6.8. program: Receiving messages from external applications The syslog-ng Premium Edition 7 Administrator Guide
The program driver starts an external application and reads messages from the standard output (stdout) of the application. It is mainly useful to receive log messages from daemons that accept incoming messages and convert them to log messages.
The program driver has a single required parameter, specifying the name of the application to start.
The program is restarted automatically if it exits.