How do I create a config.ru file and a Rakefile?

Question

I know you create a Gemfile from the command line by typing "bundle init." But how do you create config.ru file and a Rakefile?

Answer 1

Kristine, the real question is not how, but rather why would you want to create them.

Those three files serve three different purposes, and none are required for a Ruby application to get started:

• Gemfile (and its companion Gemfile.lock that gets generated by the first bundle install and should be kept as safely as the other one) – this is one you meet most often.

  It belongs and is used by a tool called Bundler. It's a dependency management tool. When your application needs some other library called "gem", you can list it in your Gemfile, do bundle install and later on when you run your application like bundle exec ruby yourapp.rb Bundler will take care of the environment in such a way, that your application always gets the same versions of gems that you have designed it to get (those versions are actually stored in Gemfile.lock file, you can peek there).

  You can easily do without Bundler, but it usually makes sense to stick to certain gem versions. That's why people usually use it. I would highly suggest you taking a look at the tool's site.

• config.ru – this is very common for web applications. It's a Rack configuration file. There's a widely spread in Ruby world web server API called Rack. It enables decoupling web applications (like your Rails app, or Sinatra app) from the underlying web application server (like Thin, Unicorn or WEBrick).

  Though you can certainly create this on your own, you most certainly don't need to. It's been a long way in my Ruby/Rails experience before I had to actually do this. Usually this file gets bootstrapped when you create a new Rails app by calling rails new.

  And vanilla command line Ruby apps just don't need it.

• Rakefile – this is, again, a pretty wide-spread beast. What Makefile is for make, Rakefile is for rake. Rake is a Ruby tool to describe and invoke certain tasks from a command line. For example, when you do bundle exec rake db:migrate, you actually start a task described by a Rakefile.

  You can easily design your own tasks, but as you start using Rails you usually don't need to. rails new drops a Rakefile for you that's just enough to start with, and unless you're doing some really custom (that should, exempli gratia, involve calling your Rails app code from the command line), there's no necessity in fiddling with it.

  Needless to say, if you're doing some simple Ruby console app that just asks your name and greets you, you don't need this file either.

Hope this helps you getting your head around this and smooths your ride into the Rails world!