How do I assign a value to a variable if there is no default value in a bash shell script?

[shoebill]

Also see: How do I assign a value to variable when a variable has no default value?

The above article does not set the URL variable if empty.

Using the syntax ${name=word}

This does:

WEBSITE_URL=${URL="www.gnu.org"}
echo $WEBSITE_URL
echo $URL

The result is both variables will be set.

$ ./varsubs.sh #
www.gnu.org
www.gnu.org