1 SC3031

Vidar Holen edited this page 2020-09-01 18:04:50 -07:00

Table of Contents

• In POSIX sh, redirecting from/to globs is undefined.
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:
• Related resources:

In POSIX sh, redirecting from/to globs is undefined.

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

Problematic code:

#!/bin/sh
date > /tmp/log*.txt

Correct code:

To redirect from/to the only match of a glob, expand the glob first:

#!/bin/sh
set -- /tmp/log*.txt
# PS: This is a good place to verify that there was exactly one match
date > "$1"

Alternatively, use a loop to redirect from/to all if that was the intention.

Rationale:

Shells differ in whether (and how) they do pathname expansion on names in redirections. Avoid the issue by expanding the glob yourself.

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!

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