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.
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  5  .\" This code is derived from software contributed to Berkeley by
  6  .\" Chris Torek and the American National Standards Committee X3,
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 33  .\"     @(#)strstr.3	8.1 (Berkeley) 6/4/93
 34  .\" $FreeBSD$
 35  .\"
 36  .Dd October 11, 2001
 37  .Dt STRSTR 3
 38  .Os
 39  .Sh NAME
 40  .Nm strstr , strcasestr , strnstr
 41  .Nd locate a substring in a string
 42  .Sh LIBRARY
 43  .Lb libc
 44  .Sh SYNOPSIS
 45  .In string.h
 46  .Ft char *
 47  .Fn strstr "const char *haystack" "const char *needle"
 48  .Ft char *
 49  .Fn strcasestr "const char *haystack" "const char *needle"
 50  .Ft char *
 51  .Fn strnstr "const char *haystack" "const char *needle" "size_t len"
 52  .In string.h
 53  .In xlocale.h
 54  .Ft char *
 55  .Fn strcasestr_l "const char *haystack" "const char *needle" "locale_t loc"
 56  .Sh DESCRIPTION
 57  The
 58  .Fn strstr
 59  function
 60  locates the first occurrence of the null-terminated string
 61  .Fa needle
 62  in the null-terminated string
 63  .Fa haystack .
 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 needle
 76  in the string
 77  .Fa haystack ,
 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  .Pp
 90  While the
 91  .Fn strcasestr
 92  function uses the current locale, the
 93  .Fn strcasestr_l
 94  function may be passed a locale directly. See
 95  .Xr xlocale 3
 96  for more information.
 97  .Sh RETURN VALUES
 98  If
 99  .Fa needle
100  is an empty string,
101  .Fa haystack
102  is returned;
103  if
104  .Fa needle
105  occurs nowhere in
106  .Fa haystack ,
107  .Dv NULL
108  is returned;
109  otherwise a pointer to the first character of the first occurrence of
110  .Fa needle
111  is returned.
112  .Sh EXAMPLES
113  The following sets the pointer
114  .Va ptr
115  to the
116  .Qq Li Bar Baz
117  portion of
118  .Va largestring :
119  .Bd -literal -offset indent
120  const char *largestring = "Foo Bar Baz";
121  const char *smallstring = "Bar";
122  char *ptr;
123  
124  ptr = strstr(largestring, smallstring);
125  .Ed
126  .Pp
127  The following sets the pointer
128  .Va ptr
129  to
130  .Dv NULL ,
131  because only the first 4 characters of
132  .Va largestring
133  are searched:
134  .Bd -literal -offset indent
135  const char *largestring = "Foo Bar Baz";
136  const char *smallstring = "Bar";
137  char *ptr;
138  
139  ptr = strnstr(largestring, smallstring, 4);
140  .Ed
141  .Sh SEE ALSO
142  .Xr memchr 3 ,
143  .Xr memmem 3 ,
144  .Xr strchr 3 ,
145  .Xr strcspn 3 ,
146  .Xr strpbrk 3 ,
147  .Xr strrchr 3 ,
148  .Xr strsep 3 ,
149  .Xr strspn 3 ,
150  .Xr strtok 3 ,
151  .Xr wcsstr 3 ,
152  .Xr xlocale 3
153  .Sh STANDARDS
154  The
155  .Fn strstr
156  function
157  conforms to
158  .St -isoC .