File Permissions
The Linux permissions uses 'octal' number system to describe permissions.
what's octal number system
Octal number system uses base 8 to represent numbers. This means, it uses 8 symbols to represent numbers. 0,1,2,3,4,5,6,7.
Octal Representation of Permissions
When you say chmod 755 file.txt, it means, you are setting the permissions of the file.txt to 755.
- The second digit 5 represents the permissions for the group of the file.
- The first digit 7 represents the permissions for the owner of the file.
- The third digit 5 represents the permissions for others.
And each digit when converted to binary represents the read, write and execute permissions of .
| Octal | Binary | Permission |
|---|---|---|
| 0 | 000 | --- |
| 1 | 001 | --x |
| 2 | 010 | -w- |
| 3 | 011 | -wx |
| 4 | 100 | r-- |
| 5 | 101 | r-x |
| 6 | 110 | rw- |
| 7 | 111 | rwx |