string/FreeBSD/strstr.3

   1 .\" Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
   2 .\" Copyright (c) 1990, 1991, 1993
   3 .\"     The Regents of the University of California.  All rights reserved.
   4 .\"
   5 .\" This code is derived from software contributed to Berkeley by
   6 .\" Chris Torek and the American National Standards Committee X3,
   7 .\" on Information Processing Systems.
   8 .\"
   9 .\" Redistribution and use in source and binary forms, with or without
  10 .\" modification, are permitted provided that the following conditions
  11 .\" are met:
  12 .\" 1. Redistributions of source code must retain the above copyright
  13 .\"    notice, this list of conditions and the following disclaimer.
  14 .\" 2. Redistributions in binary form must reproduce the above copyright
  15 .\"    notice, this list of conditions and the following disclaimer in the
  16 .\"    documentation and/or other materials provided with the distribution.
  17 .\" 3. All advertising materials mentioning features or use of this software
  18 .\"    must display the following acknowledgement:
  19 .\"     This product includes software developed by the University of
  20 .\"     California, Berkeley and its contributors.
  21 .\" 4. Neither the name of the University nor the names of its contributors
  22 .\"    may be used to endorse or promote products derived from this software
  23 .\"    without specific prior written permission.
  24 .\"
  25 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  26 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  29 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35 .\" SUCH DAMAGE.
  36 .\"
  37 .\"     @(#)strstr.3    8.1 (Berkeley) 6/4/93
  38 .\" $FreeBSD: src/lib/libc/string/strstr.3,v 1.12 2001/11/20 14:11:07 ru Exp $
  39 .\"
  40 .Dd October 11, 2001
  41 .Dt STRSTR 3
  42 .Os
  43 .Sh NAME
  44 .Nm strstr , strcasestr , strnstr
  45 .Nd locate a substring in a string
  46 .Sh LIBRARY
  47 .Lb libc
  48 .Sh SYNOPSIS
  49 .In string.h
  50 .Ft char *
  51 .Fn strstr "const char *big" "const char *little"
  52 .Ft char *
  53 .Fn strcasestr "const char *big" "const char *little"
  54 .Ft char *
  55 .Fn strnstr "const char *big" "const char *little" "size_t len"
  56 .Sh DESCRIPTION
  57 The
  58 .Fn strstr
  59 function
  60 locates the first occurrence of the null-terminated string
  61 .Fa little
  62 in the null-terminated string
  63 .Fa big .
  64 .Pp
  65 The
  66 .Fn strcasestr
  67 function is similar to
  68 .Fn strstr ,
  69 but ignores the case of both strings.
  70 .Pp
  71 The
  72 .Fn strnstr
  73 function
  74 locates the first occurrence of the null-terminated string
  75 .Fa little
  76 in the string
  77 .Fa big ,
  78 where not more than
  79 .Fa len
  80 characters are searched.
  81 Characters that appear after a
  82 .Ql \e0
  83 character are not searched.
  84 Since the
  85 .Fn strnstr
  86 function is a
  87 .Fx
  88 specific API, it should only be used when portability is not a concern.
  89 .Sh RETURN VALUES
  90 If
  91 .Fa little
  92 is an empty string,
  93 .Fa big
  94 is returned;
  95 if
  96 .Fa little
  97 occurs nowhere in
  98 .Fa big ,
  99 .Dv NULL
 100 is returned;
 101 otherwise a pointer to the first character of the first occurrence of
 102 .Fa little
 103 is returned.
 104 .Sh EXAMPLES
 105 The following sets the pointer
 106 .Va ptr
 107 to the
 108 .Qq Li Bar Baz
 109 portion of
 110 .Va largestring :
 111 .Bd -literal -offset indent
 112 const char *largestring = "Foo Bar Baz";
 113 const char *smallstring = "Bar";
 114 char *ptr;
 115
 116 ptr = strstr(largestring, smallstring);
 117 .Ed
 118 .Pp
 119 The following sets the pointer
 120 .Va ptr
 121 to
 122 .Dv NULL ,
 123 because only the first 4 characters of
 124 .Va largestring
 125 are searched:
 126 .Bd -literal -offset indent
 127 const char *largestring = "Foo Bar Baz";
 128 const char *smallstring = "Bar";
 129 char *ptr;
 130
 131 ptr = strnstr(largestring, smallstring, 4);
 132 .Ed
 133 .Sh SEE ALSO
 134 .Xr memchr 3 ,
 135 .Xr strchr 3 ,
 136 .Xr strcspn 3 ,
 137 .Xr strpbrk 3 ,
 138 .Xr strrchr 3 ,
 139 .Xr strsep 3 ,
 140 .Xr strspn 3 ,
 141 .Xr strtok 3
 142 .Sh STANDARDS
 143 The
 144 .Fn strstr
 145 function
 146 conforms to
 147 .St -isoC .