code: def monitor(args):
      
      filename = args.get('MDFILE')
      if not filename:
          print col('Need file argument', 2)
          raise SystemExit
      last_err = ''
      last_stat = 0
      while True:
          if not os.path.exists(filename):
              last_err = 'File %s not found. Will continue trying.' % filename
          else:
              try:
                  stat = os.stat(filename)[8]
                  if stat != last_stat:
                      parsed = run_args(args)
                      print parsed
                      last_stat = stat
                  last_err = ''
              except Exception, ex:
                  last_err = str(ex)
          if last_err:
              print 'Error: %s' % last_err
          sleep()
docs: file monitor mode