command_line - rails-4.2.3 Documentation

# The Rails Command Line¶ ↑

After reading this guide, you will know:

- How to create a Rails application.

- How to generate models, controllers, database migrations, and unit tests.

- How to start a development server.

- How to experiment with objects through an interactive shell.

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

## 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 console`

- `rails server`

- `rake`

- `rails generate`

- `rails dbconsole`

- `rails new app_name`

All commands can run with `-h or --help` to list more information.

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

### `rails new`¶ ↑

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`¶ ↑

The `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.

With no further work, `rails server` will run our new shiny Rails app:

    $ cd commandsapp
    $ bin/rails server
    => Booting WEBrick
    => Rails 4.2.0 application starting in development on http://localhost:3000
    => Call with -d to detach
    => Ctrl-C to shutdown server
    [2013-08-07 02:00:01] INFO  WEBrick 1.3.1
    [2013-08-07 02:00:01] INFO  ruby 2.0.0 (2013-06-27) [x86_64-darwin11.2.0]
    [2013-08-07 02:00:01] 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 localhost:3000, you will see a basic Rails app running.

INFO: You can also use the alias “s” to start the server: `rails s`.

The server can be run on a different port using the `-p` option. The default development environment can be changed using `-e`.

    $ bin/rails server -e production -p 4000

The `-b` option binds Rails to the specified IP, by default it is localhost. You can run a server as a daemon by passing a `-d` option.

### `rails generate`¶ ↑

The `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 g`.

    $ bin/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 `--help` or `-h` to the end, for example `rails server --help`.

    $ bin/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 CreditCards open debit credit close`

        Credit card controller with URLs like /credit_cards/debit.
            Controller: app/controllers/credit_cards_controller.rb
            Test:       test/controllers/credit_cards_controller_test.rb
            Views:      app/views/credit_cards/debit.html.erb [...]
            Helper:     app/helpers/credit_cards_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.

    $ bin/rails generate controller Greetings hello
         create  app/controllers/greetings_controller.rb
          route  get "greetings/hello"
         invoke  erb
         create    app/views/greetings
         create    app/views/greetings/hello.html.erb
         invoke  test_unit
         create    test/controllers/greetings_controller_test.rb
         invoke  helper
         create    app/helpers/greetings_helper.rb
         invoke  assets
         invoke    coffee
         create      app/assets/javascripts/greetings.js.coffee
         invoke    scss
         create      app/assets/stylesheets/greetings.css.scss

What all did this generate? It made sure a bunch of directories were in our application, and created a controller file, a view file, a functional test file, a helper for the view, a JavaScript file and a stylesheet file.

Check out the controller and modify it a little (in `app/controllers/greetings_controller.rb`):

    class GreetingsController < ApplicationController
      def hello
        @message = "Hello, how are you today?"
      end
    end

Then the view, to display our message (in `app/views/greetings/hello.html.erb`):

    <h1>A Greeting for You!</h1>
    <p><%= @message %></p>

Fire up your server using `rails server`.

    $ bin/rails server
    => Booting WEBrick...

The URL will be localhost:3000/greetings/hello.

INFO: With a normal, plain-old Rails application, your URLs will generally follow the pattern of (host)/(controller)/(action), and a URL like (host)/(controller) will hit the index action of that controller.

Rails comes with a generator for data models too.

    $ bin/rails generate model
    Usage:
      rails generate model NAME [field[:type][:index] field[:type][:index]] [options]

    ...

    Active Record 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 `TableDefinition` class.

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.

    $ bin/rails generate scaffold HighScore game:string score:integer
        invoke  active_record
        create    db/migrate/20130717151933_create_high_scores.rb
        create    app/models/high_score.rb
        invoke    test_unit
        create      test/models/high_score_test.rb
        create      test/fixtures/high_scores.yml
        invoke  resource_route
         route    resources :high_scores
        invoke  scaffold_controller
        create    app/controllers/high_scores_controller.rb
        invoke    erb
        create      app/views/high_scores
        create      app/views/high_scores/index.html.erb
        create      app/views/high_scores/edit.html.erb
        create      app/views/high_scores/show.html.erb
        create      app/views/high_scores/new.html.erb
        create      app/views/high_scores/_form.html.erb
        invoke    test_unit
        create      test/controllers/high_scores_controller_test.rb
        invoke    helper
        create      app/helpers/high_scores_helper.rb
        invoke    jbuilder
        create      app/views/high_scores/index.json.jbuilder
        create      app/views/high_scores/show.json.jbuilder
        invoke  assets
        invoke    coffee
        create      app/assets/javascripts/high_scores.js.coffee
        invoke    scss
        create      app/assets/stylesheets/high_scores.css.scss
        invoke  scss
       identical    app/assets/stylesheets/scaffolds.css.scss

