In order to determine whether a database backup is needed or not, I'm trying to see whether a mysql binlog file has any data in it. (During a backup, we make a fresh binlog file and record the filename. Then later, we can check the contents of that binlog to see if anything has happened since the last backup.)

Is there any way to know when a binlog file is actually empty? Perhaps using the mysqlbinlog command?

I would check the position from SHOW MASTER STATUS, but the position seems to vary with the mysql version... is it constant within a version? My version of mysql (5.6.11) starts a new binary log at position 120.

An alternative approach would be to record the time that the binlog was created at and check to see if there were any changes made after that, but it makes me nervous relying on the speed of the backup process like that.