Question

How can I detect if the current reading of a file is done directly from the command line, or is done via loading/requiring?

There is a well known way:

__FILE__ == $0

but this does not work correctly when there is a possibility that the main file loads itself.

Answer 1

It was too easy. I will just assign a flag and check it. A slightly tricky thing was the ordering of the relevant assignments. (a) condition, (b) assigning to a flag, and (c) loading have to come in this order:

if @loaded and __FILE__ == $0
  # the main reading
  ...
else
  # not the main reading
  ...
end
...
@loaded = true
...
the_relevant_command_that_leads_to_loading_of_a_file

If I wanted them in a different order, I have to embed some of these and force this order.