Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here. ArchiveDisclaimer


Sets the first n bytes of a multibyte character string to a specified character.

unsigned char *_mbsnbset(
   unsigned char *string,
   unsigned int c,
   size_t count 


String to be altered.
Single-byte or multibyte character setting.
Number of bytes to be set.

Return Value

_mbsnbset returns a pointer to the altered string.


The _mbsnbset function sets, at most, the first count bytes of string to c. If count is greater than the length of string, the length of string is used instead of count. If c is a multibyte character and cannot be set entirely into the last byte specified by count, then the last byte will be padded with a blank character. _mbsnbset does not place a terminating null at the end of string.

_mbsnbset is similar to _mbsnset, except that it sets count bytes rather than count characters of c.

Security Note    This API incurs a potential threat brought about by a buffer overrun problem. Buffer overrun problems are a frequent method of system attack, resulting in an unwarranted elevation of privilege. For more information, see Avoiding Buffer Overruns.

Generic-Text Routine Mappings

TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined
_tcsnset _strnset _mbsnbset _wcsnset


Routine Required header Compatibility
_mbsnbset <mbstring.h> Win 98, Win Me, Win NT, Win 2000, Win XP

For additional compatibility information, see Compatibility in the Introduction.


All versions of the C run-time libraries.


// crt_mbsnbset.c

#include <mbstring.h>
#include <stdio.h>

int main( void )
   char string[15] = "This is a test";
   /* Set not more than 4 bytes of string to be *'s */
   printf( "Before: %s\n", string );
   _mbsnbset( string, '*', 4 );
   printf( "After:  %s\n", string );


Before: This is a test
After:  **** is a test

See Also

String Manipulation Routines | _mbsnbcat | _mbsnset | _mbsset | Run-Time Routines and .NET Framework Equivalents

© 2015 Microsoft