Absolute mode is slightly more difficult to read than symbolic mode but it requires less code on the command line so it is faster than symbolic mode.

Instead of using letters to symbolize permissions, absolute mode uses octal numbers to set permissions. This makes setting permissions a little faster because computers see octal numbers as three binary bits, and since there are three permissions that can be set on a file or directory for three different groups these octal numbers can be set to match each of the permission bits and turn them on or off.

Command Format

chmod octal values filename

Each separate permission has an octal value which is shown below:

Octal Value	Permission
4	read
2	write
1	execute/search

 

The octal values for the combined permissions are shown below:

 

Octal Value	Permission
7	r w x
6	r w -
5	r - x
4	r - -
3	- w x
2	- w -
1	- - x
0	- - -

Octal values for the permissions are grouped to identify a permission set. This set is generally referred to as the file's or directory's permissions.

Octal Value	Permission
644	rw-r--r--
751	rwxr-x--x
775	rwxrwxr-x
777	rwxrwxrwx

Default permissions are 644 on files and 755 on directories.