1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.Dd August 15, 2016 33.Dt MEMCMP 3 34.Os 35.Sh NAME 36.Nm memcmp 37.Nd compare byte string 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In string.h 42.Ft int 43.Fn memcmp "const void *b1" "const void *b2" "size_t len" 44.Sh DESCRIPTION 45The 46.Fn memcmp 47function 48compares byte string 49.Fa b1 50against byte string 51.Fa b2 . 52Both strings are assumed to be 53.Fa len 54bytes long. 55.Sh RETURN VALUES 56The 57.Fn memcmp 58function 59returns zero if the two strings are identical, 60otherwise returns the difference between the first two differing bytes 61(treated as 62.Vt "unsigned char" 63values, so that 64.Sq Li \e200 65is greater than 66.Sq Li \&\e0 , 67for example). 68Zero-length strings are always identical. 69.Sh SEE ALSO 70.Xr bcmp 3 , 71.Xr strcasecmp 3 , 72.Xr strcmp 3 , 73.Xr strcoll 3 , 74.Xr strxfrm 3 , 75.Xr timingsafe_memcmp 3 , 76.Xr wmemcmp 3 77.Sh STANDARDS 78The 79.Fn memcmp 80function 81conforms to 82.St -isoC . 83