Automating Project Tasks with Rake

Rake and the Rakefile are powerful tools for simplifying and automating complex, repetitive tasks, such as packaging Gems up, generating website HTML from HAML et al, performing complex repository backflips with a single command.

Samples

Here are some sample Rakefiles to get you familiar with the breadth that Rakefiles can cover.

• http://github.com/mtodd/halcyon/tree/site/Rakefile
• http://github.com/wycats/merb-core/tree/master/Rakefile
• http://github.com/macournoyer/thin/tree/master/Rakefile
• http://github.com/evanphx/rubinius/tree/master/Rakefile

Tasks

Tasks are defined with a description and a task body. For example:

desc "Remove generated content"
task :clean do
  Rake::FileList["pkg/", "doc/", "**/*~", "**/*.bak"].each do |file|
    rm_r file rescue nil
    puts "* deleted #{File.basename(file)}"
  end
end

Namespaces

Tasks can be grouped together under a namespace to provide organization and topical sub-tasks. For example:

namespace(:site) do
  desc "Remove compiled source files"
  task :clean do
    # implementation
  end
 
  desc "Generate dynamic files"
  task :generate => [:clean] do
    # implementation
  end

Prerequisites

When tasks are defined as a hash with an array (like the generate task in the site namespace above), the tasks named in the array are prerequisites and will be executed before the currently defined task.