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
- Experiment with objects through an interactive shell
- Profile and benchmark your new creation
NOTE: This tutorial assumes you have basic Rails knowledge from reading the Getting Started with Rails Guide.
WARNING. This Guide is based on Rails 3.2. Some of the code shown here will not work in earlier versions of Rails.
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:
rails new app_name
Let's create a simple Rails application to step through each of these commands in context.
The first thing we'll want to do is create a new Rails application by running the
rails new command after installing Rails.
INFO: You can install the rails gem by typing
gem install rails, if you don't have it already.
$ rails new commandsapp create create README.rdoc create Rakefile create config.ru create .gitignore create Gemfile create app ... create tmp/cache ... run bundle install
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.
rails server command launches a small web server named WEBrick which comes bundled with Ruby. You'll use this any time you want to access your application through a web browser.
INFO: WEBrick isn't your only option for serving Rails. We'll get to that later.
With no further work,
rails server will run our new shiny Rails app:
$ cd commandsapp $ rails server => Booting WEBrick => Rails 3.2.3 application starting in development on http://0.0.0.0:3000 => Call with -d to detach => Ctrl-C to shutdown server [2012-05-28 00:39:41] INFO WEBrick 1.3.1 [2012-05-28 00:39:41] INFO ruby 1.9.2 (2011-02-18) [x86_64-darwin11.2.0] [2012-05-28 00:39:41] INFO WEBrick::HTTPServer#start: pid=69680 port=3000
With just three commands we whipped up a Rails server listening on port 3000. Go to your browser and open http://localhost:3000, you will see a basic Rails app running.
INFO: You can also use the alias "s" to start the server:
The server can be run on a different port using the
-p option. The default development environment can be changed using
$ rails server -e production -p 4000
-b option binds Rails to the specified ip, by default it is 0.0.0.0. You can run a server as a daemon by passing a
rails generate command uses templates to create a whole lot of things. Running
rails generate by itself gives a list of available generators:
INFO: You can also use the alias "g" to invoke the generator command:
$ rails generate Usage: rails generate GENERATOR [args] [options] ... ... Please choose a generator below. Rails: assets controller generator ... ...
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, code that is necessary for the app to work.
Let's make our own controller with the controller generator. But what command should we use? Let's ask the generator:
INFO: All Rails console utilities have help text. As with most *nix utilities, you can try adding
-h to the end, for example
rails server --help.
$ rails generate controller Usage: rails generate controller NAME [action action] [options] ... ... Description: ... To create a controller within a module, specify the controller name as a path like 'parent_module/controller_name'. ... Example: `rails generate controller CreditCard open debit credit close` Credit card controller with URLs like /credit_card/debit. Controller: app/controllers/credit_card_controller.rb Test: test/controllers/credit_card_controller_test.rb Views: app/views/credit_card/debit.html.erb [...] Helper: app/helpers/credit_card_helper.rb
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.
Check out the controller and modify it a little (in
class GreetingsController < ApplicationController def hello @message = "Hello, how are you today?" end end
Then the view, to display our message (in
<h1>A Greeting for You!</h1> <p><%= @message %></p>
Fire up your server using
$ rails server => Booting WEBrick...
The URL will be http://localhost:3000/greetings/hello.
INFO: With a normal, plain-old Rails application, your URLs will generally follow the pattern of http://(host)/(controller)/(action), and a URL like http://(host)/(controller) will hit the index action of that controller.
Rails comes with a generator for data models too.
$ rails generate model Usage: rails generate model NAME [field[:type][:index] field[:type][:index]] [options] ... ActiveRecord options: [--migration] # Indicates when to generate migration # Default: true ... Description: Create rails files for model generator.
NOTE: For a list of available field types, refer to the API documentation for the column method for the
But instead of generating a model directly (which we'll be doing later), let's set up a scaffold. A scaffold in Rails is a full set of model, database migration for that model, controller to manipulate it, views to view and manipulate the data, and a test suite for each of the above.
We will set up a simple resource called "HighScore" that will keep track of our highest score on video games we play.
The generator checks that there exist the directories for models, controllers, helpers, layouts, functional and unit tests, stylesheets, creates the views, controller, model and database migration for HighScore (creating the
high_scores table and fields), takes care of the route for the resource, and new tests for everything.
The migration requires that we migrate, that is, run some Ruby code (living in that
20120528060026_create_high_scores.rb) to modify the schema of our database. Which database? The sqlite3 database that Rails will create for you when we run the
rake db:migrate command. We'll talk more about Rake in-depth in a little while.
$ rake db:migrate == CreateHighScores: migrating =============================================== -- create_table(:high_scores) -> 0.0017s == CreateHighScores: migrated (0.0019s) ======================================
INFO: Let's talk about unit tests. Unit tests are code that tests and makes assertions about code. In unit testing, we take a little part of code, say a method of a model, and test its inputs and outputs. Unit tests are your friend. The sooner you make peace with the fact that your quality of life will drastically increase when you unit test your code, the better. Seriously. We'll make one in a moment.
