Ruby class for capturing puts / stdout buffer

caputre_stdout.rb

require 'stringio'

class CaptureStdout
  def initialize(&blk)
    @handler = blk
  end

  def capture
    StringIO.open do |io|
      stash = $stdout
      $stdout = io
      yield
      $stdout = stash
      handle_output(io)
    end
  end

  def handle_output(io)
    @handler.call(io.string)
  end
end

# define your capturer and its behavior
c = CaptureStdout.new{|s| s.each_line{|l| puts "Received: " + l.upcase}}
# caputre!
c.capture do
  puts "hello"
  puts "world"
end

# --- output: ---
# Received: HELLO
# Received: WORLD