# Thanks to Chris F. A. Johnson <c.f.a.johnson@rogers.com> for this one
is_validip()
{
case "$*" in
""|*[!0-9.]*|*[!0-9]) return 1 ;;
esac
local IFS=.
set -- $*
[ $# -eq 4 ] &&
[ ${1:-666} -le 255 ] && [ ${2:-666} -le 255 ] &&
[ ${3:-666} -le 255 ] && [ ${4:-666} -le 254 ]
}