logalert is a logfile monitoring tool which executes a specific action whenever it matches a string (pattern) occurrence.

It reads an entire file [or starts at the end, just like 'tail -f'], keeps track of any changes, waiting for a specific string [a syslog process error, a user login, ...] and fires an
action you define when that happens.

Log rotation or temporary removal ? No problem, we can deal with that ! System administrators normaly configure a logrotation process to rotate file as they grown or based on certain time periods [daily, weekly, ...] truncating or temporily removing them - logalert keeps track of
them even so.