[Gibbon1]

The hard advice I have is: If the new company is a competitor of the old company. And the stuff you are reusing is directly related to the core business of the old company.

Absolutely don't do that.

The far end of that would be reusing bash scripts you developed as an IT guy for a now out of business drywall manufacturer for you new job as an IT guy for a manufacturer of 3D printers.

No one will notice. There is no one to care (out of business). And it's not worth a lawyers time.