NAME

chmod − change file mode

SYNTAX

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()

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 permissions), g (group) and o (other).  The letter a stands for all, or ugo. If who is omitted, the default is a but the setting of the file creation mask is taken into account.  For further information, see umask(.).

Op can be + to add permission to the file’s mode, − to take away permission and = 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 that permission is to be taken from the current mode.  Omitting permission is only useful with = to take away all permissions. 

To indicate multiple symbolic modes that are to be applied to a given file, separate the modes with commas.  These changes then will be applied in the sequence specified. 

EXAMPLES

The first example denies write permission to others.  The second makes a file executable for all.  The third gives write permission to all group members, denies read permission to others, and makes the file executable for the user. 

chmod o−w file
 chmod +x file
 chmod g+w,o-r,u+x file

RESTRICTIONS

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)

Commands