Control Messages
The Usenet news protocol knows a special category of articles that
evoke certain responses or actions by the news system. These are called
control messages. They are recognized by the presence of a
Control: field in the article header, which contains the
name of the control operation to be performed. There are several types of them,
all of which are handled by shell scripts located in
/usr/lib/news/ctl.
Most of these messages perform their action automatically at the time the article
is processed by C News without notifying the newsmaster. By default, only
checkgroups messages will be handed
to the newsmaster, but you may change this by editing the scripts.
The cancel Message
The most widely known message is cancel, with which a user can cancel an
article sent earlier. This effectively removes the article from the
spool directories, if it exists. The cancel message is forwarded to all sites
that receive news from the groups affected, regardless of whether the
article has been seen already. This takes into account the possibility
that the original article has been delayed over the cancellation
message. Some news systems allow users to cancel other people’s
messages; this is, of course, a definite no-no.
newgroup and rmgroup
Two messages dealing with creation or removal of newsgroups are the
newgroup and
rmgroup messages. Newsgroups below the “usual” hierarchies may be created only after a discussion and voting has been held among Usenet readers. The rules ...
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