mostly unrelated – but I wouldn&#x27;t have known&#x2F;cared about POSIX compliance until I ran into it:<p>On OS X, getopt is POSIX compliant. GNU utilities tend not to enforce POSIX in getopt, as a result you can do things like ls <i>.txt -la<p>On a POSIX complaint system, the optional arguments must come before any file arguments. This is super annoying to me, after having been using Linux for 15 years :)<p>Personally, I&#x27;ve been super happy with OS X for all purposes except servers, but to each their own, and that&#x27;s where Linux (and the </i>BSDs) shine – giving you access under the hood, which is awesome, but some of us just want the car to drive itself, so to speak.