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 extract those IP addresses using common unix command-line tools?

Answer 1

You could use grep to pull them out.

grep -o '[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}' file.txt