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Vidar Holen edited this page Sep 2, 2020 · 1 revision

In POSIX sh, exec flags are undefined.

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

Problematic code:

#!/bin/sh
exec -ca ls busybox

Correct code:

Switch to a shell that does support the exec flags you are using, like bash:

#!/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.

Rationale:

Flags to exec are bash and ksh extensions. dash and POSIX sh does not support them.

Exceptions:

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.

Related resources:

  • Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!

ShellCheck

Each individual ShellCheck warning has its own wiki page like SC1000. Use GitHub Wiki's "Pages" feature above to find a specific one, or see Checks.

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