Dallman Ross wrote:
Procmail has no easy way to distinguish between a var that is unset
and one that is merely empty, btw. There is an extremely advanced
way to test for that,
Those are opinions based on one's personal view of what's easy and
what's advanced. Stephen coded those constructs into procmail
intentionally, and if you're used to them from sh or sh-like shells,
they're easy enough.
and David Tamkin once showed that as well, but it's not something I
or anybody I know about ever actually needed to do in production.
Someone on this list (maybe it was Timothy Luoma?) asked how to test
whether a variable was set but null. Here's how:
* $ !${var+!}${var:+!}
It was merely an intellectual exercise,
... except perhaps for the original asker, who never said whether there
was a practical use.
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