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

ShellCheck

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In POSIX sh, &> is undefined.

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

Problematic code:

#!/bin/sh
ssh host cmd &> log

Correct code:

Use the long form instead of the shorthand:

#!/bin/sh
ssh host cmd > log 2>&1

Rationale:

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

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!