uuid_generate, uuid_generate_random, uuid_generate_time -
create a new unique UUID value
SYNOPSIS
#include <uuid/uuid.h>
void uuid_generate(uuid_t out);
void uuid_generate_random(uuid_t out);
void uuid_generate_time(uuid_t out);
DESCRIPTION
The uuid_generate function creates a new universally
unique identifier (UUID). The uuid will be generated
based on high-quality randomness from /dev/urandom, if
available. If it is not available, then uuid_generate
will use an alternative algorithm which uses the current
time, the local ethernet MAC address (if available), and
random data generated using a pseudo-random generator.
The uuid_generate_random function forces the use of the
all-random UUID format, even if a high-quality random num
ber generator (i.e., /dev/urandom) is not available, in
which case a pseudo-random generator will be subsituted.
Note that the use of a pseudo-random generator may compro
mise the uniqueness of UUID's generated in this fashion.
The uuid_generate_time function forces the use of the
alternative algorithm which uses the current time and the
local ethernet MAC address (if available). This algorithm
used to be the default one used to generate UUID, but
because of the use of the ethernet MAC address, it can
leak information about when and where the UUID was gener
ated. This can cause privacy problems in some applica
tions, so the uuid_generate function only uses this algo
rithm if a high-quality source of randomness is not avail
able.
The UUID is 16 bytes (128 bits) long, which gives approxi
mately 3.4x10^38 unique values (there are approximately
10^80 elemntary particles in the universe according to
Carl Sagan's Cosmos). The new UUID can reasonably be con
sidered unique among all UUIDs created on the local sys
tem, and among UUIDs created on other systems in the past
and in the future.
RETURN VALUE
The newly created UUID is returned in the memory location
pointed to by out.
CONFORMING TO
OSF DCE 1.1
uuid_generate was written by Theodore Y. Ts'o for the ext2
filesystem utilties.
AVAILABILITY
uuid_generate is part of libuuid from the e2fsprogs pack
age and is available from http://e2fsprogs.source
forge.net.
SEE ALSO
libuuid(3), uuid_clear(3), uuid_compare(3), uuid_copy(3),
uuidgen(1), uuid_is_null(3), uuid_parse(3), uuid_time(3),
uuid_unparse(3)
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