text: """
  Usage: webmon.py <url> [...]
  Write to stdout when a URL becomes available/unavailable, or when the content
  changes.
  """
  from twisted.web import monitor
  from twisted.internet import reactor
  import sys, time
  
  class ChangeNotified(monitor.BaseChangeNotified):
  
      def __init__(self, url):
          self.url = url
  
      def reportChange(self, old, new):
          print time.ctime(),
          if old is None:
              print self.url, "available"
          elif new is None:
              print self.url, "not available"
          else:
              print self.url, "changed"
  
  for url in sys.argv[1:]:
      notified = ChangeNotified(url)
      checker = monitor.ChangeChecker(notified, url, 30)
      checker.start()
  reactor.run()
  