Filetail

This script is a module that allows for reading lines from a continuously-growing file (such as a system log).

It handles log files that get rotated/trucated out from under us.

This is useful for writing all sorts of log-monitoring scripts. As given, it only provides a line-by-line interface (perfectly reasonable if all you're doing is reading the output of syslog); one could imagine extending it to provide more of the interface of a file object (read(), readlines(), etc.).

You may also want to tweak the sleep interval calculations if the given algorithm doesn't work for you. The goal is to figure out how long you need to sleep before getting some input; ideally, you want to get to the state where you sleep, wake up, and have exactly one line waiting for you, then sleep again.

If you sleep too long, you delay getting the input to your caller, but if you sleep too short, you waste your time sleeping and checking for input multiple times.