Rake Task Management Essentials: Deploy, test, and build software to solve real-world automation challenges using Rake.

Often, you have to transform files from one type to another using a utility. For example, compiling source code to byte code in a language such as C or Java, or converting PNG images to JPG, and so on. For these challenges, Rake has many useful arms in its arsenal.

Assume that we have a Ruby project and it has a YAML-generated config file ending with .yaml and, for some reason, we have decided to rename it so that it ends with .yml. This process might have to be repeated very often as the file is generated by a third-party tool. Hence, we have to automate this process. We could do it manually with the following command:

$ mv settings.yaml settings.yml

The Rake produces a special type of task for cases like this. This is the file task. To define a file task, use a file method. The usage of this task is similar to general tasks. Honestly, it inherits all the general task behaviors. In a file task, we can set the prerequisites and write a task action or set...

In real life, we encounter more complicated examples like we have just seen. Often, a project build contains a lot of transformations of many files.

Consider that you have a blog and it contains a lot of articles. To build the site, you have to translate each chapter from the Markdown format to HTML. This will allow you to publish the blog on the Internet.

To convert articles from Markdown to HTML, we will use the pandoc (http://johnmacfarlane.net/pandoc/) command-line utility. If you use Linux, your system's package manager may already contain it, and the installation is very easy. Use the following command to install pandoc:

$ apt-get install pandoc

Sometimes, you will have to create folders with nesting. You can create files and folders with file tasks. If you need to create a folder tree, you can achieve this with the file tasks' definitions and their dependencies. The following is an example of this usage:

file 'my_gem' do |t| mkdir t.name end
file 'my_gem/tests" => ['my_gem'] do |t| mkdir t.name end
file 'my_gem/tests/fixtures" => ['my_gem/tests/fixtures'] do |t|
  mkdir t.name
end

When you try to execute the my_gem/tests/fixtures task, it will first call the dependent my_gem/tests task and then the call will be passed to the my_gem task. The tasks create folders with their name. Finally, we will have created a ready-to-use folder path, my_gem/tests/fixtures.

Another way is to use the FileUtils#mkdir_p method, which might be used in the task action or just in the Rakefile context. However, this is not the Rake way. There is a special way to define folder tasks in the Rake language:...

Rake provides us with a few helpful modules and methods. They may be very useful in some cases, especially while working with files. Knowing them might help you keep Rakefiles clean and precise. The following is a list of these features:

The next three sections will explore them in detail.

Now that you have some knowledge, we would like to show you how Rake can be used in practice. Every Rails developer knows that the first step they have to take when they have a new project is to create the config/database.yml file. It's a rather boring process and includes a lot of manual processes. If there is a config/database.yml.template file, you are lucky and you have to just copy it to config/database.yml. However, if this template file is not in the project, you will have to copy it from another project or find it on the Internet, in the documentation, or somewhere else. The next step consists of changing the configuration itself. As usual, it includes changing the username, password, adapter, and database. Also, you have to change these variables for each environment. It's a boring process, isn't it? So, we decided that if we create a task to automate this process, it will be useful. We hope your Rake arsenal is complete...

This chapter covered the basic features of Rake for working with files. Now, you should be able to use Rake to solve any file problems that you might encounter in your daily work. At the end of the chapter, we saw an example that used this knowledge.

However, one more problem that may seem inconvenient to you is its code duplication in the file tasks' definitions. In the next chapter, you will see how to improve the code of this chapter with rules. You will be introduced to rules and see how to use them in practice.