vpfmt(3C)     11 Mar 1992 (C Programming Language Utilities)      vpfmt(3C)

NAME
     vpfmt - display error message in standard format and pass to logging
     and monitoring services

SYNOPSIS
     #include <stdarg.h>
     #include <pfmt.h>

     int vpfmt(FILE *stream, long flags, char *format, valist ap);

DESCRIPTION
     vpfmt() is the same as pfmt() except that instead of being called with
     a variable number of arguments, it is called with an argument list as
     defined by the <stdarg.h> header file.

     The <stdarg.h> header file defines the type va_list and a set of mac-
     ros for advancing through a list of arguments whose number and types
     may vary. The argument ap to vpfmt() is of type va_list. This argument
     is used with the <stdarg.h> header file macros va_start(), va_arg()
     and va_end() [see va_start(), va_arg(), and va_end() in stdarg(5)].
     The EXAMPLE section below shows their use with vpfmt().

     The macro va_alist is used as the parameter list in a function defini-
     tion as in the function called error() in the example below. The macro
     va_start(ap, ), where ap is of type va_list, must be called before any
     attempt to traverse and access unnamed arguments. Calls to va_arg(ap,
     atype) traverse the argument list. Each execution of va_arg() expands
     to an expression with the value and type of the next argument in the
     list ap, which is the same object initialized by va_start. The argu-
     ment atype is the type that the returned argument is expected to be.
     The va_end(ap) macro should be invoked when all desired arguments have
     been accessed. (The argument list in ap can be traversed again if
     va_start() is called again after va_end().) In the example below,
     va_arg() is executed first to retrieve the format string passed to
     error(). The remaining error() arguments, arg1, arg2, ..., are given
     to vpfmt() in the argument ap.

RETURN VALUE
     Upon success, vpfmt() returns the number of bytes transmitted. Upon
     failure, it returns a negative value:

     -1   write error to stream.

EXAMPLE
     The following demonstrates how vpfmt() could be used to write an
     error() routine:

          #include <pfmt.h>
          #include <stdarg.h>

          /*
           *   error should be called like



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vpfmt(3C)     11 Mar 1992 (C Programming Language Utilities)      vpfmt(3C)

           *         error(format, arg1, ...);
           */

          void error(char *format, ...)
          {
              va_list ap;
              va_start(ap, format);
              (void) vpfmt(stderr, MM_ERROR, format, ap);
              va_end(ap);
              (void) abort();
          }

SEE ALSO
     pfmt(3C), vlfmt(3C), stdarg(5).








































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