Changing File Permissions

Changing File Permissions

On computer filesystems, different files and directories have permissions that specify who and what can read, write, modify and access them.

Permission Modes

  7       5     5
 user   group  world
 r+w+x  r+x    r+x
 4+2+1  4+0+1  4+0+1  = 755

The permission mode is computed by adding up the following values for the user, the file group, and for everyone else. The diagram shows how.

• Read 4 - Allowed to read files


• Write 2 - Allowed to write/modify files


• eXecute1 - Read/write/delete/modify/directory

  6      4      4
 user   group  world
 r+w    r      r
 4+2+0  4+0+0  4+0+0  = 644

Example Permission Modes

Mode	Str Perms	Explanation
0477	-r--rwxrwx	owner has read only (4), other and group has rwx (7)
0677	-rw-rwxrwx	owner has rw only(6), other and group has rwx (7)
0444	-r--r--r--	all have read only (4)
0666	-rw-rw-rw-	all have rw only (6)
0400	-r--------	owner has read only(4), group and others have no permission(0)
0600	-rw-------	owner has rw only, group and others have no permission
0470	-r--rwx---	owner has read only, group has rwx, others have no permission
0407	-r-----rwx	owner has read only, other has rwx, group has no permission
0670	-rw-rwx---	owner has rw only, group has rwx, others have no permission
0607	-rw----rwx	owner has rw only, group has no permission and others have rwx