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 permissionThe who part 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 .
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), a (append only), l (exclusive access), and t (temporary file).
Only the owner of a file or the group leader of its group may change the file's mode.