returns 0 if parameter is a valid ip4 address, non-zero otherwise

isvalidip4.bash

# returns 0 if parameter is a valid ip4 address, non-zero otherwise

function isvalidip4()
{   #return 0 if parameter is a valid ip4 address, non-zero otherwise
    #https://groups.google.com/forum/#!original/comp.unix.shell/NDu-kAL5cHs/7Zpc6Q2Hu5YJ
    [ -z "$1" ] && return 1

    case "$*" in
        ""|*[!0-9.]*|*[!0-9]) return 1 ;;
    esac

    OLDIFS="$IFS"
    IFS=.
    set -- $*
    IFS="$OLDIFS"

    [ $# -eq 4 ] &&
        [ ${1:-666} -le 255 ] && [ ${2:-666} -le 255 ] &&
        [ ${3:-666} -le 255 ] && [ ${4:-666} -le 254 ]
}