chmod ( 1 ) USER COMMANDSchmod ( 1 )

NAME

chmod - change the access permissions of files

SYNOPSIS

chmod [ options ] mode file ...

DESCRIPTION

chmod changes the permission of each file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new permissions.

Symbolic mode strings consist of one or more comma separated list of operations that can be perfomed on the mode. Each operation is of the form user op perm where user is zero or more of the following letters:
u
User permission bits.
g
Group permission bits.
o
Other permission bits.
a
All permission bits. This is the default if none are specified.

The perm portion consists of zero or more of the following letters:
r
Read permission.
s
Setuid when u is selected for who and setgid when g is selected for who.
w
Write permission.
x
Execute permission for files, search permission for directories.
X
Same as x except that it is ignored for files that do not already have at least one x bit set.
l
Exclusive lock bit on systems that support it. Group execute must be off.
t
Sticky bit on systems that support it.

The op portion consists of one or more of the following characters:
+
Cause the permission selected to be added to the existing permissions. | is equivalent to +.
-
Cause the permission selected to be removed to the existing permissions.
=
Cause the permission to be set to the given permissions.
&
Cause the permission selected to be anded with the existing permissions.
^
Cause the permission selected to be propagated to more restrictive groups.

Symbolic modes with the user portion omitted are subject to umask(2) settings unless the = op or the --ignore-umask option is specified.

A numeric mode is from one to four octal digits (0-7), derived by adding up the bits with values 4, 2, and 1. Any omitted digits are assumed to be leading zeros. The first digit selects the set user ID (4) and set group ID (2) and save text image (1) attributes. The second digit selects permissions for the user who owns the file: read (4), write (2), and execute (1); the third selects permissionsfor other users in the file's group, with the same values; and the fourth for other users not in the file's group, with the same values.

For symbolic links, by default, chmod changes the mode on the file referenced by the symbolic link, not on the symbolic link itself. The -h options can be specified to change the mode of the link. When traversing directories with -R, chmod either follows symbolic links or does not follow symbolic links, based on the options -H, -L, and -P. The configuration parameter PATH_RESOLVE determines the default behavior if none of these options is specified.

When the -c or -v options are specified, change notifications are written to standard output using the format, %s: mode changed to %0.4o (%s), with arguments of the pathname, the numeric mode, and the resulting permission bits as would be displayed by the ls command.

For backwards compatibility, if an invalid option is given that is a valid symbolic mode specification, chmod treats this as a mode specification rather than as an option specification.

OPTIONS

-H, --metaphysical
Follow symbolic links for command arguments; otherwise don't follow symbolic links when traversing directories.
-L, --logical|follow
Follow symbolic links when traversing directories.
-P, --physical|nofollow
Don't follow symbolic links when traversing directories.
-R, --recursive
Change the mode for files in subdirectories recursively.
-c, --changes
Describe only files whose permission actually change.
-f, --quiet|silent
Do not report files whose permissioins fail to change.
-h, --symlink
Change the mode of the symbolic links on systems that support this.
-i, --ignore-umask
Ignore the umask(2) value in symbolic mode expressions. This is probably how you expect chmod to work.
-n, --show
Show actions but do not change any file modes.
-F, --reference=file
Omit the mode operand and use the mode of file instead.
-v, --verbose
Describe changed permissions of all files.

EXIT STATUS

0
All files changed successfully.
>0
Unable to change mode of one or more files.

SEE ALSO

chgrp(1), chown(1), tw(1), getconf(1), ls(1), umask(2)

IMPLEMENTATION

version
chmod (AT&T Research) 2007-09-10
author
Glenn Fowler <gsf@research.att.com>
author
David Korn <dgk@research.att.com>
copyright
Copyright © 1992-2008 AT&T Intellectual Property
license
http://www.opensource.org/licenses/cpl1.0.txt