How to truncate UBROKER log files while Broker is running on UNIX?

What is the best way on Unix to truncate WebSpeed log files while broker is running?
What is the best way on Unix to truncate AppServer log files while broker is running?
What is the best way on Unix to truncate the NameServer log file while broker is running?

Can the AdminServer logfile be truncated while the AdminServer is managing Brokers?

There are no implicit OpenEdge utilities to truncate UBroker log files.  Only databases have the PROLOG utility. OS tools however can be used. 

Care needs to be taken when the UBroker is running as certain utilities (such as using vi to edit the file) can result in the file that is currently opened by the process being unlinked to the file system and as a result the Broker will no longer write to the same file. Never delete the logfile while the Server/Broker process is writing to it.

• To empty a log file:

• To preserve the current and create a new log file with only the last 50 lines:

The above examples can be customised to requirement and will work on any of the OpenEdge Server products log files including the admserv.log and database lg files.

UBroker logfile rotation:

The size of UBroker logfiles can be managed with startup configuration parameters in the ubroker.properties file.
Since Progress 9.1x UBroker the log file threshold size can be set with brkrLogThreshold and srvrLogThreshold
Since OpenEdge 10.x the number of UBroker log files can be set with brkrNumLogFiles and srvrNumLogFiles

Never delete the number-of-logfiles configured, while the Server/Broker process is running.  Refer to Article  How to configure rolling log files for AppServer, WebSpeed and client logs ?    
 

References to Other Documentation:
Progress Article(s):
 How truncate the log file while the database is running since 10.1A