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 `20130717151933_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.

    $ bin/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.

    $ bin/rails server

Go to your browser and open localhost:3000/high_scores, now we can create new high scores (55,160 on Space Invaders!)

### `rails console`¶ ↑

The `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: `rails c`.

You can specify the environment in which the `console` command should operate.

    $ bin/rails console staging

If you wish to test out some code without changing any data, you can do that by invoking `rails console --sandbox`.

    $ bin/rails console --sandbox
    Loading development environment in sandbox (Rails 4.2.0)
    Any modifications you make will be rolled back on exit
    irb(main):001:0>

#### The app and helper objects¶ ↑

Inside the `rails console` you have access to the `app` and `helper` instances.

With the `app` method you can access url and path helpers, as well as do requests.

    >> app.root_path
    => "/"

    >> app.get _
    Started GET "/" for 127.0.0.1 at 2014-06-19 10:41:57 -0300
    ...

With the `helper` method it is possible to access Rails and your application's helpers.

    >> helper.time_ago_in_words 30.days.ago
    => "about 1 month"

    >> helper.my_custom_helper
    => "my custom helper"

### `rails dbconsole`¶ ↑

`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: `rails db`.

### `rails runner`¶ ↑

`runner` runs Ruby code in the context of Rails non-interactively. For instance:

    $ bin/rails runner "Model.long_running_method"

INFO: You can also use the alias “r” to invoke the runner: `rails r`.

You can specify the environment in which the `runner` command should operate using the `-e` switch.

    $ bin/rails runner -e staging "Model.long_running_method"

### `rails destroy`¶ ↑

Think of `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 d`.

    $ bin/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

    $ bin/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¶ ↑

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.

To get the full backtrace for running rake task you can pass the option `--trace` to command line, for example `rake db:create --trace`.

    $ bin/rake --tasks
    rake about              # List versions of all Rails frameworks and the environment
    rake assets:clean       # Remove old compiled assets
    rake assets:clobber     # 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 (specify which logs with LOGS=test,development)
    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

INFO: You can also use `rake -T` to get the list of tasks.

### `about`¶ ↑

`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.

    $ bin/rake about
    About your application's environment
    Rails version             4.2.0
    Ruby version              1.9.3 (x86_64-linux)
    RubyGems version          1.3.6
    Rack version              1.3
    JavaScript Runtime        Node.js (V8)
    Middleware                Rack::Sendfile, ActionDispatch::Static, Rack::Lock, #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x007ffd131a7c88>, Rack::Runtime, Rack::MethodOverride, ActionDispatch::RequestId, Rails::Rack::Logger, ActionDispatch::ShowExceptions, ActionDispatch::DebugExceptions, ActionDispatch::RemoteIp, ActionDispatch::Reloader, ActionDispatch::Callbacks, ActiveRecord::Migration::CheckPending, ActiveRecord::ConnectionAdapters::ConnectionManagement, ActiveRecord::QueryCache, ActionDispatch::Cookies, ActionDispatch::Session::CookieStore, ActionDispatch::Flash, ActionDispatch::ParamsParser, Rack::Head, Rack::ConditionalGet, Rack::ETag
    Application root          /home/foobar/commandsapp
    Environment               development
    Database adapter          sqlite3
    Database schema version   20110805173523

### `assets`¶ ↑

You can precompile the assets in `app/assets` using `rake assets:precompile`, and remove older compiled assets using `rake assets:clean`. The `assets:clean` task allows for rolling deploys that may still be linking to an old asset while the new assets are being built.

