(or "In dash, ... are not supported." when using
#!/bin/sh exec -ca ls busybox
Switch to a shell that does support the
exec flags you are using, like
#!/bin/bash exec -ca ls busybox
In POSIX, you can use
env to start a command with a clean environment, but there is no way to generally specifying the zeroth argument.
exec are bash and ksh extensions.
dash and POSIX
sh does not support them.
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.