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 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 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.
libuuid is part of the
util-linux-ng package since version 2.15.1 and is available
from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
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)
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Copyright 1999 Andreas Dilger (adilgerenel.ucalgary.ca) %Begin-Header% Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, and the entire permission notice in its entirety, including the disclaimer of warranties. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. The name of the author may not be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. %End-Header% Created Wed Mar 10 17:42:12 1999, Andreas Dilger |