string/FreeBSD/strtok.3

   1 .\" Copyright (c) 1998 Softweyr LLC.  All rights reserved.
   2 .\"
   3 .\" strtok_r, from Berkeley strtok
   4 .\" Oct 13, 1998 by Wes Peters <wes@softweyr.com>
   5 .\"
   6 .\" Copyright (c) 1988, 1991, 1993
   7 .\"     The Regents of the University of California.  All rights reserved.
   8 .\"
   9 .\" This code is derived from software contributed to Berkeley by
  10 .\" the American National Standards Committee X3, on Information
  11 .\" Processing Systems.
  12 .\"
  13 .\" Redistribution and use in source and binary forms, with or without
  14 .\" modification, are permitted provided that the following conditions
  15 .\" are met:
  16 .\"
  17 .\" 1. Redistributions of source code must retain the above copyright
  18 .\"    notices, this list of conditions and the following disclaimer.
  19 .\"
  20 .\" 2. Redistributions in binary form must reproduce the above
  21 .\"    copyright notices, this list of conditions and the following
  22 .\"    disclaimer in the documentation and/or other materials provided
  23 .\"    with the distribution.
  24 .\"
  25 .\" 4. Neither the name of Softweyr LLC, the University nor the names
  26 .\"    of its contributors may be used to endorse or promote products
  27 .\"    derived from this software without specific prior written
  28 .\"    permission.
  29 .\"
  30 .\" THIS SOFTWARE IS PROVIDED BY SOFTWEYR LLC, THE REGENTS AND
  31 .\" CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
  32 .\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  33 .\" MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  34 .\" DISCLAIMED.  IN NO EVENT SHALL SOFTWEYR LLC, THE REGENTS, OR
  35 .\" CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  36 .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  37 .\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  38 .\" USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  39 .\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  40 .\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  41 .\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  42 .\" SUCH DAMAGE.
  43 .\"
  44 .\"     @(#)strtok.3    8.2 (Berkeley) 2/3/94
  45 .\" $FreeBSD: src/lib/libc/string/strtok.3,v 1.26 2007/12/12 18:33:06 wes Exp $
  46 .\"
  47 .Dd November 27, 1998
  48 .Dt STRTOK 3
  49 .Os
  50 .Sh NAME
  51 .Nm strtok , strtok_r
  52 .Nd string tokens
  53 .Sh LIBRARY
  54 .Lb libc
  55 .Sh SYNOPSIS
  56 .In string.h
  57 .Ft char *
  58 .Fo strtok
  59 .Fa "char *restrict str"
  60 .Fa "const char *restrict sep"
  61 .Fc
  62 .Ft char *
  63 .Fo strtok_r
  64 .Fa "char *restrict str"
  65 .Fa "const char *restrict sep"
  66 .Fa "char **restrict lasts"
  67 .Fc
  68 .Sh DESCRIPTION
  69 .Bf -symbolic
  70 This interface is obsoleted by
  71 .Xr strsep 3 .
  72 .Ef
  73 .Pp
  74 The
  75 .Fn strtok
  76 function
  77 is used to isolate sequential tokens in a null-terminated string,
  78 .Fa str .
  79 These tokens are separated in the string by at least one of the
  80 characters in
  81 .Fa sep .
  82 The first time that
  83 .Fn strtok
  84 is called,
  85 .Fa str
  86 should be specified; subsequent calls, wishing to obtain further tokens
  87 from the same string, should pass a null pointer instead.
  88 The separator string,
  89 .Fa sep ,
  90 must be supplied each time, and may change between calls.
  91 .Pp
  92 The implementation will behave as if no library function calls
  93 .Fn strtok .
  94 .Pp
  95 The
  96 .Fn strtok_r
  97 function is a reentrant version of
  98 .Fn strtok .
  99 The context pointer
 100 .Fa last
 101 must be provided on each call.
 102 The
 103 .Fn strtok_r
 104 function
 105 may also be used to nest two parsing loops within one another, as
 106 long as separate context pointers are used.
 107 .Pp
 108 The
 109 .Fn strtok
 110 and
 111 .Fn strtok_r
 112 functions
 113 return a pointer to the beginning of each subsequent token in the string,
 114 after replacing the token itself with a
 115 .Dv NUL
 116 character.
 117 When no more tokens remain, a null pointer is returned.
 118 .Sh EXAMPLES
 119 The following uses
 120 .Fn strtok_r
 121 to parse two strings using separate contexts:
 122 .Bd -literal
 123 char test[80], blah[80];
 124 char *sep = "\e\e/:;=-";
 125 char *word, *phrase, *brkt, *brkb;
 126
 127 strcpy(test, "This;is.a:test:of=the/string\e\etokenizer-function.");
 128
 129 for (word = strtok_r(test, sep, &brkt);
 130      word;
 131      word = strtok_r(NULL, sep, &brkt))
 132 {
 133     strcpy(blah, "blah:blat:blab:blag");
 134
 135     for (phrase = strtok_r(blah, sep, &brkb);
 136          phrase;
 137          phrase = strtok_r(NULL, sep, &brkb))
 138     {
 139         printf("So far we're at %s:%s\en", word, phrase);
 140     }
 141 }
 142 .Ed
 143 .Sh SEE ALSO
 144 .Xr memchr 3 ,
 145 .Xr strchr 3 ,
 146 .Xr strcspn 3 ,
 147 .Xr strpbrk 3 ,
 148 .Xr strrchr 3 ,
 149 .Xr strsep 3 ,
 150 .Xr strspn 3 ,
 151 .Xr strstr 3 ,
 152 .Xr wcstok 3
 153 .Sh STANDARDS
 154 The
 155 .Fn strtok
 156 function
 157 conforms to
 158 .St -isoC .
 159 .Sh AUTHORS
 160 .An Wes Peters ,
 161 Softweyr LLC:
 162 .Aq wes@softweyr.com
 163 .Pp
 164 Based on the
 165 .Fx 3.0
 166 implementation.
 167 .Sh BUGS
 168 The System V
 169 .Fn strtok ,
 170 if handed a string containing only delimiter characters,
 171 will not alter the next starting point, so that a call to
 172 .Fn strtok
 173 with a different (or empty) delimiter string
 174 may return a
 175 .Pf non- Dv NULL
 176 value.
 177 Since this implementation always alters the next starting point,
 178 such a sequence of calls would always return
 179 .Dv NULL .