1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek. 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" $OpenBSD: bzero.3,v 1.12 2015/11/24 09:14:35 daniel Exp $ 31.\" 32.Dd $Mdocdate: November 24 2015 $ 33.Dt BZERO 3 34.Os 35.Sh NAME 36.Nm bzero , 37.Nm explicit_bzero 38.Nd write zeroes to a byte string 39.Sh SYNOPSIS 40.In strings.h 41.Ft void 42.Fn bzero "void *b" "size_t len" 43.In string.h 44.Ft void 45.Fn explicit_bzero "void *b" "size_t len" 46.Sh DESCRIPTION 47The 48.Fn bzero 49function writes 50.Fa len 51zero bytes to the string 52.Fa b . 53If 54.Fa len 55is zero, 56.Fn bzero 57does nothing. 58.Pp 59The 60.Fn explicit_bzero 61variant behaves the same, but will not be removed by a compiler's dead store 62optimization pass, making it useful for clearing sensitive memory such as a 63password. 64.Sh SEE ALSO 65.Xr memset 3 , 66.Xr swab 3 67.Sh HISTORY 68The 69.Fn bzero 70function first appeared in 71.Bx 4.2 . 72The 73.Fn explicit_bzero 74function first appeared in 75.Ox 5.5 . 76