strtok_s, _strtok_s_l, wcstok_s, _wcstok_s_l, _mbstok_s, _mbstok_s_l

Article
07/22/2011

Find the next token in a string, using the current locale or a locale passed in. These are versions of strtok, _strtok_l, wcstok, _wcstok_l, _mbstok, _mbstok_l with security enhancements as described in Security Features in the CRT.

char *strtok_s(
   char *strToken,
   const char *strDelimit,
   char **context
);
char *_strtok_s_l(
   char *strToken,
   const char *strDelimit,
   char **context,
   _locale_t locale
);
wchar_t *wcstok_s(
   wchar_t *strToken,
   const wchar_t *strDelimit, 
   wchar_t **context
);
wchar_t *_wcstok_s_l(
   wchar_t *strToken,
   const wchar_t *strDelimit, 
   wchar_t **context,
   _locale_t locale
);
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,
   _locale_t locale
);

Parameters

strToken
String containing token or tokens.
strDelimit
Set of delimiter characters.
context
Used to store position information between calls to strtok_s
locale
Locale to use.

Return Value

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

strToken	strDelimit	context	Return value	errno
NULL	any	pointer to a null pointer	NULL	EINVAL
any	NULL	any	NULL	EINVAL
any	any	NULL	NULL	EINVAL

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

Remarks

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
_tcstok_s	strtok_s	_mbstok_s	wcstok_s
_tcstok_s_l	_strtok_s_l	_mbstok_s_l	_wcstok_s_l

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.

Requirements

Routine	Required header
strtok_s	<string.h>
_strtok_s_l	<string.h>
wcstok_s, _wcstok_s_l	<string.h> or <wchar.h>
_mbstok_s, _mbstok_s_l	<mbstring.h>

For additional compatibility information, see Compatibility in the Introduction.

Example

// 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);
        }
    }
}

Tokens:
 A
        Another
 string
        string
 of
        parsed
 tokens
        at
 and
        the
 some
        same
 more
        time.
 tokens

.NET Framework Equivalent

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

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