sscanf, _sscanf_l, swscanf, _swscanf_l

Article
06/05/2017

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Read formatted data from a string. More secure versions of these functions are available; see sscanf_s, _sscanf_s_l, swscanf_s, _swscanf_s_l.

Syntax

int sscanf(  
   const char *buffer,  
   const char *format [,  
   argument ] ...   
);  
int _sscanf_l(  
   const char *buffer,  
   const char *format,  
   locale_t locale [,  
   argument ] ...   
);  
int swscanf(  
   const wchar_t *buffer,  
   const wchar_t *format [,  
   argument ] ...   
);  
int _swscanf_l(  
   const wchar_t *buffer,  
   const wchar_t *format,  
   locale_t locale [,  
   argument ] ...   
);

Parameters

buffer
Stored data

format
Format-control string. For more information, see Format Specifications.

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 does not include fields that were read but not assigned. A return value of 0 indicates that no fields were assigned. The return value is EOF for an error or if the end of the string is reached before the first conversion.

If buffer 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 -1 and set errno to EINVAL.

For information on these and other error codes, see _doserrno, errno, _sys_errlist, and _sys_nerr.

Remarks

The sscanf function reads data from buffer into the location given by each argument. Every argument must be a pointer to a variable with a type that corresponds to a type specifier in format. The format argument controls the interpretation of the input fields and has the same form and function as the format argument for the scanf function. If copying takes place between strings that overlap, the behavior is undefined.

Important

When reading a string with sscanf, always specify a width for the %s format (for example, "%32s" instead of "%s"); otherwise, improperly formatted input can easily cause a buffer overrun.

swscanf is a wide-character version of sscanf; the arguments to swscanf are wide-character strings. sscanfdoes not handle multibyte hexadecimal characters. swscanf does not handle Unicode full-width hexadecimal or "compatibility zone" characters. Otherwise, swscanf and sscanf behave identically.

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 & _MBCS not defined	_MBCS defined	_UNICODE defined
`_stscanf`	`sscanf`	`sscanf`	`swscanf`
`_stscanf_l`	`_sscanf_l`	`_sscanf_l`	`_swscanf_l`

Requirements

Routine	Required header
`sscanf`, `_sscanf_l`	<stdio.h>
`swscanf`, `_swscanf_l`	<stdio.h> or <wchar.h>

For additional compatibility information, see Compatibility in the Introduction.

Example

// crt_sscanf.c  
// compile with: /W3  
// This program uses sscanf to read data items  
// from a string named tokenstring, then displays them.  
  
#include <stdio.h>  
  
int main( void )  
{  
   char  tokenstring[] = "15 12 14...";  
   char  s[81];  
   char  c;  
   int   i;  
   float fp;  
  
   // Input various data from tokenstring:  
   // max 80 character string:  
   sscanf( tokenstring, "%80s", s ); // C4996  
   sscanf( tokenstring, "%c", &c );  // C4996  
   sscanf( tokenstring, "%d", &i );  // C4996  
   sscanf( tokenstring, "%f", &fp ); // C4996  
   // Note: sscanf is deprecated; consider using sscanf_s instead  
  
   // Output the data read  
   printf( "String    = %s\n", s );  
   printf( "Character = %c\n", c );  
   printf( "Integer:  = %d\n", i );  
   printf( "Real:     = %f\n", fp );  
}

String    = 15  
Character = 1  
Integer:  = 15  
Real:     = 15.000000

.NET Framework Equivalent

See Parse methods, such as System::Double::Parse.