Ruby stream command output

1_usage.sh

./parent.rb
command: ./child.rb 1
2018-09-12 14:32:09: stdout
2018-09-12 14:32:09: stderr
2018-09-12 14:32:11: stdout
2018-09-12 14:32:11: stderr
pid 97509 exit 1
97509
false
command: ./child.rb 0
2018-09-12 14:32:13: stdout
2018-09-12 14:32:13: stderr
2018-09-12 14:32:15: stdout
2018-09-12 14:32:15: stderr
pid 97513 exit 0
97513
true

child.rb

#!/usr/bin/env ruby

exit_status = ARGV[0].to_i

2.times do
  time_now = Time.now.strftime('%Y-%m-%d %H:%M:%S')
  $stdout.puts "#{time_now}: stdout"
  $stderr.puts "#{time_now}: stderr"
  sleep 2
end

exit exit_status

parent.rb

#!/usr/bin/env ruby

require 'pty'

def stream_command(command)
  puts "command: #{command}"
  begin
    PTY.spawn(command) do |stdout, stdin, pid|
      begin
        stdout.each { |line| print line }
      rescue Errno::EIO
      end
    end
  rescue PTY::ChildExited
  end

  # debug:
  puts $?
  puts $?.pid
  puts $?.success?
end

stream_command('./child.rb 1')

stream_command('./child.rb 0')