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.\" $OpenBSD: strtok.3,v 1.21 2013/06/05 03:39:23 tedu Exp $
.\"
.\" Copyright (c) 1988, 1991 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.
.\"
.Dd $Mdocdate: June 5 2013 $
.Dt STRTOK 3
.Os
.Sh NAME
.Nm strtok ,
.Nm strtok_r
.Nd string token operations
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn strtok "char *str" "const char *sep"
.Ft char *
.Fn strtok_r "char *str" "const char *sep" "char **last"
.Sh DESCRIPTION
.Bf -symbolic
This interface is obsoleted by
.Xr strsep 3 .
.Ef
.Pp
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_r
function is a version of
.Fn strtok
that takes an explicit context argument and is reentrant.
.Pp
Since
.Fn strtok
and
.Fn strtok_r
modify the string,
.Fa str
should not point to an area in the initialized data segment.
.Sh RETURN VALUES
The
.Fn strtok
and
.Fn strtok_r
functions return a pointer to the beginning of each subsequent token
in the string, after replacing the separator character itself with an
.Tn ASCII NUL
character.
When no more tokens remain, a null pointer is returned.
.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))) {
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 memchr 3 ,
.Xr strchr 3 ,
.Xr strcspn 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strspn 3 ,
.Xr strstr 3 ,
.Xr wcstok 3
.Sh STANDARDS
The
.Fn strtok
function conforms to
.St -ansiC .
.Sh HISTORY
The
.Fn strtok
function first appeared in
.At III
and was reimplemented for
.Bx 4.3 Tahoe .
The
.Fn strtok_r
function first appeared in
.Nx 1.3
and was reimplemented for
.Ox 2.7 .
.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 non-null value.
Since this implementation always alters the next starting point,
such a sequence of calls would always return
.Dv NULL .
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