Bottom Line — Specify a ruby version and RVM will automatically switch when you open different projects.

Problem

I had several Ruby and Ruby on Rails projects I was working on that used different versions of Ruby. Each time I’d open a project, I had to set the correct version of Ruby using RVM. It was a pain.

For example, I’d have to run something like this on every terminal window that I’d use with that project.

rvm use 2.6.6

Solution

If you don’t already have a Gemfile for your Ruby project, create one. Make sure to specify the Ruby version in the Gemfile.

For example, a Gemfile can look like this:

source "https://rubygems.org"
ruby '2.6.6'

Also, create a file called .ruby-version in your project directory. Inside that file, add a line with the Ruby version. For example: ruby-2.6.6

RVM will now automatically switch Ruby to the correct version the Gemfile and the .ruby-version specifies. No more manual switching required.