.\" 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. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. 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: src/lib/libc/string/strstr.3,v 1.11 2001/10/11 15:49:06 mike Exp $ .\" .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" .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 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 portablility 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 , 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 .Dq 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 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 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 -isoC .