1.\" Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com> 2.\" 3.\" Redistribution and use in source and binary forms, with or without 4.\" modification, are permitted provided that the following conditions 5.\" are met: 6.\" 1. Redistributions of source code must retain the above copyright 7.\" notice, this list of conditions and the following disclaimer. 8.\" 2. Redistributions in binary form must reproduce the above copyright 9.\" notice, this list of conditions and the following disclaimer in the 10.\" documentation and/or other materials provided with the distribution. 11.\" 3. The name of the author may not be used to endorse or promote 12.\" products derived from this software without specific prior written 13.\" permission. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" $FreeBSD$ 28.\" 29.Dd June 29, 2023 30.Dt MEMMEM 3 31.Os 32.Sh NAME 33.Nm memmem 34.Nd "locate a byte substring in a byte string" 35.Sh LIBRARY 36.Lb libc 37.Sh SYNOPSIS 38.In string.h 39.Ft "void *" 40.Fo memmem 41.Fa "const void *big" "size_t big_len" 42.Fa "const void *little" "size_t little_len" 43.Fc 44.Sh DESCRIPTION 45The 46.Fn memmem 47function 48locates the first occurrence of the byte string 49.Fa little 50in the byte string 51.Fa big . 52.Sh RETURN VALUES 53If 54.Fa little_len 55is zero 56.Fa big 57is returned (that is, an empty little is deemed to match at the beginning of 58big); 59if 60.Fa little 61occurs nowhere in 62.Fa big , 63.Dv NULL 64is returned; 65otherwise a pointer to the first character of the first occurrence of 66.Fa little 67is returned. 68.Sh SEE ALSO 69.Xr memchr 3 , 70.Xr strchr 3 , 71.Xr strstr 3 72.Sh CONFORMING TO 73.Fn memmem 74started as a GNU extension but is now available in at least 75the GNU, musl, bionic, OpenBSD, NetBSD, macOS, and illumos C runtime libraries. 76.Sh HISTORY 77The 78.Fn memmem 79function first appeared in 80.Fx 6.0 . 81It was replaced with an optimized O(n) implementation from the musl libc 82project in 83.Fx 12.0 . 84.An Pascal Gloor Aq Mt pascal.gloor@spale.com 85provided this man page along with the previous implementation. 86.Sh BUGS 87This function was broken in Linux libc up to and including version 5.0.9 88and in GNU libc prior to version 2.1. 89Prior to 90.Fx 11.0 91.Nm 92returned 93.Dv NULL 94when 95.Fa little_len 96equals 0. 97