Re: [Nmh-workers] use of 'Unseen-Sequence' with rcvstore (Was: Re: refile handling of corrupt .mh_sequences)

[Ken Hornstein]

>Does anyone know if the man page is accurate (ie., if it corresponds to
>the source code)? 

It is NOT accurate.  We've had file locking in sequences for more than
a decade, but the documentation wasn't updated.  David Levine updated
the rcvstore man page post-1.5, and it now says:

   LOCKING AND −unseen
       If you use the “Unseen‐Sequence” profile entry, rcvstore could  try  to
       read  and  update  its sequence state while another nmh process is also
       trying to do so.  This can cause the sequence state to lose track.   To
       avoid  this  just  between asynchronous invocations of rcvstore, do not
       use it without an external locking  mechanism,  for  example,  a  proc‐
       mailrc(5)  local  lockfile,  if  you  use the “Unseen‐Sequence” profile
       entry.

There are post-1.5 locking changes, but that wouldn't affect this.  Your
locking issues are almost certainly caused by Claws Mail.  I really wish
the Claws Mail folks wouldn't say that their mail is stored in MH format,
as that implies that it's safe to use with MH tools; obviously it isn't.

>Is there a recommended work-around?

Other than not using Claws Mail, or convincing the Claws Mail folks to
add locking to sequence files, I do not know of one.

>I know that some commands use filelocks (a huge can of worms in NMH)
>with sequence files...does rcvstore?

See above (the answer is "yes").  They all do.

--Ken