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Bash: Script to find active computers in a subnet using ping

The following is a simple bash script that will scan each ip address in a give subnet and report if they are alive (or accepting ping requests). The code creates processes for each ping so that it completes quickly rather than scanning each ip address sequentially.

Create a text file called “pinger.sh” and paste the following into it:

#!/bin/sh

: ${1?"Usage: $0 ip subnet to scan. eg '192.168.1.'"}

subnet=$1
for addr in `seq 0 1 255 `; do
#   ( echo $subnet$addr)
( ping -c 3 -t 5 $subnet$addr > /dev/null && echo $subnet$addr is Alive ) &
done 

Save and close, then it can be called from the command line like so:

sh pinger.sh 192.168.1.

This will scan from 192.168.1.0 to 192.168.1.255 and will return something like the following:

192.168.1.1 is Alive
192.168.1.105 is Alive
192.168.1.112 is Alive
192.168.1.149 is Alive

4 Comments

  1. Matthew

    Your example will only scan 192.168.1.1 and above. You need to change your sequence if you want .0 in there.

    for addr in ‘seq 0 1 255 ‘; do

  2. mat

    Ah good spot!

  3. anoop

    just give while loop construction for pinging any subnet

  4. +Yan

    Use arping commad. Some machines may have firewall blocking ICMP-echo, but they will respond go arping.
    arping will also not work acros networks i.e. routers will block it.

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