rack_auth_basic.rb

# config.ru

class RackApp
  def call(env)
    [200, {'Content-Type' => 'text/plain'}, ["Hello world!"]]
  end
end

class AdminRackApp
  def call(env)
    [200, {'Content-Type' => 'text/html'}, ["Hello world from my Admin area!"]]
  end
end

map "/" do 
  run RackApp.new 
end

map "/admin" do
  use Rack::Auth::Basic, "Admin area" do |username, password|
    [username, password] == ['foo', 'bar']
  end
  run AdminRackApp.new 
end