Is POSIX relevant today? I'd think that overwhelming majority of the shell scripts would require either Linux or BSD dialects. And if one wanted to limit my sh

Is POSIX relevant today? I'd think that overwhelming majority of the shell scripts would require either Linux or BSD dialects. And if one wanted to limit my shell scripts significantly, I'd limit myself to commands supported by busybox's "ash" shell -- this is a limited shell environment which is pretty widely used in initrd's and embedded devices.