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Command: strtok | Section: 3 | Source: OpenBSD | File: strtok.3
STRTOK(3) FreeBSD Library Functions Manual 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 a 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 ANSI X3.159-1989 ("ANSI C89"). The
strtok_r() function conforms to IEEE Std 1003.1-2001 ("POSIX.1").
HISTORY
The strtok() function first appeared in AT&T System III UNIX and was
reimplemented for 4.3BSD. 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.
FreeBSD 14.1-RELEASE-p8 December 11, 2024 FreeBSD 14.1-RELEASE-p8