I would probably use split or a regex to grab the IP address string (and the last octet range) from each line of the file. Then I would step from the beginning of the range to the end of the range, constructing each IP address and writing it out as I went.
So, you'll want to do the following things:
- Open the file (and do something sensible if that fails)
- process each line of the file in some sort of loop (maybe a while)
- extract the IP address substring from each line
- determine if the IP address is a singleton or a range
- if it is a singleton, write it out to your file or whatever
- if it is a range, step through from the start to the end part of the last octet, constructing a series of singleton IP addresses and writing them out.
Show us what you have tried, and we'll be glad to help!