Ruby

written June 2025 on MacOS 15.5

~~brew install ruby~~

MacOS has version 2.6 ruby preinstalled (which is outdated, current>3.0). There is nothing you can do about this.

The brew installation won't work, because the 2.6 binary takes priority over the 3.0, so nothing will work out of the box.

Check paths with type -a ruby or which -a ruby

Check versions with ruby --version, gem --version

Which is why you need Ruby Environment Manager:

Ruby Environment Manager

brew install rbenv ruby-build

rbenv install -l

rbenv install <version>

just follow Stackoverflow thread on this issue, it's to confusing and complicated to explain what is acutally going on.

The gem package manager comes preinstalled with ruby.

gem update --system to update gem

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

MacOS is defaulting to outdated 2.6 ruby. See above.