短縮URLの展開

expand_url.rb

require 'net/http'
require 'uri'

def expand_url(url)
	uri = url.kind_of?(URI) ? url : URI.parse(url)
	begin
		Net::HTTP.start(uri.host, uri.port) do |io|
			r = io.head(uri.path)
			r['Location'] ? expand_url(r['Location']) : uri.to_s	
		end
	rescue
		uri.to_s
	end
end

p expand_url("http://j.mp/fNiW4v")	#=>http://www.gehirn.co.jp/

参考(というかほぼこれ): http://blog.sorah.jp/2011/01/03/ruby-url-expand-is-strange