Using octal numbers to specify permissions
Typically, octal permissions are specified with three or four numbers,
in these positions:
1234
Each position indicates a different
type of access:
- In position 1 are the bits that set permission for set-user-ID on access, set-group-ID on access, or the sticky bit. Specifying this position is optional.
- In position 2 are the bits that set permissions for the owner of the file. Specifying this position is required.
- In position 3 are the bits that set permissions for the group that the owner belongs to. Specifying this position is required.
- In position 4 are the bits that set permissions for others. Specifying this position is required.