POSIX is part of unix history and running systems have some compatibility level with it, so in that respect it is relevant. But as for writing universally worki

POSIX is part of unix history and running systems have some compatibility level with it, so in that respect it is relevant. But as for writing universally working scripts, it is not a panacea, because systems shells are not exactly POSIX compliant. For example, bash and Linux, the standard of unix de facto, deviate from POSIX, the standard de iure. > but that is something you have to do anyway. Exactly my point.