Development Blog: Viget Labs

When you run irb, the Ruby REPL, it loads the Ruby script at ~/.irbrc, if it exists. My .irbrc file has gotten kind of big lately, and the tricks it adds to my shell are great, so I thought I’d pull it apart and show you the magic inside.

Includes and setup

require 'pp'
require 'rubygems'

# wirble is amazing
require 'wirble'
Wirble.init
Wirble.colorize

IRB.conf[:AUTO_INDENT] = true

This stuff is all pretty trivial, but incredibly useful. pp is a library that comes with Ruby that prints out nested hashes and arrays in a readable format with indentation. Requiring rubygems up front almost always saves you a line of code. It also lets you require the gem wirble, which gives you cross-session history, colored output, and auto-completion.

IRB.conf[:AUTO_INDENT] = true does exactly what it sounds like: when you write code that would normally have an indent after it, like the beginning of a block, irb indents the next line.

class Object
  # get all the methods for an object that aren't basic methods from Object
  def my_methods
    (methods - Object.instance_methods).sort
  end
end

When I need to look up methods on an object, I’m always bombarded with a mess of methods on Object. This just gets rid of them for me.

# from http://themomorohoax.com/2009/03/27/irb-tip-load-files-faster
def ls
  %x{ls}.split("\n")
end

def cd(dir)
  Dir.chdir(dir)
  Dir.pwd
end

def pwd
  Dir.pwd
end

ls is copied from a person who has the same problem as me: always typing ls inside irb. This just makes that work. I figured as long as I was doing that, I might as well implement the shell commands cd and pwd.

# also from http://themomorohoax.com/2009/03/27/irb-tip-load-files-faster
def rl(file_name = nil)
  if file_name.nil?
    if !@recent.nil?
      rl(@recent) 
    else
      puts "No recent file to reload"
    end
  else
    file_name += '.rb' unless file_name =~ /\.rb/
    @recent = file_name 
    load "#{file_name}"
  end
end

This is some slick magic to help you reload Ruby code inside irb. Normally, you can re-read a file with load "<filename>.rb", which works well, but is a lot to type over and over. rl lets you just type rl "<filename>", and once you’ve called it once, you can just type rl to reload the same file again.

alias p pp
alias quit exit

Finally, I dropped two aliases into .irbrc. pp is so great that I prefer to use it over p, and I have an inability to remember to type exit instead of quit, so I just fixed that.

You can find the entire .irbrc file at http://gist.github.com/86875. If you have any irb tips of your own, let us know in the comments!