Let's see the interface Rails created for us.
$ rails server
Go to your browser and open http://localhost:3000/high_scores, now we can create new high scores (55,160 on Space Invaders!)
console command lets you interact with your Rails application from the command line. On the underside,
rails console uses IRB, so if you've ever used it, you'll be right at home. This is useful for testing out quick ideas with code and changing data server-side without touching the website.
INFO: You can also use the alias "c" to invoke the console:
You can specify the environment in which the
console command should operate.
$ rails console staging
If you wish to test out some code without changing any data, you can do that by invoking
rails console --sandbox.
$ rails console --sandbox Loading development environment in sandbox (Rails 3.2.3) Any modifications you make will be rolled back on exit irb(main):001:0>
rails dbconsole figures out which database you're using and drops you into whichever command line interface you would use with it (and figures out the command line parameters to give to it, too!). It supports MySQL, PostgreSQL, SQLite and SQLite3.
INFO: You can also use the alias "db" to invoke the dbconsole:
runner runs Ruby code in the context of Rails non-interactively. For instance:
$ rails runner "Model.long_running_method"
INFO: You can also use the alias "r" to invoke the runner:
You can specify the environment in which the
runner command should operate using the
$ rails runner -e staging "Model.long_running_method"
destroy as the opposite of
generate. It'll figure out what generate did, and undo it.
INFO: You can also use the alias "d" to invoke the destroy command:
$ rails generate model Oops invoke active_record create db/migrate/20120528062523_create_oops.rb create app/models/oops.rb invoke test_unit create test/models/oops_test.rb create test/fixtures/oops.yml
$ rails destroy model Oops invoke active_record remove db/migrate/20120528062523_create_oops.rb remove app/models/oops.rb invoke test_unit remove test/models/oops_test.rb remove test/fixtures/oops.yml
Rake is Ruby Make, a standalone Ruby utility that replaces the Unix utility 'make', and uses a 'Rakefile' and
.rake files to build up a list of tasks. In Rails, Rake is used for common administration tasks, especially sophisticated ones that build off of each other.
You can get a list of Rake tasks available to you, which will often depend on your current directory, by typing
rake --tasks. Each task has a description, and should help you find the thing you need.
$ rake --tasks rake about # List versions of all Rails frameworks and the environment rake assets:clean # Remove compiled assets rake assets:precompile # Compile all the assets named in config.assets.precompile rake db:create # Create the database from config/database.yml for the current Rails.env ... rake log:clear # Truncates all *.log files in log/ to zero bytes rake middleware # Prints out your Rack middleware stack ... rake tmp:clear # Clear session, cache, and socket files from tmp/ (narrow w/ tmp:sessions:clear, tmp:cache:clear, tmp:sockets:clear) rake tmp:create # Creates tmp directories for sessions, cache, sockets, and pids
rake about gives information about version numbers for Ruby, RubyGems, Rails, the Rails subcomponents, your application's folder, the current Rails environment name, your app's database adapter, and schema version. It is useful when you need to ask for help, check if a security patch might affect you, or when you need some stats for an existing Rails installation.
You can precompile the assets in
rake assets:precompile and remove those compiled assets using
The most common tasks of the
db: Rake namespace are
create, and it will pay off to try out all of the migration rake tasks (
rake db:version is useful when troubleshooting, telling you the current version of the database.
More information about migrations can be found in the Migrations guide.
doc: namespace has the tools to generate documentation for your app, API documentation, guides. Documentation can also be stripped which is mainly useful for slimming your codebase, like if you're writing a Rails application for an embedded platform.
rake doc:appgenerates documentation for your application in
rake doc:guidesgenerates Rails guides in
rake doc:railsgenerates API documentation for Rails in
rake notes will search through your code for comments beginning with FIXME, OPTIMIZE or TODO. The search is done in files with extension
.slim for both default and custom annotations.
$ rake notes (in /home/foobar/commandsapp) app/controllers/admin/users_controller.rb: * [ 20] [TODO] any other way to do this? *  [FIXME] high priority for next deploy app/model/school.rb: * [ 13] [OPTIMIZE] refactor this code to make it faster * [ 17] [FIXME]
If you are looking for a specific annotation, say FIXME, you can use
rake notes:fixme. Note that you have to lower case the annotation's name.
$ rake notes:fixme (in /home/foobar/commandsapp) app/controllers/admin/users_controller.rb: *  high priority for next deploy app/model/school.rb: * [ 17]
You can also use custom annotations in your code and list them using
rake notes:custom by specifying the annotation using an environment variable
$ rake notes:custom ANNOTATION=BUG (in /home/foobar/commandsapp) app/model/post.rb: * [ 23] Have to fix this one before pushing!
