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 1.12 2001/11/20 14:11:07 ru Exp $
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  40 .Dd October 11, 2001
  41 .Dt STRSTR 3
  42 .Os
  43 .Sh NAME
  44 .Nm strcasestr ,
  45 .Nm strcasestr_l ,
  46 .Nm strnstr ,
  47 .Nm strstr
  48 .Nd locate a substring in a string
  49 .Sh LIBRARY
  50 .Lb libc
  51 .Sh SYNOPSIS
  52 .In string.h
  53 .Ft char *
  54 .Fo strcasestr
  55 .Fa "const char *s1"
  56 .Fa "const char *s2"
  57 .Fc
  58 .Ft char *
  59 .Fo strnstr
  60 .Fa "const char *s1"
  61 .Fa "const char *s2"
  62 .Fa "size_t n"
  63 .Fc
  64 .Ft char *
  65 .Fo strstr
  66 .Fa "const char *s1"
  67 .Fa "const char *s2"
  68 .Fc
  69 .In string.h
  70 .In xlocale.h
  71 .Ft char *
  72 .Fo strcasestr_l
  73 .Fa "const char *s1"
  74 .Fa "const char *s2"
  75 .Fa "locale_t loc"
  76 .Fc
  77 .Sh DESCRIPTION
  78 The
  79 .Fn strstr
  80 function
  81 locates the first occurrence of the null-terminated string
  82 .Fa s2
  83 in the null-terminated string
  84 .Fa s1 .
  85 .Pp
  86 The
  87 .Fn strcasestr
  88 function is similar to
  89 .Fn strstr ,
  90 but ignores the case of both strings.
  91 .Pp
  92 The
  93 .Fn strnstr
  94 function
  95 locates the first occurrence of the null-terminated string
  96 .Fa s2
  97 in the string
  98 .Fa s1 ,
  99 where not more than
 100 .Fa n
 101 characters are searched.
 102 Characters that appear after a
 103 .Ql \e0
 104 character are not searched.
 105 Since the
 106 .Fn strnstr
 107 function is a
 108 .Fx
 109 specific API, it should only be used when portability is not a concern.
 110 .Pp
 111 While the
 112 .Fn strcasestr
 113 function uses the current locale, the
 114 .Fn strcasestr_l
 115 function may be passed a locale directly. See
 116 .Xr xlocale 3
 117 for more information.
 118 .Sh RETURN VALUES
 119 If
 120 .Fa s2
 121 is an empty string,
 122 .Fa s1
 123 is returned;
 124 if
 125 .Fa s2
 126 occurs nowhere in
 127 .Fa s1 ,
 128 .Dv NULL
 129 is returned;
 130 otherwise a pointer to the first character of the first occurrence of
 131 .Fa s2
 132 is returned.
 133 .Sh EXAMPLES
 134 The following sets the pointer
 135 .Va ptr
 136 to the
 137 .Qq Li Bar Baz
 138 portion of
 139 .Va largestring :
 140 .Bd -literal -offset indent
 141 const char *largestring = "Foo Bar Baz";
 142 const char *smallstring = "Bar";
 143 char *ptr;
 144
 145 ptr = strstr(largestring, smallstring);
 146 .Ed
 147 .Pp
 148 The following sets the pointer
 149 .Va ptr
 150 to
 151 .Dv NULL ,
 152 because only the first 4 characters of
 153 .Va largestring
 154 are searched:
 155 .Bd -literal -offset indent
 156 const char *largestring = "Foo Bar Baz";
 157 const char *smallstring = "Bar";
 158 char *ptr;
 159
 160 ptr = strnstr(largestring, smallstring, 4);
 161 .Ed
 162 .Sh SEE ALSO
 163 .Xr memchr 3 ,
 164 .Xr strchr 3 ,
 165 .Xr strcspn 3 ,
 166 .Xr strpbrk 3 ,
 167 .Xr strrchr 3 ,
 168 .Xr strsep 3 ,
 169 .Xr strspn 3 ,
 170 .Xr strtok 3 ,
 171 .Xr xlocale 3
 172 .Sh STANDARDS
 173 The
 174 .Fn strstr
 175 function
 176 conforms to
 177 .St -isoC .