CHMOD(1) General Commands Manual CHMOD(1)
chmod - change mode
chmod mode file ...
The mode of each named file is changed according to mode, which may be
absolute or symbolic. An absolute mode is an octal number constructed
from the OR of the following modes:
4000 set user ID on execution
2000 set group ID on execution
1000 sticky bit, see chmod(2)
0400 read by owner
0200 write by owner
0100 execute (search in directory) by owner
0070 read, write, execute (search) by group
0007 read, write, execute (search) by others
A symbolic mode has the form:
[who] op permission [op permission] ...
The who part is a combination of the letters u (for user's permis-
sions), g (group) and o (other). The letter a stands for ugo. If who
is omitted, the default is a but the setting of the file creation mask
(see umask(2)) is taken into account.
Op can be + to add permission to the file's mode, - to take away per-
mission and = to assign permission absolutely (all other bits will be
Permission is any combination of the letters r (read), w (write), x
(execute), s (set owner or group id) and t (save text - sticky). Let-
ters u, g or o indicate that permission is to be taken from the current
mode. Omitting permission is only useful with = to take away all per-
The first example denies write permission to others, the second makes a
chmod o-w file
chmod +x file
Multiple symbolic modes separated by commas may be given. Operations
are performed in the order specified. The letter s is only useful with
u or g.
Only the owner of a file (or the super-user) may change its mode.
ls(1), chmod(2), chown (1), stat(2), umask(2)