[README] Improve README and acknowledge reference material.

README.md

@@ -5,7 +5,7 @@ script to record your screen in [sway](https://swaywm.org).
 
 Really, it doesn't do anything else.
 
-# Why?
+## Why?
 
 Because I had enough bringing up shells, using tiresome aliases,
 or, god forbid, firing up a whole OBS Studio just to record my screen.
@@ -13,7 +13,7 @@ or, god forbid, firing up a whole OBS Studio just to record my screen.
 I wanted a simple keyboard shortcut to toggle screen recording on and off at will,
 and I have the impression other people may wish the same.
 
-# Does it depend on anything?
+## Does it depend on anything?
 
 Yes, to use `screenrecord.sh` you need:
 
@@ -25,7 +25,7 @@ Yes, to use `screenrecord.sh` you need:
 
 These lovely utilities are often already available on many `sway` setups.
 
-# How do I use it?
+## How do I use it?
 
 1. Either clone the repo or copy the latest `screenrecord.sh`
    somewhere in your home. For the sake of this example, let's assume you
@@ -54,10 +54,17 @@ These lovely utilities are often already available on many `sway` setups.
     }
    ```
 
-# License
+## Special thanks
+
+This script is loosely based on the following gist:
+
+https://gist.github.com/ugursogukpinar/f390d9f4c829fb1b05fc74a12dd482bb
+
+## License
 
 Public domain, enjoy this code at will and use it at your own risk.
 
 See [unlicense.org](https://unlicense.org/) for details or read the `LICENSE` file.
 
+----------
 Cheers :)

screenrecord.sh

@@ -76,4 +76,7 @@ if ! isrunning; then
 elif [ ! -z "$tflag" ]; then
     # Toggle recording off
     kill -s INT -- "$pid"
+else
+    printf -- "%s: operation refused, recording already in progress.\n" "$(basename -- "$0" .sh)" >&2
+    exit 1
 fi