irbrc

begin
  require 'readline'

  class PersistentHistory
    attr_accessor :number_of_lines_of_history_to_save, :history_file

    def initialize(options = {})
      self.number_of_lines_of_history_to_save = options[:number_of_lines_of_history_to_save]
      self.history_file                       = options[:history_file]

      yield self if block_given?

      at_exit do
        save
      end

      load
    end

    def persistent_history_enabled?
      !number_of_lines_of_history_to_save.nil? && number_of_lines_of_history_to_save.to_i > 0
    end

    private
    def load
      if File.exist?(history_file)
        open(history_file) do |f|
          f.each do |l|
            Readline::HISTORY << l.chomp
          end
        end
      end
    end

    def save
      if persistent_history_enabled?
        open(history_file, 'w') do |f|
          f.puts limit(unique_history, :to => number_of_lines_of_history_to_save)
        end
      end
    end

    def limit(a, options = {})
      if options[:to] && options[:to].to_i > 0 && a.size > options[:to]
        a[-option[:to]..-1]
      else
        a
      end
    end

    def history
      Readline::HISTORY.to_a
    end

    def unique_history
      history.reverse.uniq.reverse
    end
  end

  PersistentHistory.new do |config|
    config.number_of_lines_of_history_to_save = 1000
    config.history_file = File.expand_path('~/.irb_history')
  end
rescue LoadError => e
  STDERR.puts "Warning, readline support is not available. Get a better Ruby installation..."
end