What does this case mean?

Question

bash

Please explain what does "-u=*|--user=*)" mean, what are "shift" and ";;" for?
case $i in
-u=*|--user=*)
USER="${i#*=}"
shift
;;
esac

Answer 1

1) This means that the case should work if the variable i has a value starting with the string "-u=" or with the string "--user="
2) shift shifts the positional parameters, deleting the very first one. For example, the script is called like this:
The positional parameters are as follows:

$1=1
$2=2
$3=3

After the shift command:

$1=2
$2=3
$3 пустой

3) ;; - this is part of the case structure, means the end of the list of commands included in this case.