SG LOG
SG_LOG is a wrapper macro for the SimGear logstream class. By default, the logstream class writes all output to the console. SG_LOG simplifies debugging for core developers who regularly compile from source. It allows you to easily associate your debug messages with a "channel" and with a "priority". This mechanism allows users to explicitly enable to certain log messages, while ignoring others. This can be helpful in order to troubleshoot certain problems.
Usage
Logging settings can be modified using the --log-level=[level] and --log-class=[class] command line options. Where level is one of the following:
bulkdebuginfowarnalertpopup
And class is a white space seperate list of any (combination) of the following:
allaienviromentflight- etc. See simgear/simgear/debug/debug_types.h for the complete list of available classes.
If you are interested in simply logging certain properties to a file at runtime, you can use either FlightGear's built-in logging framework, or the generic protocol.