How find out gem install options?

I'm trying to install all my gems in ~/.gems. I wanted to install ferret as user but it doesn't work, because fer开发者_如何学JAVAret need to install in /usr/bin. My question is, how to I find out which options (like install to different bin folder) exists, when I install gems?

The options you're mentioning are used by extconf.rb when the installation is being configured. Following steps would compile drivers that need to know where the system or API libraries are.

See Creating an Extension in the "Programming Ruby: The Pragmatic Programmer's Guide" book.

As shown below gem -h will show you all the options the gem command can process....