I'm pretty sure there is a number of options to achieve this, so I'm
asking here. I often need to generate small unique tokens (like for
invitation codes or unimportant authentication token).

In the past I've been using Digest::SHA1.hexdigest(some string) which
gives us something like "d2b7882fa08bb6de8dca62f16298683bfe4f0738".
It's not very user friendly though, and definitely not small.

More recently I've been using ActiveSupport::SecureRandom.base64(6)
which generates "Xst7JGF6" or "zXxWY/Y/", but sometimes it contains
non-url friendly characters like "/".

What do you use ? Is there a specific gem to achieve this in a robust
fashion (= making collisions unlikely, and specify the characters to
be used, like mixture of numbers and characters for instance ?)

cheers and thanks for your input,

  chars = ['A'..'Z', 'a'..'z', '0'..'9'].map{|r|r.to_a}.flatten
  Array.new(6).map{chars[rand(chars.size)]}

On Dec 29, 2008, at 01:44 , Thibaut Barrère wrote:

Eric pointed me to "bubble babble" which ships in digest and makes the  
hash values more readable. It converts your "Xst7JGF6" into "xikal-
fytif-ladog-locef-kixox".

I have this rufus-mnemo that turns integers into "user friendly" strings.

http://github.com/jmettraux/rufus-mnemo

After a "sudo gem install rufus-mnemo"

you can do things like

---8<---
require 'rubygems'
require 'rufus/mnemo'

s = Rufus::Mnemo::from_integer(125704)

puts s
      # => 'karasu'
--->8---

Not exactly what you want, but could be funny. It's using a restricted
syllabary (the Japanese one) to turn integers into words (and back).

As twittered, it has the potential to generate insulting words. The
generated syllables sequences are quite easy to the latin ears though.

Best regards, meilleurs voeux pour 2009,

  puts rand(36**6).to_s(36)

just want to say thank you all for the feedback and these options.
I'll gather these into a blog post later today, I think it's worth
sharing.

Thanks again!