timeout

# File lib/timeout.rb, line 43
  def timeout(sec, klass = nil)   #:yield: +sec+
    return yield(sec) if sec == nil or sec.zero?
    exception = klass || Class.new(ExitException)
    begin
      x = Thread.current
      y = Thread.start {
        sleep sec
        x.raise exception, "execution expired" if x.alive?
      }
      return yield(sec)
    rescue exception => e
      rej = /\A#{Regexp.quote(__FILE__)}:#{__LINE__-4}\z/
      (bt = e.backtrace).reject! {|m| rej =~ m}
      level = -caller(CALLER_OFFSET).size
      while THIS_FILE =~ bt[level]
        bt.delete_at(level)
        level += 1
      end
      raise if klass            # if exception class is specified, it
                                # would be expected outside.
      raise Error, e.message, e.backtrace
    ensure
      if y and y.alive?
        y.kill 
        y.join # make sure y is dead.
      end
    end
  end