Debian's which hunt

Debian's which hunt

There's a kind of fundamentalism in the Unix world that sees the POSIX specification as some sort of authority.

I think mostly it's just about reliability and portability.

If you only use features that's been ratified by POSIX then your code will be maximally portable to all Unices, no matter if they're derived from SysV or BSD, or from neither (e.g. Linux). If you want your code to be as useful to as many people as possible (or to be sellable to as many people as possible) then sticking to POSIX guarantees that. And if your code doesn't work on a platform, you get to blame the OS vendor, and to only grudgingly write a work-around (and maybe only if you get paid enough).

On the vendor side, if you want your platform to get any traction then you want as much existing code as possible to work on it, which means you need to embrace POSIX. Yeah, you can try and value-add stuff on top of that and go for the "extend" step (which traditional Unices did), but that carries a bad taste for Free Software/Linux devs (I wonder why?) and software devs don't always like to take advantage because then their software might not be usable by all their current users/customers.

Of the complaints I've seen about systemd and wayland (among others), the ones I have the most sympathy with are those from software devs who write apps that are meant to run on Linux and the BSDs, and for whom moving to the new native Linux APIs would mean either increasing their workload or dropping support for some platforms. Yes, back-compat support for init scripts and X11 exists and is supported, but some will still end up feeling like 2nd class citizens.