No rocket science here - just because I always forget… If you are using rbenv with the ruby-build plugin and want to upgrade to the latest version of ruby, you might have to update ruby-build to get the latest definitions.
$ rbenv install 2.1.3 ruby-build: definition not found: 2.1.3
ruby-build does not know about 2.1.3 yet.
$ cd ~/.rbenv/plugins/ruby-build $ git pull
$ rbenv install 2.1.1 Downloading ruby-2.1.3.tar.gz... -> http://dqw8nmjcqpjn7.cloudfront.net/0818beb7b10ce9a058cd21d85cfe1dcd233e98b7342d32e9a5d4bebe98347f01 Installing ruby-2.1.3... Installed ruby-2.1.3 to /home/ryan/.rbenv/versions/2.1.3
Of course, this assumes you installed rbenv from the git repository. If you used Homebrew on OSX, you can do something like this:
$ brew update $ brew upgrade ruby-build