Created SC3026 (markdown)

SC3026.md

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+## In POSIX sh, ^ in place of ! in glob bracket expressions is undefined.
+
+### Problematic code:
+
+```sh
+echo foo-[^0]*.jpg
+```
+
+### Correct code:
+
+```sh
+echo foo-[!0]*.jpg
+```
+
+### Rationale:
+
+`[^c]` is frequently used in most regular expression variants to mean "any character except `c`". This is so pervasive that bash, ksh, dash, and BusyBox ash, all allow it.
+
+However, strictly speaking, the only range complement syntax guaranteed to be supported across shells is `[!c]`. 
+
+### 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.
+Or just rewrite it to be on the technically correct side.
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!