Current log files when rotating?

Let's say you're using logging_collector and you've put some %-escapes
into log_filename for daily log rotation.  Perhaps it's daily rotation
with this pattern:

log_filename = 'postgresql-%Y-%m-%d.log'

Is there any good way to ask the server what log file name it's currently
writing to?  I was trying to write something that does a "tail" on the
current log, and was hoping there was a simple way to figure out which
file that goes against.  Looking for the latest timestamp or running
strftime would both work I guess, those just seemed a little heavy (was
hoping for an "alias"-sized answer) to figure out something that the
server certainly knows.

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* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD