# File lib/mixlib/shellout/unix.rb, line 39
      def run_command
        @child_pid = fork_subprocess
        @reaped = false

        configure_parent_process_file_descriptors

        # Ruby 1.8.7 and 1.8.6 from mid 2009 try to allocate objects during GC
        # when calling IO.select and IO#read. Some OS Vendors are not interested
        # in updating their ruby packages (Apple, *cough*) and we *have to*
        # make it work. So I give you this epic hack:
        GC.disable

        # CHEF-3390: Marshall.load on Ruby < 1.8.7p369 also has a GC bug related
        # to Marshall.load, so try disabling GC first.
        propagate_pre_exec_failure

        @result = nil
        @execution_time = 0

        write_to_child_stdin

        until @status
          ready_buffers = attempt_buffer_read
          unless ready_buffers
            @execution_time += READ_WAIT_TIME
            if @execution_time >= timeout && !@result
              # kill the bad proccess
              reap_errant_child
              # read anything it wrote when we killed it
              attempt_buffer_read
              # raise
              raise CommandTimeout, "Command timed out after #{@execution_time.to_i}s:\n#{format_for_exception}"
            end
          end

          attempt_reap
        end

        self
      rescue Errno::ENOENT
        # When ENOENT happens, we can be reasonably sure that the child process
        # is going to exit quickly, so we use the blocking variant of waitpid2
        reap
        raise
      ensure
        reap_errant_child if should_reap?
        # make one more pass to get the last of the output after the
        # child process dies
        attempt_buffer_read
        # no matter what happens, turn the GC back on, and hope whatever busted
        # version of ruby we're on doesn't allocate some objects during the next
        # GC run.
        GC.enable
        close_all_pipes
      end