From d6bacbfe3545bc257d671d769c1daca83e45012c Mon Sep 17 00:00:00 2001
From: Lucas Larson <91468+LucasLarson@users.noreply.github.com>
Date: Wed, 31 Mar 2021 14:07:54 -0400
Subject: [PATCH] =?UTF-8?q?create=20for=20documenting=20POSIX=20shell?=
 =?UTF-8?q?=E2=80=99s=20undefined=20`$((x=20**=20y))`=20for=20exponents?=
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+## In POSIX sh, exponentials are undefined.
+
+### Problematic code:
+
+ShellCheck noticed you're using `**`-notation with two asterisks to obtain an exponent's value. Some examples:
+
+```sh
+#!/bin/sh
+echo $((2 ** 3)) # Using `**` for an exponent is undefined in POSIX sh.
+```
+
+### Correct code:
+
+Other possibilities exist:
+```sh
+#!/bin/sh
+echo $((2 * 2 * 2))   # equivalent to `bash`'s `echo $((2 ** 3))`
+echo '2 ^ 3' | bc     # piping the formula to `bc` to parse the output https://stackoverflow.com/a/13111995
+printf '2 ^ 3\n' | bc # piping using `printf` (newline `\n` is mandatory)
+```
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX!
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