uuid_generate_time

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
       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 1.32           November 2002                UUID_GENERATE(3)