I think we should redirect stderr for compatibility with the Matlab 'system' function, and maybe later provide a different function that is more configurable, maybe with options similar to Python's subprocess library.

(Or maybe users could just call py.subprocess.run directly once I get pythonic going again.)

> Why don't we go with a user preference variable?

That sounds less than ideal. That's a global setting. And it's really the immediate caller in most cases that's going to know whether it wants stderr mixed in with stdout, because it's the one that's going to be doing parsing or processing or passing it on to some other context. An option to system() or a different system2() function seems like a better design; that way callers can individually choose which behavior they want.

"--braindead", as I understand it, doesn't mean "make it Matlab compatible". It's not supposed to affect behaviour. Octave's goal is already to be to behave like Matlab. The --braindead option is only for superficial cosmetic differences that don't really impact behaviour, such as changing the default prompt or the default matrix display formats.

Perhaps we should have a version of system (with a different name, or as an option) that can capture stderr separately, or let it go to stderr if the user wants that behavior?  It really seems better to me to not redirect stderr to stdout unless requested.