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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.
- How to profile and benchmark your new creation.
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.
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 4.0.0 application starting in development on http://0.0.0.0:3000
=> 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 http://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
.
$ rails server -e production -p 4000
The -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 -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
.
$ 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
.
$ 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.
$ 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 test_unit
create test/helpers/greetings_helper_test.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
.
$ 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]
...
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.
$ 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 test_unit
create test/helpers/high_scores_helper_test.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.
$ 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!)
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.
$ 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 4.0.0)
Any modifications you make will be rolled back on exit
irb(main):001:0>
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:
$ 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.
$ 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
.
$ 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
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
.
$ 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 (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.
$ rake about
About your application's environment
Ruby version 1.9.3 (x86_64-linux)
RubyGems version 1.3.6
Rack version 1.3
Rails version 4.1.0
JavaScript Runtime Node.js (V8)
Active Record version 4.1.0
Action Pack version 4.1.0
Action View version 4.1.0
Action Mailer version 4.1.0
Active Support version 4.1.0
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 those compiled assets using rake assets:clean
.
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 indoc/app
.rake doc:guides
generates Rails guides indoc/guides
.rake doc:rails
generates API documentation for Rails indoc/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
, .erb
, .haml
and .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?
* [132] [FIXME] high priority for next deploy
app/models/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:
* [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
.
$ rake notes:custom ANNOTATION=BUG
(in /home/foobar/commandsapp)
app/models/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.
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'
$ 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 files), 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
clearstmp/cache
.rake tmp:sessions:clear
clearstmp/sessions
.rake tmp:sockets:clear
clearstmp/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:
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 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.