.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.\"	$OpenBSD: strstr.3,v 1.10 2007/09/19 16:06:45 jmc Exp $
.\"
.Dd $Mdocdate: September 19 2007 $
.Dt STRSTR 3
.Os
.Sh NAME
.Nm strstr , strcasestr
.Nd locate a substring in a string
.Sh SYNOPSIS
.Fd #include <string.h>
.Ft char *
.Fn strstr "const char *big" "const char *little"
.Ft char *
.Fn strcasestr "const char *big" "const char *little"
.Sh DESCRIPTION
The
.Fn strstr
function locates the first occurrence of the NUL-terminated string
.Fa little
in the NUL-terminated string
.Fa big .
.Pp
The
.Fn strcasestr
function is similar to
.Fn strstr
but ignores the case of both strings.
.Pp
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 SEE ALSO
.Xr memchr 3 ,
.Xr strchr 3 ,
.Xr strcspn 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strspn 3 ,
.Xr strtok 3
.Sh STANDARDS
The
.Fn strstr
function conforms to
.St -ansiC .
.Sh HISTORY
The
.Fn strcasestr
function first appeared in
.Ox 3.8 .