Getting started with ruby-on-rails-3 – Installating Rails on mac.

You would need to install ruby before you can install rails.

Mac already comes with ruby installed based on how recent your macOS is? Depending on what ruby version you want for your development, the best way to install Ruby is to use RVM. In your terminal, type the command below listed in steps:

  1. Install rvm

    curl -sSL https://get.rvm.io | bash -s stable --ruby 
    
  2. For Rails 3, best version to install is ruby 1.9.3

    rvm install 1.9.3
    ruby -v #=> 1.9.3 
    
  3. Set your Ruby version

    rvm use 1.9.3 --default
    
  4. Install Rails (this rails version requires ruby-version >=1.9.3)

    gem install rails -v 4.2.7.1
    rails -v #=> 4.2.7.1
    
  5. Install rails app

    rails new my_first_app #(this will install the app for you.)
    cd my_first_app
    rails s #(run the server)
    
  6. Open the browser and type below in your URL.

    http://localhost:3000
    

    Message saying ‘Welcome to rails’ will be displayed or similar.

if you want to reproduce, please indicate the source:
Getting started with ruby-on-rails-3 – Installating Rails on mac. - CodeDay