How to run a ruby script

class Dungeonapp
  attr_accessor :player

  def initialize(player_name)
    @player = Player.new(player_name)
    @rooms = []
  end

  def add_room(reference, name, description, connections)
    @rooms << Room.new(reference, name, description, connections)
  end

  def start(location)
    @player. location = location
    show_current_description
  end

  def show_current_description
    puts find_room_in_dungeon(@player.location).full_description
  end

  def find_room_in_dungeon(reference)
    @rooms.detect { |room| room.reference == reference }
  end

  def find_room_in_direction(direction)
    find_room_in_dungeon(@player.location).connections[direction]
  end

  def go(direction)
    puts "You go " + direction.to_s
    @player.location = find_room_in_direction(direction)
    show_current_description
  end

  class Player
    attr_accessor :name, :location

    def initialize(name)
      @name = name
    end
  end

  class Room
    attr_accessor :reference, :name, :description, :connections

    def initialize(reference, name, description, connections)
      @reference = reference
      @name = name
      @description = description
      @connections = connections
    end

    def full_description
      @name + "\n\nYou are in " + @description
    end
  end
end


this is my dungeonapp.rb file.I am using Ubuntu.Now how to execute this
code :

my_dungeon = Dungeon.new("Fred Bloggs")
my_dungeon.add_room(:largecave, "Large Cave", "a large cavernous cave",
{
:west => :smallcave })
my_dungeon.add_room(:smallcave, "Small Cave", "a small, claustrophobic
cave", {
:east => :largecave })

Question:
1.How to run this code from out of the file,like we do in java.Do I need
to go to irb prompt or usual command prompt for firing this code out of
the file.
2.When i copy the code of this file and directly paste on the irb prompt
it automatically add prefix "dungeonapp.rb" in each line! what is the
reason behind this.

Thank you guys.I need urgent help.

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