This article has been updated in 2016
Rake is a Make-like program implemented in Ruby. Tasks and dependencies are specified in standard Ruby syntax.
Rake Features:
Rakefiles(rake’s version of Makefiles) are completely defined in standard Ruby syntax. No XML files to edit. No quirky Makefile syntax to worry aboutUsers can specify tasks with prerequisites.
Rake supports rule patterns to synthesize implicit tasks.
Flexible FileLists that act like arrays but know about manipulating file names and paths.
A library of prepackaged tasks to make building rakefiles easier. For example, tasks for building tarballs.
Supports parallel execution of tasks.
What is a task?
- A Task for running test suite
- Building or Backing up Databases
- Reporting Statistics
- Anything that needs to be Automated
These tasks; without Rake can be scattered around your project, but Rake can organize them.
Rake is a gem, written in ruby, hence it makes it easier to write code faster and leaner; has all goodies of Ruby
Don’t confuse Rake with Rack, very similar names, but completely different things. Rake is a task runner while Rack helps Ruby servers & frameworks work together.
Who Uses Rake?
Rails uses Rake for task automations. If you have done anything with Rails at all, you’re probably familiar with the rake db:migrate command or rake routes.
Notice that Rails, since version 5.0, allows you to call most rake commands with rails instead of rake, however they still are rake tasks. You can do rails db:migrate, but Rake is still doing the work.
How to Write a Rake Task
Have a look at following example
desc "Run unit tests"
task default: %w[test]
task :test do
ruby "test/unittest.rb"
end
A task named “test”, which – upon invocation – will run a unittest.rb file in Ruby.
A task named “default”. This task does nothing by itself, but it has exactly one dependency, namely the “test” task. Invoking the “default” task will cause Rake to invoke the “test” task as well.
You can put this code inside a file named Rakefile, or if you’re using Rails, you can save this under lib/tasks/test.rake.
To run this task:
rake test
What we can do using Rake? Pretty much anything that is to be automated, but here are some popular one
- Execute a Ruby script
- Run System Commands (Copy Files, Symlink, Download Files)
Following is an example to delete all files under tmp/ folder
task :clear_tmp do
rm_r FileList["tmp/*"]
end
Be careful with system commands, like rm_r (remove with recursion) as it will delete files without confirmation, if you want to add a confirmation step you can add a dependent task & raise an exception if you don’t want to continue.
Namespaces in Rake
Because tasks can have similar names, it’s easy to use the same name twice. Using namespace we can make task name more meaningful at the same time using same name under different namespace. For example, db:clean and tmp:cache:clean. This name clearly suggest what these tasks do; at the same time uses same name for tasks (albeit under different namespace)
namespace :tmp do
namespace :cache do
task :clean do
# ...
end
task :purge do
# ...
end
task :restore do
# ...
end
task :backup do
# ...
end
end
end
To run a namespaced task:
rake tmp:cache:clean
Dependent Tasks
Rake allows you to define a list of other tasks that must run before the current task in order as they are specified. With this, you can do any setup that the task needs.
task migrate: :create do
# ...
end
Or we can specify more than one dependencies
task backup: [:create, :migrate] do
# ...
end
Run A Rake Task Within Another Task
If instead of having a set of task that run BEFORE the current task, you want to invoke another task within the current task, then you can use the following code.
task :coverage do
ENV['COVERAGE'] = 'true'
Rake::Task["test"].execute
end
This can be helpful to set environment variables that enable test coverage & other options.
About The Author
I am Pankaj Baagwan, a System Design Architect. A Computer Scientist by heart, process enthusiast, and open source author/contributor/writer. Advocates Karma. Love working with cutting edge, fascinating, open source technologies.
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