I’ve been trying on and off for the last six months to get RVM (Ruby Version Manager) working on my Mac. I had no problems on linux. RVM allows you switch between different Ruby interpreters and their respective versions. For example I can test my applications in Ruby 1.9, JRuby and the new YARV bytecode interpreter.
Today I realised my mistake. When I first got the Mac I had problems with locally installed gems not working so I changed the permissions on ~/.gem to prevent mistakenly installing a gem without sudo. This is the folder RVM uses to install gems for each Ruby install. No wonder I was having problems!
To allow RVM to install to this folder I simply opened the permissions back up:
RVM is a great project and I recently listened to an interview with the author on the CodePath podcast which I highly recommend.
UPDATE: After posting my finding to the RVM Google Group Wayne informed me that the latest HEAD version of RVM no longer uses the .gem directory but instead uses .rvm. I had put off updating to HEAD as I assumed it would be unstable, but I guess as this is recommended practice that only green code is commited.