Copyright Digital Equipment Corp. All rights reserved.
Examples
1.$ LIST == "DIRECTORY"
The assignment statement in this example assigns the user-
defined synonym LIST as a global symbol definition for the DCL
command DIRECTORY.
2.$ COUNT = 0
$ LOOP:
$ COUNT = COUNT + 1
$ IF P'COUNT' .EQS. "" THEN EXIT
$ APPEND/NEW &P'COUNT' SAVE.ALL
$ DELETE &P'COUNT';*
$ IF COUNT .LT. 8 THEN GOTO LOOP
$ EXIT
This command procedure, COPYDEL.COM, appends files (specified
as parameters) to a file called SAVE.ALL. After a file has been
appended, the command procedure deletes the file. Up to eight
file names can be passed to the command procedure. The file
names are assigned to the symbols P1, P2, and so on.
The command procedure uses a counter to refer to parameters
that are passed to it. Each time through the loop, the
procedure uses an IF command to check whether the value of
the current parameter is a null string. When the IF command is
scanned, the current value of the symbol COUNT is concatenated
with the letter P. The first time through the loop, the IF
command tests P1; the second time through the loop it tests
P2, and so on. After the expression P`COUNT' is evaluated, the
substitution of the file names that correspond to P1, P2, and
so on is automatic within the context of the IF command.
The APPEND and DELETE commands do not perform any substitution
automatically, because they expect and require file
specifications as input parameters. The ampersand (&) precedes
the P`COUNT' expression for these commands to force the
appropriate symbol substitution. When these commands are
initially scanned each time through the loop, COUNT is
substituted with its current value. Then, when the commands
execute, the ampersand causes another substitution: the first
file specification is substituted for P1, the second file
specification is substituted for P2, and so on.
To invoke this procedure, use the following command:
$ @COPYDEL ALAMO.TXT BEST.DOC
The files ALAMO.TXT and BEST.DOC are each appended to the file
SAVE.ALL and are then deleted.
3.$ A = 25
$ CODE = 4 + F$INTEGER("6") - A
$ SHOW SYMBOL CODE
CODE = -15 HEX = FFFFFFF1 Octal = 1777761
This example contains two assignment statements. The first
assignment statement assigns the value 25 to the symbol A. The
second assignment statement evaluates an expression containing
an integer (4), a lexical function (F$INTEGER("6")), and the
symbol A. The result of the expression, -15, is assigned to the
symbol CODE.
4.$ FILENAME = "JOBSEARCH" - "JOB"
$ FILETYPE = ".OBJ"
$ FILESPEC = FILENAME + FILETYPE
$ TYPE 'FILESPEC'
The first command in this example assigns the symbol FILENAME
the value "SEARCH". Notice that the string "SEARCH" is the
result of the string reduction operation performed by the
expression. The second command assigns the symbol FILETYPE
the character string ".OBJ".
The symbols FILENAME and FILETYPE are then added together in an
expression assigned to the symbol FILESPEC. Because the values
of the symbols FILENAME and FILETYPE are concatenated, the
resultant value assigned to FILESPEC is the character string
"SEARCH.OBJ". The symbol FILESPEC is then used as a parameter
for the TYPE command. The single quotation marks (` ') request
the command interpreter to replace the symbol FILESPEC with its
value SEARCH.OBJ. Thus, the TYPE command types the file named
SEARCH.OBJ.
5.$ BELL[0,32] = %X07
$ SHOW SYMBOL BELL
BELL = ""
In this example, the symbol BELL is created with an arithmetic
overlay assignment statement. Because the symbol BELL is
previously undefined, the hexadecimal value 7 is inserted
over a null character string and is interpreted as the ASCII
code for the bell character on a terminal. When you issue the
command SHOW SYMBOL BELL, the terminal beeps.
If the symbol BELL had been previously defined with an integer
value, the result of displaying BELL would have been to show
its new integer value.
6.$ $=34
%DCL-W-NOCOMD, no command on line - reenter with alphabetic first
character
$ $$=34
$ SHOW SYMBOL $$
%DCL-W-UNDSYM, undefined symbol - check validity and spelling
$ SHOW SYMBOL $
$ = 34 Hex = 00000022 Octal = 00000000042
If you begin a symbol name with the dollar sign ($), use two
dollar signs ($$) because DCL discards the first instance of
the dollar sign.
7.$ COUNT = 0
$ LOOP:
$ COUNT = COUNT + 1
$ IF P'COUNT' .EQS. "" THEN EXIT
$ APPEND/NEW &P'COUNT' SAVE.ALL
$ DELETE &P'COUNT';*
$ IF COUNT .LT. 16 THEN GOTO LOOP
$ EXIT
This command procedure, COPYDEL.COM, appends files (specified
as parameters) to a file called SAVE.ALL. After a file has been
appended, the command procedure deletes the file. Up to sixteen
file names can be passed to the command procedure. The file
names are assigned to the symbols P1, P2, and so on. This is
applicable only when you set bit 3 of DCL_CTLFLAGS to 1.
The command procedure uses a counter to refer to parameters
that are passed to it. Each time through the loop, the
procedure uses an IF command to check whether the value of
the current parameter is a null string. When the IF command is
scanned, the current value of the symbol COUNT is concatenated
with the letter P. The first time through the loop, the IF
command tests P1; the second time through the loop it tests
P2, and so on. After the expression PCOUNT is evaluated, the
substitution of the file names that correspond to P1, P2, and
so on is automatic within the context of the IF command.
The APPEND and DELETE commands do not perform any substitution
automatically, because they expect and require file
specifications as input parameters. The ampersand (&) precedes
the P`COUNT' expression for these commands to force the
appropriate symbol substitution. When these commands are
initially scanned each time through the loop, COUNT is
substituted with its current value. Then, when the commands
execute, the ampersand causes another substitution: the first
file specification is substituted for P1, the second file
specification is substituted for P2, and so on.
To invoke this procedure, use the following command:
$ @COPYDEL ALAMO.TXT BEST.DOC
The files ALAMO.TXT and BEST.DOC are each appended to the file
SAVE.ALL and are then deleted.