Matt Garretson asked,
| Does [an] ... assignment to the LOG variable need a
| local lock file? Or does procmail handle contention for writes to
| $LOGFILE as a special case? Or is there a simpler reason why locking
| isn't necessary?
Procmail usually gets along without locking the logfile. Writes to it are
short (in comparison to what gets written to a folder) and usually a lock
is not needed.
If you want to make sure that only one procmail process uses the logfile at
a time, I'd recommend just plain using a global lockfile (the LOCKFILE vari-
able) rather than locking and unlocking the logfile.