NOTE. When using specific annotations and custom annotations, the annotation name (FIXME, BUG etc) is not displayed in the output lines.
rake notes will look in the
test directories. If you would like to search other directories, you can provide them as a comma separated list in an environment variable
$ export SOURCE_ANNOTATION_DIRECTORIES='rspec,vendor' $ rake notes (in /home/foobar/commandsapp) app/model/user.rb: * [ 35] [FIXME] User should have a subscription at this point rspec/model/user_spec.rb: *  [TODO] Verify the user that has a subscription works
rake routes will list all of your defined routes, which is useful for tracking down routing problems in your app, or giving you a good overview of the URLs in an app you're trying to get familiar with.
INFO: A good description of unit testing in Rails is given in A Guide to Testing Rails Applications
Rails comes with a test suite called
Test::Unit. Rails owes its stability to the use of tests. The tasks available in the
test: namespace helps in running the different tests you will hopefully write.
Rails.root/tmp directory is, like the *nix /tmp directory, the holding place for temporary files like sessions (if you're using a file store for files), process id files, and cached actions.
tmp: namespaced tasks will help you clear the
rake tmp:clearclears all the three: cache, sessions and sockets.
rake statsis great for looking at statistics on your code, displaying things like KLOCs (thousands of lines of code) and your code to test ratio.
rake secretwill give you a pseudo-random key to use for your session secret.
rake time:zones:alllists all the timezones Rails knows about.
Custom Rake Tasks
Custom rake tasks have a
.rake extension and are placed in
desc "I am short, but comprehensive description for my cool task" task :task_name => [:prerequisite_task, :another_task_we_depend_on] do # All your magic here # Any valid Ruby code is allowed end
To pass arguments to your custom rake task:
task :task_name, [:arg_1] => [:pre_1, :pre_2] do |t, args| # You can use args from here end
You can group tasks by placing them in namespaces:
namespace :db do desc "This task does nothing" task :nothing do # Seriously, nothing end end
Invocation of the tasks will look like:
rake task_name rake "task_name[value 1]" # entire argument string should be quoted rake db:nothing
NOTE: If your need to interact with your application models, perform database queries and so on, your task should depend on the
environment task, which will load your application code.
The Rails Advanced Command Line
More advanced use of the command line is focused around finding useful (even surprising at times) options in the utilities, and fitting those to your needs and specific work flow. Listed here are some tricks up Rails' sleeve.
Rails with Databases and SCM
When creating a new Rails application, you have the option to specify what kind of database and what kind of source code management system your application is going to use. This will save you a few minutes, and certainly many keystrokes.
Let's see what a
--git option and a
--database=postgresql option will do for us:
$ mkdir gitapp $ cd gitapp $ git init Initialized empty Git repository in .git/ $ rails new . --git --database=postgresql exists create app/controllers create app/helpers ... ... create tmp/cache create tmp/pids create Rakefile add 'Rakefile' create README.rdoc add 'README.rdoc' create app/controllers/application_controller.rb add 'app/controllers/application_controller.rb' create app/helpers/application_helper.rb ... create log/test.log add 'log/test.log'
We had to create the gitapp directory and initialize an empty git repository before Rails would add files it created to our repository. Let's see what it put in our database configuration:
$ cat config/database.yml # PostgreSQL. Versions 8.2 and up are supported. # # Install the ruby-postgres driver: # gem install ruby-postgres # On Mac OS X: # gem install ruby-postgres -- --include=/usr/local/pgsql # On Windows: # gem install ruby-postgres # Choose the win32 build. # Install PostgreSQL and put its /bin directory on your path. development: adapter: postgresql encoding: unicode database: gitapp_development pool: 5 username: gitapp password: ... ...
It also generated some lines in our database.yml configuration corresponding to our choice of PostgreSQL for database.
NOTE. The only catch with using the SCM options is that you have to make your application's directory first, then initialize your SCM, then you can run the
rails new command to generate the basis of your app.
server with Different Backends
Many people have created a large number of different web servers in Ruby, and many of them can be used to run Rails. Since version 2.3, Rails uses Rack to serve its webpages, which means that any webserver that implements a Rack handler can be used. This includes WEBrick, Mongrel, Thin, and Phusion Passenger (to name a few!).
NOTE: For more details on the Rack integration, see Rails on Rack.
To use a different server, just install its gem, then use its name for the first parameter to
$ sudo gem install mongrel Building native extensions. This could take a while... Building native extensions. This could take a while... Successfully installed gem_plugin-0.2.3 Successfully installed fastthread-1.0.1 Successfully installed cgi_multipart_eof_fix-2.5.0 Successfully installed mongrel-1.1.5 ... ... Installing RDoc documentation for mongrel-1.1.5... $ rails server mongrel => Booting Mongrel (use 'rails server webrick' to force WEBrick) => Rails 3.1.0 application starting on http://0.0.0.0:3000 ...