grimoire/bash/cidr

68 lines
1.2 KiB
Bash
Executable file

#!/usr/bin/env bash
bin() {
local str num=$1
while (( num > 0 )); do
str=$(( num % 2 ))$str
(( num /= 2 ))
done
while (( ${#str} < 8 )); do
str=0$str
done
printf %s "$str"
}
dec() {
local pow=$(( ${#1} - 1 )) num=0
for (( count = 0; count < ${#1}; ++count )); do
(( num += ${1:count:1} * (2 ** pow) ))
(( pow -= 1 ))
done
printf %d "$num"
}
2ip() {
local ip=( ) count
for count in {0..3}; do
ip[$count]=$(dec "${1:count * 8:8}")
done
printf %s.%s.%s.%s "${ip[@]}"
}
if (( ! $# )); then
printf 'usage: %s ip/cidr\n' "$0"
exit 1
fi
IFS=/ read -r ip size <<< "$1"
IFS=. read -ra octets <<< "$ip"
for (( count = 0; count < 4; ++count )); do
octets[$count]=$(bin "${octets[$count]}")
done
IFS= ip=${octets[*]} network=${ip:0:size} broadcast=${ip:0:size}
while (( ${#network} < 32 )); do
network+=0
broadcast+=1
done
for (( count=0; count < size; ++count )); do
mask+=1
done
for (( count=32 - size; count < 32; ++count )); do
mask+=0
done
printf 'subnet mask: %s\n' "$(2ip "$mask")"
printf 'range: %s - %s\n' "$(2ip "$network")" "$(2ip "$broadcast")"
printf 'total assignable hosts: %d\n' "$(( (2 ** (32 - size)) - 2 ))"