chmod
(1g)
Name
chmod - change file mode bits
Synopsis
chmod [OPTION]... MODE[,MODE]... FILE...
chmod [OPTION]... OCTAL-MODE FILE...
chmod [OPTION]... --reference=RFILE FILE...
Description
User Commands CHMOD(1)
NAME
chmod - change file mode bits
SYNOPSIS
chmod [OPTION]... MODE[,MODE]... FILE...
chmod [OPTION]... OCTAL-MODE FILE...
chmod [OPTION]... --reference=RFILE FILE...
DESCRIPTION
This manual page documents the GNU version of chmod. chmod
changes the file mode bits of each given 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 mode bits.
The format of a symbolic mode is
[ugoa...][[+-=][perms...]...], where perms is either zero or
more letters from the set rwxXst, or a single letter from
the set ugo. Multiple symbolic modes can be given, sepa-
rated by commas.
A combination of the letters ugoa controls which users'
access to the file will be changed: the user who owns it
(u), other users in the file's group (g), other users not in
the file's group (o), or all users (a). If none of these
are given, the effect is as if a were given, but bits that
are set in the umask are not affected.
The operator + causes the selected file mode bits to be
added to the existing file mode bits of each file; - causes
them to be removed; and = causes them to be added and causes
unmentioned bits to be removed except that a directory's
unmentioned set user and group ID bits are not affected.
The letters rwxXst select file mode bits for the affected
users: read (r), write (w), execute (or search for directo-
ries) (x), execute/search only if the file is a directory or
already has execute permission for some user (X), set user
or group ID on execution (s), restricted deletion flag or
sticky bit (t). Instead of one or more of these letters,
you can specify exactly one of the letters ugo: the permis-
sions granted to the user who owns the file (u), the permis-
sions granted to other users who are members of the file's
group (g), and the permissions granted to users that are in
neither of the two preceding categories (o).
A numeric mode is from one to four octal digits (0-7),
derived by adding up the bits with values 4, 2, and 1.
Omitted digits are assumed to be leading zeros. The first
digit selects the set user ID (4) and set group ID (2) and
restricted deletion or sticky (1) attributes. The second
digit selects permissions for the user who owns the file:
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User Commands CHMOD(1)
read (4), write (2), and execute (1); the third selects per-
missions for 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.
chmod never changes the permissions of symbolic links; the
chmod system call cannot change their permissions. This is
not a problem since the permissions of symbolic links are
never used. However, for each symbolic link listed on the
command line, chmod changes the permissions of the pointed-
to file. In contrast, chmod ignores symbolic links encoun-
tered during recursive directory traversals.
SETUID AND SETGID BITS
chmod clears the set-group-ID bit of a regular file if the
file's group ID does not match the user's effective group ID
or one of the user's supplementary group IDs, unless the
user has appropriate privileges. Additional restrictions
may cause the set-user-ID and set-group-ID bits of MODE or
RFILE to be ignored. This behavior depends on the policy
and functionality of the underlying chmod system call. When
in doubt, check the underlying system behavior.
chmod preserves a directory's set-user-ID and set-group-ID
bits unless you explicitly specify otherwise. You can set
or clear the bits with symbolic modes like u+s and g-s, and
you can set (but not clear) the bits with a numeric mode.
RESTRICTED DELETION FLAG OR STICKY BIT
The restricted deletion flag or sticky bit is a single bit,
whose interpretation depends on the file type. For directo-
ries, it prevents unprivileged users from removing or renam-
ing a file in the directory unless they own the file or the
directory; this is called the restricted deletion flag for
the directory, and is commonly found on world-writable
directories like /tmp. For regular files on some older sys-
tems, the bit saves the program's text image on the swap
device so it will load more quickly when run; this is called
the sticky bit.
OPTIONS
Change the mode of each FILE to MODE. With --reference,
change the mode of each FILE to that of RFILE.
-c, --changes
like verbose but report only when a change is made
-f, --silent, --quiet
suppress most error messages
-v, --verbose
output a diagnostic for every file processed
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User Commands CHMOD(1)
--no-preserve-root
do not treat '/' specially (the default)
--preserve-root
fail to operate recursively on '/'
--reference=RFILE
use RFILE's mode instead of MODE values
-R, --recursive
change files and directories recursively
--help
display this help and exit
--version
output version information and exit
Each MODE is of the form
'[ugoa]*([-+=]([rwxXst]*|[ugo]))+|[-+=][0-7]+'.
AUTHOR
Written by David MacKenzie and Jim Meyering.
REPORTING BUGS
Report chmod bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/core-
utils/>
General help using GNU software: <http://www.gnu.org/geth-
elp/>
Report chmod translation bugs to <http://translationpro-
ject.org/team/>
COPYRIGHT
Copyright (C) 2012 Free Software Foundation, Inc. License
GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redis-
tribute it. There is NO WARRANTY, to the extent permitted
by law.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
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User Commands CHMOD(1)
+---------------+--------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------+
|Availability | file/gnu-coreutils |
+---------------+--------------------+
|Stability | Uncommitted |
+---------------+--------------------+
SEE ALSO
chmod(2)
The full documentation for chmod is maintained as a Texinfo
manual. If the info and chmod programs are properly
installed at your site, the command
info coreutils 'chmod invocation'
should give you access to the complete manual.
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://ftp.gnu.org/gnu/coreutils/coreutils-8.16.tar.xz
Further information about this software can be found on the
open source community website at http://www.gnu.org/soft-
ware/coreutils/.
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