Agree... look at man chmod
The string "rwsr-xr-x" is read as three groups of three:
- The first group, "rws," says that the owner of this file has full access to the file, and that it is a setuid program which will execute with the owner's identity.
- The second group, "r-x", means that users who belong to this 'group' have read and execute permission, but not write.
- The third group, also "r-x", means that others (those who are neither the owner nor group-members) also can read and execute, but not write.
the permissions control whether you can:
- See a list of the files in the directory (Read).
- Insert and remove files here (Write).
- Have access to files here if you know their exact name (Execute).
When people refer to these permissions numerically, they use a digit for each "group of three" from left to right. There are eight possibilities, corresponding to the eight numbers (0-7) that can be produced by three binary bits... so-called octal
Number Binary Bits Permissions
-------- ---------- ------------
0 000 ---
1 001 --x
2 010 -w-
3 011 -wx
7 111 rwx
of course know by heart.