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by eqvinox 1 hour ago
Feels like you missed the point.

On the example of 'echo \n' - it's not defined in POSIX, therefore a script written in "POSIX shell" must simply never hit that case.

TFA kinda implies you can't target POSIX shell. That's silly, of course you can. The question is, what tools are there to check for compliance. Whether running on 14 shells is a good such tool - idk. Something specifically searching for POSIX violations might be better.
2 comments
Joker_vD 1 hour ago
Well, with C language it's pretty much the same. You are supposed to "just" never write (or rather, most of the time, to just not execute) anything that is UB. And lots and lots of people to this day continue to believe that can do this (most of the time, they're wrong).
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eqvinox 50 minutes ago
UB (specified to be undefined) and 'plain' unspecified are not the same thing.
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gaigalas 1 hour ago
The spec is not that good.

`local` for example is present in many shells (almost all of them), but they decided to leave it out uniquely because of ksh93 (scope is different). It became undefined behavior.

When the spec was written, ksh was important. Since then, it has only been revised but not updated and I consider it to be obsolete.

So, if you follow POSIX strictly, you then lose local scope on functions, which is more likely to cause bugs and hard to catch with a linter like you suggested. You're left with a broken feature set (on many other angles too) that is not actually practical. Even spellcheck makes concessions.

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echoangle 1 hour ago
I don’t get this point either. If local is not in the POSIX spec, I guess you can’t use it if you want to be POSIX compatible. Just because many shells do it doesn’t mean it’s POSIX.
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gaigalas 1 hour ago
You can target POSIX if you want to, but doing that doesn't guarantee shell scripts will work.

The blog post stresses this, the difference between POSIX and portability.

If you want portability, testing is better for now. One of the goals of these projects is to more precisely capture a retrospec (what actually works, not what was specified), it's the same thing they did with HTML5.

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