It isn't even pure bash, if it uses external commands like `bc` and `sed`. It should probably limit itself to posix shell (or bash, if they need to) and coreutils.

They are only listing `bc` and `bash` as a prerequisite, but the example uses `sed`, so this is also not complete. So a full list of all required tools would be the first step.

But I am working on embedded systems where I write lots of POSIX shell scripts that run in tiny initramfs, etc. so I am very picky with my dependencies. If I had a better language to target busybox, that would be welcome as well.