From b57b8567b32ec27fc50e949bfd773d31c0a54fbe Mon Sep 17 00:00:00 2001
From: FriendlyNeighborhoodShane <shane.880088.supw@gmail.com>
Date: Mon, 27 Jul 2020 00:19:07 +0530
Subject: [PATCH] Add notes for dynamic variables

---
 README.md | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/README.md b/README.md
index 8006cea..b1aa001 100644
--- a/README.md
+++ b/README.md
@@ -679,9 +679,33 @@ done
 
 ## Name and access a variable based on another variable
 
+### Set the dynamic part of the variable name
+
 ```shell
 $ var="world"
+```
+
+#### Option [1]: Set the variable using export
+
+**Warning:** Actually exports the variable, it will be inherited by called programs. Remember to unset.
+
+```shell
+$ export "hello_$var=value"
+```
+
+#### Option [2]: Set the variable using eval
+
+**Warning:** Does not export the variables, but is more dangerous than using export, as eval can execute arbitrary commands (try with `var="=;echo pwned;_"`). Remember to sanitize any data to only have alphanumerals and underscores.
+
+```shell
 $ eval "hello_$var=value"
+```
+
+### Access the variable in a command
+
+**NOTE:** The entire sequence is interpreted an extra time by the shell when calling eval. Note the double-escaping in the printf format.
+
+```shell
 $ eval printf '%s\\n' "\$hello_$var"
 value
 ```