sticky - sticky text and append-only directories
A special file mode, called the sticky bit (mode S_ISVTX),
is used to indicate
special treatment for files and directories. See
chmod(2) or the
file /usr/include/sys/stat.h for an explanation of file
Historically, an executable shareable file which had the
sticky bit set
was not immediately discarded from swap space after execution. The kernel
hoarded the text segment of the file for future reuse,
having to reload the program. This is no longer true on
the current virtual memory system keeps track of recently
making the sticky bit for files redundant. The sticky
still be set on files, but without any effect.
Only the superuser can set the sticky bit on a file, though
the owner of
the file may clear the sticky bit.
A directory with the `sticky bit' set places restrictions on
a file in a sticky directory may only be removed or
renamed by a
user if the user has write permission for the directory and
the user is
the owner of the file, the owner of the directory, or the
This feature is usefully applied to directories such as /tmp
be publicly writable but should deny users the license to
delete or rename each others' files.
Any user may create a sticky directory. See chmod(1) for
modifying file modes.
A sticky command appeared in Version 32V AT&T UNIX.
Neither open(2) nor mkdir(2) will create a file with the
sticky bit set.
OpenBSD 3.6 June 5, 1993
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