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 1.11 2014/01/22 22:21:25 jmc Exp $ 31.\" 32.Dd $Mdocdate: January 22 2014 $ 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 string.h 41.Ft void 42.Fn bzero "void *b" "size_t len" 43.Ft void 44.Fn explicit_bzero "void *b" "size_t len" 45.Sh DESCRIPTION 46The 47.Fn bzero 48function writes 49.Fa len 50zero bytes to the string 51.Fa b . 52If 53.Fa len 54is zero, 55.Fn bzero 56does nothing. 57.Pp 58The 59.Fn explicit_bzero 60variant behaves the same, but will not be removed by a compiler's dead store 61optimization pass, making it useful for clearing sensitive memory such as a 62password. 63.Sh SEE ALSO 64.Xr memset 3 , 65.Xr swab 3 66.Sh HISTORY 67The 68.Fn bzero 69function first appeared in 70.Bx 4.2 . 71The 72.Fn explicit_bzero 73function first appeared in 74.Ox 5.5 . 75