STRTOK(3)

NAME
strtok, strtok_r - string token operations

SYNOPSIS
#include <string.h>
char *
strtok(char *str, const char *sep);
char *
strtok_r(char *str, const char *sep, char **last);

DESCRIPTION
This interface is obsoleted by strsep(3).

The strtok() function is used to isolate sequential tokens in a NUL-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 strtok_r() function is a version of strtok() that takes an explicit context argument and is reentrant.

Since strtok() and strtok_r() modify the string, str should not point to an area in the initialized data segment.

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

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];
    char *last;
    int i = 0;
    snprintf(s, sizeof(s), "cat dog horse cow");
    for ((p = strtok_r(s, " ", &last)); p;
        (p = strtok_r(NULL, " ", &last))) {
    	if (i < MAXTOKENS - 1)
    		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".

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

STANDARDS
The strtok() function conforms to ansiC.

HISTORY
The strtok() function first appeared in AT&T UNIX III and was reimplemented for 4.3BSD Tahoe. The strtok_r() function first appeared in NetBSD 1.3 and was reimplemented for OpenBSD 2.7.

BUGS
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.