This post is a very short and very simple tip for easily opening a ruby gem up for closer inspection.
When reviewing a Rails or Sinatra application (code review), it sometimes becomes necessary to view the libraries (ruby gems) that an application is including and using. Instead of navigating to the ~/.rvm/gems/<version>@<gemset name> directory (or wherever else the gems are stored) and opening them with your text editor of choice, you can instead leverage the power of bundler.
For your *nix based systems that leverage a bashrc, bash_profile, etc.
open your ~/.bash_profile file (or whatever the appropriate bash file is)
add this line export BUNDLER_EDITOR=mate
I chose "mate" because I use TextMate. Otherwise, just link to the appropriate editor executable.
(exit and save bash_profile)
type: source ~/.bash_profile
Then, navigate to an app that contains the Gemfile, and switch to the gemset or ruby version where these gems are contained, and choose a gem that you want to open...
bundle open <gem name>
That's all there is to it.