.\"	$OpenBSD: strnstr.9,v 1.1 2023/12/21 02:57:14 jsg Exp $
.\"
.\" Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org>
.\" Copyright (c) 1990, 1991, 1993
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
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.Dd $Mdocdate: December 21 2023 $
.Dt STRNSTR 9
.Os
.Sh NAME
.Nm strnstr
.Nd locate a substring in a string
.Sh SYNOPSIS
.In lib/libkern/libkern.h
.Ft char *
.Fn strnstr "const char *big" "const char *little" "size_t len"
.Sh DESCRIPTION
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.
.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
.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 9