child process. This function is
nonreentrant.
Format
#include <unistd.h>
int vfork (void); (_DECC_V4_SOURCE)
pid_t vfork (void); (not _DECC_V4_SOURCE)
556.1 – Description
The vfork function provided by VSI C for OpenVMS
Systems differs from the fork function provided by other C
implementations. The vfork and fork Functions shows the two major
differences.
Table REF-12 The vfork and fork Functions
The vfork Function The fork Function
Used with the exec Can be used without an exec function for
functions. asynchronous processing.
Creates an Creates an exact duplicate of the parent
independent child process that branches at the point where
process that shares vfork is called, as if the parent and the
some of child are the same process at different
the parent's stages of execution.
characteristics.
The vfork function provides the setup necessary for a subsequent
call to an exec function. Although no process is created by
vfork, it performs the following steps:
o It saves the return address (the address of the vfork call)
to be used later as the return address for the call to an exec
function.
o It saves the current context.
o It returns the integer 0 the first time it is called (before
the call to an exec function is made). After the corresponding
exec function call is made, the exec function returns control
to the parent process, at the point of the vfork call, and
it returns the process ID of the child as the return value.
Unless the exec function fails, control appears to return
twice from vfork even though one call was made to vfork and
one call was made to the exec function.
The behavior of the vfork function is similar to the behavior
of the setjmp function. Both vfork and setjmp establish a return
address for later use, both return the integer 0 when they are
first called to set up this address, and both pass back the
second return value as though it were returned by them rather
than by their corresponding exec or longjmp function calls.
However, unlike setjmp, with vfork, all local automatic
variables, even those with volatile-qualified type, can have
indeterminate values if they are modified between the call to
vfork and the corresponding call to an exec routine.
556.2 – Return Values
0 Indicates successful creation of the context.
nonzero Indicates the process ID (PID) of the child
process.
-1 Indicates an error - failure to create the
child process.
557 – vfprintf
Prints formatted output based on an argument list.
Format
#include <stdio.h>
int vfprintf (FILE *file_ptr, const char *format, va_list ap);
557.1 – Arguments
file_ptr
A pointer to the file to which the output is directed.
format
A pointer to a string containing the format specification. For
more information about format and conversion specifications and
their corresponding arguments, see the "Understanding Input and
Output" chapter of the VSI C RTL Reference Manual.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
557.2 – Description
See also vprintf and vsprintf.
557.3 – Return Values
x The number of bytes written.
Negative value Indicates an output error. The function sets
errno. For a list of possible errno values
set, see fprintf.
558 – vfscanf
Reads formatted input based on an argument list.
Format
#include <stdio.h>
int vfscanf (FILE *file_ptr, const char *format, va_list ap);
558.1 – Arguments
file_ptr
A pointer to the file that provides input text.
format
A pointer to a string containing the format specification.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
558.2 – Description
The vfscanf function is the same as the fscanf function except
that instead of being called with a variable number of arguments,
it is called with an argument list that has been initialized by
va_start (and possibly subsequent va_arg calls).
If no conversion specifications are given, you can omit the input
pointers. Otherwise, the function calls must have exactly as
many input pointers as there are conversion specifications, and
the conversion specifications must match the types of the input
pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
For more information about format and conversion specifications
and their corresponding arguments, see the "Understanding Input
and Output" chapter of the VSI C RTL Reference Manual.
This function returns the number of successfully matched and
assigned input items.
See also vscanf and vsscanf.
558.3 – Return Values
n The number of successfully matched and
assigned input items.
EOF Indicates that the end-of-file was encountered
or a read error occurred. If a read error
occurs, the function sets errno to one of the
following:
o EILSEQ - Invalid character detected.
o EINVAL - Insufficient arguments.
o ENOMEM - Not enough memory available for
conversion.
o ERANGE - Floating-point calculations
overflow.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This can indicate that conversion to a
numeric value failed due to overflow.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
559 – vfwprintf
Writes output to the stream under control of the wide-character
format string.
Format
#include <wchar.h>
int vfwprintf (FILE *stream, const wchar_t *format, va_list
ap);
559.1 – Arguments
stream
A file pointer.
format
A pointer to a wide-character string containing the format
specifications.
ap
A variable list of the items needed for output.
559.2 – Description
The vfwprintf function is equivalent to the fwprintf function,
with the variable argument list replaced by the ap argument.
Initialize ap with the va_start macro (and possibly with
subsequent va_arg calls) from <stdarg.h>.
If the stream pointed to by stream has no orientation, vfwprintf
makes the stream wide-oriented.
See also fwprintf.
559.3 – Return Values
n The number of wide characters written.
Negative value Indicates an error. The function sets errno to
one of the following:
o EILSEQ - Invalid character detected.
o EINVAL - Insufficient arguments.
o ENOMEM - Not enough memory available for
conversion.
o ERANGE - Floating-point calculations
overflow.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This might indicate that conversion to a
numeric value failed because of overflow.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENOSPC - No free space on the device
containing the file.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o ESPIPE - Illegal seek in a file opened for
append.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
559.4 – Examples
The following example shows the use of the vfwprintf function
in a general error reporting routine:
#include <stdarg.h>
#include <stdio.h>
#include <wchar.h>
void error(char *function_name, wchar_t *format, . . . );
{
va_list args;
va_start(args, format);
/* print out name of function causing error */
fwprintf(stderr, L"ERROR in %s: ", function_name);
/* print out remainder of message */
vfwprintf(stderr, format, args);
va_end(args);
}
560 – vfwscanf
Reads input from the stream under control of a wide-character
format string.
Format
#include <wchar.h>
int vfwscanf (FILE *stream, const wchar_t *format, va_list
ap);
560.1 – Arguments
stream
A file pointer.
format
A pointer to a wide-character string containing the format
specifications.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
560.2 – Description
The vfwscanf function is equivalent to the fwscanf function,
except that instead of being called with a variable number of
arguments, it is called with an argument list (ap) that has been
initialized by va_start (and possibly with subsequent va_arg
calls).
If the stream pointed to by stream has no orientation, vfwscanf
makes the stream wide-oriented.
For more information about format and conversion specifications
and their corresponding arguments, see the "Understanding Input
and Output" chapter of the VSI C RTL Reference Manual.
560.3 – Return Values
n The number of successfully matched and
assigned wide-character input items.
EOF Indicates that a read error occurred before
any conversion. The function sets errno. For a
list of the values set by this function, see
vfscanf.
561 – vprintf
Prints formatted output based on an argument list.
This function is the same as the printf function except that
instead of being called with a variable number of arguments, it
is called with an argument list that has been initialized by the
va_start macro (and possibly with subsequent va_arg calls) from
<stdarg.h>.
Format
#include <stdio.h>
int vprintf (const char *format, va_list ap);
561.1 – Arguments
format
A pointer to the string containing the format specification.
ap
A variable list of the items needed for output.
561.2 – Description
See the vfprintf and vsprintf functions.
561.3 – Return Values
x The number of bytes written.
Negative value Indicates an output error. The function sets
errno. For a list of possible errno values
set, see fprintf.
562 – vscanf
Reads formatted input based on an argument list.
Format
#include <stdio.h>
int vscanf (const char *format, va_list ap);
562.1 – Arguments
format
A pointer to the string containing the format specification.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
562.2 – Description
The vscanf function is the same as the scanf function except that
instead of being called with a variable number of arguments, it
is called with an argument list (ap) that has been initialized by
the va_start macro (and possibly with subsequent va_arg calls).
For more information about format and conversion specifications
and their corresponding arguments, see the "Understanding Input
and Output" chapter of the VSI C RTL Reference Manual.
See also scanf, vfscanf, and vsscanf.
562.3 – Return Values
n The number of successfully matched and
assigned input items.
EOF Indicates that a read error occurred before
any conversion. The function sets errno. For a
list of the values set by this function, see
vfscanf.
563 – vsnprintf
Prints formatted output based on an argument list.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <stdio.h>
int vsnprintf (char *str, size_t n, const char *format,
va_list ap);
563.1 – Arguments
str
A pointer to a string that will receive the formatted output.
format
A pointer to a character string that contains the format
specification.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
563.2 – Description
The vsnprintf function is the same as the snprintf function, but
instead of being called with a variable number of arguments, it
is called with an argument list that has been initialized by va_
start (and possibly with subsequent va_arg calls).
This function does not invoke the va_end macro. Because the
function invokes the va_arg macro, the value of ap after the
return is unspecified.
Applications using vsnprintf should call va_end(ap) afterwards to
clean up.
563.3 – Return Values
x The number of bytes (excluding the terminating
null byte) that would be written to str if n
is sufficiently large.
Negative value Indicates an output error occurred. The
function sets errno. For a list of possible
errno values set, see fprintf.
564 – vsprintf
Prints formatted output based on an argument list.
This function is the same as the sprintf function except that
instead of being called with a variable number of arguments, it
is called with an argument list that has been initialized by va_
start (and possibly with subsequent va_arg calls).
Format
#include <stdio.h>
int vsprintf (char *str, const char *format, va_list ap);
564.1 – Arguments
str
A pointer to a string that will receive the formatted output.
This string is assumed to be large enough to hold the output.
format
A pointer to a character string that contains the format
specification.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
564.2 – Return Value
x The number of bytes written.
Negative value Indicates an output error occurred. The
function sets errno. For a list of possible
errno values set, see fprintf.
565 – vsscanf
Reads formatted input based on an argument list.
Format
#include <stdio.h>
int vsscanf (char *str, const char *format, va_list ap);
565.1 – Arguments
str
The address of the character string that provides the input text
to sscanf.
format
A pointer to a character string that contains the format
specification.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
565.2 – Description
The vsscanf function is the same as the sscanf function except
that instead of being called with a variable number of arguments,
it is called with an argument list that has been initialized by
va_start (and possibly with subsequent va_arg calls).
The vsscanf function is also equivalent to the vfscanf function,
except that the first argument specifies a wide-character string
rather than a stream. Reaching the end of the wide-character
string is the same as encountering EOF for the vfscanf function.
For more information about format and conversion specifications
and their corresponding arguments, see the "Understanding Input
and Output" chapter of the VSI C RTL Reference Manual.
See also vsscanf and sscanf.
565.3 – Return Values
n The number of successfully matched and
assigned input items.
EOF Indicates that a read error occurred before
any conversion. The function sets errno. For a
list of the values set by this function, see
vfscanf.
566 – vswprintf
Writes output to the stream under control of the wide-character
format string.
Format
#include <wchar.h>
int vswprintf (wchar_t *s, size_t n, const wchar_t *format,
va_list ap);
566.1 – Arguments
s
A pointer to a multibyte character sequence.
n
The maximum number of bytes that comprise the multibyte
character.
format
A pointer to a wide-character string containing the format
specifications. For more information about format and conversion
specifications and their corresponding arguments, see the
"Understanding Input and Output" chapter of the VSI C RTL
Reference Manual.
ap
A variable list of the items needed for output.
566.2 – Description
The vswprintf function is equivalent to the swprintf function,
with the variable argument list replaced by the ap argument.
Initialize ap with the va_start macro, and possibly with
subsequent va_arg calls.
See also swprintf.
566.3 – Return Values
n The number of wide characters written.
Negative value Indicates an error. The function sets errno to
one of the following:
o EILSEQ - Invalid character detected.
o EINVAL - Insufficient arguments.
o ENOMEM - Not enough memory available for
conversion.
o ERANGE - Floating-point calculations
overflow.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This might indicate that conversion to a
numeric value failed because of overflow.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENOSPC - No free space on the device
containing the file.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o ESPIPE - Illegal seek in a file opened for
append.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
567 – vswscanf
Reads input from the stream under control of the wide-character
format string.
Format
#include <wchar.h>
int vswscanf (wchar_t *s, const wchar_t *format, va_list ap);
567.1 – Arguments
s
A pointer to a wide-character string from which the input is to
be obtained.
format
A pointer to a wide-character string containing the format
specifications.
ap
A list of expressions whose results correspond to conversion
specifications given in the format specification.
567.2 – Description
The vswscanf function is equivalent to the swscanf function,
except that instead of being called with a variable number of
arguments, it is called with an argument list (ap) that has been
initialized by va_start (and possibly with subsequent va_arg
calls).
The vswscanf function is also equivalent to the vfwscanf
function, except that the first argument specifies a wide-
character string rather than a stream. Reaching the end of the
wide-character string is the same as encountering EOF for the
vfwscanf function.
For more information about format and conversion specifications
and their corresponding arguments, see the "Understanding Input
and Output" chapter of the VSI C RTL Reference Manual.
See also vfwscanf and swscanf.
567.3 – Return Values
n The number of wide characters read.
EOF Indicates that a read error occurred before
any conversion. The function sets errno. For a
list of the values set by this function, see
vfscanf.
568 – vwprintf
Writes output to an array of wide characters under control of the
wide-character format string.
Format
#include <wchar.h>
int vwprintf (const wchar_t *format, va_list ap);
568.1 – Arguments
format
A pointer to a wide-character string containing the format
specifications. For more information about format and conversion
specifications and their corresponding arguments, see the
"Understanding Input and Output" chapter of the VSI C RTL
Reference Manual.
ap
The variable list of items needed for output.
568.2 – Description
The vwprintf function is equivalent to the wprintf function,
with the variable argument list replaced by the ap argument.
Initialize ap with the va_start macro, and possibly with
subsequent va_arg calls. The vwprintf function does not invoke
the va_end macro.
See also wprintf.
568.3 – Return Values
x The number of wide characters written, not
counting the terminating null wide character.
Negative value Indicates an error. Either n or more wide
characters were requested to be written, or a
conversion error occurred, in which case errno
is set to EILSEQ.
569 – vwscanf
Reads input from an array of wide characters under control of a
wide-character format string.
Format
#include <wchar.h>
int vwscanf (const wchar_t *format, va_list ap);
569.1 – Arguments
format
A pointer to a wide-character string containing the format
specifications.
ap
A list of expressions whose resultant types correspond to the
conversion specifications given in the format specifications.
