# Thanks to Chris F. A. Johnson 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 ] }