#!/bin/sh
count () {
	local c=$1
	echo $((
	c=((c>> 1)&0x55555555)+(c&0x55555555),
	c=((c>> 2)&0x33333333)+(c&0x33333333),
	c=((c>> 4)&0x0f0f0f0f)+(c&0x0f0f0f0f),
	c=((c>> 8)&0x00ff00ff)+(c&0x00ff00ff),
	c=((c>>16)&0x0000ffff)+(c&0x0000ffff)
	))
}
validate () {
	return $((-($1)&~$1))
}
ip2int () {
	set $(echo $1 | sed 's/\./ /g')
	echo $(($1<<24|$2<<16|$3<<8|$4))
}

int2ip () {
	echo $(($1>>24&0xFF)).$(($1>>16&0xFF)).$(($1>>8&0xFF)).$(($1&0xFF))
}

[ $# "<" 2 ] && {
	echo "$0 <ip> <netmask>"
	exit 1
} 

ip=$(ip2int $1)
netmask=$(ip2int $2)

validate $netmask || { 
	echo "invalid netmask"
	exit 1
}

n=$(count $netmask)
network=$((ip&netmask))
broadcast=$((ip|~netmask))

ip=$(int2ip $ip)
netmask=$(int2ip $netmask)
network=$(int2ip $network)
broadcast=$(int2ip $broadcast)

echo "$ip/$n = $network-$broadcast"