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@thom-nic

thom-nic/cidr_iter.sh

Last active Dec 11, 2020
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Generate all IPv4 addresses in bash from a CIDR or netmask
#!/bin/bash -ue
# Modified "CIDR to IP range" function taken from https://stackoverflow.com/a/18120519/213983
# use like `cidr_iter "192.168.1.1/24"`
cidr_iter() {
# create array containing network address and subnet
local network=(${1//\// })
# split network address by dot
local iparr=(${network[0]//./ })
# if no mask given it's the same as /32
local mask=32
[[ $((${#network[@]})) -gt 1 ]] && mask=${network[1]}
# convert dot-notation subnet mask or convert CIDR to an array like (255 255 255 0)
local maskarr
if [[ ${mask} = '\.' ]]; then # already mask format like 255.255.255.0
maskarr=(${mask//./ })
else # assume CIDR like /24, convert to mask
if [[ $((mask)) -lt 8 ]]; then
maskarr=($((256-2**(8-mask))) 0 0 0)
elif [[ $((mask)) -lt 16 ]]; then
maskarr=(255 $((256-2**(16-mask))) 0 0)
elif [[ $((mask)) -lt 24 ]]; then
maskarr=(255 255 $((256-2**(24-mask))) 0)
elif [[ $((mask)) -lt 32 ]]; then
maskarr=(255 255 255 $((256-2**(32-mask))))
elif [[ ${mask} == 32 ]]; then
maskarr=(255 255 255 255)
fi
fi
# correct wrong subnet masks (e.g. 240.192.255.0 to 255.255.255.0)
[[ ${maskarr[2]} == 255 ]] && maskarr[1]=255
[[ ${maskarr[1]} == 255 ]] && maskarr[0]=255
# generate list of ip addresses
local bytes=(0 0 0 0)
for i in $(seq 0 $((255-maskarr[0]))); do
bytes[0]="$(( i+(iparr[0] & maskarr[0]) ))"
for j in $(seq 0 $((255-maskarr[1]))); do
bytes[1]="$(( j+(iparr[1] & maskarr[1]) ))"
for k in $(seq 0 $((255-maskarr[2]))); do
bytes[2]="$(( k+(iparr[2] & maskarr[2]) ))"
for l in $(seq 1 $((255-maskarr[3]))); do
bytes[3]="$(( l+(iparr[3] & maskarr[3]) ))"
printf "%d.%d.%d.%d\n" "${bytes[@]}"
done
done
done
done}
if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then
set -o pipefail
cidr_iter "$@"
fi
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