Showing Ruby, Rails and git info in your app

Some people’ve asked me how I show rendering information on ariejan.net.

There are a few things going on here, let me explain them one by one.

The current Rails version is probably the easiest you see here. Rails exposes its version information like this:

Rails.version

Ruby also exposes version information, albeit using constants:

RUBY_VERSION
=> "1.9.3"

You may know that ruby also has different patch levels for each release. You can also retrieve that information:

RUBY_PATCHLEVEL
=> 125

The you may also want to know which engine you’re using. This may be “ruby” or something different:

RUBY_ENGINE
=> "ruby"

Combine these to get a sexy ruby version string:

puts "#{RUBY_ENGINE}-#{RUBY_VERSION}-p#{RUBY_PATCHLEVEL}"
=> "ruby-1.9.3-p125"

I like to know which Unicorn produced a certain page. Retrieving the process ID is easy:

Process.pid
=> 9473

Knowing which version of your app is currently running can be useful information. To do this I created the following initializer:

# config/initializers/git_revision.rb
module AppName
  REVISION = `git log --pretty=format:'%h' -n 1`
end

This will expose the current short SHA in your application’s namespace:

AppName::REVISION
=> "ac6d3a0"

You can now use this info through-out your app to show version information.

April 2, 2012 ∙ ruby rails protip