(An alias) Create a bash alias private such that when you run private foo, the entire subtree of the file-system starting at foo (so just foo if it is a file, but foo and all of its files and subdirectories recursively if it is a directory) has its permissions changed as follows:

The user's (owner's) permissions are unchanged.

The group permissions are changed to match the owner's.

The world (others) permissions are changed to remove write permissions. Existing read and execute permissions should remain unchanged.

Put your alias in a file defprivate such that entering source defprivate would make private available in the current shell (i.e., source defprivate makes the defprivate command available for use in the current shell, but does not actually execute it immediately). Hint: g=u.