Initial import from FreeBSD RELENG_4:
[dragonfly.git] / lib / libc / string / strstr.3
CommitLineData
984263bc
MD
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 1.3.2.5 2001/12/25 00:36:53 ache 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
57The
58.Fn strstr
59function
60locates the first occurrence of the null-terminated string
61.Fa little
62in the null-terminated string
63.Fa big .
64.Pp
65The
66.Fn strcasestr
67function is similar to
68.Fn strstr ,
69but ignores the case of both strings.
70.Pp
71The
72.Fn strnstr
73function
74locates the first occurrence of the null-terminated string
75.Fa little
76in the string
77.Fa big ,
78where not more than
79.Fa len
80characters are searched.
81Characters that appear after a
82.Ql \e0
83character are not searched.
84Since the
85.Fn strnstr
86function is a
87.Fx
88specific API, it should only be used when portability is not a concern.
89.Sh RETURN VALUES
90If
91.Fa little
92is an empty string,
93.Fa big
94is returned;
95if
96.Fa little
97occurs nowhere in
98.Fa big ,
99.Dv NULL
100is returned;
101otherwise a pointer to the first character of the first occurrence of
102.Fa little
103is returned.
104.Sh EXAMPLES
105The following sets the pointer
106.Va ptr
107to the
108.Qq Li Bar Baz
109portion of
110.Va largestring :
111.Bd -literal -offset indent
112const char *largestring = "Foo Bar Baz";
113const char *smallstring = "Bar";
114char *ptr;
115
116ptr = strstr(largestring, smallstring);
117.Ed
118.Pp
119The following sets the pointer
120.Va ptr
121to
122.Dv NULL ,
123because only the first 4 characters of
124.Va largestring
125are searched:
126.Bd -literal -offset indent
127const char *largestring = "Foo Bar Baz";
128const char *smallstring = "Bar";
129char *ptr;
130
131ptr = 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
143The
144.Fn strstr
145function
146conforms to
147.St -isoC .