What does --pre do in gem install rails --pre ?

Question

What does --pre do in gem install rails --pre ?

Answer 1

The '--pre' is a shortcut for '--prerelease'.

Answer 2

--pre means that it will install the prerelease of the rails gem. For instance when Rails 3 was still in beta, you could still play around with it by getting the prerelease.

You shouldn't run this unless you want to be on edge of a gem (for development or test purposes). I wouldn't recommend putting a website in production with a gem in prerelease as they might not be stable enough yet.