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CHMOD
!!!CHMOD
NAME
SYNOPSIS
DESCRIPTION
STICKY FILES
STICKY DIRECTORIES
OPTIONS
AUTHOR
REPORTING BUGS
COPYRIGHT
SEE ALSO
----
!!NAME


chmod - change file access permissions
!!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 permissions 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
permissions.


The format of a symbolic mode is
`[[ugoa...][[[[+-=][[rwxXstugo...]...][[,...]'. Multiple symbolic
operations can be given, separated 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 permissions selected to be added
to the existing permissions of each file; `-' causes them to
be removed; and `=' causes them to be the only permissions
that the file has.


The letters `rwxXstugo' select the new permissions for the
affected users: read (r), write (w), execute (or access for
directories) (x), execute only if the file is a directory or
already has execute permission for some user (X), set user
or group ID on execution (s), sticky (t), the permissions
that the user who owns the file currently has for it (u),
the permissions that other users in the file's group have
for it (g), and the permissions that other users not in the
file's group have for it (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. Any
omitted digits are assumed to be leading zeros. The first
digit selects the set user ID (4) and set group ID (2) and
sticky (1) attributes. The second digit selects permissions
for the user who owns the file: read (4), write (2), and
execute (1); the third selects permissions 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 encountered during
recursive directory traversals.
!!STICKY FILES


On older Unix systems, the sticky bit caused executable
files to be hoarded in swap space. This feature is not
useful on modern VM systems, and the Linux kernel ignores
the sticky bit on files. Other kernels may use the sticky
bit on files for system-defined purposes. On some systems,
only the superuser can set the sticky bit on
files.
!!STICKY DIRECTORIES


When the sticky bit is set on a directory, files in that
directory may only be unlinked or renamed by root or their
owner. (Without the sticky bit, anyone able to write to the
directory can delete or rename files.) The sticky bit is
commonly found on directories, such as /tmp, which are
world-writable.

!!OPTIONS


Change the mode of each FILE to MODE.


__-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


__--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 one or more of the letters ugoa, one of the
symbols +-= and one or more of the letters
rwxXstugo.
!!AUTHOR


Written by David !MacKenzie.
!!REPORTING BUGS


Report bugs to
!!COPYRIGHT


Copyright 2001 Free Software Foundation, Inc.
This is free software; see the source for copying
conditions. There is NO warranty; not even for
MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.
!!SEE ALSO


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 chmod__


should give you access to the complete manual.
----
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Last edited on Monday, November 20, 2006 10:00:06 pm by IanMcDonald
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