pipeline_run

# File lib/open3.rb, line 609
  def pipeline_run(cmds, pipeline_opts, child_io, parent_io) # :nodoc:
    if cmds.empty?
      raise ArgumentError, "no commands"
    end

    opts_base = pipeline_opts.dup
    opts_base.delete :in
    opts_base.delete :out

    wait_thrs = []
    r = nil
    cmds.each_with_index {|cmd, i|
      cmd_opts = opts_base.dup
      if String === cmd
        cmd = [cmd]
      else
        cmd_opts.update cmd.pop if Hash === cmd.last
      end
      if i == 0
        if !cmd_opts.include?(:in)
          if pipeline_opts.include?(:in)
            cmd_opts[:in] = pipeline_opts[:in]
          end
        end
      else
        cmd_opts[:in] = r
      end
      if i != cmds.length - 1
        r2, w2 = IO.pipe
        cmd_opts[:out] = w2
      else
        if !cmd_opts.include?(:out)
          if pipeline_opts.include?(:out)
            cmd_opts[:out] = pipeline_opts[:out]
          end
        end
      end
      pid = spawn(*cmd, cmd_opts)
      wait_thrs << Process.detach(pid)
      r.close if r
      w2.close if w2
      r = r2
    }
    result = parent_io + [wait_thrs]
    child_io.each(&:close)
    if defined? yield
      begin
        return yield(*result)
      ensure
        parent_io.each(&:close)
        wait_thrs.each(&:join)
      end
    end
    result
  end