From c3a1ea74a5acea59f46603f3c2ef325cf75b7950 Mon Sep 17 00:00:00 2001
From: Vidar Holen <vidar@vidarholen.net>
Date: Mon, 7 Sep 2020 21:02:04 -0700
Subject: [PATCH] Created SC3023 (markdown)

---
 SC3023.md | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 SC3023.md

diff --git a/SC3023.md b/SC3023.md
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+## In POSIX sh, FDs outside of 0-9 are undefined.
+
+(or "In dash, ... are not supported." when using `dash`)
+
+### Problematic code:
+
+```sh
+# Open FD #10 for writing
+exec 10> file
+```
+
+### Correct code:
+
+Either rewrite the script to only use FDs in the valid range, or switch to a shell that allows a larger range like `bash` or `ksh`.
+
+### Rationale:
+
+The shell grammar is only required to recognize a single digit before redirections to set the file descriptor, which limits the portable range to 0-9.
+
+### Exceptions:
+
+None.
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!