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.\" $FreeBSD$ 39.\" 40.Dd October 11, 2001 41.Dt STRSTR 3 42.Os 43.Sh NAME 44.Nm strstr , strcasestr , strnstr 45.Nd locate a substring in a string 46.Sh LIBRARY 47.Lb libc 48.Sh SYNOPSIS 49.In string.h 50.Ft char * 51.Fn strstr "const char *big" "const char *little" 52.Ft char * 53.Fn strcasestr "const char *big" "const char *little" 54.Ft char * 55.Fn strnstr "const char *big" "const char *little" "size_t len" 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 strnstr 73function 74locates the first occurrence of the null-terminated string 75.Fa little 76in the string 77.Fa big , 78where not more than 79.Fa len 80characters are searched. 81Characters that appear after a 82.Ql \e0 83character are not searched. 84Since the 85.Fn strnstr 86function is a 87.Fx 88specific API, it should only be used when portability is not a concern. 89.Sh RETURN VALUES 90If 91.Fa little 92is an empty string, 93.Fa big 94is returned; 95if 96.Fa little 97occurs nowhere in 98.Fa big , 99.Dv NULL 100is returned; 101otherwise a pointer to the first character of the first occurrence of 102.Fa little 103is returned. 104.Sh EXAMPLES 105The following sets the pointer 106.Va ptr 107to the 108.Qq Li Bar Baz 109portion of 110.Va largestring : 111.Bd -literal -offset indent 112const char *largestring = "Foo Bar Baz"; 113const char *smallstring = "Bar"; 114char *ptr; 115 116ptr = strstr(largestring, smallstring); 117.Ed 118.Pp 119The following sets the pointer 120.Va ptr 121to 122.Dv NULL , 123because only the first 4 characters of 124.Va largestring 125are searched: 126.Bd -literal -offset indent 127const char *largestring = "Foo Bar Baz"; 128const char *smallstring = "Bar"; 129char *ptr; 130 131ptr = strnstr(largestring, smallstring, 4); 132.Ed 133.Sh SEE ALSO 134.Xr memchr 3 , 135.Xr strchr 3 , 136.Xr strcspn 3 , 137.Xr strpbrk 3 , 138.Xr strrchr 3 , 139.Xr strsep 3 , 140.Xr strspn 3 , 141.Xr strtok 3 142.Sh STANDARDS 143The 144.Fn strstr 145function 146conforms to 147.St -isoC . 148