Permissions are where Linux stops being forgiving. A file is readable or it is not, and the answer is in a string you can read once you know the three groups.
Each one is marked as you go, and the explanation arrives straight after, which is
the part worth reading.
4 questions, marked as you go.
Tasks
These need your own device. Run the command in Termux, then paste what it printed.
The marking looks at what the output means, so spacing, version numbers and
ordering do not matter. If you have not installed anything yet, the
lesson covers the setup.
Produce a mode and read it back
This creates a file, sets it to owner-only, then shows you both the permission string and the octal value, so you can see the same mode written two ways.
Run this in Termux
On your own device. Nothing on this page executes it. The command runs in
your terminal, and this box only reads what you paste back.
touch ~/secret.txt; chmod 600 ~/secret.txt; ls -l ~/secret.txt; stat -c "%a %n" ~/secret.txt
You are looking for two different views of the same mode: the symbolic one from ls, and the octal one from stat.
the symbolic mode is owner read and write only
the octal mode is 600
the listing is for the file you created
What a good answer looks like
The first line is from ls and should read -rw-------, which is the symbolic form: read and write for the owner, nothing for the group, nothing for anyone else. The second line is from stat and should be 600, which is the same thing written in octal. Being able to move between those two notations is the whole skill. If your ls line shows -rw-r--r--, the chmod did not take effect.
Marking your own work
Both halves of this are checked in your browser, with no server involved, so nothing
stops you from pasting output you did not run. The tasks are written so that the
easiest way to pass one is to actually do it and read the result, which is the whole
intention.