This rbenv plugin automatically runs rbenv rehash every time you install or uninstall a gem.
Install
Install the rbenv plugin.
git clone https://github.com/sstephenson/rbenv-gem-rehash.git /usr/local/rbenv/plugins/rbenv-gem-rehash
Upgrade
To upgrade to the latest version of rbenv-gem-rehash, use git pull.
cd /usr/local/rbenv/plugins/rbenv-gem-rehash
git pull