bigbot:

You've already received some great answers. However, they all assume that you're searching a particular log file only once. On the off chance you need to search repeatedly through the log file(s), though, you may want to alter your strategy. You might:

• Digest the log file into a more convenient form for your searches.
• Build an index of the first and last time each IP is used.
• Dump the information into a database.
• Split the file into neatly formatted chunks based on IP ranges.
• Perform multiple searches in the same pass.
• ...other optimizations left as an exercise for the reader...

...roboticus

When your only tool is a hammer, all problems look like your thumb.