569.2 – Description
The vwscanf function is equivalent to the wscanf function, except
that instead of being called with a variable number of arguments,
it is called with an argument list (ap) that has been initialized
by va_start (and possibly with subsequent va_arg calls).
For more information about format and conversion specifications
and their corresponding arguments, see the "Understanding Input
and Output" chapter of the VSI C RTL Reference Manual.
See also wscanf.
569.3 – Return Values
n The number of wide characters read.
EOF Indicates that a read error occurred before
any conversion. The function sets errno. For a
list of the values set by this function, see
vfscanf.
570 – wait
Checks the status of the child process before exiting. A child
process is terminated when the parent process terminates.
Format
#include <wait.h>
pid_t wait (int *status);
570.1 – Argument
status
The address of a location to receive the final status of the
terminated child. The child can set the status with the exit
function and the parent can retrieve this value by specifying
status.
570.2 – Description
The wait function suspends the parent process until the final
status of a terminated child is returned from the child.
On OpenVMS Version 7.0 and higher systems, the wait function is
equivalent to waitpid( 0, status, 0 ) if you include <wait.h> and
compile with the _POSIX_EXIT feature-test macro set (either with
/DEFINE=_POSIX_EXIT or with #define _POSIX_EXIT at the top of
your file, before any file inclusions).
570.3 – Return Values
x The process ID (PID) of the terminated child.
If more than one child process was created,
wait will return the PID of the terminated
child that was most recently created.
Subsequent calls will return the PID of the
next most recently created, but terminated,
child.
-1 No child process was spawned.
571 – wait3
Waits for a child process to stop or terminate.
Format
#include <wait.h>
pid_t wait3 (int *status_location, int options, struct rusage
*resource_usage);
571.1 – Arguments
status_location
A pointer to a location that contains the termination status of
the child process as defined in the <wait.h> header file.
Beginning with OpenVMS Version 7.2, when compiled with the _
VMS_WAIT macro defined, the wait3 function puts the OpenVMS
completion code of the child process at the address specified
in the status_location argument.
options
Flags that modify the behavior of the function. These flags are
defined in the Description section.
resource_usage
The location of a structure that contains the resource
utilization information for terminated child processes.
571.2 – Description
The wait3 function suspends the calling process until the request
is completed, and redefines it so that only the calling thread is
suspended.
The options argument modifies the behavior of the function. You
can combine the flags for the options argument by specifying
their bitwise inclusive OR. The flags are:
WNOWAIT Specifies that the process whose status is
returned in status_location is kept in a waitable
state. You can wait for the process again with the
same results.
WNOHANG Prevents the suspension of the calling process.
If there are child processes that stopped or
terminated, one is chosen and the waitpid function
returns its process ID, as when you do not specify
the WNOHANG flag. If there are no terminated
processes (that is, if waitpid suspends the
calling process without the WNOHANG flag), 0
(zero) is returned. Because you can never wait
for process 0, there is no confusion arising from
this return.
WUNTRACED Specifies that the call return additional
information when the child processes of the
current process stop because the child process
received a SIGTTIN, SIGTTOU, SIGSTOP, or SIGTSTOP
signal.
If the wait3 function returns because the status of a child
process is available, the process ID of the child process is
returned. Information is stored in the location pointed to by
status_location, if this pointer is not null.
The value stored in the location pointed to by status_location is
0 (zero) only if the status is returned from a terminated child
process that did one of the following:
o Returned 0 from the main function.
o Passed 0 as the status argument to the _exit or exit function.
Regardless of the status_location value, you can define this
information using the macros defined in the <wait.h> header file,
which evaluate to integral expressions. In the following macro
descriptions, the status_value argument is equal to the integer
value pointed to by the status_location argument:
WIFEXITED(status_ Evaluates to a nonzero value if status was
value) returned for a child process that terminated
normally.
WEXITSTATUS(status_If the value of WIFEXITED(status_value) is
value) nonzero, this macro evaluates to the low-order
8 bits of the status argument that the child
process passed to the _exit or exit function,
or to the value the child process returned
from the main function.
WIFSIGNALED(status_Evaluates to a nonzero value if status was
value) returned for a child process that terminated
due to the receipt of a signal that was not
intercepted.
WTERMSIG(status_ If the value of WIFSIGNALED(status_value) is
value) nonzero, this macro evaluates to the number of
the signal that caused the termination of the
child process.
WIFSTOPPED(status_ Evaluates to a nonzero value if status was
value) returned for a child process that is currently
stopped.
WSTOPSIG(status_ If the value of WIFSTOPPED(status_value) is
value) nonzero, this macro evaluates to the number
of the signal that caused the child process to
stop.
WIFCONTINUED(status_valuates to a nonzero value if status
value) was returned for a child process that has
continued.
If the information stored at the location pointed to by status_
location was stored there by a call to wait3 that specified
the WUNTRACED flag, one of the following macros evaluates to a
nonzero value:
o WIFEXITED(*status_value)
o WIFSIGNALED(*status_value)
o WIFSTOPPED(*status_value)
o WIFCONTINUED(*status_value)
If the information stored in the location pointed to by status_
location resulted from a call to wait3 without the WUNTRACED flag
specified, one of the following macros evaluates to a nonzero
value:
o WIFEXITED(*status_value)
o WIFSIGNALED(*status_value)
The wait3 function provides compatibility with BSD systems.
The resource_usage argument points to a location that contains
resource usage information for the child processes as defined in
the <resource.h> header file.
If a parent process terminates without waiting for all of its
child processes to terminate, the remaining child processes is
assigned a parent process ID equal to the process ID of the init
process.
See also exit, -exit, and init.
571.3 – Return Values
0 Indicates success. There are no stopped or
exited child processes, the WNOHANG option is
specified.
x The process_id of the child process. The
status of a child process is available.
-1 Indicates an error; errno is set to one of the
following values:
o ECHILD - There are no child processes to
wait for.
o EINTR - Terminated by receipt of a signal
intercepted by the calling process.
o EFAULT - The status_location or resource_
usage argument points to a location outside
of the address space of the process.
o EINVAL- The value of the options argument
is not valid.
572 – wait4
Waits for a child process to stop or terminate.
Format
#include <wait.h>
pid_t wait4 (pid_t process_id, union wait *status_location,
int options, struct rusage *resource_usage);
572.1 – Arguments
status_location
A pointer to a location that contains the termination status of
the child process as defined in the <wait.h> header file.
Beginning with OpenVMS Version 7.2, when compiled with the _
VMS_WAIT macro defined, the wait4 function puts the OpenVMS
completion code of the child process at the address specified
in the status_location argument.
process_id
The child process or set of child processes.
options
Flags that modify the behavior of the function. These flags are
defined in the Description section.
resource_usage
The location of a structure that contains the resource
utilization information for terminated child processes.
572.2 – Description
The wait4 function suspends the calling process until the request
is completed.
The process_id argument allows the calling process to gather
status from a specific set of child processes, according to the
following rules:
If the
process_
id is Then status is requested
Equal to -1 For any child process. In this respect, the
waitpid function is equivalent to the wait
function.
Greater than For a single child process and specifies the
0 process ID.
The wait4 function only returns the status of a child process
from this set.
The options argument to the wait4 function modifies the behavior
of the function. You can combine the flags for the options
argument by specifying their bitwise-inclusive OR. The flags
are:
WNOWAIT Specifies that the process whose status is
returned in status_location is kept in a waitable
state. You can wait for the process again with the
same results.
WNOHANG Prevents the suspension of the calling process.
If there are child processes that stopped or
terminated, one is chosen and the waitpid function
returns its process ID, as when you do not specify
the WNOHANG flag. If there are no terminated
processes (that is, if waitpid suspends the
calling process without the WNOHANG flag), 0 is
returned. Because you can never wait for process
0, there is no confusion arising from this return.
WUNTRACED Specifies that the call return additional
information when the child processes of the
current process stop because the child process
received a SIGTTIN, SIGTTOU, SIGSTOP, or SIGTSTOP
signal.
If the wait4 function returns because the status of a child
process is available, the process ID of the child process is
returned. Information is stored in the location pointed to by
status_location, if this pointer is not null.
The value stored in the location pointed to by status_location is
0 only if the status is returned from a terminated child process
that did one of the following:
o Returned 0 from the main function.
o Passed 0 as the status argument to the _exit or exit function.
Regardless of the status_location value, you can define this
information using the macros defined in the <wait.h> header file,
which evaluate to integral expressions. In the following macro
descriptions, status_value is equal to the integer value pointed
to by status_location:
WIFEXITED(status_ Evaluates to a nonzero value if status was
value) returned for a child process that terminated
normally.
WEXITSTATUS(status_If the value of WIFEXITED(status_value) is
value) nonzero, this macro evaluates to the low-order
8 bits of the status argument that the child
process passed to the _exit or exit function,
or to the value the child process returned
from the main function.
WIFSIGNALED(status_Evaluates to a nonzero value if status was
value) returned for a child process that terminated
due to the receipt of a signal that was not
intercepted.
WTERMSIG(status_ If the value of WIFSIGNALED(status_value) is
value) nonzero, this macro evaluates to the number of
the signal that caused the termination of the
child process.
WIFSTOPPED(status_ Evaluates to a nonzero value if status was
value) returned for a child process that is currently
stopped.
WSTOPSIG(status_ If the value of WIFSTOPPED(status_value) is
value) nonzero, this macro evaluates to the number
of the signal that caused the child process to
stop.
WIFCONTINUED(status_valuates to a nonzero value if status
value) was returned for a child process that has
continued.
If the information stored at the location pointed to by status_
location was stored there by a call to wait4 that specified
the WUNTRACED flag, one of the following macros evaluates to a
nonzero value:
o WIFEXITED(*status_value)
o WIFSIGNALED(*status_value)
o WIFSTOPPED(*status_value)
o WIFCONTINUED(*status_value)
If the information stored in the location pointed to by status_
location resulted from a call to wait4 without the WUNTRACED flag
specified, one of the following macros evaluates to a nonzero
value:
o WIFEXITED(*status_value)
o WIFSIGNALED(*status_value)
The wait4 function is similar to the wait3 function. However,
the wait4 function waits for a specific child as indicated by
the process_id argument. The resource_usage argument points to a
location that contains resource usage information for the child
processes as defined in the <resource.h> header file.
See also exit and _exit.
572.3 – Return Values
0 Indicates success. There are no stopped or
exited child processes, the WNOHANG option is
specified.
x The process_id of the child process. The
status of a child process is available.
-1 Indicates an error; errno is set to one of the
following values:
o ECHILD - There are no child processes to
wait for.
o EINTR - Terminated by receipt of a signal
intercepted by the calling process.
o EFAULT - The status_location or resource_
usage argument points to a location outside
of the address space of the process.
o EINVAL- The value of the options argument
is not valid.
573 – waitpid
Waits for a child process to stop or terminate.
Format
#include <wait.h>
pid_t waitpid (pid_t process_id, int *status_location, int options);
573.1 – Arguments
process_id
The child process or set of child processes.
status_location
A pointer to a location that contains the termination status of
the child process as defined in the <wait.h> header file.
Beginning with OpenVMS Version 7.2, when compiled with the _
VMS_WAIT macro defined, the waitpid function puts the OpenVMS
completion code of the child process at the address specified in
the status_location argument.
options
Flags that modify the behavior of the function. These flags are
defined in the Description section.
573.2 – Description
The waitpid function suspends the calling process until the
request is completed. It is redefined so that only the calling
thread is suspended.
If the process_id argument is -1 and the options argument is
0, the waitpid function behaves the same as the wait function.
If these arguments have other values, the waitpid function is
changed as specified by those values.
The process_id argument allows the calling process to gather
status from a specific set of child processes, according to the
following rules:
If the
process_
id is Then status is requested
Equal to -1 For any child process. In this respect, the
waitpid function is equivalent to the wait
function.
Greater than For a single child process and specifies the
0 process ID.
The waitpid function only returns the status of a child process
from this set.
The options argument to the waitpid function modifies the
behavior of the function. You can combine the flags for the
options argument by specifying their bitwise-inclusive OR. The
flags are:
WCONTINUED Specifies that the following is reported to the
calling process: the status of any continued child
process specified by the process_id argument whose
status is unreported since it continued.
WNOWAIT Specifies that the process whose status is
returned in status_location is kept in a waitable
state. You can wait for the process again with the
same results.
WNOHANG Prevents the calling process from being suspended.
If there are child processes that stopped or
terminated, one is chosen and waitpid returns its
PID, as when you do not specify the WNOHANG flag.
If there are no terminated processes (that is,
if waitpid suspends the calling process without
the WNOHANG flag), 0 (zero) is returned. Because
you can never wait for process 0, there is no
confusion arising from this return.
WUNTRACED Specifies that the call return additional
information when the child processes of the
current process stop because the child process
received a SIGTTIN, SIGTTOU, SIGSTOP, or SIGTSTOP
signal.
If the waitpid function returns because the status of a child
process is available, the process ID of the child process is
returned. Information is stored in the location pointed to by
status_location, if this pointer is not null. The value stored
in the location pointed to by status_location is 0 only if the
status is returned from a terminated child process that did one
of the following:
o Returned 0 from the main function.
o Passed 0 as the status argument to the _exit or exit function.
Regardless of the value of status_location, you can define this
information using the macros defined in the <wait.h> header file,
which evaluate to integral expressions. In the following function
descriptions, status_value is equal to the integer value pointed
to by status_location:
WIFEXITED(status_ Evaluates to a nonzero value if status was
value) returned for a child process that terminated
normally.
WEXITSTATUS(status_If the value of WIFEXITED(status_value) is
value) nonzero, this macro evaluates to the low-order
8 bits of the status argument that the child
process passed to the _exit or exit function,
or to the value the child process returned
from the main function.
WIFSIGNALED(status_Evaluates to a nonzero value if status
value) returned for a child process that terminated
due to the receipt of a signal not
intercepted.
