awk精确匹配IP地址规

if [ -z $1 ];then
    exit
fi
echo | awk -v IP="$1" '
{split( IP,ipadd,".");
      for ( i in ipadd) {
          if ( ipadd[i] > 255) {
         exit
      }
      }
}
{if (IP ~ /^[0-9]+.[0-9]+.[0-9]+.[0-9]+$/) {
    print IP
    }
}
';