Brew install ruby successfully installed ruby-2.2.3 on Mac, but playing ruby -v still shows 2.0.0.

  question, ruby

Just like the topic!

May I know what is going on?

You can look at it this way.

type ruby

The result should be

/usr/bin/ruby

This is ruby2.0 preinstalled by the system.

Brew install ruby will be installed in/usr/local/Cellar/ruby/2.2.3/bin/rubyUnder path

ruby -v
 ruby 2.0.0p481 (2014-05-08 revision 45883) [universal.x86_64-darwin14]
 @caoh ➜  ~  /usr/local/Cellar/ruby/2.2.3/bin/ruby -v
 ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-darwin14]