How can I uninstall Ruby on ubuntu?
This command should do the trick (provided that you installed it using a dpkg-based packet manager):
aptitude purge ruby
Run the following command from your terminal:
sudo apt-get purge ruby
Usually works well for me.
At first find out where ruby is?then
rm -rf /usr/local/lib/rubyrm -rf /usr/lib/rubyrm -f /usr/local/bin/rubyrm -f /usr/bin/rubyrm -f /usr/local/bin/irbrm -f /usr/bin/irbrm -f /usr/local/bin/gemrm -f /usr/bin/gem