With Ruby you can use the Domainatrix library / gem
http://www.pauldix.net/2009/12/parse-domains-from-urls-easily-with-domainatrix.html
require 'rubygems'
require 'domainatrix'
s = 'http://www.champa.kku.ac.th/dir1/dir2/file?option1&option2'
url = Domainatrix.parse(s)
url.domain
=> "kku"
great tool! :-)