Re^2: Need to Generate Unique String

You can get guaranteed uniqueness by replacing the rand call with a "hold this pid until the time changes":

  $unique = time() . $$;
  sleep 1;
[download]

Hugo

Comment on Re^2: Need to Generate Unique String Download Code

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Re^3: Need to Generate Unique String by BrowserUk (Patriarch) on Jul 29, 2004 at 21:08 UTC
Guarenteed with a given process, but if multiple copies of the process are running, with time() limited to 1 second resolution? Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "Think for yourself!" - Abigail "Memory, processor, disk in that order on the hardware side. Algorithm, algoritm, algorithm on the code side." - tachyon	[reply]
Re^4: Need to Generate Unique String by hv (Prior) on Jul 30, 2004 at 12:13 UTC
Then the sleep() should ensure the pid is not reused within the same tick, so it should still remain unique. It does depend a bit on the precise sleep() implementation though; possibly safer (and a bit faster) would be: `my $t = time; select(undef, undef, undef, 0.1) while time <= $t; $unique = "$t$$";` [download] It also assumes a monotonically increasing time: if the sysadmin may correct a fast clock backwards, it would be very difficult to cope with. (Note that ntpd will adjust the time in increments of less than a second except when the clock error is "large"; once initially synchronised, a running system corrected by ntpd should never normally skip a full second forwards or backwards.) Hugo	[reply] [d/l]
Re^3: Need to Generate Unique String by ccn (Vicar) on Jul 29, 2004 at 20:04 UTC
Or use a counter: `{ my $cnt = 0; sub unique { return $time() . $$ . $cnt++; } } $unique = unique();` [download]	[reply] [d/l]