fscanf-fscanf-l-fwscanf-fwscanf-l.md

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Learn more about: fscanf, _fscanf_l, fwscanf, _fwscanf_l	fscanf, _fscanf_l, fwscanf, _fwscanf_l	11/04/2016	fscanf _fwscanf_l _fscanf_l fwscanf	msvcrt.dll msvcr80.dll msvcr90.dll msvcr100.dll msvcr100_clr0400.dll msvcr110.dll msvcr110_clr0400.dll msvcr120.dll msvcr120_clr0400.dll ucrtbase.dll	DLLExport	apiref	fscanf fwscanf _ftscanf_l _fwscanf_l _ftscanf _fscanf_l	fscanf function fwscanf function formatted data [C++], reading from streams ftscanf_l function _ftscanf_l function _fwscanf_l function data [CRT], reading from streams _fscanf_l function ftscanf function fscanf_l function streams [C++], reading formatted data from _ftscanf function fwscanf_l function

fscanf, _fscanf_l, fwscanf, _fwscanf_l

Read formatted data from a stream. More secure versions of these functions are available; see fscanf_s, _fscanf_s_l, fwscanf_s, _fwscanf_s_l.

Syntax

int fscanf(
   FILE *stream,
   const char *format [,
   argument ]...
);
int _fscanf_l(
   FILE *stream,
   const char *format,
   _locale_t locale [,
   argument ]...
);
int fwscanf(
   FILE *stream,
   const wchar_t *format [,
   argument ]...
);
int _fwscanf_l(
   FILE *stream,
   const wchar_t *format,
   _locale_t locale [,
   argument ]...
);

Parameters

stream
Pointer to FILE structure.

format
Format-control string.

argument
Optional arguments.

locale
The locale to use.

Return value

Each of these functions returns the number of fields successfully converted and assigned; the return value doesn't include fields that were read but not assigned. A return value of 0 indicates that no fields were assigned. If an error occurs, or if the end of the file stream is reached before the first conversion, the return value is EOF for fscanf and fwscanf.

These functions validate their parameters. If stream or format is a NULL pointer, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, these functions return EOF and set errno to EINVAL.

Remarks

The fscanf function reads data from the current position of stream into the locations given by argument (if any). Each argument must be a pointer to a variable of a type that corresponds to a type specifier in format. format controls the interpretation of the input fields and has the same form and function as the format argument for scanf; see scanf for a description of format.

fwscanf is a wide-character version of fscanf; the format argument to fwscanf is a wide-character string. These functions behave identically if the stream is opened in ANSI mode. fscanf doesn't currently support input from 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 thread locale.

Generic-text routine mappings

TCHAR.H routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_ftscanf	fscanf	fscanf	fwscanf
_ftscanf_l	_fscanf_l	_fscanf_l	_fwscanf_l

For more information, see Format specification fields: scanf and wscanf functions.

Requirements

Function	Required header
fscanf, _fscanf_l	<stdio.h>
fwscanf, _fwscanf_l	<stdio.h> or <wchar.h>

For more compatibility information, see Compatibility.

Example

// crt_fscanf.c
// compile with: /W3
// This program writes formatted
// data to a file. It then uses fscanf to
// read the various data back from the file.

#include <stdio.h>

FILE *stream;

int main( void )
{
   long l;
   float fp;
   char s[81];
   char c;

   if( fopen_s( &stream, "fscanf.out", "w+" ) != 0 )
      printf( "The file fscanf.out was not opened\n" );
   else
   {
      fprintf( stream, "%s %ld %f%c", "a-string",
               65000, 3.14159, 'x' );
      // Security caution!
      // Beware loading data from a file without confirming its size,
      // as it may lead to a buffer overrun situation.

      // Set pointer to beginning of file:
      fseek( stream, 0L, SEEK_SET );

      // Read data back from file:
      fscanf( stream, "%s", s );   // C4996
      fscanf( stream, "%ld", &l ); // C4996

      fscanf( stream, "%f", &fp ); // C4996
      fscanf( stream, "%c", &c );  // C4996
      // Note: fscanf is deprecated; consider using fscanf_s instead

      // Output data read:
      printf( "%s\n", s );
      printf( "%ld\n", l );
      printf( "%f\n", fp );
      printf( "%c\n", c );

      fclose( stream );
   }
}

a-string
65000
3.141590
x

See also

Stream I/O
_cscanf, _cscanf_l, _cwscanf, _cwscanf_l
fprintf, _fprintf_l, fwprintf, _fwprintf_l
scanf, _scanf_l, wscanf, _wscanf_l
sscanf, _sscanf_l, swscanf, _swscanf_l
fscanf_s, _fscanf_s_l, fwscanf_s, _fwscanf_s_l