Sunday, June 15, 2008

IRB/Console tweaks

Today ill explain how you can tweak your irb and rails console. First you'll need an irb configuration file called '.irbrc' which should be placed in your home directory. You'll need to create one if it doesn't already exist. Now you can add the following.

#Load the readline module.
IRB.conf[:USE_READLINE] = true

#Remove the annoying irb(main):001:0 and replace with >>

#Always nice to have auto indentation
IRB.conf[:AUTO_INDENT] = true

#History configuration
IRB.conf[:SAVE_HISTORY] = 100
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb-save-history"

#Load modules if not already loaded
IRB.conf[:LOAD_MODULES] = [] unless IRB.conf.key?(:LOAD_MODULES)
unless IRB.conf[:LOAD_MODULES].include?('irb/completion')
IRB.conf[:LOAD_MODULES] << 'irb/completion' #Autocompletion of keywords
IRB.conf[:LOAD_MODULES] << 'irb/ext/save-history' #Persist history across sessions

The comments should be pretty much self-explanatory. By fat the most useful feature has to be the auto-completion of keywords. So now you can just hit tab tab to display all methods of on an object.

The next biggest feature has to be the persistence of the history across sessions. Anything that helps me save a few repetitious keystrokes is a big gain in my book.

Since console is just basically irb on steroids you will have all this functionality there too!

You can also add rails/console configurations here. Just make sure you are in the right environment before trying anything rails specific so irb doesnt blow up.

#do something rails specific

A good way to separate out your rails specific configurations is to include it in another file and just load it from .irbrc This idea and the following are slight modifications of the snack recipes from the great book Advanced Rails Recipes (Authors of the recipe are at You'll need to create a file called .railsrc in your home directory.

load "#{ENV['HOME']}/.railsrc"

One helpful method I like to have in .railsrc is the ability to turn on and off ActiveRecord logging to the console to help analyze/debug my sql.

#Enable ActiveRecord logging
def loud_logger(enable = true)
logger = (enable == true ? : nil)
ActiveRecord::Base.logger = logger

Now you can easily turn on and off your ActiveRecord logging.

>> SomeModel.first
=> # < SomeModel id: 1.. >
>> loud_logger
>> SomeModel.first
SomeModel Load (0.000442) SELECT * FROM some_models LIMIT 1
>> loud_logger false
>> SomeModel.first
=> # < SomeModel id: 1.. >


Anonymous said...


Thank you kindly.

Kris said...

Very helpful advice on setting up my terminal.