WTERMSIG(status_ If the value of WIFSIGNALED(status_value) is
value) nonzero, this macro evaluates to the number of
the signal that caused the termination of the
child process.
WIFSTOPPED(status_ Evaluates to a nonzero value if status was
value) returned for a child process that is currently
stopped.
WSTOPSIG(status_ If the value of WIFSTOPPED(status_value) is
value) nonzero, this macro evaluates to the number
of the signal that caused the child process to
stop.
WIFCONTINUED(status_valuates to a nonzero value if status
value) returned for a child process that continued.
If the information stored at the location pointed to by status_
location is stored there by a call to waitpid that specified
the WUNTRACED flag, one of the following macros evaluates to a
nonzero value:
o WIFEXITED(*status_value)
o WIFSIGNALED(*status_value)
o WIFSTOPPED(*status_value)
o WIFCONTINUED(*status_value)
If the information stored in the buffer pointed to by status_
location resulted from a call to waitpid without the WUNTRACED
flag specified, one of the following macros evaluates to a
nonzero value:
o WIFEXITED(*status_value)
o WIFSIGNALED(*status_value)
If a parent process terminates without waiting for all of its
child processes to terminate, the remaining child processes is
assigned a parent process ID equal to the process ID of the init
process.
See also exit, _exit, and wait.
573.3 – Return Values
0 Indicates success. If the WNOHANG option was
specified, and there are no stopped or exited
child processes, the waitpid function also
returns a value of 0.
-1 Indicates an error; errno is set to one of the
following values:
o ECHILD-The calling process has no existing
unwaited-for child processes. The process
or process group ID specified by the
process_id argument does not exist or is
not a child process of the calling process.
o EINTR-The function was terminated by
receipt of a signal.
If the waitpid function returns because
the status of a child process is available,
the process ID of the child is returned to
the calling process. If they return because
a signal was intercepted by the calling
process, -1 is returned.
o EFAULT- The status_location argument points
to a location outside of the address space
of the process.
o EINVAL- The value of the options argument
is not valid.
574 – wcrtomb
Converts the wide character to its multibyte character
representation.
Format
#include <wchar.h>
size_t wcrtomb (char *s, wchar_t wc, mbstate_t *ps);
574.1 – Arguments
s
A pointer to the resulting multibyte character.
wc
A wide character.
ps
A pointer to the mbstate_t object. If a NULL pointer is
specified, the function uses its internal mbstate_t object.
mbstate_t is an opaque datatype intended to keep the conversion
state for the state-dependent codesets.
574.2 – Description
If s is a NULL pointer, the wcrtomb function is equivalent to the
call:
wcrtomb (buf, L'\0', ps)
where buf is an internal buffer.
If s is not a NULL pointer, the wcrtomb function determines the
number of bytes needed to represent the multibyte character that
corresponds to the wide character specified by wc (including any
shift sequences), and stores the resulting bytes in the array
whose first element is pointed to by s. At most MB_CUR_MAX bytes
are stored.
If wc is a null wide character, a null byte is stored preceded by
any shift sequence needed to restore the initial shift state. The
resulting state described is the initial conversion state.
574.3 – Return Values
n The number of bytes stored in the resulting
array, including any shift sequences to
represent the multibyte character.
-1 Indicates an encoding error. The wc argument
is not a valid wide character. The global
errno is set to EILSEQ; the conversion state
is undefined.
575 – wcscat
Concatenates two wide-character strings.
Format
#include <wchar.h>
wchar_t *wcscat (wchar_t *wstr_1, const wchar_t *wstr_2);
575.1 – Function Variants
The wcscat function has variants named _wcscat32 and _wcscat64
for use with 32-bit and 64-bit pointer sizes, respectively.
575.2 – Arguments
wstr_1, wstr_2
Pointers to null-terminated wide-character strings.
575.3 – Description
The wcscat function appends the wide-character string wstr_2,
including the terminating null character, to the end of wstr_1.
See also wcsncat.
575.4 – Return Value
x The first argument, wstr_1, which is assumed
to be large enough to hold the concatenated
result.
575.5 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <string.h>
/* This program concatenates two wide-
character strings using */
/* the wcscat function, and then manually compares the result */
/* to the expected result */
#define S1LENGTH 10
#define S2LENGTH 8
main()
{
int i;
wchar_t s1buf[S1LENGTH + S2LENGTH];
wchar_t s2buf[S2LENGTH];
wchar_t test1[S1LENGTH + S2LENGTH];
/* Initialize the three wide-character strings */
if (mbstowcs(s1buf, "abcmnexyz", S1LENGTH) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
if (mbstowcs(s2buf, " orthis", S2LENGTH) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
if (mbstowcs(test1, "abcmnexyz orthis", S1LENGTH + S2LENGTH)
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Concatenate s1buf with s2buf, placing the result */
/* into * s1buf. Then compare s1buf with the expected */
/* result in test1. */
wcscat(s1buf, s2buf);
for (i = 0; i < S1LENGTH + S2LENGTH - 2; i++) {
/* Check that each character is correct */
if (test1[i] != s1buf[i]) {
printf("Error in wcscat\n");
exit(EXIT_FAILURE);
}
}
printf("Concatenated string: <%S>\n", s1buf);
}
Running the example produces the following result:
Concatenated string: <abcmnexyz orthis>
576 – wcschr
Scans for a wide character in a specified wide-character string.
Format
#include <wchar.h>
wchar_t *wcschr (const wchar_t *wstr, wchar_t wc);
576.1 – Function Variants
The wcschr function has variants named _wcschr32 and _wcschr64
for use with 32-bit and 64-bit pointer sizes, respectively.
576.2 – Arguments
wstr
A pointer to a null-terminated wide-character string.
wc
A character of type wchar_t.
576.3 – Description
The wcschr function returns the address of the first occurrence
of a specified wide character in a null-terminated wide-character
string. The terminating null character is considered to be part
of the string.
See also wcsrchr.
576.4 – Return Values
x The address of the first occurrence of the
specified wide character.
NULL Indicates that the wide character does not
occur in the string.
576.5 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <string.h>
#define BUFF_SIZE 50
main()
{
int i;
wchar_t s1buf[BUFF_SIZE];
wchar_t *status;
/* Initialize the buffer */
if (mbstowcs(s1buf, "abcdefghijkl lkjihgfedcba", BUFF_SIZE)
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* This program checks the wcschr function by incrementally */
/* going through a string that ascends to the middle and */
/* then descends towards the end. */
for (i = 0; (s1buf[i] != '\0') && (s1buf[i] != ' '); i++) {
status = wcschr(s1buf, s1buf[i]);
/* Check for pointer to leftmost character -test 1. */
if (status != &s1buf[i]) {
printf("Error in wcschr\n");
exit(EXIT_FAILURE);
}
}
printf("Program completed successfully\n");
}
When this example program is run, it produces the following
result:
Program completed successfully
577 – wcscmp
Compares two wide-character strings. It returns an integer that
indicates if the strings are different, and how they differ.
Format
#include <wchar.h>
int wcscmp (const wchar_t *wstr_1, const wchar_t *wstr_2);
577.1 – Arguments
wstr_1, wstr_2
Pointers to null-terminated wide-character strings.
577.2 – Description
The wcscmp function compares the wide characters in wstr_1 with
those in wstr_2. If the characters differ, the function returns:
o An integer less than 0, if the codepoint of the first
differing character in wstr_1 is less than the codepoint of
the corresponding character in wstr_2
o An integer greater than 0, if the codepoint of the first
differing character in wstr_1 is greater than the codepoint
of the corresponding character in wstr_2
If the wide-characters strings are identical, the function
returns 0.
Unlike the wcscoll function, the wcscmp function compares the
string based on the binary value of each wide character.
See also wcsncmp.
577.3 – Return Values
< 0 Indicates that wstr_1 is less than wstr_2.
> 0 Indicates that wstr_1 is greater than wstr_2.
578 – wcscoll
Compares two wide-character strings and returns an integer
that indicates if the strings differ, and how they differ.
The function uses the collating information in the LC_COLLATE
category of the current locale to determine how the comparison is
performed.
Format
#include <wchar.h>
int wcscoll (const wchar_t *ws1, const wchar_t *ws2);
578.1 – Arguments
ws1, ws2
Pointers to wide-character strings.
578.2 – Description
The wcscoll function, unlike wcscmp, compares two strings in a
locale-dependent manner. Because no value is reserved for error
indication, the application must check for one by setting errno
to 0 before the function call and testing it after the call.
See also wcsxfrm.
578.3 – Return Values
< 0 Indicates that ws1 is less than ws2.
0 Indicates that the strings are equal.
> 0 Indicates that ws1 is greater than ws2.
579 – wcscpy
Copies the wide-character string source, including the
terminating null character, into dest.
Format
#include <wchar.h>
wchar_t *wcscpy (wchar_t *dest, const wchar_t *source);
579.1 – Function Variants
The wcscpy function has variants named _wcscpy32 and _wcscpy64
for use with 32-bit and 64-bit pointer sizes, respectively.
579.2 – Arguments
dest
Pointer to the null-terminated wide-character destination string.
source
Pointer to the null-terminated wide-character source string.
579.3 – Description
The wcscpy function copies source into dest, and stops after
copying source's null character. If copying takes place between
two overlapping strings, the behavior is undefined.
See also wcsncpy.
579.4 – Return Value
x The address of source.
580 – wcscspn
Compares the characters in a wide-character string against a
set of wide characters. The function returns the length of the
initial substring that is comprised entirely of characters that
are not in the set of wide characters.
Format
#include <wchar.h>
size_t wcscspn (const wchar_t *wstr1, const wchar_t *wstr2);
580.1 – Arguments
wstr1
A pointer to a null-terminated wide-character string. If this is
a null string, 0 is returned.
wstr2
A pointer to a null-terminated wide-character string that
contains the set of wide characters for which the function will
search.
580.2 – Description
The wcscspn function scans the wide characters in the string
pointed to by wstr1 until it encounters a character found in
wstr2. The function returns the length of the initial segment of
wstr1 that is formed by characters not found in wstr2.
580.3 – Return Value
x The length of the segment.
580.4 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <string.h>
/* This test sets up 2 strings, buffer and w_string, and */
/* then uses wcscspn() to calculate the maximum segment */
/* of w_string, which consists entirely of characters */
/* NOT from buffer. */
#define BUFF_SIZE 20
#define STRING_SIZE 50
main()
{
wchar_t buffer[BUFF_SIZE];
wchar_t w_string[STRING_SIZE];
size_t result;
/* Initialize the buffer */
if (mbstowcs(buffer, "abcdefg", BUFF_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Initialize the string */
if (mbstowcs(w_string, "jklmabcjklabcdehjklmno", STRING_SIZE)
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Using wcscspn - work out the largest string in w_string */
/* which consists entirely of characters NOT from buffer */
result = wcscspn(w_string, buffer);
printf("Longest segment NOT found in w_string is: %d", result);
}
Running the example program produces the following result:
Longest segment NOT found in w_string is: 4
581 – wcsftime
Uses date and time information stored in a tm structure to create
a wide-character output string. The format of the output string
is controlled by a format string.
Format
#include <wchar.h>
size_t wcsftime (wchar_t *wcs, size_t maxsize, const char
*format, const struct tm *timeptr); (XPG4)
size_t wcsftime (wchar_t *wcs, size_t maxsize, const wchar_t
*format, const struct tm *timeptr); (ISO C)
581.1 – Function Variants
Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
test macros defined enables a local-time-based entry point to
the wcsftime function that is equivalent to the behavior before
OpenVMS Version 7.0.
581.2 – Arguments
wcs
A pointer to the resultant wide-character string.
maxsize
The maximum number of wide characters to be stored in the
resultant string.
format
A pointer to the string that controls the format of the output
string. For the XPG4 interface, this argument is a pointer to
a constant character string. For the ISO C interface, it is a
pointer to a constant wide-character string.
timeptr
A pointer to the local time structure. The tm structure is
defined in the <time.h> header file.
581.3 – Description
The wcsftime function uses data in the structure pointed to by
timeptr to create the wide-character string pointed to by wcs. A
maximum of maxsize wide characters is copied to wcs.
The format string consists of zero or more conversion
specifications and ordinary characters. All ordinary characters
(including the terminating null character) are copied unchanged
into the output string. A conversion specification defines how
data in the tm structure is formatted in the output string.
A conversion specification consists of a percent (%) character
followed by one or more optional characters (see Optional
Elements of wcsftime Conversion Specifications), and ending with
a conversion specifier (see wcsftime Conversion Specifiers).
If any of the optional characters listed in Optional Elements
of wcsftime Conversion Specifications are specified, they must
appear in the order shown in the table.
Table REF-13 Optional Elements of wcsftime Conversion
Specifications
Element Meaning
- Optional with the field width to specify that the field
is left-justified and padded with spaces. This cannot
be used with the 0 element.
0 Optional with the field width to specify that the field
is right-justified and padded with zeros. This cannot
be used with the - element.
field A decimal integer that specifies the maximum field
width width
.precision A decimal integer that specifies the precision of data
in a field.
For the d, H, I, j, m, M, o, S, U, w, W, y, and Y
conversion specifiers, the precision specifier is the
minimum number of digits to appear in the field. If
the conversion specification has fewer digits than that
specified by the precision, leading zeros are added.
For the a, A, b, B, c, D, E, h, n, N, p, r, t, T,
x, X, Z, and % conversion specifiers, the precision
specifier is the maximum number of wide characters to
appear in the field. If the conversion specification
has more characters than that specified by the
precision, characters are truncated on the right.
The default precision for the d, H, I, m, M, o, S,
U, w, W, y, and Y conversion specifiers is 2, and the
default precision for the j conversion specifier is 3.
Note that the list of optional elements of conversion
specifications from Optional Elements of wcsftime Conversion
Specifications are VSI extensions to the XPG4 specification.
wcsftime Conversion Specifiers lists the conversion specifiers.
