strtok(3) - NetBSD Manual Pages

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STRTOK(3)               NetBSD Library Functions Manual              STRTOK(3)


NAME

     strtok, strtok_r -- string tokens


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <string.h>

     char *
     strtok(char * restrict str, const char * restrict sep);

     char *
     strtok_r(char * restrict str, const char * restrict sep,
         char ** restrict lasts);


DESCRIPTION

     The strtok() function is used to isolate sequential tokens in a nul-ter-
     minated string, str.  These tokens are separated in the string by at
     least one of the characters in sep.  The first time that strtok() is
     called, str should be specified; subsequent calls, wishing to obtain fur-
     ther tokens from the same string, should pass a null pointer instead.
     The separator string, sep, must be supplied each time, and may change
     between calls.

     The strtok() function returns a pointer to the beginning of each subse-
     quent token in the string, after replacing the separator character itself
     with a NUL character.  Separator characters at the beginning of the
     string or at the continuation point are skipped so that zero length
     tokens are not returned.  When no more tokens remain, a null pointer is
     returned.

     The strtok_r() function implements the functionality of strtok() but is
     passed an additional argument, lasts, which points to a user-provided
     pointer which is used by strtok_r() to store state which needs to be kept
     between calls to scan the same string; unlike strtok(), it is not neces-
     sary to limit tokenizing to a single string at a time when using
     strtok_r().


EXAMPLES

     The following will construct an array of pointers to each individual word
     in the string s:

           #define MAXTOKENS       128

           char s[512], *p, *tokens[MAXTOKENS+1];
           char *last;
           int i = 0;

           snprintf(s, sizeof(s), "cat dog horse cow");

           for ((p = strtok_r(s, " ", &last));
               (p != NULL && i < MAXTOKENS);
               (p = strtok_r(NULL, " ", &last)), i++) {
                   tokens[i] = p;
           }
           tokens[i] = NULL;

     That is, tokens[0] will point to "cat", tokens[1] will point to "dog",
     tokens[2] will point to "horse", and tokens[3] will point to "cow".

     If the pointer variable p is not NULL when the loop terminates, there
     were more than MAXTOKENS words in the input string.


SEE ALSO

     index(3), memchr(3), rindex(3), strchr(3), strcspn(3), strpbrk(3),
     strrchr(3), strsep(3), strspn(3), strstr(3)


STANDARDS

     The strtok() function conforms to ANSI X3.159-1989 (``ANSI C89'').  The
     strtok_r() function conforms to IEEE Std 1003.1c-1995 (``POSIX.1'').  The
     restrict keyword was added in ISO/IEC 9899:1999 (``ISO C99'') and IEEE
     Std 1003.1-2001 (``POSIX.1'').


BUGS

     The System V strtok(), if handed a string containing only delimiter char-
     acters, will not alter the next starting point, so that a call to
     strtok() with a different (or empty) delimiter string may return a
     non-NULL value.  Since this implementation always alters the next start-
     ing point, such a sequence of calls would always return NULL.

NetBSD 11.99                   February 19, 2026                  NetBSD 11.99