Customizing Pry and IRB Sessions

The .irbrc file

The .irbrc file is usually placed in your home directory (~/.irbc). This file is just a regular ruby file and you can write any arbitrary ruby code that you want to be executed before the IRB session is loaded.

The .pryrc file

The .pryrc file is very similar to the .irbrc file and is placed in your home directory (~/.pryrc) and this file is loaded before the Pry session is started.

Customizing the session

If you use a particular gem every time you are in an IRB or a Pry session, you can simply include that in your .irbrc or .pryrc file so you do not have to manually require that gem every time you enter the session. An example for this would be the pretty print (pp) library. Just add the require statement in the rc file and that will load this library whenever you enter the session.

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require "pp"

Note: The following customizations are IRB specific and Pry has most of them in-built.

If you use IRB instead of Pry, you will have to install some additional gems to get the coloring enabled in the output. Pry has this in-built so you do not have to do any additional work. To enable coloring in IRB, the wirble gem should be installed. The following simple configuration will enable coloring using the wirble gem.

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require "wirble"

# Initialize Wirble
Wirble.init

# Enable colored output
Wirble.colorize

Tab completion in IRB can be enabled by

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require "irb/completion"

Automatic indentation can be set by

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IRB.conf[:AUTO_INDENT] = true

If you would like to save the history between IRB sessions, it can be achieved by

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require "irb/ext/save-history"
# Number of lines/commands to save

IRB.conf[:SAVE_HISTORY] = 100
# The location to save the history file
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb-save-history"

Per-project customization

The .[irb|pry]rc file can be customized to automatically load the environment for your project based on your current working directory. Whenever I work with Ruby projects, I keep a separate window open for my pry session. I do not want to load and initialize the project every time I enter te session. I usually have the credentials saved separately in a YAML file. So in the .pryrc file, I get the current working directory and based on the directory, I load and initialize my project. The object I initialize in the rc file will be available inside the irb/pry session, which I can then use for my interactions.

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# Obtain the present woking directory
current_dir = Dir.pwd
# Customizations required for my jenkins_api_client project. The block of
# code inside this if block will load the gem project and then initialize
# the client.
if current_dir =~ /^(.*?\/jenkin_api_client)/
  # YAML is required to parse the credentials from the login.yml file
  require"yaml"
  # Obtain the library path of your ruby project
  path = "#{$1}/lib"
  # Insert this path to the front the $LOAD_PATH
  $LOAD_PATH.unshift(path)

  # Load the project as a rubygem
  require "jenkins_api_client"
  # Initialize the client by loading credentials from the yaml file
  @client = JenkinsApi::Client.new(
      YAML.load_file(File.expand_path("~/.jenkins_api_client/login.yml"))
  )
  puts "logged-in to the Jenkins API, use the '@client' variable to use it"
# Custmoizations required for my jenkins_launcher project
elsif current_dir =~ /^(.*?\/jenkins_launcher)/
    ...
elsif current_dir =~ /^(.*?\/some_other_project)/
    ...
end

Now that I have my rc file setup to prepare my project when I am in my jenkins_api_client project directory, when I enter the Pry session, my project is loaded and ready for me to play with. If I change my directory to a different project and enter irb/pry session again, that project will be loaded instead.

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Kannans-MacBook-Pro:jenkins_api_client kannanmanickam$ pry
logged-in to the Jenkins API, use the '@client' variable to use the client
Welcome back to the Pry session, Kannan!
[1] pry(main)>

It is as simple as adding another condition to match your project and name do the initializations to load your project. The above method will work even if you are deep inside your project directory structure as the regex we use to match th current directory uses non-greedy approach.

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