How to make /opt and /sw invisibles ?

17/09/05 15:14
After installed DarwinPorts and Fink, new folders appear at the root level (/opt and /sw).
How do I make them invisibles like /etc ?
Under Panther:
add them to the /.hidden file

Under Tiger: (with the DeveloperTools installed)
/Developer/Tools/SetFile -a V /opt
/Developer/Tools/SetFile -a V /sw

(You may need to sudo).