Gnus Utility Functions A Programmers Guide to Gnus Score File Syntax
Gnus doesn't know anything about NNTP, spools, mail or virtual
groups. It only knows how to talk to virtual servers. A virtual
server is a backend and some backend variables. As examples
of the first, we have
examples of the latter we have
When Gnus asks for information from a backend---say
something, it will normally include a virtual server name in the
function parameters. (If not, the backend should use the ``current''
virtual server.) For instance,
nntp-request-list takes a virtual
server as its only (optional) parameter. If this virtual server hasn't
been opened, the function should fail.
Note that a virtual server name has no relation to some physical server name. Take this example:
(nntp "odd-one" (nntp-address "ifi.uio.no") (nntp-port-number 4324))
Here the virtual server name is `
odd-one' while the name of
the physical server is `
The backends should be able to switch between several virtual servers. The standard backends implement this by keeping an alist of virtual server environments that they pull down/push up when needed.
There are two groups of interface functions: required functions, which must be present, and optional functions, which Gnus will always check for presence before attempting to call 'em.
All these functions are expected to return data in the buffer
*nntpd*'), which is somewhat
unfortunately named, but we'll have to live with it. When I talk about
resulting data, I always refer to the data in that buffer. When I
talk about return value, I talk about the function value returned by
the function call. Functions that fail should return
nil as the
Some backends could be said to be server-forming backends, and some might be said not to be. The latter are backends that generally only operate on one group at a time, and have no concept of ``server'' -- they have a group, and they deliver info on that group and nothing more.
In the examples and definitions I will refer to the imaginary backend