Bash script to list all IPs in prefix

Question

I'm trying to create script that I can input a set of prefixes, which will then list all IP addresses within the prefixes (including network/host/broadcast).

An example would be:

./convert-prefix-to-IPs.sh 192.168.0.0/23 203.20.0.0/16
192.168.0.0
192.168.0.1
... 
192.168.0.255
192.168.1.0
.. 
192.168.1.255
203.20.0.0
..
203.20.255.255

---

There are some python/perl scripts which can do this, but I'm hoping to have a simple bash script, as it may be used on systems without perl/python (yes.. i know.. )

Answer 1

Here is what I use to generate all the IP addresses in a given CIDR block

nmap -sL -n 10.10.64.0/27 | awk '/Nmap scan report/{print $NF}'

From the nmap man page, the flags are:

-sL: List Scan - simply list targets to scan
-n: Never do DNS resolution

Just that simple

The above command outputs this

10.10.64.0
10.10.64.1
10.10.64.2
10.10.64.3
10.10.64.4
10.10.64.5
10.10.64.6
10.10.64.7
10.10.64.8
10.10.64.9
10.10.64.10
10.10.64.11
10.10.64.12
10.10.64.13
10.10.64.14
10.10.64.15
10.10.64.16
10.10.64.17
10.10.64.18
10.10.64.19
10.10.64.20
10.10.64.21
10.10.64.22
10.10.64.23
10.10.64.24
10.10.64.25
10.10.64.26
10.10.64.27
10.10.64.28
10.10.64.29
10.10.64.30
10.10.64.31

Answer 2

I too was looking for this solution and found that @scherand script worked great. I also have added to this script to give you more option. Help File below.

THIS SCRIPT WILL EXPAND A CIDR ADDRESS.

SYNOPSIS

./cidr-to-ip.sh [OPTION(only one)] [STRING/FILENAME]

DESCRIPTION

-h Displays this help screen

-f Forces a check for network boundary when given a STRING(s)

-i Will read from an Input file (file should contain one CIDR per line) (no network boundary check)

-b Will do the same as –i but with network boundary check

EXAMPLES

./cidr-to-ip.sh 192.168.0.1/24

./cidr-to-ip.sh 192.168.0.1/24 10.10.0.0/28

./cidr-to-ip.sh -f 192.168.0.0/16

./cidr-to-ip.sh -i inputfile.txt

./cidr-to-ip.sh -b inputfile.txt

#!/bin/bash    

############################
##  Methods
############################   
prefix_to_bit_netmask() {
    prefix=$1;
    shift=$(( 32 - prefix ));

    bitmask=""
    for (( i=0; i < 32; i++ )); do
        num=0
        if [ $i -lt $prefix ]; then
            num=1
        fi

        space=
        if [ $(( i % 8 )) -eq 0 ]; then
            space=" ";
        fi

        bitmask="${bitmask}${space}${num}"
    done
    echo $bitmask
}

bit_netmask_to_wildcard_netmask() {
    bitmask=$1;
    wildcard_mask=
    for octet in $bitmask; do
        wildcard_mask="${wildcard_mask} $(( 255 - 2#$octet ))"
    done
    echo $wildcard_mask;
}

check_net_boundary() {
    net=$1;
    wildcard_mask=$2;
    is_correct=1;
    for (( i = 1; i <= 4; i++ )); do
        net_octet=$(echo $net | cut -d '.' -f $i)
        mask_octet=$(echo $wildcard_mask | cut -d ' ' -f $i)
        if [ $mask_octet -gt 0 ]; then
            if [ $(( $net_octet&$mask_octet )) -ne 0 ]; then
                is_correct=0;
            fi
        fi
    done
    echo $is_correct;
}

#######################
##  MAIN
#######################
OPTIND=1;
getopts "fibh" force;

shift $((OPTIND-1))
if [ $force = 'h' ]; then
    echo ""
    echo -e "THIS SCRIPT WILL EXPAND A CIDR ADDRESS.\n\nSYNOPSIS\n  ./cidr-to-ip.sh [OPTION(only one)] [STRING/FILENAME]\nDESCRIPTION\n -h  Displays this help screen\n -f  Forces a check for network boundary when given a STRING(s)\n    -i  Will read from an Input file (no network boundary check)\n  -b  Will do the same as –i but with network boundary check\n\nEXAMPLES\n    ./cidr-to-ip.sh  192.168.0.1/24\n   ./cidr-to-ip.sh  192.168.0.1/24 10.10.0.0/28\n  ./cidr-to-ip.sh  -f 192.168.0.0/16\n    ./cidr-to-ip.sh  -i inputfile.txt\n ./cidr-to-ip.sh  -b inputfile.txt\n"
    exit
fi

if [ $force = 'i' ] || [ $force = 'b' ]; then

    old_IPS=$IPS
    IPS=$'\n'
    lines=($(cat $1)) # array
    IPS=$old_IPS
        else
            lines=$@
fi

for ip in ${lines[@]}; do
    net=$(echo $ip | cut -d '/' -f 1);
    prefix=$(echo $ip | cut -d '/' -f 2);
    do_processing=1;

    bit_netmask=$(prefix_to_bit_netmask $prefix);

    wildcard_mask=$(bit_netmask_to_wildcard_netmask "$bit_netmask");
    is_net_boundary=$(check_net_boundary $net "$wildcard_mask");

    if [ $force = 'f' ] && [ $is_net_boundary -ne 1 ] || [ $force = 'b' ] && [ $is_net_boundary -ne 1 ] ; then
        read -p "Not a network boundary! Continue anyway (y/N)? " -n 1 -r
        echo    ## move to a new line
        if [[ $REPLY =~ ^[Yy]$ ]]; then
            do_processing=1;
        else
            do_processing=0;
        fi
    fi  

    if [ $do_processing -eq 1 ]; then
        str=
        for (( i = 1; i <= 4; i++ )); do
            range=$(echo $net | cut -d '.' -f $i)
            mask_octet=$(echo $wildcard_mask | cut -d ' ' -f $i)
            if [ $mask_octet -gt 0 ]; then
                range="{$range..$(( $range | $mask_octet ))}";
            fi
            str="${str} $range"
        done
        ips=$(echo $str | sed "s, ,\\.,g"); ## replace spaces with periods, a join...

        eval echo $ips | tr ' ' '\n'
else
exit
    fi

done