string/strstr.3

   1 .\" Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
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  37 .\"     @(#)strstr.3    8.1 (Berkeley) 6/4/93
  38 .\" $FreeBSD: src/lib/libc/string/strstr.3,v 1.11 2001/10/11 15:49:06 mike Exp $
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  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 portablility 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 NULL is returned;
 100 otherwise a pointer to the first character of the first occurrence of
 101 .Fa little
 102 is returned.
 103 .Sh EXAMPLES
 104 The following sets the pointer
 105 .Va ptr
 106 to the
 107 .Dq Li Bar Baz
 108 portion of
 109 .Va largestring :
 110 .Bd -literal -offset indent
 111 const char *largestring = "Foo Bar Baz";
 112 const char *smallstring = "Bar";
 113 char *ptr;
 114
 115 ptr = strstr(largestring, smallstring);
 116 .Ed
 117 .Pp
 118 The following sets the pointer
 119 .Va ptr
 120 to NULL, because only the first 4 characters of
 121 .Va largestring
 122 are searched:
 123 .Bd -literal -offset indent
 124 const char *largestring = "Foo Bar Baz";
 125 const char *smallstring = "Bar";
 126 char *ptr;
 127
 128 ptr = strnstr(largestring, smallstring, 4);
 129 .Ed
 130 .Sh SEE ALSO
 131 .Xr memchr 3 ,
 132 .Xr strchr 3 ,
 133 .Xr strcspn 3 ,
 134 .Xr strpbrk 3 ,
 135 .Xr strrchr 3 ,
 136 .Xr strsep 3 ,
 137 .Xr strspn 3 ,
 138 .Xr strtok 3
 139 .Sh STANDARDS
 140 The
 141 .Fn strstr
 142 function
 143 conforms to
 144 .St -isoC .