Gets CIDR by query whois with specific netname (e.g. Name of ISP)

get-cidr.sh

#!/bin/bash

# First of all, you'll need ipcalc utility.
# ipcalc can be downloaded at jodies.de/ipcalc

WHOIS_QUERY = "some-netname"
whois -h whois.apnic.net $WHOIS_QUERY | grep inetnum | grep -Eo '[0-9].+' | sed 's/ //g' | xargs -I IP_RANGE sh -c 'ipcalc -rn IP_RANGE | tail -n +2'

# ######################
# Explaination
# ######################
#
# Query to whois server, you can change whois host to another whois server.
# > whois -h whois.apnic.net "LXN"

# Grap inetnum line, there are ip adddress like 10.0.0.0 - 10.0.0.255.
# > grep inetnum

# Matches IP Address range only
# > grep -Eo '[0-9].+'

# Remove spaces
# > sed 's/ //g'

# Finally, convert target ip range to cidr
# > xargs -I IP_RANGE sh -c 'ipcalc -rn IP_RANGE | tail -n +2'