What is syntax to copy only new files?

[Josef Lowder]

What is the syntax to copy only new files from a CD backup to a hard disk?

I make backups of my files onto CDs and copy them onto another computer
to maintain redunancy.  Probably there is a better way to do this (sync, etc.)
so I would also appreciate knowing what is a better way to do this.

What I have been using is this:

cp -rp /mnt/cdrom/foldername /home/joe/foldername <E>

That works, but I don't want to re-write files that are unchanged,
and I don't want to write over any files that are newer on the
destination system.  How should this syntax be changed?