How do I create a SHA1 hash in ruby?

require 'digest/sha1'
Digest::SHA1.hexdigest 'foo'

I created a helper gem which is a simple wrapper around some sha1 code

require 'rickshaw'
> Rickshaw::SHA1.hash('LICENSE.txt')

 => "4659d94e7082a65ca39e7b6725094f08a413250a" 

> "hello world".to_sha1

 => "2aae6c35c94fcfb415dbe95f408b9ce91ee846ed"