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strtok

Portability:

ISO/ANSI C conforming, UNIX compatible

SYNOPSIS

#include <string.h>

char *strtok(char *s1, const char *s2);

DESCRIPTION

strtok breaks the string pointed to by s1 into a sequence of tokens, each of which is delimited by a character from the string pointed to by s2 .

The tokens are created by a sequence of calls to strtok . In the first call in the sequence, s1 points to the string to be broken down. In subsequent calls in the sequence, s1 is NULL . The string pointed to by s2 may be different from call to call.

If s1 is not NULL (that is, the call is the first call in a sequence), then strtok searches the string pointed to by s1 for the first character that is not contained in the string pointed to by s2 . If such a character is found, then it is the start of the first token. If no such character is found, strtok returns NULL . Otherwise, the character that was found becomes the start of the first token.

After a token has been started, strtok searches for the first character contained in the string pointed to by s2 . If such a character is found, it is replaced by strtok with a null character, thereby terminating the token. If no such character is found, the token extends to the null character terminating the string pointed to by s1 . In either case, strtok returns the start of the token.

Subsequent calls to strtok behave as described in the previous paragraph, starting at the character following the null character terminating the previous token. However, if the previous token extended to the end of the string pointed to by s1 , strtok simply returns NULL .

RETURN VALUE

strtok returns a pointer to the start of a token, or NULL if there is no token.

CAUTION

The pointer that is saved by strtok is kept in an extern variable that is local to the calling load module. Therefore, in a multiload module program, a sequence of calls to strtok for a given string must be made from the same load module.

EXAMPLE

This example using strtok breaks out words separated by blanks or commas:

#include <string.h>
#include <stdio.h>
#include <stddef.h>

main()
{
   char test[] = "first,second,third,fourth";
   char* token;

   token = strtok(test, ", ");
   while(token != NULL){
      puts(token);

         /* Continue scan from where it left off. */
      token = strtok(NULL, ", ");
    }
}

RELATED FUNCTIONS

strchr , strcspn , strspn

SEE ALSO

• String Utility Functions

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Copyright © 2001 by SAS Institute Inc., Cary, NC, USA. All rights reserved.