UUID_GENERATE(3)UUID_GENERATE(3)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 algo‐
rithm which uses the current time and the local ethernet MAC address
(if available). This algorithm used to be the default one used to gen‐
erate 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 func‐
tion 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 parti‐
cles 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
http://e2fsprogs.sourceforge.net/ ⟨http://e2fsprogs.sourceforge.net/⟩
SEE ALSOuuid(3), uuidgen(1), uuid_clear(3), uuid_compare(3), uuid_copy(3),
uuid_is_null(3), uuid_parse(3), uuid_unparse(3)1.36 April 2004 UUID_GENERATE(3)
