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