How can I have console output display to stdout AND store it in a variable?

If I do this:

output = %x{some_script}

...then I have the stuff printed to stdout stored in output; but I don't see it appear on the screen.

On the other hand, if I do this:

success = system "som开发者_如何学编程e_script"

...then I see the output appear on the screen, but I don't have it stored in a variable (success just holds a boolean value).

Is there some way to get both? I'm aware I could do this:

output = %x{some_script}
puts output

But the problem there is that some_script might be a pretty long-running script, in which case I see nothing until the whole thing is finished. I'd prefer to see output as it's produced, and when it's finished to have it all stored in the output variable.

This is a solution with IO.popen:

require 'stringio'

output = StringIO.new

IO.popen("ls") do |pipe|
  pipe.each do |line|
    output.puts line
    puts line
  end
end

puts output.string # => Outputs the contents of `output` as a string

You could monkeypatch Kernel::puts, but I can only think of a kludgy global way to store the results:

class Kernel
  alias_method :old_puts, :puts
  def puts(*args)
    old_puts args
    $output << args
  end
end