Tony Finch wrote:
On Mon, 23 May 2005, Toralf Lund wrote:
Is there any way I can set the value of a main config setting like
primary_hostname to the output of a system command?
primary_hostname is one of the few configuration settings that is not
expanded. Perhaps if you explain why you want to do this we can suggest
solutions that will work.
I'm trying to set up an MTA (Exim) for outgoing messages only. For
reasons I won't go into here, hostname doesn't return the official name
of the host - but I know a way to find it. From the shell, that is.
But perhaps all I want is to override the HELO name...
Actually, one of the things that's always confused me most about the exim
config setup is the whole string expansion mechanism...
One way to think of it is an escape hatch. To a large extent you can
configure Exim without using string expansions - the flexibility comes
from things like matching against lists and the variety of ACL conditions
and router preconditions. However they can't cope with everyone's
requirements so string expansions allow you to construct your own ad-hoc
conditions and lookups.
Well. Yes. What confuses me, is that strings are sometimes expanded
sometimes not. Also, when exactly the expansion takes place and the
order of operations is not always easy to predict... And the fact that
there are several completely different "variable data" mechanisms add to
the complexity of it all. You have macros, "expansion variables", normal
configuration variables (which are related to "expansion variables", but
not directly, as far as I can tell) host and domain lists...
There is however some complexity arising from string expansions' context
sensitivity: expansion variables get set according to what has previously
happened to the message or the SMTP connection it is coming in on, and
according to where the expansion is used. The main advantage of Exim is
that it lets you get down and dirty with the details of handling email;
the main disadvantage of Exim is that it lets you get down and dirty with
the details of handling emai.
Tony.
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