Installing rbenv on Zsh (on MacOS)

Recently, I updated my Mac to the latest beta of macOS. It’s not a polished product yet, but overall it’s been a fairly enjoyable operating system.

One of the changes that will impact you as a developer is that Apple switched the default shell from Bash to Zsh (Z shell). You can, of course, change it back to Bash, but I don’t mind Zsh (or Fish) so I decided to keep it.

I needed to install htmlbeautifier, a gem used by some prettifier extensions within Visual Studio Code. If you try it with the default system installation of Ruby, you’ll get a permission error:

$ gem install htmlbeautifier
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /Library/Ruby/Gems/2.6.0 directory.

At this point, you might be tempted to simply sudo it, but that’s not a smart approach. Instead, I like to have multiple versions through an environment management system such as rbenv or asdf.

For this particular machine, I picked rbenv. Unfortunately, following the usual setup instructions didn’t really work, so I’m sharing the setup that worked for me here.

I updated brew and used it to install rbenv and ruby-build. The latter allows us to select a series of Ruby versions to chose from.

$ brew update && brew install rbenv ruby-build

To ensure that rbenv is correctly loaded when we start a new shell, I had to edit a couple of files. I added the following line to .zshenv:

export PATH="$HOME/.rbenv/bin:$PATH"

This adds gem-specific binaries to the PATH so that they are accessible to the shell without fully qualifying them with their path.

Then I added the following lines to .zshrc:

source $HOME/.zshenv
eval "$(rbenv init - zsh)"

This ensures that the previous file is sourced when a new session is started and that rbenv is initialized for Zsh.

At this point, you’ll want to source .zshrc (or simply restart the terminal of your choice like iTerm2, instead):

$ source ~/.zshrc

With rbenv ready to go, I installed the latest version of Ruby and set it as my global default for this machine.

You can determine the latest stable version by running:

$ rbenv install -l

Go ahead and run:

$ rbenv install 2.7.2
$ rbenv global 2.7.2

After restarting the terminal again, do a quick sanity test to ensure that the right version of Ruby is being selected:

$ ruby -v
ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-darwin20]

$ ruby -e "puts (1..100).reduce(:+)"
5050

Finally, you’ll be able to install htmlbeautifier, like I did:

$ gem install htmlbeautifier

No need for sudo.

I hope this helps anyone who is trying to install rbenv on zsh. It did the trick for me.