Bash script to list all IPs in prefix

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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 ex

Code

network_address_to_ips() {
  # 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
}

Example

network_address_to_ips 10.0.1.0/255.255.255.240
network_address_to_ips 10.1.0.0/24

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礼貌的吻别

2020-12-23 13:24

nmap is useful, but an overkill.

You can use prips instead. Saves you the hassle of grepping out the extra output from nmap and using awk.

Calling prips 192.168.0.0/23 will print what you need.

I use the following to skip the network address and broadcast: prips "$subnet" | sed -e '1d; $d'

Prips also has other useful options, e.g. being able to sample every n-th IP.

It's available via apt,brew,rpm and as tar.gz.

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感动是毒

2020-12-23 13:25

I have extended @rberg script a little.

check if the "network" you provide really is a network (use -f to skip the check)
handle netmasks greater than /24

Maybe this is of use for someone.

#!/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 "f" force;
shift $(( OPTIND-1 ));

for ip in $@; do
    net=$(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 ]; 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 ' ' '\012'
    fi

done

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猫巷女王i

2020-12-23 13:28
This script should do. It's (almost) pure Bash. The seq part can be replaced if a completely pure bash is required.

Since Bash apparently uses signed two-complement 4-byte integers, the script is limited to /8 mask maximum. I found ranges larger than /16 impractical anyway so this doesn't bother me at all. If someone knows a simple way to overcome this, please share :)
```
#!/usr/bin/env bash

base=${1%/*}
masksize=${1#*/}

[ $masksize -lt 8 ] && { echo "Max range is /8."; exit 1;}

mask=$(( 0xFFFFFFFF << (32 - $masksize) ))

IFS=. read a b c d <<< $base

ip=$(( ($b << 16) + ($c << 8) + $d ))

ipstart=$(( $ip & $mask ))
ipend=$(( ($ipstart | ~$mask ) & 0x7FFFFFFF ))

seq $ipstart $ipend | while read i; do
    echo $a.$(( ($i & 0xFF0000) >> 16 )).$(( ($i & 0xFF00) >> 8 )).$(( $i & 0x00FF ))
done 
```
Usage:
```
./script.sh 192.168.13.55/22
```
Tested with Bash version 4.4.23. YMMV.
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