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. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)bzero.3 8.1 (Berkeley) 6/4/93 32.\" $FreeBSD: head/lib/libc/string/bzero.3 251069 2013-05-28 20:57:40Z emaste $ 33.\" 34.Dd April 11, 2019 35.Dt BZERO 3 36.Os 37.Sh NAME 38.Nm bzero , 39.Nm explicit_bzero 40.Nd write zeroes to a byte string 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In strings.h 45.Ft void 46.Fn bzero "void *b" "size_t len" 47.Ft void 48.Fn explicit_bzero "void *b" "size_t len" 49.Sh DESCRIPTION 50The 51.Fn bzero 52function writes 53.Fa len 54zero bytes to the string 55.Fa b . 56If 57.Fa len 58is zero, 59.Fn bzero 60does nothing. 61.Pp 62The 63.Fn explicit_bzero 64variant behaves the same, but will not be removed by a compiler's dead store 65optimization pass, making it useful for clearing sensitive memory such as a 66password. 67.Sh SEE ALSO 68.Xr memset 3 , 69.Xr swab 3 70.Sh STANDARDS 71The 72.Fn bzero 73function conforms to the X/Open System Interfaces option of the 74.St -p1003.1-2004 75specification. 76It was removed from the standard in 77.St -p1003.1-2008 , 78which recommends using 79.Xr memset 3 80instead. 81.Sh HISTORY 82The 83.Fn bzero 84function appeared in 85.Bx 4.3 . 86Its prototype existed previously in 87.In string.h 88before it was moved to 89.In strings.h 90for 91.St -p1003.1-2001 92compliance. 93.Pp 94The 95.Fn explicit_bzero 96function first appeared in 97.Ox 98/ 99.Dx 5.5 . 100