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);
    /∗ print out remainder of message ∗/
    (void) vfprintf(stderr, format, ap);
    va_end(ap);
    (void) abort;
}

SEE ALSO

vprintf(3W), printf(3S), stdarg(5). 

DIAGNOSTICS

vprintf and vfprintf return the number of characters transmitted, or return −1 if an error was encountered. 

  —  C Development Set