test.rb

def ask_question(question, opts={})
  question = question + "[#{opts[:default]}] " if opts[:default]

    STDOUT.print question
    a = STDIN.readline.strip

    if opts[:default]
      a.empty? ? opts[:default] : a
    else
      a
    end
end

x = ask_question("test Y/N/(A)ll/(Q)uit ", :default => "N")
puts "=> #{x}"