Simple S3 signing for expiring URLs (Ruby)

s3sign.rb

#!/usr/bin/env ruby
require 'time'
require 'uri'
require 'cgi'
require 'base64'
require 'openssl'

expires = Time.now().to_i + Integer(ARGV[0])
url = URI.parse(ARGV[1])
access_key = ENV["AWS_ACCESS_KEY_ID"]
secret_key = ENV["AWS_SECRET_ACCESS_KEY"]

h = OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new,
                         secret_key,
                         "GET\n\n\n#{expires}\n#{url.path}")

sign = CGI::escape(Base64.encode64(h).strip)

print "#{ARGV[1]}?AWSAccessKeyId=#{access_key}&Expires=#{expires}&Signature=#{sign}\n"