Does anyone know the command to change a files attribute to hidden? please

Hidden in what way - from the OS X finder?

The way I do it in Mac is click to rename the file or folder then place a peroid at the begining of the name. This makes it hidden to Finder
Sample
.folder
.file

If you had Xcode Tools installed, in Terminal write this to hide a file/dir:
/Developer/Tools/SetFile -a -V /path-to/file
and write this if you want to show:
/Developer/Tools/SetFile -a -v /path-to/file

-a means attributes
-V (UPPERCASE) means hide
-v (lowercase) means show

The only thing I can not hide are links like /etc -> /private/etc, /tmp -> /private/tmp and /var -> /private/var

Excellent people thanks for that