STRTOK(3)

STRTOK(3) | 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 *str, const char *sep, char **lasts);

# DESCRIPTION

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`() function returns a pointer to the beginning of each subsequent 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 necessary 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];
    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)), i++) {
    	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

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.1c”).

# 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`.

August 11, 2002 | NetBSD 9.0