_fprintf_p, _fprintf_p_l, _fwprintf_p, _fwprintf_p_l
Collapse the table of content
Expand the table of content
Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here. ArchiveDisclaimer

_fprintf_p, _fprintf_p_l, _fwprintf_p, _fwprintf_p_l

Prints formatted data to a stream.

int _fprintf_p( 
   FILE *stream,
   const char *format [,
   argument ]...
int _fprintf_p_l( 
   FILE *stream,
   const char *format,
   locale_t locale [,
   argument ]...
int _fwprintf_p( 
   FILE *stream,
   const wchar_t *format [,
   argument ]...
int _fwprintf_p_l( 
   FILE *stream,
   const wchar_t *format,
   locale_t locale [,
   argument ]...


Pointer to the FILE structure.


Format-control string.


Optional arguments.


The locale to use.

_fprintf_p and _fwprintf_p return the number of characters written or return a negative value when an output error occurs.

_fprintf_p formats and prints a series of characters and values to the output stream. Each function argument (if any) is converted and output according to the corresponding format specification in format. For _fprintf_p, the format argument has the same syntax and use that it has in _printf_p. These functions support positional parameters, meaning that the order of the parameters used by the format string can be changed. For more information about positional parameters, see printf_p Positional Parameters.

_fwprintf_p is a wide-character version of _fprintf_p; in _fwprintf_p, format is a wide-character string. These functions behave identically if the stream is opened in ANSI mode. _fprintf_p doesn't currently support output into a UNICODE stream.

The versions of these functions with the _l suffix are identical except that they use the locale parameter passed in instead of the current locale.

Security noteSecurity Note:

Ensure that format is not a user-defined string.

Like the non-secure versions (see fprintf, _fprintf_l, fwprintf, _fwprintf_l), these functions validate their parameters and invoke the invalid parameter handler, as described in Parameter Validation, if either stream or format is a null pointer or if there are any unknown or badly formed formatting specifiers. If execution is allowed to continue, the functions return -1 and set errno to EINVAL.

Generic-Text Routine Mappings

Tchar.h routine

_UNICODE and _MBCS not defined

_MBCS defined

_UNICODE defined









For more information, see Format Specifications.


Required header

_fprintf_p, _fprintf_p_l


_fwprintf_p, _fwprintf_p_l

<stdio.h> or <wchar.h>

For more compatibility information, see Compatibility in the Introduction.

// crt_fprintf_p.c
// This program uses _fprintf_p to format various
// data and print it to the file named FPRINTF_P.OUT. It
// then displays FPRINTF_P.OUT on the screen using the system
// function to invoke the operating-system TYPE command.

#include <stdio.h>
#include <process.h>

int main( void )
    FILE    *stream = NULL;
    int     i = 10;
    double  fp = 1.5;
    char    s[] = "this is a string";
    char    c = '\n';

    // Open the file
    if ( fopen_s( &stream, "fprintf_p.out", "w" ) == 0)
        // Format and print data
        _fprintf_p( stream, "%2$s%1$c", c, s );
        _fprintf_p( stream, "%d\n", i );
        _fprintf_p( stream, "%f\n", fp );

        // Close the file
        fclose( stream );

    // Verify our data
    system( "type fprintf_p.out" );
this is a string 10 1.500000
© 2015 Microsoft