SC3002 – ShellCheck Wiki

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In POSIX sh, extglob is undefined.

(or "In dash, ... is not supported." when using dash)

Problematic code:

rm !(*.hs)

Correct code:

Either switch the shebang to a shell that does support extglob, like bash or ksh, or rewrite in terms of a loop with a case or grep match:

for file in *
  case "$file" in
    *.hs) true;;
    *) rm "$file" ;;


Extglobs are extensions in bash and ksh, while your shebang says you're using sh or dash.


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.