SC3020 – ShellCheck Wiki

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In POSIX sh, &> is undefined.

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

Problematic code:

ssh host cmd &> log

Correct code:

Use the long form instead of the shorthand:

ssh host cmd > log 2>&1


&> is a bash and ksh extension for redirecting both stdout and stderr. In dash and POSIX sh, use 2>&1 explicitly.


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.