The "Set Group-ID" Flag

• The "sgid" (Set Group-ID) flag, is mostly meaningful when set for a File containing an executable program, or for a Directory.
• When set for a File, it means that when a User runs this File, the launched process will have the permissions of the Group-owner of the File, rather than the permissions of the default-Group of the User running the program.
• When set for a Directory, it means that new Files created in this Directory, will belong to the Group-owner of this Directory, rather then to the default-Group of the User creating them.

Originally written by guy keren