@cassidoo's interview question from July 11, 2021

inRange.sh

#!/usr/bin/env bash
set -eu -o pipefail

# Given an IPv4 address and a netmask in CIDR notation, return a boolean
# specifying whether the IP address is inside the given range. 

# requirements:
# # bash version >= 4
# # 'grepcidr' command (http://www.pc-tools.net/unix/grepcidr/)

if [ "${BASH_VERSINFO:-0}" -lt 4 ]; then
	echo "$(basename $0): Bash version 4 or greater is required. Found BASH_VERSION: ${BASH_VERSION}"
	exit 1
fi

declare -A DEPS=( ["grepcidr"]="grepcidr" )
ERR=""
for DEP in "${!DEPS[@]}"; do
	if ! command -v "${DEP}" >/dev/null; then
		ERR="${ERR}\nDependency not satisfied: ${DEP}; please install this to continue. On macOS you can do 'brew install ${DEPS[$DEP]}'"
	fi
done
if [ ! -z "${ERR}" ]; then
	echo -e "${ERR}"
	exit 1
fi

if [ $# -ne 2 ]; then
	echo -e "$(basename $0): enter an IPv4 address and a netmask in CIDR notation, e.g\n\t192.168.4.27 192.168.0.0/16"
	exit 1
fi

IPV4=$1
CIDR=$2

TMPFILE="$(mktemp)"
echo "${IPV4}" > $TMPFILE

if grepcidr "${CIDR}" "${TMPFILE}" >/dev/null; then
	echo "true"
else
	echo "false"
fi

MONTASIO:~ andrewrich$ ~/Documents/scripts/inRange.sh 192.168.4.27 192.168.0.0/16
true
MONTASIO:~ andrewrich$ ~/Documents/scripts/inRange.sh 192.168.4.27 192.168.1.0/24
false