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.

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.

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

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)

STANDARDS
The strtok() function conforms to ansiC.

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.