Created SC3022 (markdown)

SC3022.md

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+## In POSIX sh, named file descriptors is undefined.
+
+(or "In dash, ... is not supported." when using `dash`)
+
+### Problematic code:
+
+```sh
+exec {n}> "$output"
+echo "Your fd is $n"
+```
+
+### Correct code:
+
+There is no simple, mechanical alternative for POSIX sh, but you can either switch to a shell that does support this (like `bash`), or hard code (or `eval`) a specific file descriptor.  
+
+### Rationale:
+
+The syntax for opening an arbitrary file descriptor and assigning it to a variable for later use is a `bash` and `ksh` extension. It does not work on POSIX sh or `dash`.
+
+### Exceptions:
+
+None
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!