I use the incremental backups through cpanel but I would like to not have certain files be backed up. core.* files

If I make a exclude file and place it in the root folder How can I have the cpanel back up system see it for all accounts being backed up.

Also is there a way to limit the file name that is backed up for a example a name with 30 or more characters like superlongridiculuslytoolongofafilename.php