uuid_generate_random(3)

1UUID_GENERATE(3)           Library Functions Manual           UUID_GENERATE(3)
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NAME

6       uuid_generate,  uuid_generate_random, uuid_generate_time - create a new
7       unique UUID value
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SYNOPSIS

10       #include <uuid/uuid.h>
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12       void uuid_generate(uuid_t out);
13       void uuid_generate_random(uuid_t out);
14       void uuid_generate_time(uuid_t out);
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DESCRIPTION

17       The uuid_generate function creates a new universally unique  identifier
18       (UUID).   The  uuid  will be generated based on high-quality randomness
19       from  /dev/urandom,  if  available.   If  it  is  not  available,  then
20       uuid_generate  will use an alternative algorithm which uses the current
21       time, the local ethernet MAC address (if available),  and  random  data
22       generated using a pseudo-random generator.
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24       The uuid_generate_random function forces the use of the all-random UUID
25       format,  even  if  a  high-quality  random  number   generator   (i.e.,
26       /dev/urandom) is not available, in which case a pseudo-random generator
27       will be subsituted.  Note that the use of a pseudo-random generator may
28       compromise the uniqueness of UUID's generated in this fashion.
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30       The uuid_generate_time function forces the use of the alternative algo‐
31       rithm which uses the current time and the local  ethernet  MAC  address
32       (if available).  This algorithm used to be the default one used to gen‐
33       erate UUID, but because of the use of the ethernet MAC address, it  can
34       leak information about when and where the UUID was generated.  This can
35       cause privacy problems in some applications, so the uuid_generate func‐
36       tion only uses this algorithm if a high-quality source of randomness is
37       not available.
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39       The UUID is  16  bytes  (128  bits)  long,  which  gives  approximately
40       3.4x10^38 unique values (there are approximately 10^80 elemntary parti‐
41       cles in the universe according to Carl Sagan's Cosmos).  The  new  UUID
42       can  reasonably  be  considered  unique  among all UUIDs created on the
43       local system, and among UUIDs created on other systems in the past  and
44       in the future.
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RETURN VALUE

47       The newly created UUID is returned in the memory location pointed to by
48       out.
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CONFORMING TO

51       OSF DCE 1.1
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AUTHOR

54       Theodore Y. Ts'o
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AVAILABILITY

57       http://e2fsprogs.sourceforge.net/ ⟨http://e2fsprogs.sourceforge.net/⟩
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