389 lines
8.8 KiB
Groff
389 lines
8.8 KiB
Groff
.\" $OpenBSD: chmod.1,v 1.42 2017/06/07 09:41:57 jmc Exp $
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.\" $NetBSD: chmod.1,v 1.8 1995/03/21 09:02:07 cgd Exp $
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.\"
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.\" Copyright (c) 1989, 1990, 1993, 1994
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the Institute of Electrical and Electronics Engineers, Inc.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)chmod.1 8.4 (Berkeley) 3/31/94
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.\"
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.Dd $Mdocdate: June 7 2017 $
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.Dt CHMOD 1
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.Os
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.Sh NAME
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.Nm chmod
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.Nd change file modes
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.Sh SYNOPSIS
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.Nm chmod
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.Op Fl h
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.Oo
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.Fl R
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.Op Fl H | L | P
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.Oc
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.Ar mode
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.Ar
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.Sh DESCRIPTION
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The
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.Nm
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utility modifies the file mode bits of the listed files
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as specified by the
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.Ar mode
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operand.
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The mode of a file dictates its permissions, among other attributes.
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl H
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If the
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.Fl R
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option is also specified, symbolic links on the command line are followed.
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Symbolic links encountered in the tree traversal are not followed.
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.It Fl h
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Treat symbolic links like other files: modify links instead of
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following them.
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The
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.Fl h
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and
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.Fl R
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options are mutually exclusive.
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.It Fl L
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If the
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.Fl R
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option is also specified, all symbolic links are followed.
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.It Fl P
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If the
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.Fl R
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option is also specified, no symbolic links are followed.
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.It Fl R
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Recurse.
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Where
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.Ar file
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is a directory,
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change the mode of the directory and all the files and directories
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in the file hierarchy below it.
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.El
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.Pp
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Symbolic links have modes,
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but those modes have no effect on the kernel's access checks.
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The
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.Fl H ,
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.Fl L ,
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and
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.Fl P
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options are ignored unless the
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.Fl R
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option is specified;
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if none of them are given,
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the default is to not follow symbolic links.
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In addition, these options override each other and the
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command's actions are determined by the last one specified.
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.Pp
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Only the file's owner or the superuser is permitted to change
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the mode of a file.
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.Ss Absolute modes
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Absolute modes are specified according to the following format:
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.Bd -filled -offset indent
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.Nm chmod
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.Ar nnnn
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.Ar
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.Ed
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.Pp
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An absolute mode is an octal number (specified as
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.Ar nnnn ,
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where
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.Ar n
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is a number from 0 to 7) constructed by ORing
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any of the following values:
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.Pp
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.Bl -tag -width 6n -compact -offset indent
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.It Li 0400
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Allow read by owner.
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.It Li 0200
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Allow write by owner.
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.It Li 0100
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Allow execution (or search in directories) by owner.
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.It Li 0700
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Allow read, write, and execute/search by owner.
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.It Li 0040
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Allow read by group.
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.It Li 0020
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Allow write by group.
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.It Li 0010
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Allow execution (or search in directories) by group.
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.It Li 0070
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Allow read, write, and execute/search by group.
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.It Li 0004
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Allow read by others.
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.It Li 0002
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Allow write by others.
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.It Li 0001
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Allow execution (or search in directories) by others.
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.It Li 0007
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Allow read, write, and execute/search by others.
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.El
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.Pp
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In addition to the file permission modes, the following mode bits are
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available:
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.Pp
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.Bl -tag -width 6n -compact -offset indent
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.It Li 4000
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Set-user-ID on execution.
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.It Li 2000
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Set-group-ID on execution.
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.It Li 1000
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Enable sticky bit; see
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.Xr sticky 8
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and
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.Xr chmod 2 .
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.El
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.Pp
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The execute bit for a directory is often referred to as the
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.Dq search
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bit.
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In order to access a file, a user must have execute permission in each
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directory leading up to it in the filesystem hierarchy.
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For example, to access the file
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.Pa /bin/ls ,
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execute permission is needed on
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.Pa / ,
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.Pa /bin ,
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and, of course, the
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.Pa ls
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binary itself.
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.Ss Symbolic modes
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Symbolic modes are specified according to the following format:
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.Bd -filled -offset indent
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.Nm chmod
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.Sm off
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.Op Ar who
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.Ar op
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.Oo Ar perm Oc , Ar ...
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.Sm on
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.Ar
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.Ed
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.Pp
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The
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.Ar who
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symbols indicate whose permissions are to be changed or assigned:
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.Pp
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.Bl -tag -width 4n -compact -offset indent
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.It u
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User (owner) permissions.
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.It g
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Group permissions.
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.It o
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Others permissions.
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.It a
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All of the above.
