Linux Permissions - What does Octal mean? N00b


I grasp the idea of read / write / execute

Its split into 3 groups after the D for directory.  Owner Group and Others.  

Octal?


fcekAsked:
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farzanjCommented:
Octal means base 8 number : 0 through 7, then the next number is 10

This is how it works.  Say 1 means yes, 0 means no.
If you want
Read      1    yes
Write      0     no
Execute  1    yes

Then you have 101 which in octal is number 5
If you say yes to read, write and execute
Then you have 111  --- which is 7

Also, it goes by users, groups, others.

So first octal digit is for users, the second digit for groups and last for others

Octal would only mean that a digit would never exceed 7.
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Dave BaldwinFixer of ProblemsCommented:
This http://en.wikipedia.org/wiki/Filesystem_permissions  should tell you all about it.
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fcekAuthor Commented:


Ok the penny is beginning to drop as they say.


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arnoldCommented:
Octal deals with the base of all numbers similar to the decimal system
0  1    2
1 10 100
Octal is base 8
1  8  64

However, Octal numbers like their HEX brotheren, can be represented by 0's and 1's in the base-2
three digits on base 2 represents an octal digit
1 2 4

four digit on base 2 represents a HEX digit
1 2 4 8



Execute has a 0 or 1 value
Write has a 2 or 0 value
Read has a 4 or 0 value
In octal it is represented as:

Read x2^2 +write *2^1+execute*2^0
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