The following functions may be used in the filter statement, as described in Filters.
| Name | Description | 
|---|---|
| facility() | Filter messages based on the sending facility. | 
| filter() | Call another filter function. | 
| host() | Filter messages based on the sending host. | 
| in-list() | File-based whitelisting and blacklisting. | 
| level() or priority() | Filter messages based on their priority. | 
| match() | Use a regular expression to filter messages based on a specified header or content field. | 
| message() | Use a regular expression to filter messages based on their content. | 
| netmask() and netmask6() | Filter messages based on the IP address of the sending host. | 
| program() | Filter messages based on the sending application. | 
| source() | Select messages of the specified syslog-ng PE source statement. | 
| tags() | Select messages having the specified tag. | 
