1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $OpenBSD: strstr.3,v 1.10 2007/09/19 16:06:45 jmc Exp $ 33.\" 34.Dd $Mdocdate: September 19 2007 $ 35.Dt STRSTR 3 36.Os 37.Sh NAME 38.Nm strstr , strcasestr 39.Nd locate a substring in a string 40.Sh SYNOPSIS 41.Fd #include <string.h> 42.Ft char * 43.Fn strstr "const char *big" "const char *little" 44.Ft char * 45.Fn strcasestr "const char *big" "const char *little" 46.Sh DESCRIPTION 47The 48.Fn strstr 49function locates the first occurrence of the NUL-terminated string 50.Fa little 51in the NUL-terminated string 52.Fa big . 53.Pp 54The 55.Fn strcasestr 56function is similar to 57.Fn strstr 58but ignores the case of both strings. 59.Pp 60If 61.Fa little 62is an empty string, 63.Fa big 64is returned; 65if 66.Fa little 67occurs nowhere in 68.Fa big , 69.Dv NULL 70is returned; 71otherwise a pointer to the first character of the first occurrence of 72.Fa little 73is returned. 74.Sh SEE ALSO 75.Xr memchr 3 , 76.Xr strchr 3 , 77.Xr strcspn 3 , 78.Xr strpbrk 3 , 79.Xr strrchr 3 , 80.Xr strsep 3 , 81.Xr strspn 3 , 82.Xr strtok 3 83.Sh STANDARDS 84The 85.Fn strstr 86function conforms to 87.St -ansiC . 88.Sh HISTORY 89The 90.Fn strcasestr 91function first appeared in 92.Ox 3.8 . 93