Can't install Ruby Compass on Mac Big Sur 11.5.2-CodePudding

I'm trying to get Compass installed on a 2020 Mac Book Pro running Big Sur (11.5.2).

When I try and run:

gem install compass

I get the error:

You don't have write permissions for the /Library/Ruby/Gems/2.6.0 directory

If I try and run:

sudo gem install compass

I get the error:

ERROR:  Error installing compass:
    ERROR: Failed to build gem native extension.

    current directory: /Library/Ruby/Gems/2.6.0/gems/ffi-1.15.4/ext/ffi_c

I've tried installing and updating Ruby. I've tried updating the system Ruby, but the system doesn't allow a more recent version than the below:

Updating rubygems-update
Fetching rubygems-update-3.3.3.gem
Successfully installed rubygems-update-3.3.3
Parsing documentation for rubygems-update-3.3.3
Installing ri documentation for rubygems-update-3.3.3
Installing darkfish documentation for rubygems-update-3.3.3
Done installing documentation for rubygems-update after 206 seconds
Parsing documentation for rubygems-update-3.3.3
Done installing documentation for rubygems-update after 0 seconds
Installing RubyGems 3.3.3
ERROR:  While executing gem ... (Errno::EPERM)
    Operation not permitted @ rb_sysopen - /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/gem

 % ruby -v
ruby 2.6.3p62 (2019-04-16 revision 67580) [universal.x86_64-darwin20]

Not sure what to do or try next.

Anyone have any ideas on how to get Compass installed?

CodePudding user response：

This really decomposes to two issues, as you noticed with the sudo call.

(1) You're trying to write gems to the protected directory for your system Ruby.

In most development environments, it's best to install a Ruby version manager that allows you to install multiple Rubies side-by-side for different projects. Purely subjectively, I'd recommend rbenv to manage only Ruby, or asdf to manage Ruby versions along with other languages versions. However, the question of which Ruby version manager to use is very well tread already, so you can pick the solution that's best for your needs with existing information.

(2) You're installing a gem with native extensions, which means that you need the underlying C libraries installed on your system to build correctly (assuming you're using CRuby, the default Ruby implementation). You'll need to install libffi-dev on your machine to build that gem correctly. Based on this question, it seems a simple brew install libffi should work for that.

Lastly, I'll suggest that it's idiomatic to use the bundler gem to manage gems per-project with Ruby. I'd reconsider if you really want to run this gem system-wide, or if it might vary versions across multiple projects.