Sticky bit

The sticky bit is an access right flag that can be assigned to files and directory on Unix systems.

Historically, the sticky bit was used only with executable files. When set, it told the Operating system to keep the running program in memory for later executions (possibly even by other users). Since that age, the performances of persistent storage technologies have greatly increased and this usage has been obsoleted.

Nowadays, the sticky bit can be used with directories. When set for a directory, it means that a user may only modify and delete the files and directories in that directory he or she owns. When clear for a directory, the usual rules apply, and the write access right alone allows a user to create, modify and delete files and directories in that directory, regardless of their owner.

The sticky bit is often set for the /tmp directory.