How to pass command line arguments to a rake task

Question

I have a rake task that needs to insert a value into multiple databases.

I'd like to pass this value into the rake task from the command line, or from another rake task.

How can I do this?

Answer 1

You can specify formal arguments in rake by adding symbol arguments to the task call. For example:

require 'rake'  task :my_task, [:arg1, :arg2] do |t, args|   puts "Args were: #{args} of class #{args.class}"   puts "arg1 was: '#{args[:arg1]}' of class #{args[:arg1].class}"   puts "arg2 was: '#{args[:arg2]}' of class #{args[:arg2].class}" end  task :invoke_my_task do   Rake.application.invoke_task("my_task[1, 2]") end  # or if you prefer this syntax... task :invoke_my_task_2 do   Rake::Task[:my_task].invoke(3, 4) end  # a task with prerequisites passes its  # arguments to it prerequisites task :with_prerequisite, [:arg1, :arg2] => :my_task #<- name of prerequisite task  # to specify default values,  # we take advantage of args being a Rake::TaskArguments object task :with_defaults, :arg1, :arg2 do |t, args|   args.with_defaults(:arg1 => :default_1, :arg2 => :default_2)   puts "Args with defaults were: #{args}" end 

Then, from the command line:

 > rake my_task[1,false] Args were: {:arg1=>"1", :arg2=>"false"} of class Rake::TaskArguments arg1 was: '1' of class String arg2 was: 'false' of class String  > rake "my_task[1, 2]" Args were: {:arg1=>"1", :arg2=>"2"}  > rake invoke_my_task Args were: {:arg1=>"1", :arg2=>"2"}  > rake invoke_my_task_2 Args were: {:arg1=>3, :arg2=>4}  > rake with_prerequisite[5,6] Args were: {:arg1=>"5", :arg2=>"6"}  > rake with_defaults Args with defaults were: {:arg1=>:default_1, :arg2=>:default_2}  > rake with_defaults['x','y'] Args with defaults were: {:arg1=>"x", :arg2=>"y"} 

As demonstrated in the second example, if you want to use spaces, the quotes around the target name are necessary to keep the shell from splitting up the arguments at the space.

Looking at the code in rake.rb, it appears that rake does not parse task strings to extract arguments for prerequisites, so you can't do task :t1 => "dep[1,2]". The only way to specify different arguments for a prerequisite would be to invoke it explicitly within the dependent task action, as in :invoke_my_task and :invoke_my_task_2.

Note that some shells (like zsh) require you to escape the brackets: rake my_task\['arg1'\]

Answer 2

Options and dependencies need to be inside arrays:

namespace :thing do   desc "it does a thing"   task :work, [:option, :foo, :bar] do |task, args|     puts "work", args   end      task :another, [:option, :foo, :bar] do |task, args|     puts "another #{args}"     Rake::Task["thing:work"].invoke(args[:option], args[:foo], args[:bar])     # or splat the args     # Rake::Task["thing:work"].invoke(*args)   end  end 

Then

rake thing:work[1,2,3] => work: {:option=>"1", :foo=>"2", :bar=>"3"}  rake thing:another[1,2,3] => another {:option=>"1", :foo=>"2", :bar=>"3"} => work: {:option=>"1", :foo=>"2", :bar=>"3"} 

NOTE: variable task is the task object, not very helpful unless you know/care about Rake internals.

RAILS NOTE:

If running the task from Rails, it's best to preload the environment by adding => [:environment] which is a way to setup dependent tasks.

  task :work, [:option, :foo, :bar] => [:environment] do |task, args|     puts "work", args   end