Installing Ruby was a pain in 2015 the first time I tried, and I can't believe that 9 years later I would struggle to install it again!

Luckily the world has overcomed most of the issues i had almost a decade ago, also because the community delivered some great tools like rvm to do the job for us.

In my case, however, I used asdf.

What is ASDF ?

You have nvm to switch between nodeJS versions, rvm to switch between Ruby versions, pyenv for python... They basically do the same thing, downloading and allowing to choose dinamically which version you want to use for a given project, so a relatively new tool has joined the group: asdf!

The idea behind asdf is to be multi-language, so you can list, download, and use any version of any (supported) language!

This post will focus on MacOS for latest hardware at the time being, specifically the M2 chip.

The best way to install asdf is to follow the official howto, basically using brew, and follow the relevant part for your shell (which is zsh by default on Mac now).

Once everything is working, you can install the ruby plugin:

asdf plugin add ruby https://github.com/asdf-vm/asdf-ruby.git

Time to install Ruby

If you "simply" install Ruby, as reccomended by the tool, you'll get this:

$ asdf install ruby 3.3.4 
ruby-build: using openssl@3 from homebrew
==> Downloading ruby-3.3.4.tar.gz...

...

*** Following extensions are not compiled:
openssl:
        Could not be configured. It will not be installed.
        /private/var/folders/8r/rdh70zf146vdrx054gm3lx3h0000gn/T/ruby-build.20240822143802.92522.9rg23R/ruby-3.3.4/ext/openssl/extconf.rb:122: OpenSSL library could not be found. You might want to use --with-openssl-dir=<dir> option to specify the prefix where OpenSSL is installed.
        Check /var/folders/8r/rdh70zf146vdrx054gm3lx3h0000gn/T/ruby-build.20240822143802.92522.9rg23R/ruby-3.3.4/ext/openssl/mkmf.log for more details.
psych:
        Could not be configured. It will not be installed.
        Check /var/folders/8r/rdh70zf146vdrx054gm3lx3h0000gn/T/ruby-build.20240822143802.92522.9rg23R/ruby-3.3.4/ext/psych/mkmf.log for more details.

BUILD FAILED (macOS 14.5 on arm64 using ruby-build 20240727)

Let's fix it

The issue, as far as I understood, is that asdf is trying to compile the specified Ruby version but for another architecture. The M2 chip, infact, from time to time pretends some special flags for compilation. The problem is that we figure this out only after some research; errors do not tell us anything special.

So we're going to install the missing libraries, but compiled for the ARM architecture:

arch -x86_64 brew install openssl libyaml

Now we can proceed in installing Ruby:

arch -x86_64 asdf install ruby 3.3.4 

If after this you try to run ruby -v and still see ruby 2.6, which is the default coming with MacOS, simply restart the shell and you'll see the latest version installed.

Enjoy!