I tried it like this:
1: apt install ruby
2: Put your code in test.rb
3: ruby test.rb
I then I got:
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
\e[0m
current directory: /var/lib/gems/3.1.0/gems/stringio-3.1.1/ext/stringio
/usr/bin/ruby3.1 -I /usr/lib/ruby/vendor_ruby -r ./siteconf20240626-4044-iylnuy.rb extconf.rb
mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h
You might have to install separate package for the ruby development
environment, ruby-dev or ruby-devel for example.
So I tried:
4: apt install ruby-dev
5: ruby test.rb
Then I got:
[4147, #<Thread:0x00007f9a4af6bc60 run>, #<NameError: uninitialized constant Gem::Source
(defined?(@source) && @source) || Gem::Source::Installed.new
^^^^^^^^