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

Actually @Nick Desjardins answered perfect. But just for education: you can use dirty approach: using ENV argument

task :my_task do
  myvar = ENV['myvar']
  puts "myvar: #{myvar}"
end 

rake my_task myvar=10
#=> myvar: 10

Answer 2

The ways to pass argument are correct in above answer. However to run rake task with arguments, there is a small technicality involved in newer version of rails

It will work with rake "namespace:taskname['argument1']"

Note the Inverted quotes in running the task from command line.

Answer 3

desc 'an updated version'
task :task_name, [:arg1, :arg2] => [:dependency1, :dependency2] do |t, args|
    puts args[:arg1]
end

Answer 4

To pass arguments to the default task, you can do something like this. For example, say "version" is your argument:

task :default, [:version] => [:build]

task :build, :version do |t,args|
  version = args[:version]
  puts version ? "version is #{version}" : "no version passed"
end

Then you can call it like so:

$ rake
no version passed

or

$ rake default[3.2.1]
version is 3.2.1

or

$ rake build[3.2.1]
version is 3.2.1

However, I have not found a way to avoid specifying the task name (default or build) while passing in arguments. Would love to hear if anyone knows of a way.

Answer 5

I couldn't figure out how to pass args and also the :environment until I worked this out:

namespace :db do
  desc 'Export product data'
  task :export, [:file_token, :file_path] => :environment do |t, args|
    args.with_defaults(:file_token => "products", :file_path => "./lib/data/")

       #do stuff [...]

  end
end

And then I call like this:

rake db:export['foo, /tmp/']

Answer 6

I like the "querystring" syntax for argument passing, especially when there are a lot of arguments to be passed.

Example:

rake "mytask[width=10&height=20]"

The "querystring" being:

width=10&height=20

Warning: note that the syntax is rake "mytask[foo=bar]" and NOT rake mytask["foo=bar"]

When parsed inside the rake task using Rack::Utils.parse_nested_query , we get a Hash:

=> {"width"=>"10", "height"=>"20"}

(The cool thing is that you can pass hashes and arrays, more below)

This is how to achieve this:

require 'rack/utils'

task :mytask, :args_expr do |t,args|
  args.with_defaults(:args_expr => "width=10&height=10")
  options = Rack::Utils.parse_nested_query(args[:args_expr])
end

Here's a more extended example that I'm using with Rails in my delayed_job_active_record_threaded gem:

bundle exec rake "dj:start[ebooks[workers_number]=16&ebooks[worker_timeout]=60&albums[workers_number]=32&albums[worker_timeout]=120]"

Parsed the same way as above, with an environment dependency (in order load the Rails environment)

namespace :dj do
  task :start, [ :args_expr ] => :environment do |t, args|
    # defaults here...
    options = Rack::Utils.parse_nested_query(args[:args_expr])  
  end
end

Gives the following in options

=> {"ebooks"=>{"workers_number"=>"16", "worker_timeout"=>"60"}, "albums"=>{"workers_number"=>"32", "worker_timeout"=>"120"}}