I've found example script for using getopt command in shell.
#!/bin/bash
args=$(getopt ab $*)
set -- $args
for i;
do
case "$i" in
-a)shift; echo "it was a";;
-b)shift; echo "it was b";;
esac;
done
It work well, but I don't understand where is variable $i assigned. How it knows that it must iterate through $arg. Can you explain this?