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.\" $OpenBSD: strtok.3,v 1.22 2017/08/31 10:57:47 jca Exp $
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.\"
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.\" Copyright (c) 1988, 1991 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the American National Standards Committee X3, on Information
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.\" Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: August 31 2017 $
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.Dt STRTOK 3
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.Os
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.Sh NAME
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.Nm strtok ,
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.Nm strtok_r
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.Nd string token operations
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.Sh SYNOPSIS
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.In string.h
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.Ft char *
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.Fn strtok "char *str" "const char *sep"
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.Ft char *
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.Fn strtok_r "char *str" "const char *sep" "char **last"
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.Sh DESCRIPTION
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.Bf -symbolic
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This interface is obsoleted by
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.Xr strsep 3 .
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.Ef
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.Pp
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The
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.Fn strtok
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function is used to isolate sequential tokens in a NUL-terminated string,
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.Fa str .
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These tokens are separated in the string by at least one of the
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characters in
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.Fa sep .
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The first time that
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.Fn strtok
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is called,
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.Fa str
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should be specified; subsequent calls, wishing to obtain further tokens
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from the same string, should pass a null pointer instead.
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The separator string,
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.Fa sep ,
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must be supplied each time, and may change between calls.
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.Pp
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The
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.Fn strtok_r
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function is a version of
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.Fn strtok
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that takes an explicit context argument and is reentrant.
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.Pp
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Since
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.Fn strtok
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and
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.Fn strtok_r
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modify the string,
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.Fa str
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should not point to an area in the initialized data segment.
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.Sh RETURN VALUES
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The
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.Fn strtok
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and
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.Fn strtok_r
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functions return a pointer to the beginning of each subsequent token
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in the string, after replacing the separator character itself with an
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.Tn ASCII NUL
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character.
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When no more tokens remain, a null pointer is returned.
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.Sh EXAMPLES
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The following will construct an array of pointers to each individual word in
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the string
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.Va s :
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.Bd -literal -offset indent
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#define MAXTOKENS 128
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char s[512], *p, *tokens[MAXTOKENS];
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char *last;
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int i = 0;
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snprintf(s, sizeof(s), "cat dog horse cow");
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for ((p = strtok_r(s, " ", &last)); p;
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(p = strtok_r(NULL, " ", &last))) {
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if (i < MAXTOKENS - 1)
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tokens[i++] = p;
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}
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tokens[i] = NULL;
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.Ed
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.Pp
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That is,
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.Li tokens[0]
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will point to
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.Qq cat ,
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.Li tokens[1]
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will point to
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.Qq dog ,
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.Li tokens[2]
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will point to
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.Qq horse ,
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and
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.Li tokens[3]
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will point to
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.Qq cow .
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.Sh SEE ALSO
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.Xr memchr 3 ,
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.Xr strchr 3 ,
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.Xr strcspn 3 ,
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.Xr strpbrk 3 ,
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.Xr strrchr 3 ,
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.Xr strsep 3 ,
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.Xr strspn 3 ,
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.Xr strstr 3 ,
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.Xr wcstok 3
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.Sh STANDARDS
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The
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.Fn strtok
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function conforms to
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.St -ansiC .
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The
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.Fn strtok_r
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function conforms to
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.St -p1003.1-2001 .
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.Sh HISTORY
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The
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.Fn strtok
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function first appeared in
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.At III
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and was reimplemented for
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.Bx 4.3 Tahoe .
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The
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.Fn strtok_r
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function first appeared in
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.Nx 1.3
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and was reimplemented for
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.Ox 2.7 .
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.Sh BUGS
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The System V
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.Fn strtok ,
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if handed a string containing only delimiter characters,
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will not alter the next starting point, so that a call to
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.Fn strtok
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with a different (or empty) delimiter string
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may return a non-null value.
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Since this implementation always alters the next starting point,
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such a sequence of calls would always return
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.Dv NULL .
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