Someone care to explain this pattern to me ... ?

[Jeffrey M. Vinocur]

On Tue, 2 Oct 2007, Marc G. Fournier wrote:

> @*,comp.*,mailing.*,sci.*,pgsql.*,news.*,alt.webhosting,
> alt.paidwebhosting,alt.www.*,tor.*,can.*,ont.*,hfx.*,ns.*, [...]
> 
> From reading the man page, the @* at the start should negate everything else,
> no?  But I'm definitely both sending, and receiving, news ... so is the @* at
> the start actually *doing* anything?

Yes -- conceptually, it's prohibiting crossposts to groups not listed 
there.  So if you had a private local hierarchy, and someone tried to 
crosspost between that hierarchy and some alt.* group, that post wouldn't 
be sent along even if the rest of the traffic in the alt.* group would.

To get to the nitty gritty, the way it works is:  take an article, and
look at each group in the Newsgroups line.  Match that group name against
the pattern in newsfeeds, making use of the last piece of the pattern that
matches.  If there's only a single group, it's very easy (so if the 
article is going to news.software.nntp, first it matches @*, but then it 
matches news.* and therefore gets sent).  The complicated piece is 
crossposted articles -- if any of the crossposted groups matches just @* 
and nothing else later in the pattern, the article won't be sent.

The alternative to @*, by the way, is !*, which leans towards less 
restricion.  So for articles posted to a single group, it's exactly the 
same.  For crossposts, however, if any of the crossposted groups matches 
just !* that doesn't matter as long as at least one of the groups matches 
something later in the pattern.


-- 
Jeffrey M. Vinocur
jeff at litech.org