LOCKFILE syntax, questions

I found a need for a general lockfile in something I'm doing.  I
don't have experience setting my own, but at first went with
this:

 :0 flags
     * conditions
   {
      DUMMY=`lockfile -l 30 $SPAMSNAG.lock;    \
             cat $mytmpfile.sa >> $SPAMSNAG && \
             rm -f $mytmpfile.sa $SPAMSNAG.lock`

     :0  # no lockfile here; .myspam is a directory, not a flat file
       .myspam
  }

That works fine.  But then I read a posting from Philip on Wednesday
and realized (I had forgotten) procmail can run LOCKFILE as an
internal command.  So I changed the above.  Now I have in the braces:

   {
      # what's the file to use?  Lock it
      LOCKFILE = $SPAMSNAG$LOCKEXT
      LOCKTIMEOUT = 30

      DUMMY=`cat $mytmpfile.sa >> $SPAMSNAG && rm -f $mytmpfile.sa`

      # unlock file
      LOCKFILE

     :0  # no lockfile here; .myspam is a directory, not a flat file
       .myspam
  }

Okay, but I'm not entirely sure that it works.  I run a procmail process
that triggers this in the background, and meanwhile I keep doing dir
listings.
I never see the lockfile.  I saw it on my initial command-set.  Does
anybody
have an idea or some reassurance that this (canonical, I suppose) way is
better?

I do see in the verbose log this:

        procmail: Assigning "LOCKFILE=spamsnag.lock"
        procmail: Locking "spamsnag.lock"

(So why can't I see the lockfile in my dir listing?)


Oh, and -- mimicking Philip's style from the post that jogged my
memory about LOCKFILE -- I first had in place of DUMMY in the second
version:

      # do whatever to create or alter file contents
      #:0 c
      # | cat $mytmpfile.sa >> $SPAMSNAG && rm -f $mytmpfile.sa


I think that worked as well, but the verbose logs troubled me,
because they read 

 procmail: Executing " cat $mytmpfile.sa >> $SPAMSNAG && rm -f
$mytmpfile.sa"
 procmail: Error while writing to " cat $mytmpfile.sa >> $SPAMSNAG && 
        rm -f $mytmpfile.sa"
 procmail: Assigning "LASTFOLDER= cat $mytmpfile.sa >> $SPAMSNAG && 
        rm -f $mytmpfile.sa"

That "Error" scares me.  I think it's not really an error, but an
indication that the piped commands don't do anything with what's
fed them?  Oh, yeah, that might be it.  I suppose I need an `i'
flag on that recipe.

Anyway, which syntax is better?

Thanks,
Dallman

-- 
Dallman Ross

"If you find a path with no obstacles, it probably does not lead to
anywhere."
        Thoughts of Rev. Sunnan Kubose, from _Zen in the Markets_ 

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