In which status the `Internal error!` invoked?

问题

I have read some code on bash's getopt ,let me simplify what i have seen hrere.
bash sample on getopt containing Internal error!

docase(){
TEMP=`getopt -o ab: -- "$@"`
eval set -- "$TEMP"
while true ; do
    case "$1" in
        -a) echo "Option a" ; shift ;;
        -b) echo "Option b, argument \`$2'" ; shift 2 ;;
        --) shift ; break ;;
        *) echo "Internal error!" ;;
    esac
done
}

I have tried many status to invoke Internal error! with docase g ,docase -g,docase --g,never happened.

In which status the Internal error! invoked for the above code ?
Maybe it is better to delete *) echo "Internal error!" ;;?

回答1:

docase(){
TEMP=`getopt -o ab: -- "$@"`
eval set -- "$TEMP"
while true ; do
    case "$1" in
        -a) echo "Option a" ; shift ;;
        -b) echo "Option b, argument \`$2'" ; shift 2 ;;
        --) shift ;;
        *) echo "Internal error!" ;;
    esac
done
}

To delete break in --) shift ; break ;; invoke infinite Internal error!.

docase(){
TEMP=`getopt -o ab: -- "$@"`
eval set -- "$TEMP"
while true ; do
    case "$1" in
        -a) echo "Option a" ; shift ;;
        -b) echo "Option b, argument \`$2'" ; shift 2 ;;
        --) shift ;;
        *) echo "Internal error!" ;break;;
    esac
done
}

To add a break in *) echo "Internal error!" invoke Internal error! only once.

来源：https://stackoverflow.com/questions/51742613/in-which-status-the-internal-error-invoked