Using Bundler with a non-Rails Ruby project

Bundler is a Ruby Gem to help you manage the various gem dependencies in your application.

It has gotten a lot of attention as it is ,er, bundled with Rails3 and represents a welcome addition to that framework. But you can use Bundler in any Ruby application to help make deployments go smoothly.

For a regular Ruby application the steps involved are simple:

1: Install Bundler on your system

$ gem install bundler

2: Create a file called 'GemFile' at the top level of your application directory
Add gem sources to this and each gem that your application relies on. This example includes the main gem sources and a single gem

source :rubygems
source :rubyforge
source :gemcutter

gem "json"

3: Run 'bundle install'
This will now install any missing gems. It does harm to run it more than once.

$ bundle install
Fetching source index for http://rubygems.org/
Fetching source index for http://rubygems.org/
Fetching source index for http://rubygems.org/
Using json (1.4.6)
Using bundler (1.0.3)
Your bundle is complete! It was installed into /Users/jones/.rvm/gems/ruby-1.9.2-p0

If you look in your application directory you will see a new file called Gemfile.lock. Bundler uses this and you want to keep it, adding it to your git repository (or equivalent). You can also find a .bundle directory containing a config file. I guess you can use this for fancier configurations, but a basic app you can ignore it.

4: Deploy your app
Now when you deploy your app in a new location (with the bundler gem installed) you can simply run 'bundle install' in your app directory and you'll be good to go.