The wcsftime function uses fields in the LC_TIME category of
the program's current locale to provide a value. For example, if
%B is specified, the function accesses the mon field in LC_TIME
to find the full month name for the month specified in the tm
structure. The result of using invalid conversion specifiers is
undefined.
Table REF-14 wcsftime Conversion Specifiers
SpecifierReplaced by
a The locale's abbreviated weekday name.
A The locale's full weekday name.
b The locale's abbreviated month name.
B The locale's full month name.
c The locale's appropriate date and time representation.
C The century number (the year divided by 100 and
truncated to an integer) as a decimal number (00 - 99).
d The day of the month as a decimal number (01 - 31).
D Same as %m/%d/%y.
e The day of the month as a decimal number (1 - 31) in a
2-digit field with the leading space character fill.
Ec The locale's alternative date and time representation.
EC The name of the base year (period) in the locale's
alternative representation.
Ex The locale's alternative date representation.
Ey The offset from the base year (%EC) in the locale's
alternative representation.
EY The locale's full alternative year representation.
h Same as %b.
H The hour (24-hour clock) as a decimal number (00 - 23).
I The hour (12-hour clock) as a decimal number (01 - 12).
j The day of the year as a decimal number (001 - 366).
m The month as a decimal number (01 - 12).
M The minute as a decimal number (00 - 59).
n The new-line character.
Od The day of the month using the locale's alternative
numeric symbols.
Oe The date of the month using the locale's alternative
numeric symbols.
OH The hour (24-hour clock) using the locale's alternative
numeric symbols.
OI The hour (12-hour clock) using the locale's alternative
numeric symbols.
Om The month using the locale's alternative numeric
symbols.
OM The minutes using the locale's alternative numeric
symbols.
OS The seconds using the locale's alternative numeric
symbols.
Ou The weekday as a number in the locale's alternative
representation (Monday=1).
OU The week number of the year (Sunday as the first day
of the week) using the locale's alternative numeric
symbols.
OV The week number of the year (Monday as the first day
of the week) as a decimal number (01 -53) using the
locale's alternative numeric symbols. If the week
containing January 1 has four or more days in the new
year, it is considered as week 1. Otherwise, it is
considered as week 53 of the previous year, and the
next week is week 1.
Ow The weekday as a number (Sunday=0) using the locale's
alternative numeric symbols.
OW The week number of the year (Monday as the first day
of the week) using the locale's alternative numeric
symbols.
Oy The year without the century using the locale's
alternative numeric symbols.
p The locale's equivalent of the AM/PM designations
associated with a 12-hour clock.
r The time in AM/PM notation.
R The time in 24-hour notation (%H:%M).
S The second as a decimal number (00 - 61).
t The tab character.
T The time (%H:%M:%S).
u The weekday as a decimal number between 1 and 7
(Monday=1).
U The week number of the year (the first Sunday as the
first day of week 1) as a decimal number (00 - 53).
V The week number of the year (Monday as the first day
of the week) as a decimal number (00 - 53). If the week
containing January 1 has four or more days in the new
year, it is considered as week 1. Otherwise, it is
considered as week 53 of the previous year, and the
next week is week 1.
w The weekday as a decimal number (0 [Sunday] - 6).
W The week number of the year (the first Monday as the
first day of week 1) as a decimal number (00 - 53).
x The locale's appropriate date representation
X The locale's appropriate time representation
y The year without century as a decimal number (00 - 99).
Y The year with century as a decimal number.
Z Time-zone name or abbreviation. If time-zone information
is not available, no character is output.
% Literal % character.
581.4 – Return Values
x The number of wide characters placed into the
array pointed to by wcs, not including the
terminating null character.
0 Indicates an error occurred. The contents of
the array are indeterminate.
581.5 – Example
/* Exercise the wcsftime formatting routine. */
/* NOTE: the format string is an "L" (or wide character) */
/* string indicating that this call is NOT in */
/* the XPG4 format, but rather in ISO C format. */
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <wchar.h>
#include <locale.h>
#include <errno.h>
#define NUM_OF_DATES 7
#define BUF_SIZE 256
/* This program formats a number of different dates, once using the */
/* C locale and then using the fr_FR.ISO8859-1 locale. Date and time */
/* formatting is done using wcsftime(). */
main()
{
int count,
i;
wchar_t buffer[BUF_SIZE];
struct tm *tm_ptr;
time_t time_list[NUM_OF_DATES] =
{500, 68200000, 694223999,
694224000, 704900000, 705000000,
705900000};
/* Display dates using the C locale */
printf("\nUsing the C locale:\n\n");
setlocale(LC_ALL, "C");
for (i = 0; i < NUM_OF_DATES; i++) {
/* Convert to a tm structure */
tm_ptr = localtime(&time_list[i]);
/* Format the date and time */
count = wcsftime(buffer, BUF_
SIZE, L"Date: %A %d %B %Y%nTime: %T%n%n",
tm_ptr);
if (count == 0) {
perror("wcsftime");
exit(EXIT_FAILURE);
}
/* Print the result */
printf("%S", buffer);
}
/* Display dates using the fr_FR.ISO8859-1 locale */
printf("\nUsing the fr_FR.ISO8859-1 locale:\n\n");
setlocale(LC_ALL, "fr_FR.ISO8859-1");
for (i = 0; i < NUM_OF_DATES; i++) {
/* Convert to a tm structure */
tm_ptr = localtime(&time_list[i]);
/* Format the date and time */
count = wcsftime(buffer, BUF_
SIZE, L"Date: %A %d %B %Y%nTime: %T%n%n",
tm_ptr);
if (count == 0) {
perror("wcsftime");
exit(EXIT_FAILURE);
}
/* Print the result */
printf("%S", buffer);
}
}
Running the example program produces the following result:
Using the C locale:
Date: Thursday 01 January 1970
Time: 00:08:20
Date: Tuesday 29 February 1972
Time: 08:26:40
Date: Tuesday 31 December 1991
Time: 23:59:59
Date: Wednesday 01 January 1992
Time: 00:00:00
Date: Sunday 03 May 1992
Time: 13:33:20
Date: Monday 04 May 1992
Time: 17:20:00
Date: Friday 15 May 1992
Time: 03:20:00
Using the fr_FR.ISO8859-1 locale:
Date: jeudi 01 janvier 1970
Time: 00:08:20
Date: mardi 29 février 1972
Time: 08:26:40
Date: mardi 31 décembre 1991
Time: 23:59:59
Date: mercredi 01 janvier 1992
Time: 00:00:00
Date: dimanche 03 mai 1992
Time: 13:33:20
Date: lundi 04 mai 1992
Time: 17:20:00
Date: vendredi 15 mai 1992
Time: 03:20:00
582 – wcslen
Returns the number of wide characters in a wide-character
string. The returned length does not include the terminating
null character.
Format
#include <wchar.h>
size_t wcslen (const wchar_t *wstr);
582.1 – Argument
wstr
A pointer to a null-terminated wide-character string.
582.2 – Return Value
x The length of the wide-character string,
excluding the terminating null wide character.
583 – wcsncat
Concatenates a counted number of wide-characters from one string
to another.
Format
#include <wchar.h>
wchar_t *wcsncat (wchar_t *wstr_1, const wchar_t *wstr_2,
size_t maxchar);
583.1 – Function Variants
The wcsncat function has variants named _wcsncat32 and _wcsncat64
for use with 32-bit and 64-bit pointer sizes, respectively.
583.2 – Arguments
wstr_1, wstr_2
Pointers to null-terminated wide-character strings.
maxchar
The maximum number of wide characters from wstr_2 that are copied
to wstr_1. If maxchar is 0, no characters are copied from wstr_2.
583.3 – Description
The wcsncat function appends wide characters from the wide-
character string wstr_2 to the end of wstr_1, up to a maximum of
maxchar characters. A terminating null wide character is always
appended to the result of the wcsncat function. Therefore, the
maximum number of wide characters that can end up in wstr_1 is
wcslen(wstr_1) + maxchar + 1).
See also wcscat.
583.4 – Return Value
x The first argument, wstr_1, which is assumed
to be large enough to hold the concatenated
result.
583.5 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <string.h>
/* This program concatenates two wide-
character strings using */
/* the wcsncat function, and then manually compares the result */
/* to the expected result */
#define S1LENGTH 10
#define S2LENGTH 8
#define SIZE 3
main()
{
int i;
wchar_t s1buf[S1LENGTH + S2LENGTH];
wchar_t s2buf[S2LENGTH];
wchar_t test1[S1LENGTH + S2LENGTH];
/* Initialize the three wide-character strings */
if (mbstowcs(s1buf, "abcmnexyz", S1LENGTH) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
if (mbstowcs(s2buf, " orthis", S2LENGTH) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
if (mbstowcs(test1, "abcmnexyz orthis", S1LENGTH + SIZE)
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Concatenate s1buf with SIZE characters from s2buf, */
/* placing the result into s1buf. Then compare s1buf */
/* with the expected result in test1. */
wcsncat(s1buf, s2buf, SIZE);
for (i = 0; i <= S1LENGTH + SIZE - 2; i++) {
/* Check that each character is correct */
if (test1[i] != s1buf[i]) {
printf("Error in wcsncat\n");
exit(EXIT_FAILURE);
}
}
printf("Concatenated string: <%S>\n", s1buf);
}
Running the example produces the following result:
Concatenated string: <abcmnexyz or>
584 – wcsncmp
Compares not more than maxchar characters of two wide-character
strings. It returns an integer that indicates if the strings are
different, and how they differ.
Format
#include <wchar.h>
int wcsncmp (const wchar_t *wstr_1, const wchar_t *wstr_2,
size_t maxchar);
584.1 – Arguments
wstr_1, wstr_2
Pointers to null-terminated wide-character strings.
maxchar
The maximum number of characters to search in both wstr_1 and
wstr_2. If maxchar is 0, no comparison is performed and 0 is
returned (the strings are considered equal).
584.2 – Description
The strings are compared until a null character is encountered,
the strings differ, or maxchar is reached. If characters differ,
wcsncmp returns:
o An integer less than 0 if the codepoint of the first differing
character in wstr_1 is less than the codepoint of the
corresponding character in wstr_2
o An integer greater than 0 if the codepoint of the first
differing character in wstr_1 is greater than the codepoint
of the corresponding character in wstr_2
If no differences are found after comparing maxchar characters,
the function returns 0.
See also wcscmp.
584.3 – Return Values
< 0 Indicates that wstr_1 is less than wstr_2.
0 Indicates that wstr_1 equals wstr_2.
> 0 Indicates that wstr_1 is greater than wstr_2.
585 – wcsncpy
Copies wide characters from source into dest. The function copies
up to a maximum of maxchar characters.
Format
#include <wchar.h>
wchar_t *wcsncpy (wchar_t *dest, const wchar_t *source, size_t
maxchar);
585.1 – Function Variants
The wcsncpy function has variants named _wcsncpy32 and _wcsncpy64
for use with 32-bit and 64-bit pointer sizes, respectively.
585.2 – Arguments
dest
Pointer to the null-terminated wide-character destination string.
source
Pointer to the null-terminated wide-character source string.
maxchar
The maximum number of wide characters to copy from source to
dest.
585.3 – Description
The wcsncpy function copies no more than maxchar characters from
source to dest. If source contains less than maxchar characters,
null characters are added to dest until maxchar characters have
been written to dest.
If source contains maxchar or more characters, as many characters
as possible are copied to dest. The null terminator of source is
not copied to dest.
See also wcscpy.
585.4 – Return Value
x The address of dest.
586 – wcspbrk
Searches a wide-character string for the first occurrence of one
of a specified set of wide characters.
Format
#include <wchar.h>
wchar_t *wcspbrk (const wchar_t *wstr, const wchar_t
*charset);
586.1 – Function Variants
The wcspbrk function has variants named _wcspbrk32 and _wcspbrk64
for use with 32-bit and 64-bit pointer sizes, respectively.
586.2 – Arguments
wstr
A pointer to a wide-character string. If this is a null string,
NULL is returned.
charset
A pointer to a wide-character string containing the set of wide
characters for which the function will search.
586.3 – Description
The wcspbrk function scans the wide characters in the string,
stops when it encounters a wide character found in charset, and
returns the address of the first character in the string that
appears in the character set.
586.4 – Return Values
x The address of the first wide character in the
string that is in the set.
NULL Indicates that none of the characters are in
charset.
587 – wcsrchr
Scans for the last occurrence of a wide character in a given
string.
Format
#include <wchar.h>
wchar_t *wcsrchr (const wchar_t *wstr, wchar_t wc);
587.1 – Function Variants
The wcsrchr function has variants named _wcsrchr32 and _wcsrchr64
for use with 32-bit and 64-bit pointer sizes, respectively.
587.2 – Arguments
wstr
A pointer to a null-terminated wide-character string.
wc
A character of type wchar_t.
587.3 – Description
The wcsrchr function returns the address of the last occurrence
of a given wide character in a null-terminated wide-character
string. The terminating null character is considered to be part
of the string.
See also wcschr.
587.4 – Return Values
x The address of the last occurrence of the
specified wide character.
NULL Indicates that the wide character does not
occur in the string.
587.5 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <string.h>
#define BUFF_SIZE 50
#define STRING_SIZE 6
main()
{
int i;
wchar_t s1buf[BUFF_SIZE],
w_string[STRING_SIZE];
wchar_t *status;
wchar_t *pbuf = s1buf;
/* Initialize the buffer */
if (mbstowcs(s1buf, "hijklabcdefg ytuhijklfedcba", BUFF_SIZE)
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Initialize the string to be searched for */
if (mbstowcs(w_string, "hijkl", STRING_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* This program checks the wcsrchr function by searching for */
/* the last occurrence of a string in the buffer s1buf and */
/* prints out the contents of s1buff from the location of
/* the string found. */
status = wcsrchr(s1buf, w_string[0]);
/* Check for pointer to start of rightmost character string. */
if (status == pbuf) {
printf("Error in wcsrchr\n");
exit(EXIT_FAILURE);
}
printf("Program completed successfully\n");
printf("String found : [%S]\n", status);
}
Running the example produces the following result:
Program completed successfully
String found : [hijklfedcba]
588 – wcsrtombs
Converts a sequence of wide characters into a sequence of
corresponding multibyte characters.
