.irbrc

require 'rubygems'
require 'irb/completion'
require 'ap'

unless IRB.version.include?('DietRB')
  IRB::Irb.class_eval do
    def output_value
      ap @context.last_value
    end
  end
else # MacRuby
  IRB.formatter = Class.new(IRB::Formatter) do
    def inspect_object(object)
      object.ai
    end
  end.new
end


def ri(*names)
  system(%{ri #{names.map {|name| name.to_s}.join(" ")}})
end

#######################################
#  Ryan Bates' Rails Logger hack      #
# (http://railscasts.com/episodes/56) #
#######################################
if ENV.include?('RAILS_ENV') && !Object.const_defined?('RAILS_DEFAULT_LOGGER')
  require 'logger'
  RAILS_DEFAULT_LOGGER = Logger.new(STDOUT)
end

#################################################
# Ben Bleything's Shell-style History for irb   #
# (http://blog.bleything.net/pages/irb_history) #
############################################################
# Adds shell-style history display and replay to irb.      #
# The magic happens in the h, h!, and hw methods.          #
# == Authors                                               #
# * Ben Bleything <[email protected]>                      #
# == Copyright                                             #
# Copyright (c) 2007 Ben Bleything                         #
# This code released under the terms of the BSD license.   #
# == Version                                               #
#  $Id: history.rb 50 2007-07-30 18:55:09Z ben $           #
############################################################
# Lists the last how_many lines of history (defaults to 50).  Aliased to h.
def history( how_many = 50 )
    history_size = Readline::HISTORY.size

    # no lines, get out of here
    puts "No history" and return if history_size == 0

    start_index = 0

    # not enough lines, only show what we have
    if history_size <= how_many
        how_many  = history_size - 1
        end_index = how_many
    else
        end_index = history_size - 1 # -1 to adjust for array offset
        start_index = end_index - how_many 
    end

    start_index.upto( end_index ) {|i| print_line i}
    nil
end
alias :h  :history

# replay lines from history.  Aliased to h!
#
# h! by itself will replay the most recent line.  You can also pass in a
# range, array, or any mixture of the three.
#
# We subtract 2 from HISTORY.size because -1 is the command we just issued.
def history_do( *lines )
    lines = [Readline::HISTORY.size - 2] if lines.empty?

    to_eval = get_lines( lines )

    to_eval.each {|l| Readline::HISTORY << l}

    IRB.CurrentContext.workspace.evaluate self, to_eval.join(';')
end
alias :h! :history_do

# writes history to a named file.  This is useful if you want to show somebody
# something you did in irb, or for rapid prototyping.  Aliased to hw.
#
# Uses similar calling semantics to h!, that is, you can pass in fixnums,
# ranges, arrays, or any combination thereof.
def history_write( filename, *lines )
    File.open( filename, 'w' ) do |f|
        get_lines( lines ).each do |l|
            f.puts l
        end
    end
end
alias :hw :history_write

private

# simple getter to fetch from Readline
def get_line(line_number)
    Readline::HISTORY[line_number]
end

# the code what powers the line fetcherating.  Accepts an array and iterates
# over each entry, fetching that line from the history and placing it into a
# temporary array which is ultimately returned.
def get_lines( lines )
    out = []

    lines.each do |line|
        case line
        when Fixnum
            out << get_line( line )
        when Range
            line.to_a.each do |l|
                out << get_line( l )
            end
        end
    end

    return out
end

# prints out the contents of the line from history, along with a line number,
# if desired.
def print_line(line_number, show_line_numbers = true)
    print "[%04d] " % line_number if show_line_numbers
    puts get_line(line_number)
end 

The history code by Ben is used in DietRB as well, so you don't need to define those yourself and could move it into the ‘unless IRB.version.include?('DietRB')’ clause.

Cool. I didn't know that. Thanks for the tip!

No problem :) I need to to work on the DietRB docs, there aren't really any, so it's hard to know what features are available…