freebsd-dev/lib/libc/string/strstr.3

.\" Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
.\" Copyright (c) 1990, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)strstr.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd October 11, 2001
.Dt STRSTR 3
.Os
.Sh NAME
.Nm strstr , strcasestr , strnstr
.Nd locate a substring in a string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In string.h
.Ft char *
.Fn strstr "const char *big" "const char *little"
.Ft char *
.Fn strcasestr "const char *big" "const char *little"
.Ft char *
.Fn strnstr "const char *big" "const char *little" "size_t len"
.In string.h
.In xlocale.h
.Ft char *
.Fn strcasestr_l "const char *big" "const char *little" "locale_t loc"
.Sh DESCRIPTION
The
.Fn strstr
function
locates the first occurrence of the null-terminated string
.Fa little
in the null-terminated string
.Fa big .
.Pp
The
.Fn strcasestr
function is similar to
.Fn strstr ,
but ignores the case of both strings.
.Pp
The
.Fn strcasestr_l
function does the same as
.Fn strcasestr
but takes an explicit locale rather than using the current locale.
.Pp
The
.Fn strnstr
function
locates the first occurrence of the null-terminated string
.Fa little
in the string
.Fa big ,
where not more than
.Fa len
characters are searched.
Characters that appear after a
.Ql \e0
character are not searched.
Since the
.Fn strnstr
function is a
.Fx
specific API, it should only be used when portability is not a concern.
.Sh RETURN VALUES
If
.Fa little
is an empty string,
.Fa big
is returned;
if
.Fa little
occurs nowhere in
.Fa big ,
.Dv NULL
is returned;
otherwise a pointer to the first character of the first occurrence of
.Fa little
is returned.
.Sh EXAMPLES
The following sets the pointer
.Va ptr
to the
.Qq Li Bar Baz
portion of
.Va largestring :
.Bd -literal -offset indent
const char *largestring = "Foo Bar Baz";
const char *smallstring = "Bar";
char *ptr;

ptr = strstr(largestring, smallstring);
.Ed
.Pp
The following sets the pointer
.Va ptr
to
.Dv NULL ,
because only the first 4 characters of
.Va largestring
are searched:
.Bd -literal -offset indent
const char *largestring = "Foo Bar Baz";
const char *smallstring = "Bar";
char *ptr;

ptr = strnstr(largestring, smallstring, 4);
.Ed
.Sh SEE ALSO
.Xr memchr 3 ,
.Xr memmem 3 ,
.Xr strchr 3 ,
.Xr strcspn 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strspn 3 ,
.Xr strtok 3 ,
.Xr wcsstr 3
.Sh STANDARDS
The
.Fn strstr
function
conforms to
.St -isoC .