The latest version of Radiator (radiator-0.3.10) now offers helper methods for common tasks like voting, posting, and transfers.
Here's how to get it to work right from the command line (see the Install Ruby section of How to Write a Discord Bot in Ruby if you need help installing ruby):
$ gem install radiator
$ ACCOUNT_NAME=<your account> WIF=<your wif> ruby -rradiator -e "puts Steem.new.vote!(10000, 'inertia', 'radiator-helper-methods')"
And that's all you need to do in order to vote from the command line.
Here's a link to the full documentation on these helper methods:
http://www.rubydoc.info/github/inertia186/radiator/master/Radiator/Chain