https://news.ycombinator.com/item?id=10104203
Although I would agree that there's a slight hole there: you still need to port stuff like coreutils and all the dependencies, which has been done of course. But I'd be happier if something like busybox was actually portable.
The Autoconf system is predicated on the idea that writing a portable shells script is hard, and so we hide the shell programming behind a mountain of M4 macros.
It's not necessarily easier to port a shell script today than 22 years ago, which was not written with portability in mind. There are more shells with more extensions, and then beyond the language concerns, and the environments have exploded. A shell script can easily depend on all sorts of cruft you've never heard of. Oh, just install these five things from the following github repos ...
https://pubs.opengroup.org/onlinepubs/9699919799/
> Sure systems seen try to somewhat be POSIX compliance
The mainstream systems you know and use adhere very rigorously to POSIX. GNU Libc, Kernel, Coreutils, ... and their counterparts in BSD Unixes, proprietary Unixes, Cygwin and whatnot all take POSIX seriously.
POSIX is very helpful, and smart coders and sysadmins use it as one of their references for required behavior.