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 June 4, 1993 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 only the first number of characters, identified by 79.Fa len , 80are searched. 81Since the 82.Fn strnstr 83function is a 84.Fx 85specific API, it should only be used when portablility is not a concern. 86.Sh RETURN VALUES 87If 88.Fa little 89is an empty string, 90.Fa big 91is returned; 92if 93.Fa little 94occurs nowhere in 95.Fa big , 96NULL is returned; 97otherwise a pointer to the first character of the first occurrence of 98.Fa little 99is returned. 100.Sh EXAMPLES 101The following sets the pointer 102.Va ptr 103to the 104.Dq Li Bar Baz 105portion of 106.Va largestring : 107.Bd -literal -offset indent 108const char *largestring = "Foo Bar Baz"; 109const char *smallstring = "Bar"; 110char *ptr; 111 112ptr = strstr(largestring, smallstring); 113.Ed 114.Pp 115The following sets the pointer 116.Va ptr 117to NULL, because only the first 4 characters of 118.Va largestring 119are searched: 120.Bd -literal -offset indent 121const char *largestring = "Foo Bar Baz"; 122const char *smallstring = "Bar"; 123char *ptr; 124 125ptr = strnstr(largestring, smallstring, 4); 126.Ed 127.Sh SEE ALSO 128.Xr memchr 3 , 129.Xr strchr 3 , 130.Xr strcspn 3 , 131.Xr strpbrk 3 , 132.Xr strrchr 3 , 133.Xr strsep 3 , 134.Xr strspn 3 , 135.Xr strtok 3 136.Sh STANDARDS 137The 138.Fn strstr 139function 140conforms to 141.St -isoC . 142