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4.\" This code is derived from software contributed to Berkeley by
5.\" Chris Torek and the American National Standards Committee X3,
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32.\"     from: @(#)memset.3	8.1 (Berkeley) 6/4/93
33.\"	$NetBSD: memset.3,v 1.12 2013/06/24 07:56:49 wiz Exp $
34.\"
35.Dd June 23, 2013
36.Dt MEMSET 3
37.Os
38.Sh NAME
39.Nm memset
40.Nd write a byte to byte string
41.Sh LIBRARY
42.Lb libc
43.Sh SYNOPSIS
44.In string.h
45.Ft void *
46.Fn memset "void *b" "int c" "size_t len"
47.Sh DESCRIPTION
48The
49.Fn memset
50function
51writes
52.Fa len
53bytes of value
54.Fa c
55(converted to an unsigned char) to the string
56.Fa b .
57.Sh RETURN VALUES
58The
59.Fn memset
60function
61returns the original value of
62.Fa b .
63.Pp
64Note that the compiler may optimize away a call to
65.Fn memset
66if it can prove that the string will not be used by the program again,
67for example if it is allocated on the stack and about to out of scope.
68If you want to guarantee that zeros are written to memory, for example
69to sanitize a buffer holding a cryptographic secret, use
70.Xr explicit_memset 3 .
71.Sh SEE ALSO
72.Xr bzero 3 ,
73.Xr explicit_memset 3 ,
74.Xr swab 3
75.Sh STANDARDS
76The
77.Fn memset
78function
79conforms to
80.St -ansiC .
81