.\" Copyright (c) 1990, 1991 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.
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.\" modification, are permitted provided that the following conditions
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.\"    may be used to endorse or promote products derived from this software
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.\"	$OpenBSD: strstr.3,v 1.9 2007/05/31 19:19:32 jmc Exp $
.\"
.Dd $Mdocdate: May 31 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 .