Ok, based on feedback here and elsewhere, here's a version that uses getopt_long() from libc. It supports both --ppid (like Linux ps) and -P (like pgrep), and it seemed reasonable to add obvious long opts for --pid, --tty and --jail too. I decided not to try to add Linux-like --user, --User, --group, --Group in this patch (-u, -U, -g, -G all look a bit unportable and complicated). Thoughts?

Tested, the bad code removal works as described. +1 for getting rid of the BACKWARD zones by default, to match base. LGTM.

I suppose we could update tzsetup(8) to use the new version too, if we're going to install it. So here's a patch that teaches that to handle the modern format with multi-country first field, and gets rid of the hardcoded "Arctic" menu because it went away in the data (concretely that means that people in https://en.wikipedia.org/wiki/Svalbard would need to choose Europe -> Norway, whose timezone they share as I assume they are well aware, being "a full part of the Kingdom of Norway").

Please re-read what I suggested in previous reply.

Got rid of allocation/copying.
Show POSIX segments as "(unlinked)" if their name has gone.
Show SysV segments with their key_t (same way it is displayed in ipcs output).

An obvious example of another user would be SysV shm. I suppose it should show the key (in hex format?) as the "path". Then of course you would use jail_adjust = false.

Thanks for working on this! I took it for a quick spin and have some initial feedback.

Here's a better version (the last one had an unintended stray change).
Note: this is a refactoring suggested by mjg, to support his future plans to change the representation of panic state to something small in __read_frequently. The new macro will hide those details from all these call sites, though for now it just does what it was doing before (with the addition of the prediction).