The sticky bit is an access permission that affects the handling
of executable files and directories.
- If it's set for an executable file, the kernel keeps the executable in
memory for a while after the program ends—the exact length of time depends on what else
is happening in the system. This can improve the performance if you run a program (for
example, a compiler or linker) frequently.
- For a directory, it affects who can delete a file in the directory.
You always need to have write permission on the directory, but
if the sticky bit is set for the directory, you also need to be the
owner of the file or directory or have write permission on the file.
If the third character in a set of permissions is t (for example, r-t), the sticky bit and
execute permission are both set; T indicates that only the
sticky bit is set.