2011-02-14 20:36:03 +01:00
|
|
|
.\" Copyright (c) 1990, 1991, 1993
|
|
|
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
|
|
|
.\"
|
|
|
|
|
.\" This code is derived from software contributed to Berkeley by
|
|
|
|
|
.\" Chris Torek and the American National Standards Committee X3,
|
|
|
|
|
.\" on Information Processing Systems.
|
|
|
|
|
.\"
|
|
|
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
|
|
|
.\" modification, are permitted provided that the following conditions
|
|
|
|
|
.\" are met:
|
|
|
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
|
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
|
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
|
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
|
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
|
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
|
|
|
.\" may be used to endorse or promote products derived from this software
|
|
|
|
|
.\" without specific prior written permission.
|
|
|
|
|
.\"
|
|
|
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
|
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
|
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
|
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
|
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
|
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
|
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
|
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
|
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
|
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
|
|
|
.\" SUCH DAMAGE.
|
|
|
|
|
.\"
|
|
|
|
|
.\" from: @(#)memset.3 8.1 (Berkeley) 6/4/93
|
2013-12-06 12:04:52 +01:00
|
|
|
.\" $NetBSD: memset.3,v 1.12 2013/06/24 07:56:49 wiz Exp $
|
2011-02-14 20:36:03 +01:00
|
|
|
.\"
|
2013-12-06 12:04:52 +01:00
|
|
|
.Dd June 23, 2013
|
2011-02-14 20:36:03 +01:00
|
|
|
.Dt MEMSET 3
|
|
|
|
|
.Os
|
|
|
|
|
.Sh NAME
|
|
|
|
|
.Nm memset
|
|
|
|
|
.Nd write a byte to byte string
|
|
|
|
|
.Sh LIBRARY
|
|
|
|
|
.Lb libc
|
|
|
|
|
.Sh SYNOPSIS
|
|
|
|
|
.In string.h
|
|
|
|
|
.Ft void *
|
|
|
|
|
.Fn memset "void *b" "int c" "size_t len"
|
|
|
|
|
.Sh DESCRIPTION
|
|
|
|
|
The
|
|
|
|
|
.Fn memset
|
|
|
|
|
function
|
|
|
|
|
writes
|
|
|
|
|
.Fa len
|
|
|
|
|
bytes of value
|
|
|
|
|
.Fa c
|
|
|
|
|
(converted to an unsigned char) to the string
|
|
|
|
|
.Fa b .
|
|
|
|
|
.Sh RETURN VALUES
|
|
|
|
|
The
|
|
|
|
|
.Fn memset
|
|
|
|
|
function
|
|
|
|
|
returns the original value of
|
|
|
|
|
.Fa b .
|
2013-12-06 12:04:52 +01:00
|
|
|
.Pp
|
|
|
|
|
Note that the compiler may optimize away a call to
|
|
|
|
|
.Fn memset
|
|
|
|
|
if it can prove that the string will not be used by the program again,
|
|
|
|
|
for example if it is allocated on the stack and about to out of scope.
|
|
|
|
|
If you want to guarantee that zeros are written to memory, for example
|
|
|
|
|
to sanitize a buffer holding a cryptographic secret, use
|
|
|
|
|
.Xr explicit_memset 3 .
|
2011-02-14 20:36:03 +01:00
|
|
|
.Sh SEE ALSO
|
|
|
|
|
.Xr bzero 3 ,
|
2013-12-06 12:04:52 +01:00
|
|
|
.Xr explicit_memset 3 ,
|
2011-02-14 20:36:03 +01:00
|
|
|
.Xr swab 3
|
|
|
|
|
.Sh STANDARDS
|
|
|
|
|
The
|
|
|
|
|
.Fn memset
|
|
|
|
|
function
|
|
|
|
|
conforms to
|
|
|
|
|
.St -ansiC .
|
