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sudo arp-scan --interface=eth0 --localnet

I know the above command works fine but it outputs everything like MAC address etc, etc.
But I need to find only IP addresses. Is it possible ?

I just used awk,tail and head to achieve what you want:

sudo arp-scan --interface=eth0 --localnet| awk '{print $1}'|tail -n +3|head -n -2

this gives the output as

192.168.1.1

192.168.1.3

as I have only these two in my Lan.

Here awk '{print $1}' prints the ip address which is situated in the first column.
tail and head removes unnecessary stuff like the header and just shows the ip addresses.

I would do this using just grep:

$ sudo arp-scan --interface=eth0 --localnet | grep -oP '^[d.]+'

192.168.0.1 

192.168.0.2 

192.168.0.3 

192.168.0.10    

192.168.0.23    

192.168.0.72    

192.168.27.1    

192.168.27.14

192.168.27.30

Explanation:

The -P tells grep to use Perl Compatible Regular Expressions, where d matches any number. The -o means "print only the matching part of the line". The regular expression I used means match the longest string (that's what the + means) of consecutive numbers (d) or dots (.) that are at the beginning of the line (^).

Here is a one liner to get the IP address using the ifconfig command:

~$ ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'

192.168.1.10

Does that do what you wanted? Or did you need the arp-scan command?

I re-read and see I missed the point of the question. arp-scan shows the local IP addresses for the network and I only showed the IP of the machine with ifconfig. Below is a version of the above terdon solution only not using the PCRE library. Ubuntu had an issue with pcre and grep when I tried it.

$ sudo arp-scan --interface=eth0 --localnet | grep -o ^[0-9.]*

another option to simplify @Stormvirux answer is to use the --quiet or -q and --plain or -x arguments provided with arp-scan instead of piping to head and tail commands the final command will be simpler as it will pipe only to awk :

arp-scan -qx --localnet | awk '{print $1}'

and here is a much detailed explanation from arp-scan --help :

--quiet or -q       Only display minimal output. No protocol decoding.

            If this option is specified, then only the IP address

            and MAC address are displayed for each responding host.

            No protocol decoding is performed and the OUI mapping

            files are not used.



--plain or -x       Display plain output showing only responding hosts.

            This option suppresses the printing of the header and

            footer text, and only displays one line for each

            responding host. Useful if the output will be

            parsed by a script.