Format
#include <wchar.h>
size_t wcsrtombs (char *dst, const wchar_t **src, size_t len,
mbstate_t *ps);
588.1 – Function Variants
The wcsrtombs function has variants named _wcsrtombs32 and
_wcsrtombs64 for use with 32-bit and 64-bit pointer sizes,
respectively.
588.2 – Arguments
dst
A pointer to the destination array for converted multibyte
character sequence.
src
An address of the pointer to an array containing the sequence of
wide characters to be converted.
len
The maximum number of bytes that can be stored in the array
pointed to by dst.
ps
A pointer to the mbstate_t object. If a NULL pointer is
specified, the function uses its internal mbstate_t object.
mbstate_t is an opaque datatype intended to keep the conversion
state for the state-dependent codesets.
588.3 – Description
The wcsrtombs function converts a sequence of wide characters
from the array indirectly pointed to by src into a sequence of
corresponding multibyte characters, beginning in the conversion
state described by the object pointed to by ps.
If dst is a not a NULL pointer, the converted characters are then
stored into the array pointed to by dst. Conversion continues up
to and including a terminating null wide character, which is also
stored.
Conversion stops earlier in two cases:
o When a code is reached that does not correspond to a valid
multibyte character
o If dst is not a NULL pointer, when the next multibyte
character would exceed the limit of len total bytes to be
stored into the array pointed to by dst
Each conversion takes place as if by a call to the wcrtomb
function.
If dst is not a NULL pointer, the pointer object pointed to by
src is assigned either a NULL pointer (if the conversion stopped
because it reached a terminating null wide character) or the
address just beyond the last wide character converted (if any).
If conversion stopped because it reached a terminating null
wide character, the resulting state described is the initial
conversion state.
If the wcsrtombs function is called as a counting function,
which means that dst is a NULL pointer, the value of the internal
mbstate_t object will remain unchanged.
See also wcrtomb.
588.4 – Return Values
x The number of bytes stored in the resulting
array, not including the terminating null (if
any).
-1 Indicates an encoding error-a character that
does not correspond to a valid multibyte
character was encountered; errno is set to
EILSEQ; the conversion state is undefined.
589 – wcsspn
Compares the characters in a wide-character string against a set
of wide characters. The function returns the length of the first
substring comprised entirely of characters in the set of wide
characters.
Format
#include <wchar.h>
size_t wcsspn (const wchar_t *wstr1, const wchar_t *wstr2);
589.1 – Arguments
wstr1
A pointer to a null-terminated wide-character string. If this
string is a null string, 0 is returned.
wstr2
A pointer to a null-terminated wide-character string that
contains the set of wide characters for which the function will
search.
589.2 – Description
The wcsspn function scans the wide characters in the wide-
character string pointed to by wstr1 until it encounters a
character not found in wstr2. The function returns the length of
the first segment of wstr1 formed by characters found in wstr2.
589.3 – Return Value
x The length of the segment.
589.4 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <string.h>
/* This test sets up 2 strings, buffer and w_string. It */
/* then uses wcsspn() to calculate the maximum segment */
/* of w_string that consists entirely of characters */
/* from buffer. */
#define BUFF_SIZE 20
#define STRING_SIZE 50
main()
{
wchar_t buffer[BUFF_SIZE];
wchar_t w_string[STRING_SIZE];
size_t result;
/* Initialize the buffer */
if (mbstowcs(buffer, "abcdefg", BUFF_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Initialize the string */
if (mbstowcs(w_
string, "abcedjklmabcjklabcdehjkl", STRING_SIZE)
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Using wcsspn - work out the largest string in w_string */
/* that consists entirely of characters from buffer */
result = wcsspn(w_string, buffer);
printf("Longest segment found in w_
string is: %d", result);
}
Running the example program produces the following result:
Longest segment found in w_string is: 5
590 – wcsstr
Locates the first occurrence in the string pointed to by s1 of
the sequence of wide characters in the string pointed to by s2.
Format
#include <wchar.h>
wchar_t *wcsstr (const wchar_t *s1, const wchar_t *s2);
590.1 – Function Variants
The wcsstr function has variants named _wcsstr32 and _wcsstr64
for use with 32-bit and 64-bit pointer sizes, respectively.
590.2 – Arguments
s1, s2
Pointers to null-terminated, wide-character strings.
590.3 – Description
If s2 points to a wide-character string of 0 length, the wcsstr
function returns s1.
590.4 – Return Values
x A pointer to the located string.
NULL Indicates an error; the string was not found.
591 – wcstod
Converts a given wide-character string to a double-precision
number.
Format
#include <wchar.h>
double wcstod (const wchar_t *nptr, wchar_t **endptr);
591.1 – Arguments
nptr
A pointer to the wide-character string to be converted to a
double-precision number.
endptr
The address of an object where the function can store the address
of the first unrecognized wide character that terminates the
scan. If endptr is a NULL pointer, the address of the first
unrecognized wide character is not retained.
591.2 – Description
The wcstod function recognizes an optional sequence of white-
space characters (as defined by iswspace), then an optional plus
or minus sign, then a sequence of digits optionally containing a
radix character, then an optional letter (e or E) followed by an
optionally signed integer. The first unrecognized character ends
the conversion.
The string is interpreted by the same rules used to interpret
floating constants.
The radix character is defined in the program's current locale
(category LC_NUMERIC).
This function returns the converted value. For wcstod, overflows
are accounted for in the following manner:
o If the correct value causes an overflow, HUGE_VAL (with a plus
or minus sign according to the sign of the value) is returned
and errno is set to ERANGE.
o If the correct value causes an underflow, 0 is returned and
errno is set to ERANGE.
If the string starts with an unrecognized wide character, *endptr
is set to nptr and a 0 value is returned.
591.3 – Return Values
x The converted string.
0 Indicates the conversion could not be
performed. The function sets errno to one
of:
o EINVAL - No conversion could be performed.
o ERANGE - The value would cause an
underflow.
o ENOMEM - Not enough memory available for
internal conversion buffer.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
592 – wcstok
Locates text tokens in a given wide-character string.
Format
#include <wchar.h>
wchar_t *wcstok (wchar_t *ws1, const wchar_t *ws2); (XPG4)
wchar_t *wcstok (wchar_t *ws1, const wchar_t *ws2, wchar_t
**ptr); (ISO C)
592.1 – Function Variants
The wcstok function has variants named _wcstok32 and _wcstok64
for use with 32-bit and 64-bit pointer sizes, respectively.
592.2 – Arguments
ws1
A pointer to a wide-character string containing zero or more text
tokens.
ws2
A pointer to a separator string consisting of one or more wide
characters. The separator string can differ from call to call.
ptr
ISO C Standard only. Used only when ws1 is NULL, ptr is a caller-
provided wchar_t pointer into which wcstok stores information
necessary for it to continue scanning the same wide-character
string.
592.3 – Description
A sequence of calls to wcstok breaks the wide-character string
pointed to by ws1 into a sequence of tokens, each of which is
delimited by a wide character from the wide-character string
pointed to by ws2.
The wcstok function keeps track of its position in the wide-
character string between calls and, as successive calls are made,
the function works through the wide-character string, identifying
the text token following the one identified by the previous call.
Tokens in ws1 are delimited by null characters that wcstok
inserts into ws1. Therefore, ws1 cannot be a const object.
The following sections describe differences between the XPG4
Standard and ISO C Standard interface to wcstok.
XPG4 Standard Behavior
The first call to the wcstok function searches the wide-character
string for the first character that is not found in the separator
string pointed to by ws2. The first call returns a pointer to the
first wide character in the first token and writes a null wide
character into ws1 immediately following the returned token.
Subsequent calls to wcstok search for a wide character that is
in the separator string pointed to by ws2. Each subsequent call
(with the value of the first argument remaining NULL) returns a
pointer to the next token in the string originally pointed to by
ws1. When no tokens remain in the string, wcstok returns a NULL
pointer.
ISO C Standard Behavior
For the first call in the sequence, ws1 points to a wide-
character string. In subsequent calls for the same string, ws1
is NULL. When ws1 is NULL, the value pointed to by ptr matches
that stored by the previous call for the same wide-character
string. Otherwise, the value pointed to by ptr is ignored.
The first call in the sequence searches the wide-character
string pointed to by ws1 for the first wide character that is not
contained in the current separator wide-character string pointed
to by ws2. If no such wide character is found, then there are no
tokens in the wide-character string pointed to by ws1, and wcstok
returns a NULL pointer.
The wcstok function then searches from there for a wide character
that is contained in the current separator wide-character string.
If no such wide character is found, the current token extends
to the end of the wide-character string pointed to by ws1, and
subsequent searches in the same wide-character string for a token
return a NULL pointer. If such a wide character is found, it
is overwritten by a null wide character, which terminates the
current token.
In all cases, wcstok stores sufficient information in the pointer
pointed to by ptr so that subsequent calls with a NULL pointer
for ws1 and the unmodified pointer value for ptr start searching
just past the element overwritten by a null wide character (if
any).
592.4 – Return Values
x A pointer to the first character of a token.
NULL Indicates that no token was found.
592.5 – Examples
1./* XPG4 version of wcstok call */
#include <wchar.h>
#include <string.h>
#include <stdio.h>
main()
{
wchar_t str[] = L"...ab..cd,,ef.hi";
printf("|%S|\n", wcstok(str, L"."));
printf("|%S|\n", wcstok(NULL, L","));
printf("|%S|\n", wcstok(NULL, L",."));
printf("|%S|\n", wcstok(NULL, L",."));
}
2./* ISO C version of wcstok call */
#include <wchar.h>
#include <string.h>
#include <stdio.h>
main()
{
wchar_t str[] = L"...ab..cd,,ef.hi";
wchar_t *savptr = NULL;
printf("|%S|\n", wcstok(str, L".", &savptr));
printf("|%S|\n", wcstok(NULL, L",", &savptr));
printf("|%S|\n", wcstok(NULL, L",.", &savptr));
printf("|%S|\n", wcstok(NULL, L",.", &savptr));
}
Running this example produces the following results:
$ $ RUN WCSTOK_EXAMPLE
|ab|
|.cd|
|ef|
|hi|
$
593 – wcstol
Converts a wide-character string in a specified base to a long
integer value.
Format
#include <wchar.h>
long int wcstol (const wchar_t *nptr, wchar_t **endptr, int base);
593.1 – Function Variants
The wcstol function has variants named _wcstol32 and _wcstol64
for use with 32-bit and 64-bit pointer sizes, respectively.
593.2 – Arguments
nptr
A pointer to the wide-character string to be converted to a long
integer.
endptr
The address of an object where the function can store a pointer
to the first unrecognized character encountered in the conversion
process (the character that follows the last character processed
in the string being converted). If endptr is a NULL pointer, the
address of the first unrecognized character is not retained.
base
The value, 2 through 36, to use as the base for the conversion.
If base is 16, leading zeros after the optional sign are ignored,
and 0x or 0X is ignored.
If base is 0, the sequence of characters is interpreted by the
same rules used to interpret an integer constant. After the
optional sign:
o A leading 0 indicates octal conversion.
o A leading 0x or 0X indicates hexadecimal conversion.
o Any other combination of leading characters indicates decimal
conversion.
593.3 – Description
The wcstol function recognizes strings in various formats,
depending on the value of the base. This function ignores any
leading white-space characters (as defined by the iswspace
function) in the given string. It recognizes an optional plus
or minus sign, then a sequence of digits or letters that can
represent an integer constant according to the value of the base.
The first unrecognized character ends the conversion.
593.4 – Return Values
x The converted value.
0 Indicates that the string starts with an
unrecognized wide character or that the value
for base is invalid. If the string starts with
an unrecognized wide character, *endptr is set
to nptr. The function sets errno to EINVAL.
LONG_MAX or LONG_ Indicates that the converted value would cause
MIN a positive or negative overflow, respectively.
The function sets errno to ERANGE.
594 – wcstombs
Converts a sequence of wide-character codes to a sequence of
multibyte characters.
Format
#include <stdlib.h>
size_t wcstombs (char *s, const wchar_t *pwcs, size_t n);
594.1 – Arguments
s
A pointer to the array containing the resulting multibyte
characters.
pwcs
A pointer to the array containing the sequence of wide-character
codes.
n
The maximum number of bytes to be stored in the array pointed to
by s.
594.2 – Description
The wcstombs function converts a sequence of codes corresponding
to multibyte characters from the array pointed to by pwcs to a
sequence of multibyte characters that are stored into the array
pointed to by s, up to a maximum of n bytes. The value returned
is equal to the number of characters converted or a -1 if an
error occurred.
This function is affected by the LC_CTYPE category of the
program's current locale.
If s is NULL, this function call is a counting operation and n is
ignored.
See also wctomb.
594.3 – Return Values
x The number of bytes stored in s, not including
the null terminating byte. If s is NULL,
wcstombs returns the number of bytes required
for the multibyte character array.
(size_t) -1 Indicates an error occurred. The function sets
errno to EILSEQ - invalid character sequence,
or a wide-character code does not correspond
to a valid character.
595 – wcstoul
Converts the initial portion of the wide-character string pointed
to by nptr to an unsigned long integer.
Format
#include <wchar.h>
unsigned long int wcstoul (const wchar_t *nptr, wchar_t
**endptr, int base);
595.1 – Function Variants
The wcstoul function has variants named _wcstoul32 and _wcstoul64
for use with 32-bit and 64-bit pointer sizes, respectively.
595.2 – Arguments
nptr
A pointer to the wide-character string to be converted to an
unsigned long.
endptr
The address of an object where the function can store the address
of the first unrecognized character encountered in the conversion
process (the character that follows the last character in the
string being converted). If endptr is a NULL pointer, the address
of the first unrecognized character is not retained.
base
The value, 2 through 36, to use as the base for the conversion.
