File and Directory Permissions #

Understanding read, write and executable permissions.

If we do ls -l:

$ .rw-rw-r-- user family 168 B  Sun Nov 13 01:59:08 2022 things.txt

Here as we can see a dot “.” at the head part of the output line shows that this is a regular file.

When going through permissions there are four parts of it which can be seen in form of drwx-rw-r--.

r –> Read permission
w –> Write permission
x –> Executing permission
“-” –> No permission

More Important notation for file types #

How permissions are evaluated #

When a user tries to read or write to a file, the users permisisons are evaluated in a linear left to right manner:

1. First owner permissions will be looked at and action will be taken based on its permissions.
2. If the owner has none of the required permissions then group permissions will be looked at and action is taken accordingly.
3. Lastly if the user is not int he group or does not exist then last set of permissions will be looked at and action is taken accordingly.