Editing File-system permissions (section)

===Changing permission behavior with setuid, setgid, and sticky bits===
Three additional single-bit attributes apply to each file that are related to permissions and stored in the file mode along with permissions.

* The ''[[Setuid|set user ID]]'', ''setuid'', or SUID mode. Executing a file with this bit set results in a process with [[User identifier (Unix)|user ID]] set to the file's owning user. This enables users to be treated temporarily as root (or another user).
* The ''[[Setgid|set group ID]]'', ''setgid'', or SGID permission. Executing a file with this bit set results in a process with [[Group identifier (Unix)|group ID]] set to the file's owning group. When applied to a directory, new files and directories created under that directory inherit their group from that directory. (Default behavior is to use the primary group of the effective user when setting the group of new files and directories, except on BSD-derived systems which behave as though the setgid bit is always set on all directories (see [[Setuid]]).)
* The ''[[Sticky bit|sticky]]'' mode (also known as the ''Text'' mode). The classical behavior of the sticky bit on executable files has been to encourage the [[Kernel (operating system)|kernel]] to retain the resulting process image in memory beyond termination; however, such use of the sticky bit is now restricted to only a minority of Unix-like operating systems ([[HP-UX]] and [[UnixWare]]). On a directory, the sticky permission prevents users from renaming, moving or deleting contained files owned by users other than themselves, even if they have write permission to the directory. Only the directory owner and superuser are exempt from this.