class Watcher
	def initialize
		@pid = ARGV[0]
		@handlers = []
	end

	def register(&block)
		@handlers << block
	end

	def run
		last = nil
		loop do 
			cur = File.readlink("/proc/#{@pid}/cwd")
			if cur != last
				@handlers.each do |h|
					h.call cur
				end
			end
			last = cur
		end
	end
end

if __FILE__ == $0

	if !ARGV[0]
		STDERR.puts "Usage: ruby events.rb $$ &"
		exit 1
	end
	w = Watcher.new
	w.register { |ev|
		puts "Got #{ev}"
	}
	w.run
end