Groovy script must return the current HTTP URL

I am writing a groovy script that would return me the current HTTP URL. What method needs to be called in order to get this done ? Need to start the test/service with groovy script  module - Give a URL in address bar (www.google.co.in) - The script must display the URL from address bar immediately.

It's like subscribe and notify. The groovy script must subscribe (point towards) the address bar and notify (print out) the URL from the address bar immediately.