I remembered why I used the mv command. Because point of using mktemp is to get a unique output filename and it’s silly to have it create a file called fyhuji then output to fyhuji.png, which almost certainly won’t but may possibly exist already, and then delete fyhuji. And some versions of mktemp allow specifying a suffix to create a uniquely named file that ends .png, but some don’t.

I’ve just noticed your blog removed the # from comment lines in my script, but left the # on the interpreter line alone.