From: Paul M Foster <paulf(_at_)quillandmouse(_dot_)com>
Alrighty, then I don't know what a filter is. I would have assumed that
anything is a filter when email is piped to it. It seems by your answer
that a "filter" would be something which is "non-delivery". According
to the man page, that's only things which 1) give the email back to
procmail for handling, 2) start a nesting block, or 3) recipes that use
the "c" flag. Is this correct? If so, some of the FAQ stuff I've seen
seems incorrect. Often when formail is used, the "f" flag is also used.
. . . .
Don Hammond has given some good information. And I only have a minute
here before I must run off. But I want to respond to this point,
because the question confused me also for years until about a year ago.
I finally realized that what the procmail man pages and some of the
stronger programming types here are content to call a "filter," I
wanted in my head to call a "function." That made it perfectly clear
to me what it does. It works like a classic function box. Something
goes in one end, and something altered comes out the other. But
then procmail accepts the something other back without complaint
(because the -f flag was used) and keeps on going with the as-yet-
undelivered message.
I have a <gasp> fuzzy humanities background rather than a hard engineering
one, though I have done some amount of programming and enjoy it, and
have worked with computers professionally for years. But my lay
explanation still might (a) not be quite right (and if not, I'd
welcome corrections); and (b) not sit entirely well with the harder-
core CS types who could object to the imprecision inherent in my
poor-man's explanation. But anyway, the "function" thing is the
thought that helped me the most with this concept.
--
(Use <dman+noacks(_at_)nomotek(_dot_)com> to avoid a weekly auto-ack)
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