Understanding RubyGems, Macports, and /opt/ versus /Library/

Question

I'm not looking to keyword spam here, and this question is in the least tangential to a previous question of mine that's currently pending. Caveat emptor.

Most references to Ruby on the Mac have things set up with the conventions mentioned in this question. Stored in /Library/, that is. My whole setup is somehow stored like this:

I'd like to understand the differences here and what on earth I did to end up with things stored in /opt/. Did it have anything to do with installing MacPorts?

And if there's not a good reason for this setup, I'd love to move in a more conventional direction. I'm pretty sure I have extra copies of at least some things lying around with things organized in this manner. And I know some important things are stored in /Library/ (my Less.CSS gem for one).

Thanks so much for any insights you can give.

Answer 1

MacPorts installs itself, as well as its ports, under /opt/local, to avoid "polluting" /usr, /usr/local, etc. If you installed RubyGems via MacPorts, it'll exist under /opt/local; likewise, any gem you install (globally) will also be under /opt/local.

If you install RubyGems manually, or use the version that ships with OS X, it'll install gems under /Library instead. That's why some tutorials reference /Library instead of /opt/local.

If you use a version of Ruby provided by MacPorts, it's probably easier and better to store gems under /opt/local; conversely, if you use the Ruby that ships with OS X, or you installed your own version, it might be better to keep gems under /Library. But it doesn't matter which place you keep them, or whether you have gems spread across both directories.