I'm left wondering why you would ever want to do that. There are automated processes that "rotate" the logs on a regular basis, so they should never become "too full". I can come up with exactly two reasons why you might want to do this.
1: You're trying to cover your tracks after doing something to a computer you shouldn't have
2: You're trying to clear out all the "noise" so you can more readily spot any anomalous entries when trying to pin down a rather elusive problem
The number of times that option 2 would be the case are probably very far and few between.

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