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.El
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.Pp
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Do not confuse the
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.Sq o
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symbol with
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.Dq owner .
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It is the user bit,
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.Sq u ,
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that refers to the owner of the file.
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.Pp
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The
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.Ar op
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symbols represent the operation performed, as follows:
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.Bl -tag -width 4n -offset indent
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.It +
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If no value is supplied for
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.Ar perm ,
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the
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.Sq +
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operation has no effect.
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If no value is supplied for
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.Ar who ,
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each permission bit specified in
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.Ar perm ,
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for which the corresponding bit in the file mode creation mask
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is clear, is set.
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Otherwise, the mode bits represented by the specified
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.Ar who
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and
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.Ar perm
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values are set.
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.It \&\-
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If no value is supplied for
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.Ar perm ,
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the
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.Sq \-
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operation has no effect.
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If no value is supplied for
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.Ar who ,
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each permission bit specified in
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.Ar perm ,
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for which the corresponding bit in the file mode creation mask
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is clear, is cleared.
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Otherwise, the mode bits represented by the specified
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.Ar who
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and
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.Ar perm
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values are cleared.
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.It =
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The mode bits specified by the
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.Ar who
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value are cleared or, if no
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.Ar who
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value is specified, the user, group
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and other mode bits are cleared.
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Then, if no value is supplied for
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.Ar who ,
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each permission bit specified in
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.Ar perm ,
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for which the corresponding bit in the file mode creation mask
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is clear, is set.
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Otherwise, the mode bits represented by the specified
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.Ar who
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and
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.Ar perm
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values are set.
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.El
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.Pp
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The
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.Ar perm
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(permission symbols) represent the portions of the mode bits as follows:
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.Pp
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.Bl -tag -width Ds -compact -offset indent
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.It r
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Read bits.
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.It s
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Set-user-ID and set-group-ID on execution bits.
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.It t
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Sticky bit.
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.It w
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Write bits.
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.It x
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Execute/search bits.
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.It X
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The execute/search bits if the file is a directory or any of the
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execute/search bits are set in the original (unmodified) mode.
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.It u
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User permission bits in the mode of the original file.
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.It g
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Group permission bits in the mode of the original file.
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.It o
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Other permission bits in the mode of the original file.
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.El
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.Pp
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Each clause (given in a comma-delimited list on the command line) specifies
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one or more operations to be performed on the mode bits, and each operation is
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applied in the order specified.
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.Pp
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Operations upon the
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.Dq other
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permissions (specified by the symbol
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.Sq o
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by itself), in combination with the
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.Ar perm
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symbols
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.Sq s
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or
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.Sq t ,
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are ignored.
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.Sh EXIT STATUS
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.Ex -std chmod
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.Sh EXAMPLES
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Set file readable by anyone and writable by the owner only:
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.Pp
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.Dl $ chmod 644 file
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.Pp
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Deny write permission to group and others:
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.Pp
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.Dl $ chmod go-w file
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.Pp
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Set the read and write permissions to the usual defaults, but
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retain any execute permissions that are currently set:
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.Pp
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.Dl $ chmod =rwX file
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.Pp
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Make a directory or file searchable/executable by everyone if it is
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already searchable/executable by anyone:
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.Pp
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.Dl $ chmod +X file
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.Pp
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Any of these commands will make a file readable/executable by everyone and
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writable by the owner only:
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.Bd -literal -offset indent
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$ chmod 755 file
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$ chmod u=rwx,go=rx file
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$ chmod u=rwx,go=u-w file
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.Ed
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.Pp
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Clear all mode bits for group and others:
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.Pp
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.Dl $ chmod go= file
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.Pp
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Set the group bits equal to the user bits, but clear the group write bit:
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.Pp
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.Dl $ chmod g=u-w file
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.Sh SEE ALSO
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.Xr chflags 1 ,
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.Xr chgrp 1 ,
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.Xr find 1 ,
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.Xr install 1 ,
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.Xr chmod 2 ,
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.Xr stat 2 ,
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.Xr umask 2 ,
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.Xr fts 3 ,
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.Xr setmode 3 ,
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.Xr symlink 7 ,
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.Xr chown 8 ,
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.Xr sticky 8
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.Sh STANDARDS
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The
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.Nm
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utility is compliant with the
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.St -p1003.1-2008
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specification.
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.Pp
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The flags
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.Op Fl HLP
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are extensions to that specification.
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.Pp
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The
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.Sq t
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perm symbol (sticky bit) is marked by
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.St -p1003.1-2008
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as being an
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X/Open System Interfaces
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option.
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.Sh HISTORY
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A
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.Nm
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command appeared in
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.At v1 .
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.Sh BUGS
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There's no
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.Ar perm
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option for the naughty bits.
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