Ruby Process.spawn with pipes

example.rb

100.times do
  r,w = IO.pipe
  pid1 = Process.spawn(Hash.new, "echo", "foo\nbar\nbaz\nfood", out: w)
  pid2 = Process.spawn(Hash.new, "grep", "foo", in: r)
  foo = Process.waitpid2(pid1)
  
  # don't forget to close the write pipe, otherwise this will hang on the second process indefinitely
  w.close
  bar = Process.waitpid2(pid2)
  
  # this isn't necessary since the write end of the pipe has been closed,
  r.close
end