Can somebody tell me why my command language interpreter shell shows me an empty string as the result after the command
$ echo $VERSION
And only after executing this command
$ . /etc/os-release
it begins to show me the result of that command
$ echo $VERSION
18.04.3 LTS (Bionic Beaver)
can you, please, explain me what happens after that command? Why had not shell shown it before? Why does shell show it now?