My notes, things I have learned, and documentation I have created.

egrep ‘[[:digit:]]{1,3}’\.'[[:digit:]]{1,3}’\.'[[:digit:]]{1,3}’\.'[[:digit:]]{1,3}’ filename

egrep “[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}” filename

Note: this will not exclude invalid IP addresses such as 500.500.500.500, but it is something to start with.

If doing a copy an paste, the single quotes need to be typed manually until I figure out how enter them correctly.