Uninstall all installed gems, in OSX?

Question

There are instances where I would like to revert and uninstall all previous gem installations.

For instance, I needed to assist a friend migrate their rails developm

Answer 1

gem list --no-version | grep -v -e 'psych' -e 'rdoc' -e 'openssl' -e 'json' -e 'io-console' -e 'bigdecimal' | xargs sudo gem uninstall -ax

grep here is excluding default gems. All other gems will be uninstalled. You can also precede it with sudo in case you get permission issues.