If you only use defined behavior and it works, it is compatible.

It’s like saying C99 isn’t a compiler. True, but you can still write C99 code, right?

* https://unix.stackexchange.com/a/496642/5132

because the problem here is educating people with slipshod ideas about 'sh' being 'the POSIX shell' or (worse) 'the Bourne shell'. Both M. Chazelas and M. Gaigalas are making the point that 'sh' is a language that one aims to write in, not one of the many programs that sort of, sometimes, if invoked in the right way, implement that language; and a subordinate point that people are generally very poor about doing that when yet they insist that they are writing 'POSIX shell script'.

Fun facts: Standardization led by existing practice is not a simple process.

* https://unix.stackexchange.com/a/493743/5132

POSIX/SUS standardization is not a static thing. The long discussed thorny issue of echo has now subtly changed from all of those explanations given about it over the years, because in 2024 the standard was changed.

* https://pubs.opengroup.org/onlinepubs/9799919799/utilities/e...

M. Chazelas's own quite famous 2013 StackExchange answer on the subject has not yet been updated with the change that now incorporates -e and -E into the rule. Amusingly, it was M. Chazelas that raised defect 1222 that caused this change.

* https://unix.stackexchange.com/a/65819/5132

* https://www.austingroupbugs.net/view.php?id=1222

    osh-0.37$ echo "c:\new"
    c:\new

    osh-0.37$ shopt --set no_parse_backslash
    osh-0.37$ echo "c:\new"
      echo "c:\new"
              ^
    [ interactive ]:6: Invalid char escape in double quoted string (OILS-ERR-12)

    echo "c:\\new"  # with two backslashes 

    \ " ` $

Nine Reasons to Use OSH - https://oils.pub/osh.html

This post was thought provoking, I wonder, is the hidden argument here that the posix spec for a shell is not well specified if there is so much variance between the implementations?

Or is the fundamental issue simply a matter of history? Both?

This would include the MirBSD mksh, and oksh from OpenBSD.

They are much smaller than ksh93 and bash, and I would suggest that their syntax extensions be given preference, as they originally represented ksh88 (from which the POSIX shell standard was derived).

Smells a lot of AI writing.

[1] https://shellspec.info/

> POSIX is a specification. Not a program. The thing that actually runs your script is bash, dash, ash, ksh, yash, or one of a dozen others.

“When someone says ‘write it in ECMAScript,’ they mean well.

“ECMAScript is specification. Not a program. The thing that actually runs your script is Node.js, Bun, Deno, Rhino, or one of a dozen others.”

See how silly that sounds?