A Guide to The Rails Command Line

Rails comes with every command line tool you'll need to

  • Create a Rails application

  • Generate models, controllers, database migrations, and unit tests

  • Start a development server

  • Mess with objects through an interactive shell

  • Profile and benchmark your new creation

… and much, much more! (Buy now!)

This tutorial assumes you have basic Rails knowledge from reading the Getting Started with Rails Guide.

1. Command Line Basics

There are a few commands that are absolutely critical to your everyday usage of Rails. In the order of how much you'll probably use them are:

  • console

  • server

  • rake

  • generate

  • rails

Let's create a simple Rails application to step through each of these commands in context.

1.1. rails

The first thing we'll want to do is create a new Rails application by running the rails command after installing Rails.

Note You know you need the rails gem installed by typing gem install rails first, right? Okay, okay, just making sure. 
$ rails commandsapp

     create
     create  app/controllers
     create  app/helpers
     create  app/models
     ...
     ...
     create  log/production.log
     create  log/development.log
     create  log/test.log

Rails will set you up with what seems like a huge amount of stuff for such a tiny command! You've got the entire Rails directory structure now with all the code you need to run our simple application right out of the box.

Note This output will seem very familiar when we get to the generate command. Creepy foreshadowing!

1.2. server

Let's try it! The server command launches a small web server written in Ruby named WEBrick which was also installed when you installed Rails. You'll use this any time you want to view your work through a web browser.

Note WEBrick isn't your only option for serving Rails. We'll get to that in a later section. [XXX: which section]

Here we'll flex our server command, which without any prodding of any kind will run our new shiny Rails app:

$ cd commandsapp
$ ./script/server
=> Booting WEBrick...
=> Rails 2.2.0 application started on http://0.0.0.0:3000
=> Ctrl-C to shutdown server; call with --help for options
[2008-11-04 10:11:38] INFO  WEBrick 1.3.1
[2008-11-04 10:11:38] INFO  ruby 1.8.5 (2006-12-04) [i486-linux]
[2008-11-04 10:11:38] INFO  WEBrick::HTTPServer#start: pid=18994 port=3000

WHOA. With just three commands we whipped up a Rails server listening on port 3000. Go! Go right now to your browser and go to http://localhost:3000. I'll wait.

See? Cool! It doesn't do much yet, but we'll change that.

1.3. generate

The generate command uses templates to create a whole lot of things. You can always find out what's available by running generate by itself. Let's do that:

$ ./script/generate
Usage: ./script/generate generator [options] [args]

...
...

Installed Generators
  Builtin: controller, integration_test, mailer, migration, model, observer, performance_test, plugin, resource, scaffold, session_migration

...
...
Note You can install more generators through generator gems, portions of plugins you'll undoubtedly install, and you can even create your own!

Using generators will save you a large amount of time by writing boilerplate code for you — necessary for the darn thing to work, but not necessary for you to spend time writing. That's what we have computers for, right?

Let's make our own controller with the controller generator. But what command should we use? Let's ask the generator:

Note All Rails console utilities have help text. For commands that require a lot of input to run correctly, you can just try the command without any parameters (like rails or ./script/generate). For others, you can try adding —help or -h to the end, as in ./script/server —help. 
$ ./script/generate controller
Usage: ./script/generate controller ControllerName [options]

...
...

Example:
    `./script/generate controller CreditCard open debit credit close`

    Credit card controller with URLs like /credit_card/debit.
        Controller: app/controllers/credit_card_controller.rb
        Views:      app/views/credit_card/debit.html.erb [...]
        Helper:     app/helpers/credit_card_helper.rb
        Test:       test/functional/credit_card_controller_test.rb

Modules Example:
    `./script/generate controller 'admin/credit_card' suspend late_fee`

    Credit card admin controller with URLs /admin/credit_card/suspend.
        Controller: app/controllers/admin/credit_card_controller.rb
        Views:      app/views/admin/credit_card/debit.html.erb [...]
        Helper:     app/helpers/admin/credit_card_helper.rb
        Test:       test/functional/admin/credit_card_controller_test.rb

Ah, the controller generator is expecting parameters in the form of generate controller ControllerName action1 action2. Let's make a Greetings controller with an action of hello, which will say something nice to us.

$ ./script/generate controller Greeting hello
     exists  app/controllers/
     exists  app/helpers/
     create  app/views/greeting
     exists  test/functional/
     create  app/controllers/greetings_controller.rb
     create  test/functional/greetings_controller_test.rb
     create  app/helpers/greetings_helper.rb
     create  app/views/greetings/hello.html.erb

Look there! Now what all did this generate? It looks like it made sure a bunch of directories were in our application, and created a controller file, a functional test file, a helper for the view, and a view file. All from one command!