source: vendor/bash/3.1/tests/getopts4.sub@ 3951

aflag=
bflag=

while getopts :ab: name "$@"
do
        case $name in
        a)      aflag=1 ;;
        b)      bflag=1
                bval=$OPTARG;;
        :)      echo $0: error: option \`$OPTARG\' requires an argument
                echo Usage: $0 [-a] [-b value] args
                exit 2;;
        ?)      echo $0: error: illegal option character \`$OPTARG\'
                echo Usage: $0 [-a] [-b value] args
                exit 2;;
        esac

done

if [ ! -z "$aflag" ] ; then echo -a specified ; fi
if [ ! -z "$bflag" ] ; then echo -b $bval specified ; fi

if [ "$OPTIND" -gt 1 ]
then
        shift $(( $OPTIND - 1 ))
fi

echo remaining args: "$*"

exit 0