If you want to clear `public/assets` completely, you can use `rake assets:clobber`.

### `db`¶ ↑

The most common tasks of the `db:` Rake namespace are `migrate` and `create`, and it will pay off to try out all of the migration rake tasks (`up`, `down`, `redo`, `reset`). `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`¶ ↑

The `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:app` generates documentation for your application in `doc/app`.

- `rake doc:guides` generates Rails guides in `doc/guides`.

- `rake doc:rails` generates API documentation for Rails in `doc/api`.

### `notes`¶ ↑

`rake notes` will search through your code for comments beginning with FIXME, OPTIMIZE or TODO. The search is done in files with extension `.builder`, `.rb`, `.rake`, `.yml`, `.yaml`, `.ruby`, `.css`, `.js` and `.erb` for both default and custom annotations.

    $ bin/rake notes
    (in /home/foobar/commandsapp)
    app/controllers/admin/users_controller.rb:
      * [ 20] [TODO] any other way to do this?
      * [132] [FIXME] high priority for next deploy

    app/models/school.rb:
      * [ 13] [OPTIMIZE] refactor this code to make it faster
      * [ 17] [FIXME]

You can add support for new file extensions using `config.annotations.register_extensions` option, which receives a list of the extensions with its corresponding regex to match it up.

    config.annotations.register_extensions("scss", "sass", "less") { |annotation| /\/\/\s*(#{annotation}):?\s*(.*)$/ }

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.

    $ bin/rake notes:fixme
    (in /home/foobar/commandsapp)
    app/controllers/admin/users_controller.rb:
      * [132] high priority for next deploy

    app/models/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 `ANNOTATION`.

    $ bin/rake notes:custom ANNOTATION=BUG
    (in /home/foobar/commandsapp)
    app/models/article.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.

By default, `rake notes` will look in the `app`, `config`, `lib`, `bin` and `test` directories. If you would like to search other directories, you can provide them as a comma separated list in an environment variable `SOURCE_ANNOTATION_DIRECTORIES`.

    $ export SOURCE_ANNOTATION_DIRECTORIES='spec,vendor'
    $ bin/rake notes
    (in /home/foobar/commandsapp)
    app/models/user.rb:
      * [ 35] [FIXME] User should have a subscription at this point
    spec/models/user_spec.rb:
      * [122] [TODO] Verify the user that has a subscription works

### `routes`¶ ↑

`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.

### `test`¶ ↑

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 Minitest. 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.

### `tmp`¶ ↑

The `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 sessions), process id files, and cached actions.

The `tmp:` namespaced tasks will help you clear and create the `Rails.root/tmp` directory:

- `rake tmp:cache:clear` clears `tmp/cache`.

- `rake tmp:sessions:clear` clears `tmp/sessions`.

- `rake tmp:sockets:clear` clears `tmp/sockets`.

- `rake tmp:clear` clears all the three: cache, sessions and sockets.

- `rake tmp:create` creates tmp directories for sessions, cache, sockets, and pids.

### Miscellaneous¶ ↑

- `rake stats` is great for looking at statistics on your code, displaying things like KLOCs (thousands of lines of code) and your code to test ratio.

- `rake secret` will give you a pseudo-random key to use for your session secret.

- `rake time:zones:all` lists all the timezones Rails knows about.

### Custom Rake Tasks¶ ↑

Custom rake tasks have a `.rake` extension and are placed in `Rails.root/lib/tasks`. You can create these custom rake tasks with the `bin/rails generate task` command.

    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:

    $ bin/rake task_name
    $ bin/rake "task_name[value 1]" # entire argument string should be quoted
    $ bin/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 pg driver:
    #   gem install pg
    # On OS X with Homebrew:
    #   gem install pg -- --with-pg-config=/usr/local/bin/pg_config
    # On OS X with MacPorts:
    #   gem install pg -- --with-pg-config=/opt/local/lib/postgresql84/bin/pg_config
    # On Windows:
    #   gem install pg
    #       Choose the win32 build.
    #       Install PostgreSQL and put its /bin directory on your path.
    #
    # Configure Using Gemfile
    # gem 'pg'
    #
    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.