Manual pages › Standard input and output (3S)

vprintf(3S)

print formatted output of a variable argument list

From the original Amiga UNIX 2.1 manual. Some things it mentions may not be in this release.

NAME

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

SYNOPSIS

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

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

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

DESCRIPTION

vprintf, vfprintf and vsprintf are the same as printf, fprintf, and sprintf respectively, except that instead of being called with a variable number of arguments, they are 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 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)]. The EXAMPLE section below shows their use with vprintf.

EXAMPLE

The following demonstrates how vfprintf could be used to write an error routine:

#include <stdio.h>
#include <stdarg.h>
/*
 *   error should be called like
 *         error(function_name, format, arg1, ...);
 */
void error(char *function_name, char *format, ...)
{
    va_list ap;

    va_start(ap, format);
    /* print out name of function causing error */
    (void) fprintf(stderr, "ERR in %s: ", function_name);
    va_arg(ap, char*);
    /* print out remainder of message */
    (void) vfprintf(stderr, format, ap);
    va_end(ap);
    (void) abort;
}

DIAGNOSTICS