How do I test for an empty string in a Bash case statement?

How do I test for an empty string in a Bash case statement?

string bash null case

bash

Regular expressions in a Bash case statement

regex bash case glob

bash

What is the reason for the weird syntax of the "case" statement in a bash/zsh script?

bash shell case zsh

bash

Trapping getopt invalid options

bash shell case getopt

bash

Setting a variable in a one-liner Bash script

bash case

bash

Bash: Sort text file by bytewise case sensitive sort command or using python sort command

python linux bash sorting case

bash