Most shell families precede the spec. Both bash and ksh had features at the time the spec was written that are not in it. It's weird.

My main point is that following the spec doesn't guarantee shell scripts will be portable, which is a common misconception.

> My main point is that following the spec doesn't guarantee shell scripts will be portable, which is a common misconception.

That feels like a failure in the spec. Your example illustrates it: echo has unspecified behavior that literally prevents it from being portable.

Is it possible portability is just not a feature of posix?

	▲	gaigalas 5 hours ago \| parent [-]
		I honestly don't know! What I know is that there is an intersection of features that work with polyfills and tweaks in all shells. That intersection has a lot of the spec, but also has a lot that is not specified anywhere. I started to build something here 12 years ago: https://github.com/Mosai/workshop. Then here 2 years ago: https://github.com/alganet/coral Now I'm attacking it from another angle, trying to document what I learned methodically and share the tools I made for me with everyone else.