Patrick Oscity

Software Craftsman

Offline Ruby/Rails Documentation

18 May 2014

Undoubtedly, we software developers spend a good portion of our time reading documentation, often online. Recently, I have been traveling a lot and although I have my mobile phone set up for tethering, the internet connection is very fragile at times. Waiting for pages to load forever is not really fun, so I needed a way to access the most important Ruby and Rails documentation offline. Since there are quite a few steps involved in setting this up, I thought I’d share it and hope it will be useful for others as well.

Please be aware that this guide is written for OS X users; if you use a different operating system, you will need to adjust the steps accordingly.


Pow lets you start a local server that serves apps under a local url like http://app-name.dev. This makes it convenient to access the documentation we will set up below and frees you from need to keep servers running on localhost with meaningless port numbers that noone can remember. You can install it via

curl get.pow.cx | sh

For more information, visit pow.cx. I recommend using Pow in conjunction with the powder gem, which provides a convenience wrapper around the bare shell commands that are used to manage up Pow apps. The most important command we will use is powder link [APP_NAME], which sets up your app to be served locally by Pow. You can install powder from Rubygems via

gem install powder

Ruby Core Documentation

Pre-rendered Ruby core documentation is available from ruby-doc.org. To serve it locally via Pow, you can do:

mkdir ruby-doc-dev
cd ruby-doc-dev
curl -O http://www.ruby-doc.org/downloads/ruby_2_1_1_core_rdocs.tgz
tar xvf ruby_2_1_1_core_rdocs.tgz
mv ruby_2_1_1_core public
powder link ruby-doc

Your Ruby documentation is now available at http://ruby-doc.dev. Of course, adjust the version number to your needs and/or download multiple versions.

Gem Documentation

gem install yard

Save the following file as ~/Library/LaunchAgents/YardDocs.plist and adjust the path to the yard executable as needed.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">

Next, start the server and set up Pow to do the port forwarding.

launchctl load -w ~/Library/LaunchAgents/YardDocs.plist
echo '8808' > ~/.pow/gem-doc

Your Ruby documentation is now available at http://gem-doc.dev. If you are missing some gems in the list or have disabled documentation generation to speed up Bundler as I did, you can regenerate all Gem documentations with the following command:

gem rdoc --all

Rails API Documentation

Rails documentation can be generated directly from a Rails app, so the first step is to make a minimal Rails app that will serve the only purpose of displaying documentation.

mkdir rails-api-dev

First, add the rails gem in the desired version to your Gemfile. You will also need the sdoc, redcarpet and nokogiri gems to generate the documentation, so go ahead and add these as well.

# Gemfile

source 'https://rubygems.org'

gem 'rails', '4.1.1'

gem 'sdoc'
gem 'redcarpet'
gem 'nokogiri'

Then, install all the Gems with

bundle install

Rails expects an application to be present before it lets you run the Rake task to generate the documentation. You can fake an entire Rails application directly in the Rakefile like this:

# Rakefile

require 'rails/all'

module FakeApp
  class Application < Rails::Application; end


Now, you have Rails’ Rake tasks at your disposal and are able to generate the documentation:

rake doc:rails

To serve the documentation with Pow, you need to add a Rackup file at config.ru

# config.ru

require 'rack'

use Rack::Static, urls: ['/'], root: 'doc/api', index: 'index.html'
run ->{}

and finally you can serve it via Pow:

powder link rails-api

Rails Guides

To read the Rails Guides locally, you can simply clone the folder that you have created for the Rails API Documentation.

cd ..
cp -R rails-api-dev rails-guides-dev
cd rails-guides-dev

This time, you need to run a different Rake task to generate the guides:

rake doc:guides

Since the guides end up in a different directory than the API documentation, you will need to adjust the location specified in the Rackup file as well:

# config.ru

require 'rack'

use Rack::Static, urls: ['/'], root: 'doc/guides', index: 'index.html'
run ->{}

Finally, you can set up Pow to serve the Rails Guides:

rm .powder
powder link rails-guides