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

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!

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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