Header File 

stdio.h  

Category 

Input/output Routines 

Prototype 

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

int vfwprintf(FILE *stream, const wchar_t *format, va_list arglist); 

Description 

Writes formatted output to a stream. 

The v...printf functions are known as alternate entry points for the ...printf functions. They behave exactly like their ...printf counterparts, but they accept a pointer to a list of arguments instead of an argument list. 

For details on format specifiers, see Printf Format Specifiers.  

vfprintf accepts a pointer to a series of arguments, applies to each argument a format specifier contained in the format string pointed to by format, and outputs the formatted data to a stream. There must be the same number of format specifiers as arguments. 

Return Value 

On success, vfprintf returns the number of bytes output. 

On error, it returns EOF. 

Example  

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
FILE *fp;
int vfpf(char *fmt, ...)
{
   va_list argptr;
   int cnt;
   va_start(argptr, fmt);
   cnt = vfprintf(fp, fmt, argptr);
   va_end(argptr);
   return(cnt);
}
int main(void)
{
   int inumber = 30;
   float fnumber = 90.0;
   char string[4] = "abc";
   fp = tmpfile();
   if (fp == NULL)
   {
      perror("tmpfile() call");
      exit(1);
   }
   vfpf("%d %f %s", inumber, fnumber, string);
   rewind(fp);
   fscanf(fp,"%d %f %s", &inumber, &fnumber, string);
   printf("%d %f %s\n", inumber, fnumber, string);
   fclose(fp);
   return 0;
}

Portability