open4 threaded io handlers

open4_threaded.rb

require 'open4'
CASE = 'ruby -e "STDERR.puts \'a\'*70000; STDOUT.puts \'Hi\'"'
puts CASE
puts "---"

status = Open4.open4(CASE) do |pid, stdin, stdout, stderr|
  stdin.close
  threads = [
    Thread.new { stdout.each_line { |l| puts "STDOUT: #{l}" } },
    Thread.new { stderr.each_line { |l| puts "STDERR: #{l}" } }
  ]
  threads.each(&:join)
end

puts status