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.\" 33.Dd August 24, 2015 34.Dt BZERO 3 35.Os 36.Sh NAME 37.Nm bzero , 38.Nm explicit_bzero 39.Nd write zeroes to a byte string 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In strings.h 44.Ft void 45.Fn bzero "void *b" "size_t len" 46.Ft void 47.Fn explicit_bzero "void *b" "size_t len" 48.Sh DESCRIPTION 49The 50.Fn bzero 51function 52writes 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 HISTORY 71A 72.Fn bzero 73function 74appeared in 75.Bx 4.3 . 76Its prototype existed previously in 77.In string.h 78before it was moved to 79.In strings.h 80for 81.St -p1003.1-2001 82compliance. 83.Pp 84The 85.Fn explicit_bzero 86function first appeared in 87.Ox 5.5 88and 89.Fx 11.0 . 90.Pp 91.St -p1003.1-2008 92removes the specification of 93.Fn bzero 94and it is marked as LEGACY in 95.St -p1003.1-2004 . 96For portability with other systems new programs should use 97.Xr memset 3 . 98