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. Neither the name of the University nor the names of its contributors 18.\" may be used to endorse or promote products derived from this software 19.\" without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31.\" SUCH DAMAGE. 32.\" 33.\" @(#)strstr.3 8.1 (Berkeley) 6/4/93 34.\" $FreeBSD: head/lib/libc/string/strstr.3 251069 2013-05-28 20:57:40Z emaste $ 35.\" 36.Dd October 11, 2001 37.Dt STRSTR 3 38.Os 39.Sh NAME 40.Nm strstr , strcasestr , strnstr 41.Nd locate a substring in a string 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In string.h 46.Ft char * 47.Fn strstr "const char *big" "const char *little" 48.Ft char * 49.Fn strcasestr "const char *big" "const char *little" 50.Ft char * 51.Fn strnstr "const char *big" "const char *little" "size_t len" 52.In string.h 53.In xlocale.h 54.Ft char * 55.Fn strcasestr_l "const char *big" "const char *little" "locale_t loc" 56.Sh DESCRIPTION 57The 58.Fn strstr 59function 60locates the first occurrence of the null-terminated string 61.Fa little 62in the null-terminated string 63.Fa big . 64.Pp 65The 66.Fn strcasestr 67function is similar to 68.Fn strstr , 69but ignores the case of both strings. 70.Pp 71The 72.Fn strcasestr_l 73function does the same as 74.Fn strcasestr 75but takes an explicit locale rather than using the current locale. 76.Pp 77The 78.Fn strnstr 79function 80locates the first occurrence of the null-terminated string 81.Fa little 82in the string 83.Fa big , 84where not more than 85.Fa len 86characters are searched. 87Characters that appear after a 88.Ql \e0 89character are not searched. 90Since the 91.Fn strnstr 92function is a 93.Fx 94specific API, it should only be used when portability is not a concern. 95.Sh RETURN VALUES 96If 97.Fa little 98is an empty string, 99.Fa big 100is returned; 101if 102.Fa little 103occurs nowhere in 104.Fa big , 105.Dv NULL 106is returned; 107otherwise a pointer to the first character of the first occurrence of 108.Fa little 109is returned. 110.Sh EXAMPLES 111The following sets the pointer 112.Va ptr 113to the 114.Qq Li Bar Baz 115portion of 116.Va largestring : 117.Bd -literal -offset indent 118const char *largestring = "Foo Bar Baz"; 119const char *smallstring = "Bar"; 120char *ptr; 121 122ptr = strstr(largestring, smallstring); 123.Ed 124.Pp 125The following sets the pointer 126.Va ptr 127to 128.Dv NULL , 129because only the first 4 characters of 130.Va largestring 131are searched: 132.Bd -literal -offset indent 133const char *largestring = "Foo Bar Baz"; 134const char *smallstring = "Bar"; 135char *ptr; 136 137ptr = strnstr(largestring, smallstring, 4); 138.Ed 139.Sh SEE ALSO 140.Xr memchr 3 , 141.Xr memmem 3 , 142.Xr strchr 3 , 143.Xr strcspn 3 , 144.Xr strpbrk 3 , 145.Xr strrchr 3 , 146.Xr strsep 3 , 147.Xr strspn 3 , 148.Xr strtok 3 , 149.Xr wcsstr 3 150.Sh STANDARDS 151The 152.Fn strstr 153function 154conforms to 155.St -isoC . 156