(or "In dash, ... is not supported." when using
#!/bin/sh rm !(*.hs)
Either switch the shebang to a shell that does support extglob, like
ksh, or rewrite in terms of a loop with a
#!/bin/sh for file in * do case "$file" in ) true;; *.hs*) rm "$file" ;; esac done
Extglobs are extensions in bash and ksh, while your shebang says you're using
If you only intend to target shells that supports this feature, you can change the shebang to a shell that guarantees support, or ignore this warning.
You can use
# shellcheck disable=SC3000-SC4000 to ignore all such compatibility warnings.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.