How to configure log monitoring

[stepassia]

Hi to all, I've set a log monitoring item with active check. I need to fine any NEW line with SOMESTRING.
In the Item key I've set: log[/path/to/log.log,"SOMESTRING",,skip]
but with the skip mode I get a ZBX Unsopportted

With log[/path/to/log.log,"SOMESTRING"] it's ok but the item collect all line (I suppose), not only the new line whit the SOMESTRING string.
I don't know how to configure a trigger to get an alert only when a new line with SOMESTRING appear in the log file...

What's wrong?
Thanks a lot

[kloczek]

As always DebugLevel=4 in agent settings -> restart agent -> observe agent logs around using log[] key.
I'm guessing that it is the matter of permission for zabbix user to the log file and you already have in agent logs notifications about permission denied.

[stepassia]

Hi kloczek, the agent collect the log so, any permission denied error. The problem is that: for any new occurrence in log, the item collect any previous occurrences...
Thanks
Stefano