1.\" Copyright (c) 2001 Mike Barcroft <mike@FreeBSD.org> 2.\" Copyright (c) 1990, 1991, 1993 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" This code is derived from software contributed to Berkeley by 6.\" Chris Torek and the American National Standards Committee X3, 7.\" on Information Processing Systems. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the University of 20.\" California, Berkeley and its contributors. 21.\" 4. Neither the name of the University nor the names of its contributors 22.\" may be used to endorse or promote products derived from this software 23.\" without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35.\" SUCH DAMAGE. 36.\" 37.\" @(#)strstr.3 8.1 (Berkeley) 6/4/93 38.\" $FreeBSD: src/lib/libc/string/strstr.3,v 1.3.2.5 2001/12/25 00:36:53 ache Exp $ 39.\" $DragonFly: src/lib/libc/string/strstr.3,v 1.3 2004/03/11 12:28:50 hmp Exp $ 40.\" 41.Dd October 11, 2001 42.Dt STRSTR 3 43.Os 44.Sh NAME 45.Nm strstr , strcasestr , strnstr 46.Nd locate a substring in a string 47.Sh LIBRARY 48.Lb libc 49.Sh SYNOPSIS 50.In string.h 51.Ft char * 52.Fn strstr "const char *big" "const char *little" 53.Ft char * 54.Fn strcasestr "const char *big" "const char *little" 55.Ft char * 56.Fn strnstr "const char *big" "const char *little" "size_t len" 57.Sh DESCRIPTION 58The 59.Fn strstr 60function 61locates the first occurrence of the null-terminated string 62.Fa little 63in the null-terminated string 64.Fa big . 65.Pp 66The 67.Fn strcasestr 68function is similar to 69.Fn strstr , 70but ignores the case of both strings. 71.Pp 72The 73.Fn strnstr 74function 75locates the first occurrence of the null-terminated string 76.Fa little 77in the string 78.Fa big , 79where not more than 80.Fa len 81characters are searched. 82Characters that appear after a 83.Ql \e0 84character are not searched. 85Since the 86.Fn strnstr 87function is a 88.Fx / Dx 89specific API, it should only be used when portability is not a concern. 90.Sh RETURN VALUES 91If 92.Fa little 93is an empty string, 94.Fa big 95is returned; 96if 97.Fa little 98occurs nowhere in 99.Fa big , 100.Dv NULL 101is returned; 102otherwise a pointer to the first character of the first occurrence of 103.Fa little 104is returned. 105.Sh EXAMPLES 106The following sets the pointer 107.Va ptr 108to the 109.Qq Li Bar Baz 110portion of 111.Va largestring : 112.Bd -literal -offset indent 113const char *largestring = "Foo Bar Baz"; 114const char *smallstring = "Bar"; 115char *ptr; 116 117ptr = strstr(largestring, smallstring); 118.Ed 119.Pp 120The following sets the pointer 121.Va ptr 122to 123.Dv NULL , 124because only the first 4 characters of 125.Va largestring 126are searched: 127.Bd -literal -offset indent 128const char *largestring = "Foo Bar Baz"; 129const char *smallstring = "Bar"; 130char *ptr; 131 132ptr = strnstr(largestring, smallstring, 4); 133.Ed 134.Sh SEE ALSO 135.Xr memchr 3 , 136.Xr strchr 3 , 137.Xr strcspn 3 , 138.Xr strpbrk 3 , 139.Xr strrchr 3 , 140.Xr strsep 3 , 141.Xr strspn 3 , 142.Xr strtok 3 143.Sh STANDARDS 144The 145.Fn strstr 146function 147conforms to 148.St -isoC . 149