# File monit/lib/symbiosis/monitor/process.rb, line 16
        def pid
          raise ArgumentError, "pidfile not set" if @pidfile.nil?
          begin
            #
            # Try to read the pidfile
            #
            pid = File.open(@pidfile,'r'){|fh| fh.read}.chomp
            #
            # Sanity check the PID found.
            #
            raise ArgumentError, "Bad PID in #{@pidfile}" unless pid =~ /^\d+$/
            return pid

          rescue Errno::ENOENT
            #
            # pidfile missing...
            #
            return nil
          end
        end