Ruby的Rake工具其實是模仿的Make，我們寫一個簡單的Rakefile看看:

desc "Rake Test"
task :main
  puts "Hello, Rake!"
  
task :default => :main

然后我們在Rakefile當前目錄運行rake或rake -f Rakefile即可
其中我們定義了一個main task，并且將其設為默認task
我們再看看怎樣寫結合Rails的Rakefile,Rails在lib/tasks目錄里查找并加載所有以.rake作為后綴名的Rakefile，如lib/tasks/load_musicians.rake:

desc "Load musicians and the instruments they play into the database."
task :load_musicians => ['musicians.csv', :environment] do |t|
  before_count = Musicians.count
  File.read(t.prerequisites.first).each do |line|
    given_name, surname, instrument = line.split(/,/)
    Musician.create(:given_name => given_name,
                    :surname => surname,
                    :instrument => instrument)
  end
  puts "Loaded #{Musicians.count - before_count} musicians."
end

然后我們可以運行rake load_musicians命令來調用load_musicians task
該task的dependency列表中包含:environment，這是用來初始化Rails環境以及建立數據庫連接
如果我們自定義的task需要migrate，則我們可以這樣寫:

task :load_musicians => ['musicians.csv', :migrate] do |t|

則我們運行該task時會先rake db:migrate，而且:migrate已經初始化了Rails環境，我們不用再寫:environment了