procmail
[Top] [All Lists]

RE: Dallman - virussnag file - question

2003-09-20 15:02:29
David W. Tamkin wrote:

Dallman Ross wrote,

One does need to keep in mind, though, that in procmail there is
no real difference between unset and set-to-null; at least in
how we read or expand the parameters inside procmail.

That's by our choice, Dallman.  There *normally* is no real 
difference to procmail users between null variables and 
unset ones.  In most cases we care only about whether a 
variable is non-null or not non-null, so we use conditions 
like these:

  * var ?? .

or

  * var ?? ^^^^

which treat the null and the unset alike.  But that's a user choice. 
When a situation arises where it makes a difference, procmail 
can handle it. . . .

I'll never forget what happened on this list when someone 
asked, "How do I test whether a variable is set but null?"  A 
flood of replies came, none of them . . . helpful . . . .

When I checked email and saw the load of wrong answers, I 
just shook and shook my head.  Then I sighed and posted,

* $ !${VAR+!}${VAR:+!}

Thanks for the wisdom, David.  That all must have happened in the
circa nine or ten months that transpired three years ago when I 
was not following this list, I'm afraid.  Other than that period, 
and perhaps one other of around the same length, I've been here 
for ten years.  But I have absolutely no recollection of that.  
If it was more recently, it may have zoomed right over my head, 
anyway; and sometimes I don't have time for more than skimming here.

That code of yours there looks like it'd dripping with gravitas,
and I'm not being facetious.  But I confess that my brain is
numb and I don't quite get it.  So maybe you can explain; I'd
be grateful.

Dallman


_______________________________________________
procmail mailing list
procmail(_at_)lists(_dot_)RWTH-Aachen(_dot_)DE
http://MailMan.RWTH-Aachen.DE/mailman/listinfo/procmail