Formats and sends data to a stream.

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

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

#include <wchar.h>
#include <stdarg.h>

int vfwprintf(FILE *stream, const char *format, va_list ap);
int vfwprintf_s(FILE *stream, const char *format, va_list ap);

Parameters

stream

Pointer to FILE structure indicating the output stream.

format

Formatted string. This parameter has the same form and function as in printf.

ap

Pointer to list of arguments. This parameter has type va_list and points to a list of arguments that are converted and output according to the corresponding format specifications in format.

Remarks

These functions are similar to their counterparts fprintf and fwprintf, but each accepts a pointer to a variable-argument list instead of additional arguments.

vfwprintf is a wide-character version of vfprintf; format is a wide-character string. vfwprintf and vfprintf behave identically if the stream is opened in ANSI mode. vprintf does not currently support output into a UNICODE stream.

vfprintf_s and vfwprintf_s perform parameter validation. If format is NULL then the function returns -1 and errno is set to EINVAL.

Return Values

The number of characters written, not counting the terminating null character.

Success.

A negative value if an output error occurs.

Failure.

Generic Text Routines

Requirements