strtok_s, _strtok_s_l, wcstok_s, _wcstok_s_l, _mbstok_s, _mbstok_s_l


For the latest documentation on Visual Studio 2017 RC, see Visual Studio 2017 RC Documentation.

Finds the next token in a string, by using the current locale or a locale that's passed in. These versions of strtok, _strtok_l, wcstok, _wcstok_l, _mbstok, _mbstok_l have security enhancements, as described in Security Features in the CRT.

System_CAPS_ICON_important.jpg Important

_mbstok_s and _mbstok_s_l cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported with /ZW.

      char *strtok_s(  
char *strToken,  
const char *strDelimit,  
   char **context  
char *_strtok_s_l(  
char *strToken,  
const char *strDelimit,  
   char **context,  
wchar_t *wcstok_s(  
wchar_t *strToken,  
const wchar_t *strDelimit,   
wchar_t *_wcstok_s_l(  
wchar_t *strToken,  
const wchar_t *strDelimit,   
unsigned char *_mbstok_s(  
unsigned char*strToken,  
const unsigned char *strDelimit,   
   char **context  
unsigned char *_mbstok_s(  
unsigned char*strToken,  
const unsigned char *strDelimit,   
   char **context,  


String containing token or tokens.

Set of delimiter characters.

Used to store position information between calls to strtok_s

Locale to use.

Returns a pointer to the next token found in strToken. They return NULL when no more tokens are found. Each call modifies strToken by substituting a NULL character for the first delimiter that occurs after the returned token.

Error Conditions

strTokenstrDelimitcontextReturn valueerrno
NULLanypointer to a null pointerNULLEINVAL

If strToken is NULL but context is a pointer to a valid context pointer, there is no error.

The strtok_s function finds the next token in strToken. The set of characters in strDelimit specifies possible delimiters of the token to be found in strToken on the current call. wcstok_s and _mbstok_sare wide-character and multibyte-character versions of strtok_s. The arguments and return values of wcstok_s and _wcstok_s_l are wide-character strings; those of _mbstok_s and _mbstok_s_l are multibyte-character strings. These three functions behave identically otherwise.

This function validates its parameters. If an error condition occurs, as in the Error Conditions table, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, these functions set errno to EINVAL and return NULL.

Generic-Text Routine Mappings

TCHAR.H routine_UNICODE & _MBCS not defined_MBCS defined_UNICODE defined

On the first call to strtok_s the function skips leading delimiters and returns a pointer to the first token in strToken, terminating the token with a null character. More tokens can be broken out of the remainder of strToken by a series of calls to strtok_s. Each call to strtok_s modifies strToken by inserting a null character after the token returned by that call. The context pointer keeps track of which string is being read and where in the string the next token is to be read. To read the next token from strToken, call strtok_s with a NULL value for the strToken argument, and pass the same context parameter. The NULL strToken argument causes strtok_s to search for the next token in the modified strToken. The strDelimit argument can take any value from one call to the next so that the set of delimiters may vary.

Since the context parameter supersedes the static buffers used in strtok and _strtok_l, it is possible to parse two strings simultaneously in the same thread.

The output value is affected by the setting of the LC_CTYPE category setting of the locale; see setlocale for more information. 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.

RoutineRequired header

<string.h> or <wchar.h>


For additional compatibility information, see Compatibility.

// crt_strtok_s.c  
// In this program, a loop uses strtok_s  
// to print all the tokens (separated by commas  
// or blanks) in two strings at the same time.  
#include <string.h>  
#include <stdio.h>  
char string1[] =  
    "A string\tof ,,tokens\nand some  more tokens";  
char string2[] =  
    "Another string\n\tparsed at the same time.";  
char seps[]   = " ,\t\n";  
char *token1 = NULL;  
char *token2 = NULL;  
char *next_token1 = NULL;  
char *next_token2 = NULL;  
int main( void )  
    printf( "Tokens:\n" );  
    // Establish string and get the first token:  
    token1 = strtok_s( string1, seps, &next_token1);  
    token2 = strtok_s ( string2, seps, &next_token2);  
    // While there are tokens in "string1" or "string2"  
    while ((token1 != NULL) || (token2 != NULL))  
        // Get next token:  
        if (token1 != NULL)  
            printf( " %s\n", token1 );  
            token1 = strtok_s( NULL, seps, &next_token1);  
        if (token2 != NULL)  
            printf("        %s\n", token2 );  
            token2 = strtok_s (NULL, seps, &next_token2);  


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

String Manipulation
Interpretation of Multibyte-Character Sequences
strcspn, wcscspn, _mbscspn, _mbscspn_l
strspn, wcsspn, _mbsspn, _mbsspn_l