They are not the same. For example, `[[` apparently works on Alpine's ash but not on Debian's dash. BusyBox ash has some bash compatibility options enabled in Alpine.

It's ironic that a post about shell differences glosses over this. Maybe not surprising that slop is sloppy.

The post is not about shell differences, there's too many of them. It's about portability.

I want users to test instead of rote memorizing. And I'm giving them tools:

    docker run --rm alganet/shell-versions:all -c 'PATH=; [[ 1 == 1 ]] || echo fail'