SC3060 – ShellCheck Wiki

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In POSIX sh, string replacement is undefined.

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

Problematic code:

#!/bin/sh
echo "${var//foo/bar}"

Correct code:

Either switch the shebang to bash or ksh, or rewrite the expansion using a tool like sed:

#!/bin/sh
echo "$var" | sed 's/foo/bar/g'

Rationale:

String replacement in parameter expansion is a bash and ksh extension. dash and POSIX sh does not support it.

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 is a static analysis tool for shell scripts. This page is part of its documentation.