Using rbenv to support multiple versions of ruby on MacOS

This guide covers using the brew package manager to install rbenv on MacOS to enable you to install multiple versions of ruby and switch between them.

Apple bundles ruby with its operating system but the version is generally outdated and often unsuitable for developers working on their latest project. Later versions of Mac OSX through to MacOS Sierra include Ruby 2.0. Earlier OSX variants, specifically the “cats” (Mountain Lion, Lion, Snow Leopard), ship with Ruby 1.8.7. The current stable version at the time of this post is 2.4.x.

rvm is another tool that, similar to rbenv, can be used to switch between multiple versions of ruby. Overall, rbenv has a lighter touch on the MacOS system, and so is the preferred choice for this guide.

Prerequisites

  • brew

Steps

Install rbenv and ruby-build with brew:

brew install rbenv ruby-build

Add rbenv to your bash profile so that it loads every time you open the Terminal app:

echo 'if which rbenv > /dev/null; then eval "$(rbenv init -)"; fi' >> ~/.bash_profile
source ~/.bash_profile

Thanks to: https://gorails.com/setup/osx/10.12-sierra for the snippet.

Next, close and re-open your Terminal app to ensure that rbenv is initialized from your updated bash profile.

Now you can install any ruby version that you like. The following example installs v2.4.0.

rbenv install 2.4.0

rbenv gives you options when choosing which version of ruby you’d like to use:

rbenv shell 2.4.0 temporarily changes the ruby version in your current shell and forces its use over other versions that might be specified by a .ruby-version file in your current working directory. This command works by setting the RBENV_VERSION environment variable in your session. To remove it, run unset RBENV_VERSION.

rbenv local 2.4.0 creates a .ruby-version file in your current directory such that any time ruby is invoked from that directory (or a subtree), rbenv will select the version of ruby that you specified. This is useful for project folders, and you can check the .ruby-version file into your project’s revision control.

rbenv global 2.4.0 changes your default ruby to the specified version in all cases where a version is not specified (e.g. due to a .ruby-version file or if the RBENV_VERSION environment variable is set). Your current Terminal session and any other sessions will be affected.

You can confirm the ruby version in play with the command:

ruby -v

If you don’t see your desired ruby version number in the command’s output (e.g. 2.4.0) and find an older one instead (e.g. 2.0.0 the MacOS default), be sure to close the Terminal and start fresh with a completely terminal window/session, and take note if your working folder has a .ruby-version file set and what the value of the RBENV_VERSION environment variable is (echo $RBENV_VERSION).

Once you are working in a newer ruby environment, you may need to check the gems and other libraries in a project that was started with an earlier version, to ensure they are compatible or need an update.

Published by

@firxworx

Kevin Firko (@firxworx) is an entrepreneur, developer, and digital project manager based in Toronto, Canada. He works on ventures and client projects through Bitcurve, the independent digital design and development studio he founded in 2008.