My Apache log files are not set up to be rotated—not sure why my Ubuntu install didn’t do that. But there are dozens of them and rather than clearing them out individually, I decided to delete all of them. After I deleted them, Apache didn’t recreate them. It turns out that Apache creates them when it is restarted so a restart of Apache recreated the files. I like to edit them with BBEdit, so I needed to also change permissions and the group.
sudo chmod -R u+rwX,go+rwX,o-w .
sudo chgrp adm *