41a5ad6012
Three minor changes to the manpage of chmod(1). 1. At the description of -H option, I added that symlinks are not followed _by default_ to show that links can be followed, but the default chmod behavior is not to do so. 2. Moved a misplaced .Va file command up to the place it belongs. 3. Simplified the grammar that describes symbolic modes. PR: 16749 Submitted by: Giorgos Keramidas <keramida@ceid.upatras.gr>
348 lines
9.2 KiB
Groff
348 lines
9.2 KiB
Groff
.\" 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" $FreeBSD$
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.\"
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.Dd March 31, 1994
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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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.Oo
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.Fl f
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.Fl R
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.Op Fl H | Fl L | Fl P
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.Fl v
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.Oc
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.Ar mode
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.Ar file ...
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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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.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 specified, symbolic links on the command line are followed.
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(Symbolic links encountered in the tree traversal are not followed by
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default.)
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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 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 specified, no symbolic links are followed.
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.It Fl R
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Change the modes of the file hierarchies rooted in the files
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instead of just the files themselves.
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.It Fl f
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Do not display a diagnostic message if
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.Nm
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could not modify the mode for
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.Va file .
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.It Fl v
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Cause
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.Nm
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to be verbose, showing files as the mode is modified.
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.El
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.Pp
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Symbolic links do not have modes, so unless the
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.Fl H
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or
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.Fl L
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option is set,
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.Nm
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on a symbolic link always succeeds and has no effect.
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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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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 owner of a file or the super-user is permitted to change
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the mode of a file.
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.Sh DIAGNOSTICS
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The
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.Nm
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utility exits 0 on success, and >0 if an error occurs.
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.Sh MODES
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Modes may be absolute or symbolic.
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An absolute mode is an octal number constructed from the sum of
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one or more 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 4000
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(the set-user-ID-on-execution bit) Executable files with this bit set
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will run with effective uid set to the uid of the file owner.
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Directories with the set-user-id bit set will force all files and
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sub-directories created in them to be owned by the directory owner
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and not by the uid of the creating process, if the underlying file
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system supports this feature: see
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.Xr chmod 2
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and the
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.Ar suiddir
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option to
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.Xr mount 8 .
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.It Li 2000
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(the set-group-ID-on-execution bit) Executable files with this bit set
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will run with effective gid set to the gid of the file owner.
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.It Li 1000
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(the sticky bit)
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When set on a directory, unprivileged users can delete and rename
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only those files in the directory that are owned by them, regardless of
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the permissions on the directory. Under FreeBSD, the sticky bit is
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ignored for executable files and may only be set for directories (see
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.Xr sticky 8 ).
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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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For files, allow execution by owner. For directories, allow the owner to
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search in the directory.
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.It Li 0040
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Allow read by group members.
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.It Li 0020
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Allow write by group members.
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.It Li 0010
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For files, allow execution by group members. For directories, allow
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group members to search in the directory.
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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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For files, allow execution by others. For directories allow others to
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search in the directory.
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.El
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.Pp
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For example, the absolute mode that permits read, write and execute by
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the owner, read and execute by group members, read and execute by
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others, and no set-uid or set-gid behaviour is 755
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(400+200+100+040+010+004+001).
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.Pp
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The symbolic mode is described by the following grammar:
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.Bd -literal -offset indent
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mode ::= clause [, clause ...]
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clause ::= [who ...] [action ...] action
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action ::= op [perm ...]
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who ::= a | u | g | o
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op ::= + | \- | =
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perm ::= r | s | t | w | x | X | u | g | o
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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 ``u'', ``g'', and ``o'' specify the user, group, and other parts
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of the mode bits, respectively.
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The
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.Ar who
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symbol ``a'' is equivalent to ``ugo''.
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.Pp
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.ne 1i
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The
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.Ar perm
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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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The read bits.
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.It s
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The set-user-ID-on-execution and set-group-ID-on-execution bits.
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.It t
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The sticky bit.
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.It w
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The write bits.
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.It x
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The 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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Operations with the
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.Ar perm
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symbol ``X'' are only meaningful in conjunction with the
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.Ar op
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symbol ``+'', and are ignored in all other cases.
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.It u
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The user permission bits in the mode of the original file.
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.It g
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The group permission bits in the mode of the original file.
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.It o
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The other permission bits in the mode of the original file.
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.El
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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
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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 ``+'' 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 ``\-'' 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 who value is specified, the owner, 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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Each
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.Ar clause
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specifies one or more operations to be performed on the mode
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bits, and each operation is applied to the mode bits in the
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order specified.
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.Pp
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Operations upon the other permissions only (specified by the symbol
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``o'' by itself), in combination with the
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.Ar perm
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symbols ``s'' or ``t'', are ignored.
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.Sh EXAMPLES
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.Bl -tag -width "u=rwx,go=u-w" -compact
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.It Li 644
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make a file readable by anyone and writable by the owner only.
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.Pp
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.It Li go-w
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deny write permission to group and others.
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.Pp
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.It Li =rw,+X
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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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.It Li +X
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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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.It Li 755
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.It Li u=rwx,go=rx
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.It Li u=rwx,go=u-w
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make a file readable/executable by everyone and writable by the owner only.
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.Pp
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.It Li go=
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clear all mode bits for group and others.
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.Pp
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.It Li g=u-w
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set the group bits equal to the user bits, but clear the group write bit.
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.El
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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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.Sh COMPATIBILITY
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The
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.Fl v
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option is non-standard and its use in scripts is not recommended.
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.Sh SEE ALSO
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.Xr chflags 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 mount 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 expected to be
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.St -p1003.2
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compatible with the exception of the
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.Ar perm
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symbols
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.Dq t
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and
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.Dq X
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which are not included in that standard.
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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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