Example irbrc to show using rails or gem specific features when they are available.

irbrc.rb

require 'pp'
require 'bigdecimal'

File.join(ENV["PWD"],'lib').tap do |lib|
  if File.directory?(lib)
    $LOAD_PATH.unshift(lib) unless defined?(Rails)
  end
end

class BigDecimal
  @@auto_round = 3
  def self.auto_round=(val)
    @@auto_round = val
  end
  def inspect
    round(@@auto_round).to_s
  end
end

def r
  require 'redis' unless defined?(Redis)
  begin
    Redis.current.tap(&:inspect) # needed to know if connection failed
  rescue
    Redis.current = Redis.new(:path => "/tmp/redis.sock")
  end
end

if defined?(ActiveRecord::Base)
  class ActiveRecord::Base
    def self.sample
      s = scoped
      c = s.count
      s.offset(rand(c)).first
    end
  end
end