I am aware of the command lttng view. But it can only be used to view a session after it has been stopped.
To view data before a session is stopped/finished either use the rotation feature, introduced in LTTng 2.11, or use the live session mode.
Both modes have pros and cons but the rotation feature is the way to go most of the time especially if trace analysis automation is on your road map.
You can also use the snapshot session mode but this is really used for "flight recorder" type of tracing workload.