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

Answer 1

Most of the methods described above did not work for me, maybe they are deprecated in the newer versions. The up-to-date guide can be found here: http://guides.rubyonrails.org/command_line.html#custom-rake-tasks

a copy-and-paste ans from the guide is here:

task :task_name, [:arg_1] => [:pre_1, :pre_2] do |t, args|
  # You can use args from here
end

Invoke it like this

bin/rake "task_name[value 1]" # entire argument string should be quoted

Answer 2

Another commonly used option is to pass environment variables. In your code you read them via ENV['VAR'], and can pass them right before the rake command, like

$ VAR=foo rake mytask

Answer 3

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 4

In addition to answer by kch (I didn't find how to leave a comment to that, sorry):

You don't have to specify variables as ENV variables before the rake command. You can just set them as usual command line parameters like that:

rake mytask var=foo

and access those from your rake file as ENV variables like such:

p ENV['var'] # => "foo"

Answer 5

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

Answer 6

I just wanted to be able to run:

$ rake some:task arg1 arg2

Simple, right? (Nope!)

Rake interprets arg1 and arg2 as tasks, and tries to run them. So we just abort before it does.

namespace :some do
  task task: :environment do
    arg1, arg2 = ARGV

    # your task...

    exit
  end
end

Take that, brackets!

Disclaimer: I wanted to be able to do this in a pretty small pet project. Not intended for "real world" usage since you lose the ability to chain rake tasks (i.e. rake task1 task2 task3). IMO not worth it. Just use the ugly rake task[arg1,arg2].