Shell Script (Bash) to Edit Output from a Command

Question

Shell Script (Bash) to Edit Output from a Command

I'm trying to make a shell script to determine the range of IP Addresses on my own personal wireless network. When I run this command:

ifconfig

I get this key information:

inet 192.168.1.228

broadcast 192.168.1.255

netmask 255.255.255.0

So now I know that the range is 192.168.1.0-255 (or 192.168.1.0/24). I tried to run this script I made:

#!/bin/bash

ifconfig | awk '/broadcast/ {print $6}'

This will output my max ip range:

192.168.1.255

How can I make this script find my max range like this but instead it writes it like this:

192.168.1.0-255

or

192.168.1.0/24

Any help is much appreciated!

Answer 1

The simplest solution is to use ip address instead of ifconfig which you should do anyway.

And you can get the netmask from the ifconfig output and calculate the number of 1-bits with this:

echo 255.255.255.0 |
    awk -F. '{print "obase=2;" $1 "*2^24+" $2 "*2^16+" $3 "*2^8+" $4}' |
    bc |
    awk '{ sub("10*$","1", $0); print length($0); }'