Ruby でコマンドをパイプで接続して実行し、各子プロセスの Exit status を取得するサンプル

cmd_pipe.rb

def cmd_pipe(*commands)
  raise TypeError unless commands.is_a?(Array)
  raise ArgumentError if commands.size < 2

  pids = []
  pipes = []
  pipe_next = nil
  until((cmd = commands.shift).nil?)
    pipe_in = pipe_next || $stdin

    if commands.empty?
      pipe_out = $stdout
    else
      pipe_next, pipe_out = IO.pipe
      pipes << pipe_next << pipe_out
    end

    pids << spawn(cmd, in: pipe_in, out: pipe_out)
  end
  pipes.each(&:close)

  pids.map { |pid| Process.waitpid2(pid)[1] }
end

# $ cmd1 | cmd2
cmd_piep('cmd1', 'cmd2')