In connection with filters, I am about to extend the string expansion
facilities in Exim to allow the substitution of the contents of any
message header. I need some additional syntax between the $ that
introduces expansion and the header name so that the headers can never
be confused with other expansion variables. Two ideas have come to mind:
(1) Use an additional special characters, such as another $, giving
things like $$from $$reply-to etc.
(2) Use a prefix word, such as "header", giving things like
$header_from $header_reply-to
and so on. This has the benefit that it is clear how to bracket it as
${header_reply-to} whereas the other form might be $${reply-to} or
${$reply-to}.
Any views? I'm inclined to (2) myself at the moment as I think it makes
it quite clear what it means - and filter files will be written by the
inexperienced...
What should be done in cases where there is more than one of the
particular header? I propose to concatenate all their contents.
--
Philip Hazel University Computing Service,
ph10@??? New Museums Site, Cambridge CB2 3QG,
P.Hazel@??? England. Phone: +44 1223 334714
