Perl : How to Create Unique String/Number?

[EchoAngel]

Hi Monks, I was looking to create this unique random string mix with numbers and letters. I was thinking of a length of 10-20. How can I do this?

[Fletch]

Data::UUID

Update: Just to clarify, this is probably what you want to use rather than just a random string if uniqueness is important; with the random solutions you'll need to keep a canonical list and make sure there's no dupes yourself. The UUID scheme shouldn't make a dupe of anyone else's value for another 1395-ish years if you set it up correctly.

[fglock]

use Digest::MD5; 
print Digest::MD5::md5_base64( rand ), "\n";

# BxaMo0Fkirbh1A+9JbbvjQ

update: see String::Random

[amw1]

While a random string _may_ be unique there's nothing that really guarantees(sp?) that it will be. UUID's however are. There is a perl module Data::UUID that will generate these things for you.

I have not used the module but I have used uuid's in the past for unique identifiers.

man uuidgen may give you more info.

[Roy Johnson]

my @alphabet = (('a'..'z'), 0..9);
my %collection;
for (1..30) {
  my $len = rand(11) + 10;
  my $key = join '', map {$alphabet[rand(@alphabet)]} 1..$len;
  $collection{$key} ? redo : $collection{$key}++;
}
print join "\n", keys %collection;

[friedo]

I usually use something like this:

my @a = map { chr } (33..126); # printable ASCII chars
my $string;
$string .= $a[rand(@a)] for 1..20;

[sleepingsquirrel]

Might not be exactly what you're looking for, but maybe a place to start.

#!/usr/bin/perl -w

$len =  11 + int(rand(10));
$r  .=  chr(48 + rand(74)) for (1..$len);
$r   =~ s/\W//g;
print "$r\n";

[TedPride]

Depending on what your needs are, a MD5 hash on time and user IP is probably best. The time-IP combination is not repeatable, and MD5 has an almost certain probability of creating a unique hash given a unique input.

[thor]

The time-IP combination is not repeatable

Time to what granularity? If you're talking to second-level granularity, I'll have to disagree. What about requests coming from behind a proxy? All of the internet traffic from my place of work seems to come from the same IP (and for all intents and purposes it does) regardless of the computer that's actually issuing the request. What happens when a lot of traffic is generated from one such place? If you think it can't happen, think again. Data::UUID is the way to go. Smarter people than you and I have thought about this problem and come up with that solution.

[EchoAngel]

mmm, what characters should I not put because I want to generate an unique string that would be used for naming files?