xref: /freebsd/lib/libc/string/bzero.3 (revision 59c8e88e72633afbc47a4ace0d2170d00d51f7dc)
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31.Dd August 24, 2015
32.Dt BZERO 3
33.Os
34.Sh NAME
35.Nm bzero ,
36.Nm explicit_bzero
37.Nd write zeroes to a byte string
38.Sh LIBRARY
39.Lb libc
40.Sh SYNOPSIS
41.In strings.h
42.Ft void
43.Fn bzero "void *b" "size_t len"
44.Ft void
45.Fn explicit_bzero "void *b" "size_t len"
46.Sh DESCRIPTION
47The
48.Fn bzero
49function
50writes
51.Fa len
52zero bytes to the string
53.Fa b .
54If
55.Fa len
56is zero,
57.Fn bzero
58does nothing.
59.Pp
60The
61.Fn explicit_bzero
62variant behaves the same, but will not be removed by a compiler's dead store
63optimization pass, making it useful for clearing sensitive memory such as a
64password.
65.Sh SEE ALSO
66.Xr memset 3 ,
67.Xr swab 3
68.Sh HISTORY
69A
70.Fn bzero
71function
72appeared in
73.Bx 4.3 .
74Its prototype existed previously in
75.In string.h
76before it was moved to
77.In strings.h
78for
79.St -p1003.1-2001
80compliance.
81.Pp
82The
83.Fn explicit_bzero
84function first appeared in
85.Ox 5.5
86and
87.Fx 11.0 .
88.Pp
89.St -p1003.1-2008
90removes the specification of
91.Fn bzero
92and it is marked as LEGACY in
93.St -p1003.1-2004 .
94For portability with other systems new programs should use
95.Xr memset 3 .
96