config.ru

require 'rack-rewrite'

DOMAIN = 'www.production-hacks.com' # also works with non-www url such as 'google.com'

# Redirect to the www version of the domain in production
use Rack::Rewrite do
  r301 %r{.*}, "http://#{DOMAIN}$&", :if => Proc.new {|rack_env|
    rack_env['SERVER_NAME'] != DOMAIN && ENV['RACK_ENV'] == "production"
  }
end