how to check how many ruby version on mac code example

Example 1: how to check ruby version

// Command line:
$ ruby -v

// Within irb type "RUBY_VERSION"
# => "2.4.1"

// If using RVM:
$ rvm current
# => ruby-2.4.1

Example 2: check all ruby version ubuntu

rvm list

rvm rubies
   ruby-1.9.1-p431 [ i386 ]
=* ruby-1.9.2-p320 [ i386 ]
# => - current
# =* - current && default
#  * - default