crawler.rb

require 'thread'

class Crawler
  def initialize(root='.', pattern='**/*.rb', period=5)
    @root = File.expand_path(root)
    @pattern = pattern
    @period = period
    @last = {}
    @queue = SizedQueue.new(2)
  end

  def pop
    @queue.pop
  end

  def updated?(fname)
    mtime = File.mtime(fname)
    mtime != @last[fname]
  ensure
    @last[fname] = mtime
  end

  def do_crawl
    Dir.chdir(@root)
    Dir.glob(@pattern).each do |fname|
      @queue.push(fname) if updated?(fname)
    end
  end

  def stop
    @running = false
  end

  def start
    @running = true
    Thread.new do
      while @running
        do_crawl
        sleep(@period)
      end
    end
  end
end

c = Crawler.new('.', '**/*.rb')
c.start
10.times do
  p c.pop
end