NAME

chmod − change mode

SYNOPSIS

chmod mode file ... 

DESCRIPTION

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 following form:

[who] op permission [op permission] ...

The who segment is a combination of the letters u (for user’s permissions), 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 considered. 

Op can be a plus (+) to add permission to the file’s mode, a minus to cancel permission and an equal sign (=) to assign permission absolutely (all other bits will be reset). 

Permission is any combination of the letters r (read), w (write), x (execute), s (set owner or group id) and t (save text − sticky).  Letters u, g or o indicate permission is to be taken from the current mode.  Omitting permission is only useful with an equal sign (=) to cancel all permissions. 

The first example denies write permission to others, and the second makes a file executable as follows:

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. 

SEE ALSO

ls(1), chmod(2), stat(2), umask(2), chown(8)

October 19, 1983  —  @(#)chmod.11.1%Q%%Y%