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.\" $OpenBSD: sticky.8,v 1.8 2003/12/20 09:09:46 jmc Exp $
.\" $NetBSD: sticky.8,v 1.3 1994/11/30 19:36:27 jtc Exp $
.\"
.\" Copyright (c) 1980, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)sticky.8 8.1 (Berkeley) 6/5/93
.\"
.Dd June 5, 1993
.Dt STICKY 8
.Os
.Sh NAME
.Nm sticky
.Nd sticky text and append-only directories
.Sh DESCRIPTION
A special file mode, called the
.Em sticky bit
(mode S_ISVTX),
is used to indicate special treatment for files and directories.
See
.Xr chmod 2
or
the file
.Pa /usr/include/sys/stat.h
for an explanation of file modes.
.Sh STICKY FILES
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,
thus avoiding having to reload the program.
This is no longer true on modern systems;
the current virtual memory system keeps track of recently used executables,
making the sticky bit for files redundant.
The sticky bit can still be set on files, but without any effect.
.Pp
Only the superuser can set the sticky bit on a file,
though the owner of the file may clear the sticky bit.
.Sh STICKY DIRECTORIES
A directory with the
.Sq sticky bit
set places restrictions on file deletion:
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 superuser.
This feature is usefully applied to directories such as
.Pa /tmp
which must be publicly writable but
should deny users the license to arbitrarily
delete or rename each others' files.
.Pp
Any user may create a sticky directory.
See
.Xr chmod 1
for details about modifying file modes.
.Sh HISTORY
A
.Nm
command appeared in Version 32V AT&T UNIX.
.Sh BUGS
Neither
.Xr open 2
nor
.Xr mkdir 2
will create a file with the sticky bit set.
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