follow-redirect.rb: checks where shortened URLs are going

follow-redirect.rb

#!/usr/bin/ruby
# redirect.rb: checks where shortened URLs are going
#
# usage: ruby redirect.rb http://example.com/
#        shows URLs while being redirected
#
# Copyright 2011 (C) zunda <zunda at freeshell.org>
#
# Permission is granted for use, copying, modification,
# distribution, and distribution of modified versions of this
# work as long as the above copyright notice is included.
#

require 'uri'
require 'net/http'

def follow(url, redirects = 5, &block)
	yield(url)
	raise RuntimeError, "Too many redirects" if redirects == 0
	uri = URI.parse(url)
	begin
		Net::HTTP.start(uri.host, uri.port) do |http|
			request = Net::HTTP::Head.new(uri.request_uri)
			response = http.request(request)
			case response
			when Net::HTTPRedirection
				follow(response['location'], redirects - 1, &block)
			when Net::HTTPNotFound
				raise RuntimeError, "Not Found"
			end
		end
	rescue Errno::EHOSTUNREACH => e
		raise RuntimeError, e
	rescue Errno::ECONNREFUSED => e
		raise RuntimeError, e
	rescue Errno::ECONNRESET => e
		raise RuntimeError, e
	end
end

begin
	follow(ARGV.shift) do |url|
		puts url
	end
rescue RuntimeError => e
	puts e.message
end