uuid_generate_time

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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 genera-
       tor will be subsituted.	Note that the use of a pseudo-random  genera-
       tor 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	 par-
       ticles  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
       uuid_generate  was written by Theodore Y. Ts’o for the ext2 filesystem
       utilties.

AVAILABILITY
       uuid_generate is part of libuuid from the  e2fsprogs  package  and  is
       available from http://e2fsprogs.sourceforge.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)



E2fsprogs version 1.35		February 2004		     UUID_GENERATE(3)