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STRTOK(3) Library Functions Manual STRTOK(3)

strtok, strtok_r — string tokens

Standard C Library (libc, -lc)

#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);

This interface is obsoleted by strsep(3).

The () function is used to isolate sequential tokens in a null-terminated 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 further 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 implementation will behave as if no library function calls ().

The () function is a reentrant version of strtok(). The context pointer last must be provided on each call. The strtok_r() function may also be used to nest two parsing loops within one another, as long as separate context pointers are used.

The () and strtok_r() functions return a pointer to the beginning of each subsequent token in the string, after replacing the token itself with a NUL character. When no more tokens remain, a null pointer is returned.

The following uses strtok_r() to parse two strings using separate contexts:

char test[80], blah[80];
char *sep = "\\/:;=-";
char *word, *phrase, *brkt, *brkb;

strcpy(test, "This;is.a:test:of=the/string\\tokenizer-function.");

for (word = strtok_r(test, sep, &brkt);
     word;
     word = strtok_r(NULL, sep, &brkt))
{
    strcpy(blah, "blah:blat:blab:blag");

    for (phrase = strtok_r(blah, sep, &brkb);
         phrase;
         phrase = strtok_r(NULL, sep, &brkb))
    {
        printf("So far we're at %s:%s\n", word, phrase);
    }
}

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

The strtok() function conforms to ISO/IEC 9899:1990 (“ISO C90”).

Wes Peters, Softweyr LLC: ⟨wes@softweyr.com⟩

Based on the FreeBSD 3.0 implementation.

The System V strtok(), if handed a string containing only delimiter characters, 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 starting point, such a sequence of calls would always return NULL.

November 27, 1998 macOS