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Rake

By · Reviewed & last updated · Part of Ruby Tutorial

Rake is Rubys make. Tasks live in a Rakefile (or under lib/tasks/*.rake in Rails), grouped into namespaces, and form a dependency graph — running a task runs its prerequisites first. It is the right place for cron-style chores: data backfills, report generation, cache warm-ups, deployment helpers.

A Rakefile with namespaces, deps, and arguments

EXAMPLE
# Rakefile
require "fileutils"
require "json"

# Default task runs when you type just `rake`
task default: %i[test lint]

desc "Run the test suite"
task :test do
  sh "bundle exec rspec --fail-fast"
end

desc "Run RuboCop"
task :lint do
  sh "bundle exec rubocop --parallel"
end

namespace :db do
  desc "Apply pending migrations"
  task :migrate do
    sh "bundle exec rails db:migrate"
  end

  desc "Reset and reseed the dev database"
  task reset: %i[migrate] do
    sh "bundle exec rails db:reset db:seed"
  end

  # Task with arguments and a prerequisite
  desc "Backfill nullable column for a date range — rake db:backfill[2026-01-01,2026-06-01]"
  task :backfill, [:from, :to] => :migrate do |_t, args|
    args.with_defaults(from: "2026-01-01", to: Date.today.to_s)
    sh %{bundle exec rails runner "Order.where(paid_at: \#{args.from}..\#{args.to}).find_each(&:backfill!)"}
  end
end

namespace :report do
  desc "Write a daily revenue JSON to tmp/"
  file "tmp/revenue.json" do |t|
    FileUtils.mkdir_p("tmp")
    data = { generated_at: Time.now, rows: [] }
    File.write(t.name, JSON.pretty_generate(data))
  end

  task :daily => "tmp/revenue.json"
end

# Discoverability: `rake -T` prints every task with its desc.
# Force a re-run even if `file` task says it is up to date: `rake -f`.

# Invoke programmatically:
#   Rake::Task["db:reset"].invoke
#   Rake::Task["db:backfill"].invoke("2026-05-01", "2026-05-31")

Why it matters

Always give tasks a `desc` — without one, the task is invisible to `rake -T`, which is how teammates discover what you have built. Reach for `file` tasks when output is genuinely a file: Rake compares mtimes and skips work that is already up to date.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
# Rakefile
task :hello do
    puts 'hi from rake'
end
# Run: bundle exec rake hello
Try it Yourself »

Discussion

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