If base is 16, leading zeros after the optional sign are ignored,
and 0x or 0X is ignored.
If base is 0, the sequence of characters is interpreted by
the same rules used to interpret an integer constant: after
the optional sign, a leading 0 indicates octal conversion, a
leading 0x or 0X indicates hexadecimal conversion, and any other
combination of leading characters indicates decimal conversion.
595.3 – Description
The wcstoul function recognizes strings in various formats,
depending on the value of the base. It ignores any leading
white-space characters (as defined by the iswspace function)
in the string. It recognizes an optional plus or minus sign,
then a sequence of digits or letters that may represent an
integer constant according to the value of the base. The first
unrecognized wide character ends the conversion.
595.4 – Return Values
x The converted value.
0 Indicates that the string starts with an
unrecognized wide character or that the value
for base is invalid. If the string starts with
an unrecognized wide character, *endptr is set
to nptr. The function sets errno to EINVAL.
ULONG_MAX Indicates that the converted value would
cause an overflow. The function sets errno
to ERANGE.
595.5 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <errno.h>
#include <limits.h>
/* This test calls wcstoul() to convert a string to an */
/* unsigned long integer. wcstoul outputs the resulting */
/* integer and any characters that could not be converted. */
#define MAX_STRING 128
main()
{
int base = 10,
errno;
char *input_string = "1234.56";
wchar_t string_array[MAX_STRING],
*ptr;
size_t size;
unsigned long int val;
printf("base = [%d]\n", base);
printf("String to convert = %s\n", input_string);
if ((size = mbstowcs(string_array, input_string, MAX_STRING)) ==
(size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
printf("wchar_t string is = [%S]\n", string_array);
errno = 0;
val = wcstoul(string_array, &ptr, base);
if (errno == 0) {
printf("returned unsigned long int from wcstoul = [%u]\n", val);
printf("wide char terminating scan(ptr) = [%S]\n\n", ptr);
}
if (errno == ERANGE) {
perror("error value is :");
printf("ULONG_MAX = [%u]\n", ULONG_MAX);
printf("wcstoul failed, val = [%d]\n\n", val);
}
}
Running the example program produces the following result:
base = [10]
String to convert = 1234.56
wchar_t string is = [1234.56]
returned unsigned long int from wcstoul = [1234]
wide char terminating scan(ptr) = [.56]
596 – wcswcs
Locates the first occurrence in the string pointed to by wstr1
of the sequence of wide characters in the string pointed to by
wstr2.
Format
#include <wchar.h>
wchar_t *wcswcs (const wchar_t *wstr1, const wchar_t *wstr2);
596.1 – Function Variants
The wcswcs function has variants named _wcswcs32 and _wcswcs64
for use with 32-bit and 64-bit pointer sizes, respectively.
596.2 – Arguments
wstr1, wstr2
Pointers to null-terminated wide-character strings.
596.3 – Return Values
Pointer A pointer to the located wide-character
string.
NULL Indicates that the wide-character string was
not found.
596.4 – Example
#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
/* This test uses wcswcs() to find the occurrence of each */
/* subwide-character string, string1 and string2, within */
/* the main wide-character string, lookin. */
#define BUF_SIZE 50
main()
{
static char lookin[] = "that this is a test was at the end";
char string1[] = "this",
string2[] = "the end";
wchar_t buffer[BUF_SIZE],
input_buffer[BUF_SIZE];
/* Convert lookin to wide-character format. */
/* Buffer and print it out. */
if (mbstowcs(buffer, lookin, BUF_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
printf("Buffer to look in: %S\n", buffer);
/* Convert string1 to wide-character format and use */
/* wcswcs() to locate it within buffer */
if (mbstowcs(input_buffer, string1, BUF_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
printf("this: %S\n", wcswcs(buffer, input_buffer));
/* Convert string2 to wide-character format and use */
/* wcswcs() to locate it within buffer */
if (mbstowcs(input_buffer, string2, BUF_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
printf("the end: %S\n", wcswcs(buffer, input_buffer));
exit(1);
}
Running this example produces the following results:
Buffer to look in: that this is a test was at the end
this: this is a test was at the end
the end: the end
597 – wcswidth
Determines the number of printing positions on a display device
that are required for a wide-character string.
Format
#include <wchar.h>
int wcswidth (const wchar_t *pwcs, size_t n);
597.1 – Arguments
pwcs
A pointer to a wide-character string.
n
The maximum number of characters in the string.
597.2 – Description
The wcswidth function returns the number of printing positions
required to display the first n characters of the string pointed
to by pwcs. If there are less than n wide characters in the
string, the function returns the number of positions required
for the whole string.
597.3 – Return Values
x The number of printing positions required.
0 If pwcs is a null character.
-1 Indicates that one (or more) of the wide
characters in the string pointed to by pwcs
is not a printable character.
598 – wcsxfrm
Changes a wide-character string such that the changed string can
be passed to the wcscmp function and produce the same result as
passing the unchanged string to the wcscoll function.
Format
#include <wchar.h>
size_t wcsxfrm (wchar_t *ws1, const wchar_t *ws2, size_t
maxchar);
598.1 – Arguments
ws1, ws2
Pointers to wide-character strings.
maxchar
The maximum number of wide characters, including the null wide-
character terminator, allowed to be stored in s1.
598.2 – Description
The wcsxfrm function transforms the string pointed to by ws2
and stores the resulting string in the array pointed to by ws1.
No more than maxchar wide characters, including the null wide
terminator, are placed into the array pointed to by ws1.
If the value of maxchar is less than the required size to store
the transformed string (including the terminating null), the
contents of the array pointed to by ws1 is indeterminate. In such
a case, the function returns the size of the transformed string.
If maxchar is 0, then, ws1 is allowed to be a NULL pointer, and
the function returns the required size of the ws1 array before
making the transformation.
The wide-character string comparison functions, wcscoll and
wcscmp, can produce different results given the same two wide-
character strings to compare. This is because wcscmp does a
straightforward comparison of the code point values of the
characters in the strings, whereas wcscoll uses the locale
information to do the comparison. Depending on the locale, the
wcscoll comparison can be a multipass operation, which is slower
than wcscmp.
The wcsxfrm function transforms wide-character strings in such
a way that if you pass two transformed strings to the wcscmp
function, the result is the same as passing the two original
strings to the wcscoll function. The wcsxfrm function is useful
in applications that need to do a large number of comparisons on
the same wide-character strings using wcscoll. In this case, it
may be more efficient (depending on the locale) to transform the
strings once using wcsxfrm and then use the wcscmp function to do
comparisons.
598.3 – Return Values
x Length of the resulting string pointed to
by ws1, not including the terminating null
character.
(size_t) -1 Indicates that an error occurred. The function
sets errno to EINVAL - The string pointed to
by ws2 contains characters outside the domain
of the collating sequence.
598.4 – Example
#include <wchar.h>
#include <stdio.h>
#include <stdlib.h>
#include <locale.h>
/* This program verifies that two transformed strings, */
/* when passed through wcsxfrm and then compared, provide */
/* the same result as if passed through wcscoll without */
/* any transformation. */
#define BUFF_SIZE 20
main()
{
wchar_t w_string1[BUFF_SIZE];
wchar_t w_string2[BUFF_SIZE];
wchar_t w_string3[BUFF_SIZE];
wchar_t w_string4[BUFF_SIZE];
int errno;
int coll_result;
int wcscmp_result;
size_t wcsxfrm_result1;
size_t wcsxfrm_result2;
/* setlocale to French locale */
if (setlocale(LC_ALL, "fr_FR.ISO8859-1") == NULL) {
perror("setlocale");
exit(EXIT_FAILURE);
}
/* Convert each of the strings into wide-character format. */
if (mbstowcs(w_string1, "<a`>bcd", BUFF_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
if (mbstowcs(w_string2, "abcz", BUFF_SIZE) == (size_t)-1) {
perror("mbstowcs");
exit(EXIT_FAILURE);
}
/* Collate string 1 and string 2 and store the result. */
errno = 0;
coll_result = wcscoll(w_string1, w_string2);
if (errno) {
perror("wcscoll");
exit(EXIT_FAILURE);
}
else {
/* Transform the strings (using wcsxfrm) into */
/* w_string3 and w_string4. */
wcsxfrm_result1 = wcsxfrm(w_string3, w_string1, BUFF_SIZE);
if (wcsxfrm_result1 == ((size_t) - 1))
perror("wcsxfrm");
else if (wcsxfrm_result1 > BUFF_SIZE) {
perror("\n** String is too long **\n");
exit(EXIT_FAILURE);
}
else {
wcsxfrm_result2 = wcsxfrm(w_string4, w_string2, BUFF_SIZE);
if (wcsxfrm_result2 == ((size_t) - 1)) {
perror("wcsxfrm");
exit(EXIT_FAILURE);
}
else if (wcsxfrm_result2 > BUFF_SIZE) {
perror("\n** String is too long **\n");
exit(EXIT_FAILURE);
}
/* Compare the two transformed strings and verify that */
/* the result is the same as the result from wcscoll on */
/* the original strings. */
else {
wcscmp_result = wcscmp(w_string3, w_string4);
if (wcscmp_result == 0 && (coll_result == 0)) {
printf("\nReturn value from wcscoll() and return value"
" from wcscmp() are both zero.");
printf("\nThe program was successful\n\n");
}
else if ((wcscmp_result < 0) && (coll_result < 0)) {
printf("\nReturn value from wcscoll() and return value"
" from wcscmp() are less than zero.");
printf("\nThe program was successful\n\n");
}
else if ((wcscmp_result > 0) && (coll_result > 0)) {
printf("\nReturn value from wcscoll() and return value"
" from wcscmp() are greater than zero.");
printf("\nThe program was successful\n\n");
}
else {
printf("** Error **\n");
printf("\nReturn values are not of the same type");
}
}
}
}
}
Running the example program produces the following result:
Return value from wcscoll() and return value
from wcscmp() are less than zero.
The program was successful
599 – wctob
Determines if a wide character corresponds to a single-
byte multibyte character and returns its multibyte character
representation.
Format
#include <stdio.h>
#include <wchar.h>
int wctob (wint_t c);
599.1 – Argument
c
The wide character to be converted to a single-byte multibyte
character.
599.2 – Description
The wctob function determines whether the specified wide
character corresponds to a single-byte multibyte character when
in the initial shift state and, if so, returns its multibyte
character representation.
599.3 – Return Values
x The single-byte representation of the wide
character specified.
EOF Indicates an error. The wide character
specified does not correspond to a single-byte
multibyte character.
600 – wctomb
Converts a wide character to its multibyte character
representation.
Format
#include <stdlib.h>
int wctomb (char *s, wchar_t wchar);
600.1 – Arguments
s
A pointer to the resulting multibyte character.
wchar
The code for the wide character.
600.2 – Description
The wctomb function converts the wide character specified by
wchar to its multibyte character representation. If s is NULL,
then 0 is returned. Otherwise, the number of bytes comprising the
multibyte character is returned. At most, MB_CUR_MAX bytes are
stored in the array object pointed to by s.
This function is affected by the LC_CTYPE category of the
program's current locale.
600.3 – Return Values
x The number of bytes comprising the multibyte
character corresponding to wchar.
0 If s is NULL.
-1 If wchar is not a valid character.
601 – wctrans
Returns the description of a mapping, corresponding to specified
property, that can later be used in a call to towctrans.
Format
#include <wctype.h>
wctrans_t wctrans (const char *property);
601.1 – Argument
property
The name of the mapping. The following property names are defined
for all locales:
o "toupper"
o "tolower"
Additional property names may also be defined in the LC_CTYPE
category of the current locale.
601.2 – Description
The wctrans function constructs a value with type wctrans_t that
describes a mapping between wide characters identified by the
property argument.
See also towctrans.
601.3 – Return Values
nonzero According to the LC_CTYPE category of the
current program locale, the string specified
as a property argument is the name of an
existing character mapping. The value returned
can be used in a call to the towctrans
function.
0 Indicates an error. The property argument
does not identify a character mapping in the
current program's locale.
602 – wctype
Used for defining a character class. The value returned by this
function is used in calls to the iswctype function.
Format
#include <wctype.h> (ISO C)
#include <wchar.h> (XPG4)
wctype_t wctype (const char *char_class);
602.1 – Argument
char_class
A pointer to a valid character class name.
602.2 – Description
The wctype function converts a valid character class defined for
the current locale to an object of type wctype_t. The following
character class names are defined for all locales:
alnum cntrl lower space
alpha digit print upper
blank graph punct xdigit
Additional character class names may also be defined in the LC_
CTYPE category of the current locale.
See also iswctype.
602.3 – Return Values
x An object of type wctype_t that can be used in
calls to the iswctype function.
0 If the character class name is not valid for
the current locale.
