Manage ruby versions with direnv

If you are not a ruby developer, a ruby version manager might be overkill if you only need it from time to time.

direnv is a tool that manages your environment depending on the current directory¹. At first, I started using it to manage environment variables for specific projects. After that, it replaced version managers for languages I use less often, like python and javascript (node). Once my projects had everything neatly configured in .envrc files, it made sense to include the ruby version as well.

How?

$ brew install direnv

First, install direnv and configure your shell to use it.

$ brew install chruby

Then install chruby², but do not configure your shell to source it. Instead, we will do this via direnv. Edit ~/.direnvrc and append the following:

source /usr/local/opt/chruby/share/chruby/chruby.sh

# Uncomment to use with rubies installed with ruby-build:
# RUBIES+=(~/.rbenv/versions/*)

# use ruby [version]
use_ruby() {
	local ver=$1
	if [[ -z $ver ]] && [[ -f .ruby-version ]]; then
		ver=$(cat .ruby-version)
	fi
	if [[ -z $ver ]]; then
		echo Unknown ruby version
		exit 1
	fi
	chruby $ver
}

If your ruby versions are not in ~/.rubies, uncomment the RUBIES line and set the value appropriately.

Relaunch your shell, navigate to your project, run direnv edit ., and add the following (assuming you have 2.5.1 installed):

use ruby 2.5.1

Your shell should now be ready with the specified ruby version.

See also: Manage project dependencies with direnv.