vprintf(3S)

NAME
     vprintf, vfprintf, vsnprintf, vsprintf - print formatted output of a
     variable argument list

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

     int vprintf (const char *format, va_list arg);

     int vfprintf (FILE *stream, const char *format, va_list arg);

     int vsnprintf (char *s, size_t len, const char *format, va_list arg);

     int vsprintf (char *s, const char *format, va_list arg);

DESCRIPTION
     vprintf, vfprintf, vsnprintf, and vsprintf are the same as printf,
     fprintf, snprintf, and sprintf respectively, except that instead of being
     called with a variable number of arguments, they are called with an
     argument list, arg, as defined by stdarg(5).  The arg parameter must be
     initialized by the va_start macro (and possibly subsequent va_arg calls).
     The vprintf, vfprintf, vsnprintf, and vsprintf functions do not invoke
     the va_end macro.

EXAMPLE
     The following demonstrates the use of vfprintf to write an error routine.

     The stdarg.h header file defines the type va_list and a set of macros for
     advancing through a list of arguments whose number and types may vary.
     The argument ap to the vprint family of routines 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)].

     #include <stdio.h>
     #include <stdarg.h>

     /*
      *   error should be called as:
      *   error(function_name, format, arg1, arg2 ...);
      */
     void
     error(char *function_name, char *format, ...)
     {
          va_list args;

          va_start(args, format);
          /* print out name of function causing error */
          fprintf(stderr, "ERROR in %s: ", function_name);
          /* print out remainder of message */
          vfprintf(stderr, format, args);
          va_end(args);
     }

SEE ALSO
     printf(3S), stdarg(5).

DIAGNOSTICS
     vprintf, vfprintf, vsnprintf, and vsprintf return the number of
     characters transmitted, or return -1 if an error was encountered.