Another way to go about it...
Since you've got two types of permissions, you're probably better off doing it in two commands. It's possible to do it all in one, but unnecessarily difficult (in my opinion). Anyway,
find is your friend:
Code:
find /path/to/top/directory -type f -exec chmod 660 {} \;
find /path/to/top/directory -type d -exec chmod 770 {} \;
First command locates only regular files (-type f) located in the top-level directory and subdirectories. For each file found, the chmod command gets executed. The curly braces ( {} ) get replaced with the matching filename when executed. The \; signals where the end of the command is (for the -exec option).
Similarly, the second command finds only directories. It will match the directory given on the commandline and all its subdirectories. It will also perform a similar chmod but with a different set of permissions (770 as opposed to the 660 for files).