NAME
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 number 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
compromise 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 generated.
This can cause privacy problems in some applications, so the
uuid_generate function only uses this algorithm if a high-quality
source of randomness is not available.
The UUID is 16 bytes (128 bits) long, which gives approximately
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 considered unique among all UUIDs created on the
local system, 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
AUTHOR
Theodore Y. Ts’o
AVAILABILITY
libuuid is part of the util-linux-ng package since version 2.15.1 and
is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
SEE ALSO
uuid(3), uuidgen(1), uuid_clear(3), uuid_compare(3), uuid_copy(3),
uuid_is_null(3), uuid_parse(3), uuid_time(3), uuid_unparse(3)