On Thu, 9 Sep 2004 12:37:21 -0500
Danny Sauer
Chadley wrote regarding '[SLE] octal permission mode' on Thu, Sep 09 at 08:24:
Greetings,
In my studies I have come across octal permision mode with the find command. What on earth does it do, mean, refer to ?
The section is as follows find -perm mode : List file with the octal permission mode
I can find a decent understandable answer in the man pages or google.
It says that because the file permissions are specified using a number represented in octal - base 8. There are three bits for each of the four permission groups, each of which can be on or off - AKA 1 or 0. Three positions with 2 possiblities each gives 2^3, or 8. Hence, octal is the most convenient way to group the 4 sets of three binary digits. octal 0755 = binary 000111101101 = "ls output" ---rwxr-xr-x. It could just as easily be hexadecimal (1ED) or decimal (493), but the base-8 system is a lot handier for human use.
If you've ever done a "chmod 0755 ~/public_html" then you've seen octal permission modes - the 0755 in there. Like everyone else said, "man chmod" th figure out exactly what each bit means.
I just want to add to this:
As mentioned above, the file permissions are stored effectively as 3
groups of 3 bits representing read-write-execute. The octal code as
mentioned above is used to easily refer to bits:
Octal Binary
0 000
1 001
2 010
3 011
4 100
5 101
6 110
7 111
So, instead of having to deal with binary directly, the octal system was
used.
--
Jerry Feldman