Share via

_strset_s, _strset_s_l, _wcsset_s, _wcsset_s_l, _mbsset_s, _mbsset_s_l

Sets characters of a string to a character. These versions of _strset, _strset_l, _wcsset, _wcsset_l, _mbsset, _mbsset_l have security enhancements, as described in Security features in the CRT.


_mbsset_s and _mbsset_s_l cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported in Universal Windows Platform apps.


errno_t _strset_s(
   char *str,
   size_t numberOfElements,
   int c
errno_t _strset_s_l(
   char *str,
   size_t numberOfElements,
   int c,
   _locale_t locale
errno_t _wcsset_s(
   wchar_t *str,
   size_t numberOfElements,
   wchar_t c
errno_t *_wcsset_s_l(
   wchar_t *str,
   size_t numberOfElements,
   wchar_t c,
   _locale_t locale
errno_t _mbsset_s(
   unsigned char *str,
   size_t numberOfElements,
   unsigned int c
errno_t _mbsset_s_l(
   unsigned char *str,
   size_t numberOfElements,
   unsigned int c,
   _locale_t locale


Null-terminated string to be set.

The size of the str buffer.

Character setting.

Locale to use.

Return value

Zero if successful, otherwise an error code.

These functions validate their arguments. If str is a null pointer, or the numberOfElements argument is less than or equal to 0, or the block passed in isn't null-terminated, then the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, these functions return EINVAL and set errno to EINVAL.


The _strset_s function sets all the characters of str to c (converted to char), except the terminating null character. _wcsset_s and _mbsset_s are wide-character and multibyte-character versions of _strset_s. The data types of the arguments and return values vary accordingly. These functions behave identically otherwise.

The output value is affected by the setting of the LC_CTYPE category setting of the locale. For more information, see setlocale. The versions of these functions without the _l suffix use the current locale for this locale-dependent behavior; the versions with the _l suffix are identical except that they use the locale parameter passed in instead. For more information, see Locale.

The debug library versions of these functions first fill the buffer with 0xFE. To disable this behavior, use _CrtSetDebugFillThreshold.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Generic-text routine mappings

TCHAR.H routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_tcsset_s _strset_s _mbsset_s _wcsset_s
_tcsset_s_l _strset_s_l _mbsset_s_l _wcsset_s_l


Routine Required header
_strset_s <string.h>
_strset_s_l <tchar.h>
_wcsset_s <string.h> or <wchar.h>
_wcsset_s_l <tchar.h>
_mbsset_s, _mbsset_s_l <mbstring.h>

For more compatibility information, see Compatibility.


// crt_strset_s.c
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

int main( void )
   char string[] = "Fill the string with something.";
   printf( "Before: %s\n", string );
   _strset_s( string, _countof(string), '*' );
   printf( "After:  %s\n", string );
Before: Fill the string with something.
After:  *******************************

See also

String manipulation
Interpretation of multibyte-character sequences
_mbsnbset, _mbsnbset_l
memset, wmemset
strcat, wcscat, _mbscat
strcmp, wcscmp, _mbscmp
strcpy, wcscpy, _mbscpy
_strnset, _strnset_l, _wcsnset, _wcsnset_l, _mbsnset, _mbsnset_l