602.4 – Example
#include <locale.h>
#include <wchar.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
/* This test will set up a number of character class using wctype() */
/* and then verify whether calls to iswctype() using these classes */
/* produce the same results as calls to the is**** routines. */
main()
{
wchar_t w_char;
wctype_t ret_val;
char *character = "A";
/* Convert character to wide character format - w_char */
if (mbtowc(&w_char, character, 1) == -1) {
perror("mbtowc");
exit(EXIT_FAILURE);
}
/* Check if results from iswalnum() matches check on */
/* alnum character class */
if ((iswalnum((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("alnum"))))
printf("[%C] is a member of the character class alnum\n", w_char);
else
printf("[%C] is not a member of the character class alnum\n", w_char);
/* Check if results from iswalpha() matches check on */
/* alpha character class */
if ((iswalpha((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("alpha"))))
printf("[%C] is a member of the character class alpha\n", w_char);
else
printf("[%C] is not a member of the character class alpha\n", w_char);
/* Check if results from iswcntrl() matches check on */
/* cntrl character class */
if ((iswcntrl((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("cntrl"))))
printf("[%C] is a member of the character class cntrl\n", w_char);
else
printf("[%C] is not a member of the character class cntrl\n", w_char);
/* Check if results from iswdigit() matches check on */
/* digit character class */
if ((iswdigit((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("digit"))))
printf("[%C] is a member of the character class digit\n", w_char);
else
printf("[%C] is not a member of the character class digit\n", w_char);
/* Check if results from iswgraph() matches check on */
/* graph character class */
if ((iswgraph((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("graph"))))
printf("[%C] is a member of the character class graph\n", w_char);
else
printf("[%C] is not a member of the character class graph\n", w_char);
/* Check if results from iswlower() matches check on */
/* lower character class */
if ((iswlower((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("lower"))))
printf("[%C] is a member of the character class lower\n", w_char);
else
printf("[%C] is not a member of the character class lower\n", w_char);
/* Check if results from iswprint() matches check on */
/* print character class */
if ((iswprint((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("print"))))
printf("[%C] is a member of the character class print\n", w_char);
else
printf("[%C] is not a member of the character class print\n", w_char);
/* Check if results from iswpunct() matches check on */
/* punct character class */
if ((iswpunct((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("punct"))))
printf("[%C] is a member of the character class punct\n", w_char);
else
printf("[%C] is not a member of the character class punct\n", w_char);
/* Check if results from iswspace() matches check on */
/* space character class */
if ((iswspace((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("space"))))
printf("[%C] is a member of the character class space\n", w_char);
else
printf("[%C] is not a member of the character class space\n", w_char);
/* Check if results from iswupper() matches check on */
/* upper character class */
if ((iswupper((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("upper"))))
printf("[%C] is a member of the character class upper\n", w_char);
else
printf("[%C] is not a member of the character class upper\n", w_char);
/* Check if results from iswxdigit() matches check on */
/* xdigit character class */
if ((iswxdigit((wint_t) w_char)) &&
(iswctype((wint_t) w_char, wctype("xdigit"))))
printf("[%C] is a member of the character class xdigit\n", w_char);
else
printf("[%C] is not a member of the character class xdigit\n", w_char);
}
Running this example produces the following result:
[A] is a member of the character class alnum
[A] is a member of the character class alpha
[A] is not a member of the character class cntrl
[A] is not a member of the character class digit
[A] is a member of the character class graph
[A] is not a member of the character class lower
[A] is a member of the character class print
[A] is not a member of the character class punct
[A] is not a member of the character class space
[A] is a member of the character class upper
[A] is a member of the character class xdigit
603 – wcwidth
Determines the number of printing positions on a display device
required for the specified wide character.
Format
#include <wchar.h>
int wcwidth (wchar_t wc);
603.1 – Argument
wc
A wide character.
603.2 – Description
The wcwidth function determines the number of column positions
needed for the specified wide character wc. The value of wc must
be a valid wide character in the current locale.
603.3 – Return Values
x The number of printing positions required for
wc.
0 If wc is a null character.
-1 Indicates that wc does not represent a valid
printing wide character.
604 – wmemchr
Locates the first occurrence of a specified wide character in an
array of wide characters.
Format
#include <wchar.h>
wchar_t wmemchr (const wchar_t *s, wchar_t c, size_t n);
604.1 – Function Variants
The wmemchr function has variants named _wmemchr32 and _wmemchr64
for use with 32-bit and 64-bit pointer sizes, respectively.
604.2 – Arguments
s
A pointer to an array of wide characters to be searched.
c
The wide character value to search for.
n
The maximum number of wide characters in the array to be
searched.
604.3 – Description
The wmemchr function locates the first occurrence of the
specified wide character in the initial n wide characters of
the array pointed to by s.
604.4 – Return Values
x A pointer to the first occurrence of the wide
character in the array.
NULL The specified wide character does not occur in
the array.
605 – wmemcmp
Compares two arrays of wide characters.
Format
#include <wchar.h>
int wmemcmp (const wchar_t *s1, const wchar_t *s2, size_t n);
605.1 – Arguments
s1, s2
Pointers to wide-character arrays.
n
The maximum number of wide characters to be compared.
605.2 – Description
The wmemcmp function compares the first n wide characters of
the array pointed to by s1 with the first n wide characters of
the array pointed to by s2. The wide characters are compared not
according to locale-dependent collation rules, but as integral
objects of type wchar_t.
605.3 – Return Values
0 Arrays are equal.
Positive value The first array is greater than the second.
Negative value The first array is less than the second.
606 – wmemcpy
Copies a specified number of wide characters from one wide-
character array to another.
Format
#include <wchar.h>
wchar_t wmemcpy (wchar_t *dest, const wchar_t *source, size_t n);
606.1 – Function Variants
The wmemcpy function has variants named _wmemcpy32 and _wmemcpy64
for use with 32-bit and 64-bit pointer sizes, respectively.
606.2 – Arguments
dest
A pointer to the destination array.
source
A pointer to the source array.
n
The number of wide characters to be copied.
606.3 – Description
The wmemcpy function copies n wide characters from the array
pointed to by source to the array pointed to by dest.
606.4 – Return Value
x The value of dest.
607 – wmemmove
Copies a specified number of wide characters from one wide-
character array to another.
Format
#include <wchar.h>
wchar_t wmemmove (wchar_t *dest, const wchar_t *source, size_t n);
607.1 – Function Variants
The wmemmove function has variants named _wmemmove32 and
_wmemmove64 for use with 32-bit and 64-bit pointer sizes,
respectively.
607.2 – Arguments
dest
A pointer to the destination array.
source
A pointer to the source array.
n
The number of wide characters to be moved.
607.3 – Description
The wmemmove function copies n wide characters from the location
pointed to by source to the location pointed to by dest.
The wmemmove and wmemcpy routines perform the same function,
except that wmemmove ensures that the original contents of the
source array are copied to the destination array even if the two
arrays overlap. Where such overlap is possible, programs that
require portability should use wmemmove, not wmemcopy.
607.4 – Return Value
x The value of dest.
608 – wmemset
Sets a specified value to a specified number of wide characters
in an array of wide characters.
Format
#include <wchar.h>
wchar_t wmemset (wchar_t *s, wchar_t c, size_t n);
608.1 – Function Variants
The wmemset function has variants named _wmemset32 and _wmemset64
for use with 32-bit and 64-bit pointer sizes, respectively.
608.2 – Arguments
s
A pointer to the array of wide characters.
c
The value to be placed in the first n wide characters of the
array.
n
The number of wide characters to be set to the specified value c.
608.3 – Description
The wmemset function copies the value of c into each of the first
n wide characters of the array pointed to by s.
608.4 – Return Value
x The value of s.
609 – wprintf
Performs formatted output from the standard output (stdout). See
Chapter 2 for information on format specifiers.
Format
#include <wchar.h>
int wprintf (const wchar_t *format, . . . );
609.1 – Arguments
format
A pointer to a wide-character string containing the format
specifications.
. . .
Optional expressions whose resultant types correspond to
conversion specifications given in the format specification.
If no conversion specifications are given, the output sources can
be omitted. Otherwise, the function calls must have exactly as
many output sources as there are conversion specifications, and
the conversion specifications must match the types of the output
sources.
Conversion specifications are matched to output sources in left-
to-right order. Excess output pointers, if any, are ignored.
609.2 – Description
The wprintf function is equivalent to the fwprintf function with
the stdout argument interposed before the wprintf arguments.
609.3 – Return Values
n The number of wide characters written.
Negative value Indicates an error. The function sets errno to
one of the following:
o EILSEQ - Invalid character detected.
o EINVAL - Insufficient arguments.
o ENOMEM - Not enough memory available for
conversion.
o ERANGE - Floating-point calculations
overflow.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This might indicate that conversion to a
numeric value failed because of overflow.
The function can also set errno to the
following as a result of errors returned from
the I/O subsystem:
o EBADF - The file descriptor is not valid.
o EIO - I/O error.
o ENOSPC - No free space on the device
containing the file.
o ENXIO - Device does not exist.
o EPIPE - Broken pipe.
o ESPIPE - Illegal seek in a file opened for
append.
o EVMSERR - Nontranslatable OpenVMS error.
vaxc$errno contains the OpenVMS error code.
This indicates that an I/O error occurred
for which there is no equivalent C error
code.
610 – wrapok
In the UNIX system environment, allows the wrapping of a word
from the right border of the window to the beginning of the
next line. This routine is provided only for UNIX software
compatibility and serves no function in the OpenVMS environment.
Format
#include <curses.h>
wrapok (WINDOW *win, bool boolf);
610.1 – Arguments
win
A pointer to the window.
boolf
A Boolean TRUE or FALSE value. If boolf is FALSE, scrolling
is not allowed. This is the default setting. The bool type is
defined in the <curses.h> header file as follows:
#define bool int
611 – write
Writes a specified number of bytes from a buffer to a file.
Format
#include <unistd.h>
ssize_t write (int file_desc, void *buffer, size_t nbytes);
(ISO POSIX-1)
int write (int file_desc, void *buffer, int nbytes);
(Compatibility)
611.1 – Arguments
file_desc
A file descriptor that refers to a file currently opened for
writing or updating.
buffer
The address of contiguous storage from which the output data is
taken.
nbytes
The maximum number of bytes involved in the write operation.
611.2 – Description
If the write is to an RMS record file and the buffer contains
embedded new-line characters, more than one record may be written
to the file. Even if there are no embedded new-line characters,
if nbytes is greater than the maximum record size for the file,
more than one record will be written to the file. The write
function always generates at least one record.
If the write is to a mailbox and the third argument, nbytes,
specifies a length of 0, an end-of-file message is written to
the mailbox. This occurs for mailboxes created by the application
using SYS$CREMBX, but not for mailboxes created to implement
POSIX pipes. For more information see the "Subprocess Functions"
chapter of the VSI C RTL Reference Manual.
611.3 – Return Values
x The number of bytes written.
-1 Indicates errors, including undefined file
descriptors, illegal buffer addresses, and
physical I/O errors.
612 – writev
Writes to a file.
Format
#include <uio.h>
ssize_t writev (int file_desc, const struct iovec *iov, int
iovcnt);
ssize_t __writev64 (int file_desc, const struct
__iovec64 *iov, int iovcnt);
(Integrity servers, Alpha)
612.1 – Function Variants
The writev function has variants named _writev32 and __writev64
for use with 32-bit and 64-bit pointer sizes, respectively.
612.2 – Arguments
file_desc
A file descriptor that refers to a file currently opened for
writing or updating.
iov
Array of iovec structures from which the output data is gathered.
iovcnt
The number of buffers specified by the members of the iov array.
612.3 – Description
The writev function is equivalent to write but gathers the output
data from the iovcnt buffers specified by the members of the iov
array: iov[0], iov[1], ..., iov[iovcnt-1]. The iovcnt argument
is valid if greater than 0 and less than or equal to {IOV_MAX},
defined in <limits.h>.
Each iovec entry specifies the base address and length of an area
in memory from which data should be written. The writev function
writes a complete area before proceeding to the next.
If filedes refers to a regular file and all of the iov_len
members in the array pointed to by iov are 0, writev returns 0
and has no other effect.
For other file types, the behavior is unspecified.
If the sum of the iov_len values is greater than SSIZE_MAX, the
operation fails and no data is transferred.
Upon successful completion, writev returns the number of bytes
actually written. Otherwise, it returns a value of -1, the file
pointer remains unchanged, and errno is set to indicate an error.
612.4 – Return Values
x The number of bytes written.
-1 Indicates an error. The file times do not
change, and the function sets errno to one of
the following values:
o EBADF - The file_desc argument is not a
valid file descriptor open for writing.
o EINTR - The write operation was terminated
due to the receipt of a signal, and no data
was transferred.
o EINVAL - The sum of the iov_len values in
the iov array would overflow an ssize_t, or
the iovcnt argument was less than or equal
to 0, or greater than {IOV_MAX}.
o EIO - A physical I/O error has occurred.
o ENOSPC - There was no free space remaining
on the device containing the file.
o EPIPE - An attempt is made to write to a
pipe or FIFO that is not open for reading
by any process, or that only has one end
open. A SIGPIPE signal will also be sent to
the thread.
613 – wscanf
Reads input from the standard input (stdin) under control of the
wide-character format string.
Format
#include <wchar.h>
int wscanf (const wchar_t *format, . . . );
613.1 – Arguments
format
A pointer to a wide-character string containing the format
specifications.
. . .
Optional expressions whose results correspond to conversion
specifications given in the format specification.
If no conversion specifications are given, you can omit the input
pointers. Otherwise, the function calls must have exactly as
many input pointers as there are conversion specifications, and
the conversion specifications must match the types of the input
pointers.
Conversion specifications are matched to input sources in left-
to-right order. Excess input pointers, if any, are ignored.
613.2 – Description
The wscanf function is equivalent to the fwscanf function with
the stdin arguments interposed before the wscanf arguments.
613.3 – Return Values
n The number of input items assigned. The number
can be less than provided for, even zero, in
the event of an early matching failure.
EOF Indicates an error. An input failure occurred
before any conversion.
614 – y0,y1,yn
Compute Bessel functions of the second kind.
This function is supported on OpenVMS Integrity servers and
Alpha only.
Format
#include <math.h>
double y0 (double x);
float y0f (float x);
long double y0l (long double x);
double y1 (double x);
float y1f (float x);
long double y1l (long double x);
double yn (int n, double x);
float ynf (int n, float x);
long double ynl (int n, long double x);
614.1 – Arguments
x
A positive, real value.
n
An integer.
614.2 – Description
The y0 functions return the value of the Bessel function of the
second kind of order 0.
The y1 functions return the value of the Bessel function of the
second kind of order 1.
The yn functions return the value of the Bessel function of the
second kind of order n.
614.3 – Return Values
x The relevant Bessel value of x of the second
kind.
-HUGE_VAL The x argument is 0.0; errno is set to ERANGE.
NaN The x argument is negative or NaN; errno is
set to EDOM.
