string/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>
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  50 .\"     @(#)strtok.3    8.2 (Berkeley) 2/3/94
  51 .\" $FreeBSD: src/lib/libc/string/strtok.3,v 1.24 2002/12/18 12:45:11 ru Exp $
  52 .\"
  53 .Dd November 27, 1998
  54 .Dt STRTOK 3
  55 .Os
  56 .Sh NAME
  57 .Nm strtok , strtok_r
  58 .Nd string tokens
  59 .Sh LIBRARY
  60 .Lb libc
  61 .Sh SYNOPSIS
  62 .In string.h
  63 .Ft char *
  64 .Fo strtok
  65 .Fa "char *restrict str"
  66 .Fa "const char *restrict sep"
  67 .Fc
  68 .Ft char *
  69 .Fo strtok_r
  70 .Fa "char *restrict str"
  71 .Fa "const char *restrict sep"
  72 .Fa "char **restrict lasts"
  73 .Fc
  74 .Sh DESCRIPTION
  75 .Bf -symbolic
  76 This interface is obsoleted by
  77 .Xr strsep 3 .
  78 .Ef
  79 .Pp
  80 The
  81 .Fn strtok
  82 function
  83 is used to isolate sequential tokens in a null-terminated string,
  84 .Fa str .
  85 These tokens are separated in the string by at least one of the
  86 characters in
  87 .Fa sep .
  88 The first time that
  89 .Fn strtok
  90 is called,
  91 .Fa str
  92 should be specified; subsequent calls, wishing to obtain further tokens
  93 from the same string, should pass a null pointer instead.
  94 The separator string,
  95 .Fa sep ,
  96 must be supplied each time, and may change between calls.
  97 .Pp
  98 The implementation will behave as if no library function calls
  99 .Fn strtok .
 100 .Pp
 101 The
 102 .Fn strtok_r
 103 function is a reentrant version of
 104 .Fn strtok .
 105 The context pointer
 106 .Fa last
 107 must be provided on each call.
 108 The
 109 .Fn strtok_r
 110 function
 111 may also be used to nest two parsing loops within one another, as
 112 long as separate context pointers are used.
 113 .Pp
 114 The
 115 .Fn strtok
 116 and
 117 .Fn strtok_r
 118 functions
 119 return a pointer to the beginning of each subsequent token in the string,
 120 after replacing the token itself with a
 121 .Dv NUL
 122 character.
 123 When no more tokens remain, a null pointer is returned.
 124 .Sh EXAMPLES
 125 The following uses
 126 .Fn strtok_r
 127 to parse two strings using separate contexts:
 128 .Bd -literal
 129 char test[80], blah[80];
 130 char *sep = "\e\e/:;=-";
 131 char *word, *phrase, *brkt, *brkb;
 132
 133 strcpy(test, "This;is.a:test:of=the/string\e\etokenizer-function.");
 134
 135 for (word = strtok_r(test, sep, &brkt);
 136      word;
 137      word = strtok_r(NULL, sep, &brkt))
 138 {
 139     strcpy(blah, "blah:blat:blab:blag");
 140
 141     for (phrase = strtok_r(blah, sep, &brkb);
 142          phrase;
 143          phrase = strtok_r(NULL, sep, &brkb))
 144     {
 145         printf("So far we're at %s:%s\en", word, phrase);
 146     }
 147 }
 148 .Ed
 149 .Sh SEE ALSO
 150 .Xr memchr 3 ,
 151 .Xr strchr 3 ,
 152 .Xr strcspn 3 ,
 153 .Xr strpbrk 3 ,
 154 .Xr strrchr 3 ,
 155 .Xr strsep 3 ,
 156 .Xr strspn 3 ,
 157 .Xr strstr 3 ,
 158 .Xr wcstok 3
 159 .Sh STANDARDS
 160 The
 161 .Fn strtok
 162 function
 163 conforms to
 164 .St -isoC .
 165 .Sh BUGS
 166 The System V
 167 .Fn strtok ,
 168 if handed a string containing only delimiter characters,
 169 will not alter the next starting point, so that a call to
 170 .Fn strtok
 171 with a different (or empty) delimiter string
 172 may return a
 173 .Pf non- Dv NULL
 174 value.
 175 Since this implementation always alters the next starting point,
 176 such a sequence of calls would always return
 177 .Dv NULL .
 178 .Sh AUTHORS
 179 .An Wes Peters ,
 180 Softweyr LLC:
 181 .Aq wes@softweyr.com
 182 .Pp
 183 Based on the
 184 .Fx 3.0
 185 implementation.