$ gem help examples
Some examples of 'gem' usage.
* Install 'rake', either from local directory or remote server:
gem install rake
* Install 'rake', only from remote server:
gem install rake --remote
* Install 'rake' from remote server, and run unit tests,
and generate RDocs:
gem install --remote rake --test --rdoc --ri
...
* See information about RubyGems:
gem environment