Ruby Cookbook

Chapter 19. Automating Tasks with Rake

Even when your software is written, tested, and packaged, you’re still not done. You’ve got to start working on the next version, and the next… Every release you do, in some cases every change you make to your code, will send you running through a maze of repetitive tasks that have nothing to do with programming.

Fortunately, there’s a way to automate these tasks, and the best part is that you can do it by writing more Ruby code. The answer is Rake.

Rake is a build language, Ruby’s answer to Unix make and Java’s Ant. It lets you define tasks: named code bocks that carry out specific actions, like building a gem or running a set of unit tests. Invoke Rake, and your predefined tasks will happily do the work you once did: compiling C extensions, splicing files together, running unit tests, or packaging a new release of your software. If you can define it, Rake can run it.

Rake is available as the rake gem; if you’ve installed Rails, you already have it. Unlike most gems, it doesn’t just install libraries: it installs a command-line program called rake, which contains the logic for actually performing Rake tasks. For ease of use, you may need to add to your PATH environment variable the directory containing the rake script: something like /usr/lib/ruby/gems/1.8/gems/rake-0.6.2/bin/. That way you can just run rake from the command line.

A Rakefile is just a Ruby source file that has access to some special methods: task, file, directory, and a few others. ...