Programatically Determining the Version of a Chef Cookbook

If you're scripting around your Chef cookbooks, you may want to do things like work out the version of the cookbook, so you can i.e. use it for reporting, check if the cookbook is already uploaded, etc.

You may think, well, it's in the following format, why don't I just parse it with i.e. a regex:

version '2.1.0'

Well, unfortunately this won't work (aside from if you generally avoid regex) as the metadata.rb file, which stores the cookbook's metadata, is just plain Ruby, so it allows you to execute any Ruby code, such as looking it up from file, performing a long-running HTTP request, or anything really.

Fortunately, we can use the utility class Chef::Cookbook::Metadata to parse the metadata, resolve any arbitrary Ruby code, and give us the version number:

require 'chef'

m = Chef::Cookbook::Metadata.new
m.from_file 'metadata.rb'
puts m.version

This also works for any other metadata of the cookbook we want to retrieve.