fish shell has been burned in the few places it strictly implements POSIX.

The most vivid example is test, aka /bin/[. POSIX specifies that, if test is invoked with one argument, you must "Exit true (0) if $1 is not null; otherwise, exit false" [1].

This means that `test --help` is forbidden from printing any help. It means that `test -d $argv` expands to `test -d` if $argv is empty, which then must "succeed" because "-d" is not null. It bites users over and over again [2].

Implementing this POSIX piece has resulted in more headaches, not fewer. I regret implementing a POSIX-conformant test, I wish I had just picked mostly-compatible but also-sane semantics.

1: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/t...

2: https://stackoverflow.com/questions/29635083/fish-shell-chec...

> It means that `test -d $argv` expands to `test -d` if $argv is empty, which then must "succeed" because "-d" is not null. It bites users over and over again [2].

To be fair, while the POSIX behaviour is obviously wrong, using `$argv` on a bourne-style shell[0] is also wrong; that should be either `test -d "$argv"` or (if I recall the syntax correctly) `test -d "${argv[@]}"` if you actually intended argv to be a list rather than a single directory ("argv" suggests the former, but `test -d X` only accepts a single argument).

0: more specifically, a shell that does word splitting at the wrong place (after parameter expansion)

Last published in 2018 (and actively being worked on) is not outdated.

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.

Larry Wall said It's easier to port a shell than a shell script in 1998 ... 22 years later I still think that holds.

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.

I think it's easier to write a portable shell script today than 30 years ago.

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 ...

Yes, if you care about portability. Anything that's not Linux likely won't have GNU grep installed by default. This includes macOS and the BSDs.

If this is your own dotfiles or utilities, sure, but if I'm working on something collaborative, yes, I care about the standard.

I stick to POSIX in my dotfiles precisely because I carry it around on many different systems and that’s the only thing that can keep it sane.

Same here — I felt it would detract from the point I was trying to make so I didn’t mention it, especially since I don’t think most people run multiple OS’s :) At the least though, I would assume people regularly have collaborators that run different OS’s.

If I would create something which needs that degree of portability I would never use a shell script.

It's just way too easy to run into a unexpected gotcha on some platform/configuration.

Yeah I agree with this. I claimed a few years ago that you could view https://www.oilshell.org/ as a "better POSIX", and I still hold that view.

http://www.oilshell.org/blog/2018/01/28.html#limit-to-posix

Recent comment about this:

https://news.ycombinator.com/item?id=24428347

POSIX is just too limited and not what people use in practice.

If you want a portable shell script, in many cases my (biased) advice would be to make your script work on both bash and Oil. (Obviously there are short shell scripts which you may want to run on BSD, etc. This is more about big scripts, which POSIX falls down for.)

Oil already runs some of the biggest shell scripts in the world, many of them unmodified. Moreoever, when there's a patch necessary to run it, it often IMPROVES the program.

http://www.oilshell.org/blog/2020/06/release-0.8.pre6.html#p...

You'll be less tied to the vagaries of bash.

If anyone's script doesn't run under Oil, I'm interested. See https://github.com/oilshell/oil/wiki/What-Is-Expected-to-Run...