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_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