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.\" 35.Dd October 11, 2001 36.Dt STRSTR 3 37.Os 38.Sh NAME 39.Nm strstr , strcasestr , strnstr 40.Nd locate a substring in a string 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In string.h 45.Ft char * 46.Fn strstr "const char *big" "const char *little" 47.Ft char * 48.Fn strcasestr "const char *big" "const char *little" 49.Ft char * 50.Fn strnstr "const char *big" "const char *little" "size_t len" 51.In string.h 52.In xlocale.h 53.Ft char * 54.Fn strcasestr_l "const char *big" "const char *little" "locale_t loc" 55.Sh DESCRIPTION 56The 57.Fn strstr 58function 59locates the first occurrence of the null-terminated string 60.Fa little 61in the null-terminated string 62.Fa big . 63.Pp 64The 65.Fn strcasestr 66function is similar to 67.Fn strstr , 68but ignores the case of both strings. 69.Pp 70The 71.Fn strcasestr_l 72function does the same as 73.Fn strcasestr 74but takes an explicit locale rather than using the current locale. 75.Pp 76The 77.Fn strnstr 78function 79locates the first occurrence of the null-terminated string 80.Fa little 81in the string 82.Fa big , 83where not more than 84.Fa len 85characters are searched. 86Characters that appear after a 87.Ql \e0 88character are not searched. 89Since the 90.Fn strnstr 91function is a 92.Fx 93specific API, it should only be used when portability is not a concern. 94.Sh RETURN VALUES 95If 96.Fa little 97is an empty string, 98.Fa big 99is returned; 100if 101.Fa little 102occurs nowhere in 103.Fa big , 104.Dv NULL 105is returned; 106otherwise a pointer to the first character of the first occurrence of 107.Fa little 108is returned. 109.Sh EXAMPLES 110The following sets the pointer 111.Va ptr 112to the 113.Qq Li Bar Baz 114portion of 115.Va largestring : 116.Bd -literal -offset indent 117const char *largestring = "Foo Bar Baz"; 118const char *smallstring = "Bar"; 119char *ptr; 120 121ptr = strstr(largestring, smallstring); 122.Ed 123.Pp 124The following sets the pointer 125.Va ptr 126to 127.Dv NULL , 128because only the first 4 characters of 129.Va largestring 130are searched: 131.Bd -literal -offset indent 132const char *largestring = "Foo Bar Baz"; 133const char *smallstring = "Bar"; 134char *ptr; 135 136ptr = strnstr(largestring, smallstring, 4); 137.Ed 138.Sh SEE ALSO 139.Xr memchr 3 , 140.Xr memmem 3 , 141.Xr strchr 3 , 142.Xr strcspn 3 , 143.Xr strpbrk 3 , 144.Xr strrchr 3 , 145.Xr strsep 3 , 146.Xr strspn 3 , 147.Xr strtok 3 , 148.Xr wcsstr 3 149.Sh STANDARDS 150The 151.Fn strstr 152function 153conforms to 154.St -isoC . 155.Sh HISTORY 156The 157.Fn strnstr 158function was introduced by 159.Fx 4.5 160and is non-standard. 161