How to install and use different versions of ruby?

Question

I'm learning rails from different books that use different versions of both ruby and rails. Right now I have ruby 1.87 installed on my Mac OS X Snow Leopard (in /usr/bin), but need to also use ruby 1.9 for a different rails application.

Can anyone tell me how to make this work? I'm new to this, so as many instructions as possible would be greatly appreciated.

Answer 1

Use Ruby Version Manager. It was meant for keeping multiple versions of Ruby in the same system, even allowing them to use different Gem sets and configurations. You won't mess with your system's Ruby as well, which is another benefit. All your Rubies will be stored in ~/.rvm/rubies, and therefore separated from the system.

There are a few easy steps to get started.

0. Prerequisites

You need Git installed.

• OS X doesn't ship with it. Install it using the Git OS X installer if you don't care for the ultra-latest version. Otherwise, install it over Homebrew.
• Linux versions might have it, otherwise just install the git-core package with apt-get or yum.

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1. Install RVM

Open up a Terminal and enter

bash < <(curl -s https://rvm.beginrescueend.com/install/rvm)

This takes a while. Read through everything the installer tells you. After the installation, add RVM to your profile (you should have been told that):

echo '[[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" # Load RVM function' >> ~/.bash_profile

Then, close and reopen the terminal, and type rvm to see if everything works. You should get a greeting message.

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2. Install Rubies

Install your Ruby versions with RVM now. First of all, enter rvm list known to see a list of all Rubies you can install through RVM. If you've decided, install them like so:

rvm install 1.8.7-head
rvm install 1.9.2

This may take a while, as they are downloaded and compiled on your system. When you're done, you can switch between them.

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3. Switch your Rubies

If you have a default Ruby you want to use, change it with the following command.

rvm --default use 1.9.2

To use – for example – the newly installed 1.8.7-head version, just type:

rvm use 1.8.7-head

To switch back to the system's default Ruby (e.g. OS X), type:

rvm use system

You can also reset RVM to use the system Ruby again. This will somewhat disable RVM:

rvm reset

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4. Where to go from that?

Now you should be set. This is all you need to know in the beginning. For further resources, check the following articles:

• The complete CLI usage manual
• Using named Gem sets for switching different versions of Rails, for example.
• Using RVM in scripting

Of course, when working in Rails, don't forget to also update your Rubies and RubyGems (in the latter case with gem update --system).