sticky bit

operating system The bit in the mode of a Unix file

which, if set for an executable, tells the kernel to keep

the code loaded in swap space even after it has finished

executing on the assumption that it is likely to be used again

soon. This performance optimisation was included in some

early (and recent?) versions of Unix to save reloading

frequently used programs such as the shell or vi from

disk.

If the sticky bit is set on a directory, an unprivileged user

may not delete or rename files of other users in that

directory even if he has write access to the directory.

The Unix "ls" command displays a set sticky bit as a "t" in

the permissions of a file or directory.

(1997-02-26)