What do you mean by "get the new Ruby into place"?
If you are trying to run it from the command line using just the command
ruby, the system will search each of the paths specified in
/etc/paths in order until it finds a match. In Snow Leopard, the default
/etc/paths file looks like this:
So when you enter
ruby at the command line, the system looks for
/usr/bin/ruby first, finds it, and doesn't check the rest of the paths (so it never gets to
/usr/local/bin/ruby). To confirm this, you can enter
which ruby at the command line, and the system will print the path of the executable that it would use for that command.
If you want to run your newer version of Ruby from the command line, simply enter
/usr/local/bin/ruby instead of
If you are using another program that is using Ruby indirectly, there's probably an option somewhere to specify the path to
EDIT: As a last resort, you can overwrite the built-in system version of Ruby with your newer version. Use the following commands, and enter your administrator password when prompted:
cp /usr/bin/ruby ~/Desktop/ruby_OLD
sudo cp /usr/local/bin/ruby /usr/bin/ruby
If something breaks, put it back with this command:
sudo mv ~/Desktop/ruby_OLD /usr/bin/ruby
As others have mentioned, though, using a tool like RVM to manage Ruby would be a better idea than upgrading the built-in installation.