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 gen-erated generated
erated 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-qual-ity high-quality
ity random number generator (i.e., /dev/urandom) is not available, in which case a pseudo-random gen-erator generator
erator will be subsituted. Note that the use of a pseudo-random generator may compromise the unique-ness uniqueness
ness 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
http://e2fsprogs.sourceforge.net/
SEE ALSO
uuid(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)
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