.\" Copyright (c) 1988, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     from: @(#)strtok.3	8.2 (Berkeley) 2/3/94
.\"	$NetBSD: strtok.3,v 1.23 2008/08/29 05:48:40 dholland Exp $
.\"
.Dd August 11, 2002
.Dt STRTOK 3
.Os
.Sh NAME
.Nm strtok, strtok_r
.Nd string tokens
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn strtok "char * restrict str" "const char * restrict sep"
.Ft char *
.Fn strtok_r "char *str" "const char *sep" "char **lasts"
.Sh DESCRIPTION
The
.Fn strtok
function
is used to isolate sequential tokens in a nul-terminated string,
.Fa str .
These tokens are separated in the string by at least one of the
characters in
.Fa sep .
The first time that
.Fn strtok
is called,
.Fa str
should be specified; subsequent calls, wishing to obtain further tokens
from the same string, should pass a null pointer instead.
The separator string,
.Fa sep ,
must be supplied each time, and may change between calls.
.Pp
The
.Fn strtok
function
returns a pointer to the beginning of each subsequent token in the string,
after replacing the separator character itself with a
.Dv 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.
.Pp
The
.Fn strtok_r
function implements the functionality of
.Fn strtok
but is passed an additional argument,
.Fa lasts ,
which points to a user-provided pointer which is used by
.Fn strtok_r
to store state which needs to be kept between calls to scan the same string;
unlike
.Fn strtok ,
it is not necessary to limit tokenizing to a single string at a time
when using
.Fn strtok_r .
.Sh EXAMPLES
The following will construct an array of pointers to each individual word in
the string
.Va s :
.Bd -literal -offset indent
#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;
.Ed
.Pp
That is,
.Li tokens[0]
will point to
.Qq cat ,
.Li tokens[1]
will point to
.Qq dog ,
.Li tokens[2]
will point to
.Qq horse ,
and
.Li tokens[3]
will point to
.Qq cow .
.Sh SEE ALSO
.Xr index 3 ,
.Xr memchr 3 ,
.Xr rindex 3 ,
.Xr strchr 3 ,
.Xr strcspn 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strspn 3 ,
.Xr strstr 3
.Sh STANDARDS
The
.Fn strtok
function
conforms to
.St -ansiC .
The
.Fn strtok_r
function conforms to
.St -p1003.1c-95 .
.Sh BUGS
The System V
.Fn strtok ,
if handed a string containing only delimiter characters,
will not alter the next starting point, so that a call to
.Fn strtok
with a different (or empty) delimiter string
may return a
.Pf non- Dv NULL
value.
Since this implementation always alters the next starting point,
such a sequence of calls would always return
.Dv NULL .