_snscanf_s, _snscanf_s_l, _snwscanf_s, _snwscanf_s_l
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_snscanf_s, _snscanf_s_l, _snwscanf_s, _snwscanf_s_l

Reads formatted data of a specified length from a string. These are versions of _snscanf, _snscanf_l, _snwscanf, _snwscanf_l with security enhancements as described in Security Enhancements in the CRT.

int __cdecl _snscanf_s(
   const char * input,
   size_t length,
   const char * format,
int __cdecl _snscanf_s_l(
   const char * input,
   size_t length,
   const char * format,
   locale_t locale,
int __cdecl _snwscanf_s(
   const wchar_t * input,
   size_t length,
   const wchar_t * format,
int __cdecl _snwscanf_s_l(
   const wchar_t * input,
   size_t length,
   const wchar_t * format,
   locale_t locale,


Input string to examine.


Number of characters to examine in input.


One or more format specifiers.

... (optional)

Variables that will be used to store the values extracted from the input string by the format specifiers in format.


The locale to use.

Both 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. For more information, see sscanf_s, _sscanf_s_l, swscanf_s, _swscanf_s_l.

If input 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.

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

This function is like sscanf_s except that it provides the ability to specify a fixed number of characters to examine from the input string. For more information, see sscanf_s, _sscanf_s_l, swscanf_s, _swscanf_s_l.

The buffer size parameter is required with the type field characters c, C, s, S, and [. For more information, see scanf Type Field Characters.


The size parameter is of type unsigned, not size_t.

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










Required header

_snscanf_s, _snscanf_s_l


_snwscanf_s, _snwscanf_s_l

<stdio.h> or <wchar.h>

For more compatibility information, see Compatibility in the Introduction.

// crt_snscanf_s.c
// This example scans a string of 
// numbers, using both the character
// and wide character secure versions
// of the snscanf function.

#include <stdio.h>

int main( )
    char        str1[] = "15 12 14...";
    wchar_t     str2[] = L"15 12 14...";
    char        s1[3];
    wchar_t     s2[3];
    int         i;
    float       fp;

    i = _snscanf_s( str1, 6,  "%s %f", s1, 3, &fp);
    printf_s("_snscanf_s converted %d fields: ", i);
    printf_s("%s and %f\n", s1, fp);

    i = _snwscanf_s( str2, 6,  L"%s %f", s2, 3, &fp);
    wprintf_s(L"_snwscanf_s converted %d fields: ", i);
    wprintf_s(L"%s and %f\n", s2, fp);
_snscanf_s converted 2 fields: 15 and 12.000000 _snwscanf_s converted 2 fields: 15 and 12.000000

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

© 2015 Microsoft