Reads formatted input based on an argument list.

    Format

      #include  <stdio.h>

      int vfscanf  (FILE *file_ptr, const char *format, va_list ap);

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.

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.

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.