A bash script that generates a list of CIDRs given a Azure IP Ranges JSON file

gen_cidr_list.sh

#!/bin/bash

# Generates a list of CIDRs given an Azure IP Ranges JSON file
# https://www.microsoft.com/en-us/download/confirmation.aspx?id=56519

INPUT_FILENAME=$1; # Name of the JSON file downloaded from MS website (ServiceTags_Public_YYYYMMDD.json)
OUTPUT_FILENAME=cidr_list.txt

if [ -z $INPUT_FILENAME ]
then
    printf "Incorrect usage. Please use: ./gen_cidr_list.sh [json_file]\n";
    printf "Example: ./gen_cidr.sh ServiceTags_Public_20201012.json\n";
else
    # Help:
    #
    # .values[]
    #       extract everything from the "values" array
    #
    # select(.id == "AzureCloud.brazilsouth").properties.addressPrefixes
    #       get only IP addresses from Brazil South Azure Cloud
    #
    # .[]
    #       flat the result into simple strings
    #
    # select(. | test("^([0-9]{1,3}\\.){3}[0-9]{1,3}(\/([0-9]|[1-2][0-9]|3[0-2]))?$"))
    #       select only IPs in IPV4 CIDR format
    #

    jq --raw-output '.values[] | select(.id == "AzureCloud.brazilsouth").properties.addressPrefixes | .[] | select(. | test("^([0-9]{1,3}\\.){3}[0-9]{1,3}(\/([0-9]|[1-2][0-9]|3[0-2]))?$"))' $INPUT_FILENAME > $OUTPUT_FILENAME
    echo "File created: $OUTPUT_FILENAME"
fi