ruby安装

Linux安装：

apt-get install ruby

看官方推荐的：

http://www.ruby-lang.org/en/documentation/installation/#apt

Debian GNU/Linux and Ubuntu use the apt package manager. You can use it like this:

$ sudo apt-get install ruby-full

As of writing, the ruby-full package provides Ruby 1.9.3, which is an old stable release, on Debian and Ubuntu.

用ruby-full安装会安装rubygems，

1. prompt$ which gem