LOG and LOGRT only have the ability to return the matching string, or a modified one with the <output> paremeter but there is currently no way to monitor or get only the count numbers an error occur.
For applications that write thousands of errors to a log file this is critical and a must have feature.
Right now we are trying to use log/logrt in some of our application for for instance, we have some cases that when the error start to happen it is repeated about 50.000 times every minute, which is MASSIVE amount of data to be sent to a proxy/server. Of course, this has caused major havoc in the zabbix installation as all the items start to lag and it can be about 5 hours without records until these log records are stored in the history_log table. So we can simply do not use the log items.
What we would like to have is a item that only counts the number of matches a file has based in a pattern but acts like a monitor, so it will only return the matches since the last check.
With that feature we can then create triggers and graphs that display how often an error is being generated over the time.