0 Underflow occurred; errno is set to ERANGE.
HUGE_VAL Overflow occurred; errno is set to ERANGE.
615 – Version-Dependency Tables
New functions are added to the VSI C Run-Time Library with each
version of VSI C. These functions are implemented and shipped with
the OpenVMS operating system, while the documentation and header
files containing their prototypes are shipped with versions of
the VSI C compiler.
You might have a newer version of VSI C that has header files
and documentation for C RTL functions that are not supported on
your older OpenVMS system. For example, if your target operating
system platform is OpenVMS Version 7.2, you cannot use C RTL
functions introduced on OpenVMS Version 7.3, even though they are
documented in this manual.
The following tables list what C RTL functions are supported
on recent OpenVMS versions. This is helpful for determining the
functions to avoid using on your target OpenVMS platforms.
615.1 – All OpenVMS Versions
The following functions are available on all OpenVMS VAX, Alpha,
and Integrity servers versions:
abort abs access acos
alarm asctime asin assert
atan2 atan atexit atof
atoi atoll (Alpha) atol atoq (Alpha)
box brk bsearch cabs
calloc ceil cfree chdir
chmod chown clearerr clock
close cosh cos creat
ctermid ctime cuserid decc$crtl_init
decc$fix_time decc$from_vms decc$match_wild
decc$record_read decc$record_write decc$set_reentrancy
decc$to_vms decc$translate_vms
delete delwin difftime div
dup2 dup ecvt endwin
execle execlp execl execve
execvp execv exit _exit
exp fabs fclose fcvt
fdopen feof ferror fflush
fgetc fgetname fgetpos fgets
fileno floor fmod fopen
fprintf fputc fputs fread
free freopen frexp fscanf
fseek fsetpos fstat fsync
ftell ftime fwait fwrite
gcvt getchar getcwd getc
getegid getenv geteuid getgid
getname getpid getppid gets
getuid getw gmtime gsignal
hypot initscr isalnum isalpha
isapipe isascii isatty iscntrl
isdigit isgraph islower isprint
ispunct isspace isupper isxdigit
kill labs ldexp ldiv
llabs (Alpha) lldiv(Alpha) localeconv localtime
log10 log longjmp longname
lseek lwait malloc mblen
mbstowcs mbtowc memchr memcmp
memcpy memmove memset mkdir
mktemp mktime modf mvwin
mv[w]addstr newwin nice open
overlay overwrite pause perror
pipe pow printf putchar
putc puts putw qabs (Alpha)
qdiv (Alpha) qsort raise rand
read realloc remove rename
rewind sbrk scanf scroll
setbuf setgid setjmp setlocale
setuid setvbuf sigblock signal
sigpause sigstack(VAX) sigvec sinh
sin sleep sprintf sqrt
srand sscanf ssignal stat
strcat strchr strcmp strcoll
strcpy strcspn strerror strftime
strlen strncat strncmp strncpy
strpbrk strrchr strspn strstr
strtod strtok strtoll strtol (Alpha)
strtoq (Alpha) strtoull (Alpha) strtoul strtouq (Alpha)
strxfrm subwin system tanh
tan times time tmpfile
tmpnam toascii tolower _tolower
touchwin toupper _toupper ttyname
umask ungetc vaxc$calloc_opt vaxc$cfree_opt
vaxc$crtl_init vaxc$establish vaxc$free_opt vaxc$malloc_opt
vaxc$realloc_opt va_arg va_count va_end
va_start va_start_1 vfork vfprintf
vprintf vsprintf wait wcstombs
wctomb write [w]addch [w]addstr
[w]clear [w]clrattr [w]clrtobot [w]clrtoeol
[w]delch [w]deleteln [w]erase [w]getch
[w]getstr [w]inch [w]insch [w]insertln
[w]insstr [w]move [w]printw [w]refresh
[w]scanw [w]setattr [w]standend [w]standout
615.2 – V6.2 and Higher
The following additional functions are available on OpenVMS VAX
and OpenVMS Alpha Version 6.2 and higher:
catclose catgets catopen fgetwc
fgetws fputwc fputws getopt
getwc getwchar iconv iconv_close
iconv_open iswalnum iswalpha iswcntrl
iswctype iswdigit iswgraph iswlower
iswprint iswpunct iswspace iswupper
iswxdigit nl_langinfo putwc putwchar
strnlen strptime towlower towupper
ungetwc wcscat wcschr wcscmp
wcscoll wcscpy wcscspn wcsftime
wcslen wcsncat wcsncmp wcsncpy
wcspbrk wcsrchr wcsspn wcstol
wcstoul wcswcs wcswidth wcsxfrm
wcstod wctype wcwidth wcstok
615.3 – V7.0 and Higher
The following additional functions are available on OpenVMS VAX
and OpenVMS Alpha Version 7.0 and higher:
basename bcmp bcopy btowc
bzero closedir confstr dirname
drand48 erand48 ffs fpathconf
ftruncate ftw fwide fwprintf
fwscanf getclock getdtablesizegetitimer
getlogin getpagesize getpwnam getpwuid
gettimeofday index initstate jrand48
lcong48 lrand48 mbrlen mbrtowc
mbsinit mbsrtowcs memccpy mkstemp
mmap mprotect mrand48 msync
munmap nrand48 opendir pathconf
pclose popen putenv random
readdir rewinddir rindex rmdir
seed48 seekdir setenv setitimer
setstate sigaction sigaddset sigdelset
sigemptyset sigfillset sigismember siglongjmp
sigpending sigprocmask sigsetjmp sigsuspend
srand48 srandom strcasecmp strdup
strfmon strncasecmp strsep swab
swprintf swscanf sysconf telldir
tempnam towctrans truncate tzset
ualarm uname unlink unsetenv
usleep vfwprintf vswprintf vwprintf
wait3 wait4 waitpid wcrtomb
wcsrtombs wcsstr wctob wctrans
wmemchr wmemcmp wmemcpy wmemmove
wmemset wprintf wscanf
615.4 – V7.0 Alpha and Higher
The following additional functions are available on OpenVMS Alpha
Version 7.0 and higher:
_basename32 _basename64 _bsearch32 _bsearch64
_calloc32 _calloc64 _catgets32 _catgets64
_ctermid32 _ctermid64 _cuserid32 _cuserid64
_dirname32 _dirname64 _fgetname32 _fgetname64
_fgets32 _fgets64 _fgetws32 _fgetws64
_gcvt32 _gcvt64 _getcwd32 _getcwd64
_getname32 _getname64 _gets32 _gets64
_index32 _index64 _longname32 _longname64
_malloc32 _malloc64 _mbsrtowcs32 _mbsrtowcs64
_memccpy32 _memccpy64 _memchr32 _memchr64
_memcpy32 _memcpy64 _memmove32 _memmove64
_memset32 _memset64 _mktemp32 _mktemp64
_mmap32 _mmap64 _qsort32 _qsort64
_realloc32 _realloc64 _rindex32 _rindex64
_strcat32 _strcat64 _strchr32 _strchr64
_strcpy32 _strcpy64 _strdup32 _strdup64
_strncat32 _strncat64 _strncpy32 _strncpy64
_strpbrk32 _strpbrk64 _strptime32 _strptime64
_strrchr32 _strrchr64 _strsep32 _strsep64
_strstr32 _strstr64 _strtod32 _strtod64
_strtok32 _strtok64 _strtol32 _strtol64
_strtoll32 _strtoll64 _strtoq32 _strtoq64
_strtoul32 _strtoul64 _strtoull32 _strtoull64
_strtouq32 _strtouq64 _tmpnam32 _tmpnam64
_wcscat32 _wcscat64 _wcschr32 _wcschr64
_wcscpy32 _wcscpy64 _wcsncat32 _wcsncat64
_wcsncpy32 _wcsncpy64 _wcspbrk32 _wcspbrk64
_wcsrchr32 _wcsrchr64 _wcsrtombs32 _wcsrtombs64
_wcsstr32 _wcsstr64 _wcstok32 _wcstok64
_wcstol32 _wcstol64 _wcstoul32 _wcstoul64
_wcswcs32 _wcswcs64 _wmemchr32 _wmemchr64
_wmemcpy32 _wmemcpy64 _wmemmove32 _wmemmove64
_wmemset32 _wmemset64
615.5 – V7.2 and Higher
The following additional functions are available on OpenVMS VAX
and OpenVMS Alpha Version 7.2 and higher:
asctime_r ctime_r decc$set_child_standard_streams
decc$write_eof_to_mbx decc$validated lclose
dlerror dlopen dlsym
fcntl gmtime_r localtime_r
wchar
615.6 – V7.3 and Higher
The following additional functions are available on OpenVMS VAX
and OpenVMS Alpha Version 7.3 and higher:
fchown
link
utime
utimes
writev
615.7 – V7.3-1 and Higher
The following additional functions are available on OpenVMS Alpha
Version 7.3-1 and higher:
access fseeko
chmod ftello
chown ftw
fstat readdir_r
stat
vfscanf vfwscanf
vscanf vwscanf
vsscanf vswscanf
decc$feature_get_index
decc$feature_get_name
decc$feature_get_value
decc$feature_set_value
615.8 – V7.3-2 and Higher
The following additional functions are available on OpenVMS Alpha
Version 7.3-2 and higher:
a64l clock_getres clock_gettime clock_settime
endgrent getgrent getgrgid getgrgid_r
getgrnam getgrnam_r getpgid getpgrp
_getpwnam64 getpwnam_r _getpwnam_r64 _getpwent64
getpwuid _getpwuid64 getpwuid_r _getpwuid_r64
getsid l64a nanosleep poll
pread pwrite rand_r readv
_readv64 seteuid setgrent setpgid
setpgrp setregid setreuid setsid
sighold sigignore sigrelse sigtimedwait
sigwait sigwaitinfo snprintf ttyname_r
vsnprintf __writev64 decc$set_child_default_dir
615.9 – V8.2 and Higher
The following additional functions are available on OpenVMS Alpha
and Integrity servers Version 8.2 and higher:
clearerr_unlocked feof_unlocked
ferror_unlocked fgetc_unlocked
fputc_unlocked flockfile
ftrylockfile funlockfile
getc_unlocked getchar_unlocked
putc_unlocked putchar_unlocked
statvfs fstatvfs
_glob32 _glob64
_globfree32 _globfree64
socketpair
615.10 – V8.3 and Higher
The following additional functions are available on OpenVMS Alpha
and Integrity servers Version 8.3 and higher:
crypt fchmod
encrypt lstat
setkey readlink
lchown symlink
realpath unlink
615.11 – V8.4 and Higher
The following additional functions are available on OpenVMS Alpha
and Integrity servers Version 8.4 and higher:
ftok sem_init
semctl sem_open
semget sem_post
semop sem_timedwait
sem_close sem_trywait
sem_destroy sem_unlink
sem_getvalue sem_wait
616 – Prototypes Duplicated to Nonstandard Headers
The various standards dictate which header file must define
each of the standard functions. This is the included header file
documented with each function prototype in the Reference Section
of this manual.
However, many of the functions defined by the standards already
existed on several operating systems and were defined in
different header files. This is especially true on OpenVMS
systems with the header files <processes.h>, <unixio.h>, and
<unixlib.h>.
So, to provide upward compatibility for these functions, their
prototypes are duplicated in both the expected header file as
well as the header file defined by the standards.
Duplicated Prototypes lists these functions.
Table B-1 Duplicated Prototypes
Duplicated
Function in Standard says
access <unixio.h> <unistd.h>
alarm <signal.h> <unistd.h>
bcmp <string.h> <strings.h>
bcopy <string.h> <strings.h>
bzero <string.h> <strings.h>
chdir <unixio.h> <unistd.h>
chmod <unixio.h> <stat.h>
chown <unixio.h> <unistd.h>
close <unixio.h> <unistd.h>
creat <unixio.h> <fcntl.h>
ctermid <stdio.h> <unistd.h>
cuserid <stdio.h> <unistd.h>
dirname <string.h> <libgen.h>
dup <unixio.h> <unistd.h>
dup2 <unixio.h> <unistd.h>
ecvt <unixlib.h> <stdlib.h>
execl <processes.h> <unistd.h>
execle <processes.h> <unistd.h>
execlp <processes.h> <unistd.h>
execv <processes.h> <unistd.h>
execve <processes.h> <unistd.h>
execvp <processes.h> <unistd.h>
_exit <stdlib.h> <unistd.h>
fcvt <unixlib.h> <stdlib.h>
ffs <string.h> <strings.h>
fsync <stdio.h> <unistd.h>
ftime <time.h> <timeb.h>
gcvt <unixlib.h> <stdlib.h>
getcwd <unixlib.h> <unistd.h>
getegid <unixlib.h> <unistd.h>
getenv <unixlib.h> <stdlib.h>
geteuid <unixlib.h> <unistd.h>
getgid <unixlib.h> <unistd.h>
getopt <stdio.h> <unistd.h>
getpid <unixlib.h> <unistd.h>
getppid <unixlib.h> <unistd.h>
getuid <unixlib.h> <unistd.h>
index <string.h> <strings.h>
isatty <unixio.h> <unistd.h>
lseek <unixio.h> <unistd.h>
mkdir <unixlib.h> <stat.h>
mktemp <unixio.h> <stdlib.h>
nice <stdlib.h> <unistd.h>
open <unixio.h> <fcntl.h>
pause <signal.h> <unistd.h>
pipe <processes.h> <unistd.h>
read <unixio.h> <unistd.h>
rindex <string.h> <strings.h>
sbrk <stdlib.h> <unistd.h>
setgid <unixlib.h> <unistd.h>
setuid <unixlib.h> <unistd.h>
sleep <signal.h> <unistd.h>
strcasecmp <string.h> <strings.h>
strncasecmp <string.h> <strings.h>
system <processes.h> <stdlib.h>
times <time.h> <times.h>
umask <stdlib.h> <stat.h>
vfork <processes.h> <unistd.h>
wait <processes.h> <wait.h>
write <unixio.h> <unistd.h>