A Custom filter is a user-defined filter representing a logical expression. It consists of subfilters which are combined by the logical operations OR, AND and NOT. A subfilter can be an atomic Module, Case or String filter or a reference to another Custom filter.
Custom filters are organized in a tree where subfilters on the same layer represent OR expressions and parent - child relations represent AND expressions.
Custom filters and their subfilters -- as well as atomic Module, Case and String filters -- are used to filter logmessages.
ITLogBook represents custom filters graphically. Read the topic about the filterset pane.
To help you to quickly become an expert in the composition of custom filters we’ve prepared a tutorial about that topic. It contains several examples of filters.
Note:
Besides custom filters there are Loglevel and time filters. See kinds of filters.