How do you extract IP addresses from files using a regex in a linux shell?

Question

How to extract a text part by regexp in linux shell? Lets say, I have a file where in every line is an IP address, but on a different position. What is the simplest way to e

Answer 1

You can use some shell helper I made: https://github.com/philpraxis/ipextract

included them here for convenience:

#!/bin/sh
ipextract () 
{ 
egrep --only-matching -E  '(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)' 
}

ipextractnet ()
{ 
egrep --only-matching -E  '(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)/[[:digit:]]+' 
}

ipextracttcp ()
{ 
egrep --only-matching -E  '[[:digit:]]+/tcp' 
}

ipextractudp ()
{ 
egrep --only-matching -E  '[[:digit:]]+/udp' 
}

ipextractsctp ()
{ 
egrep --only-matching -E  '[[:digit:]]+/sctp' 
}

ipextractfqdn ()
{ 
egrep --only-matching -E  '[a-zA-Z0-9]+[a-zA-Z0-9\-\.]*\.[a-zA-Z]{2,}' 
}

Load it / source it (when stored in ipextract file) from shell:

$ . ipextract

Use them:

$ ipextract < /etc/hosts
127.0.0.1
255.255.255.255
$

For some example of real use:

ipextractfqdn < /var/log/snort/alert | sort -u
dmesg | ipextractudp