xref: /freebsd/lib/libc/string/bzero.3 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)

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.Dd August 24, 2015
.Dt BZERO 3
.Os
.Sh NAME
.Nm bzero ,
.Nm explicit_bzero
.Nd write zeroes to a byte string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In strings.h
.Ft void
.Fn bzero "void *b" "size_t len"
.Ft void
.Fn explicit_bzero "void *b" "size_t len"
.Sh DESCRIPTION
The
.Fn bzero
function
writes
.Fa len
zero bytes to the string
.Fa b .
If
.Fa len
is zero,
.Fn bzero
does nothing.
.Pp
The
.Fn explicit_bzero
variant behaves the same, but will not be removed by a compiler's dead store
optimization pass, making it useful for clearing sensitive memory such as a
password.
.Sh SEE ALSO
.Xr memset 3 ,
.Xr swab 3
.Sh HISTORY
A
.Fn bzero
function
appeared in
.Bx 4.3 .
Its prototype existed previously in
.In string.h
before it was moved to
.In strings.h
for
.St -p1003.1-2001
compliance.
.Pp
The
.Fn explicit_bzero
function first appeared in
.Ox 5.5
and
.Fx 11.0 .
.Pp
.St -p1003.1-2008
removes the specification of
.Fn bzero
and it is marked as LEGACY in
.St -p1003.1-2004 .
For portability with other systems new programs should use
.Xr memset 3 .