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Linux 2.6 - man page for uuid_generate_random (linux section 3)

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       uuid_generate, uuid_generate_random, uuid_generate_time - create a new unique UUID value

       #include <uuid/uuid.h>

       void uuid_generate(uuid_t out);
       void uuid_generate_random(uuid_t out);
       void uuid_generate_time(uuid_t out);

       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 cur-
       rent 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 substituted.	Note that the use of a pseudo-random gen-
       erator may compromise the uniqueness of UUIDs 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 pri-
       vacy 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 elementary 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

       The newly created UUID is returned in the memory location pointed to by out.

       OSF DCE 1.1

       Theodore Y. Ts'o

       libuuid	is  part  of  the  util-linux  package since version 2.15.1 and is available from

       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)

util-linux				     May 2009				 UUID_GENERATE(3)
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