Manual dla chmod

CHMOD(1) User Commands CHMOD(1)

chmod - change file mode bits

chmod [OPTION]... MODE[,MODE]... FILE...
chmod [OPTION]... --reference=RFILE FILE...

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 directories) (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 dele-
tion flag or sticky bit (t). Instead of one or more of these letters,
you can specify exactly one of the letters ugo: the permissions granted
to the user who owns the file (u), the permissions 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

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, except that if the first digit is omitted, a
directory's set user and group ID bits are not affected. 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 permis-
sions 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 sym-
bolic 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.

The restricted deletion flag or sticky bit is a single bit, whose
interpretation depends on the file type. For directories, it prevents
unprivileged users from removing or renaming 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
systems, 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.

Change the mode of each FILE to MODE.

-c, --changes
like verbose but report only when a change is made

do not treat `/' specially (the default)

fail to operate recursively on `/'

-f, --silent, --quiet
suppress most error messages

-v, --verbose
output a diagnostic for every file processed

use RFILE's mode instead of MODE values

-R, --recursive
change files and directories recursively

--help display this help and exit

output version information and exit

Each MODE is of the form `[ugoa]*([-+=]([rwxXst]*|[ugo]))+'.

Written by David MacKenzie and Jim Meyering.

Report bugs to <>.

Copyright (C) 2007 Free Software Foundation, Inc.
This is free software. You may redistribute copies of it under the
terms of the GNU General Public License
<>. There is NO WARRANTY, to the
extent permitted by law.


The full documentation for chmod is maintained as a Texinfo manual. If
the info and chmod programs are properly installed at your site, the

info chmod

should give you access to the complete manual.

GNU coreutils 6.9 March 2007 CHMOD(1)