Currently "ifconfig -a" command listing status of network interfaces may be accomplished with flags -d or -u to limit the list to interfaces that are down or up.
This change allows it to filter the list by name of interface group with additional flag -g groupname (or -G groupname to negate condition). Note this is different from "ifconfig -g groupname" that shows interface names only and that behaviour is not affected with the change.
groupname may contain shell patterns. Both -g and -G flags may be specified same time to apply both filters.