Ruby Cookbook, 2nd Edition

Chapter 21. 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 a standard library in Ruby 2.1. For Ruby 1.8, it is available as the rake gem.

A Rakefile is just a Ruby source file that has access to some special methods: task, file, directory, and a few others. Calling one of these methods defines a task, which can be run by the command-line rake program, or called as a dependency by other tasks.

The most commonly used method is the generic one: task. This method takes the name of the task to define, and a code block that implements the task. Here’s a simple Rakefile that defines two tasks, cross_bridge and build_bridge, one of ...