1.\" $NetBSD: memmem.3,v 1.4 2024/11/01 16:36:58 nia Exp $ 2.\" 3.\" Copyright (c) 2005 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Perry E. Metzger of Metzger, Dowdeswell & Co. LLC. 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.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGE. 29.\" 30.Dd November 1, 2024 31.Dt MEMMEM 3 32.Os 33.Sh NAME 34.Nm memmem 35.Nd locate substring in byte string 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In string.h 40.Ft void * 41.Fn memmem "const void *block" "size_t blen" "const void *pat" "size_t plen" 42.Sh DESCRIPTION 43The 44.Fn memmem 45function locates the first occurrence of the binary string 46.Fa pat 47of size 48.Fa plen 49bytes in the byte string 50.Fa block 51of size 52.Fa blen 53bytes. 54.Sh RETURN VALUES 55The 56.Fn memmem 57function returns a pointer to the substring located, or 58.Dv NULL 59if no such substring exists within 60.Fa block . 61.Pp 62If 63.Fa plen 64is zero, 65.Fa block 66is returned, i.e. a zero length 67.Fa pat 68is deemed to match the start of the string, as with 69.Xr strstr 3 . 70.Sh SEE ALSO 71.Xr bm 3 , 72.Xr memchr 3 , 73.Xr strchr 3 , 74.Xr strstr 3 75.Sh STANDARDS 76The 77.Nm 78function conforms to 79.St -p1003.1-2024 . 80.Sh HISTORY 81.Fn memmem 82first appeared in the Free Software Foundation's glibc library. 83