From 2996258978a15a8426484c2ee7965b3a2efa2e11 Mon Sep 17 00:00:00 2001 From: Vidar Holen Date: Tue, 1 Sep 2020 17:38:20 -0700 Subject: [PATCH] Created SC3056 (markdown) --- SC3056.md | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 SC3056.md diff --git a/SC3056.md b/SC3056.md new file mode 100644 index 0000000..498baec --- /dev/null +++ b/SC3056.md @@ -0,0 +1,37 @@ +## In POSIX sh, name matching prefixes are undefined. + +(or "In dash, ... are not supported." when using `dash`) + +### Problematic code: + +```sh +#!/bin/sh +echo "${!ANDROID_*}" +``` + +### Correct code: + +The easiest solution is to switch to a shell that *does* support name matching prefixes, like `bash`: + +```sh +#!/bin/bash +echo "${!ANDROID_*}" +``` + +Alternatively, extract the data you want from `env` or `set` + +### Rationale: + +Using `${!name*}` to find all variable names with a given prefix is a bash and ksh extension that `dash` and POSIX `sh` does not support. + +### 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!