nmh (and MH) do not currently lock the .mh_sequences file. That's why
many people (including myself) using the directory locking in procmail.
Except that if one is using "show" to look at messages, you can still
end up corrupting your sequences file when both show and procmail try to
access it at the same time.
One way around this is to wrap 'show' with a shell script that uses
'lockfile' for procmail-style locking. Is there a better way?
Currently that's the only way. But you have to be careful, since
many MH/nmh commands call other MH/nmh commands (show calls mhn -show).
So you can run into deadlock problems.
--
Richard Coleman
coleman(_at_)math(_dot_)gatech(_dot_)edu