Today I learned

My usual approach when writing Rake tasks is to import a library and then use its API:

require_relative '../slides'

namspace :slides do
  desc 'Create an empty slideshow'
  task :new do
    Slides.new.write_to_disk
  end
end

Sometimes that is impractical: the API is not public, or you need to invoke a standalone script which only has a command line interface.

I found out Rake implements a ruby method which lets you invoke the ruby program directly:

task :new do
  ruby 'create_slideshow.rb'
  puts 'Created a new slideshow.'
end

There is also a sh method, which allows you to run system commands. Make sure to use the multiple argument version and avoid passing it unfiltered user input.