pty_expect_qemu.rb

require 'pty'
require 'expect'

qemu_command = "qemu-system-x86_64 -enable-kvm -cdrom ~/alpines/alpine-virt-3.6.2-x86_64.iso -nographic"

PTY.spawn qemu_command do |r, w, pid|
  p pid

  r.expect /localhost login: / do |message|
    puts "The message is #{message}."
    w.puts "root"
  end

  p r.read 10
end