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早期freebsd实现

It is important to note that \pgm{bbc} performs its calculations on
BBoard-ID:s and not the messages actually present in a BBoard.
This means that the numbers given by \pgm{bbc} are maximal end-points.
When \pgm{bbc} says $n$, \pgm{bbc} means ``at most $n$''.

Naturally, \pgm{bbc} can be invoked with the \switch{check} option and one or
more BBoards listed on its command line.
For example \example bbc\ -check\ info-c\ poli-sci\endexample is completely
acceptable~---~it tells \pgm{bbc} to check on the BBoards \eg{info-c} and
\eg{poli-sci} only.

There are two ways to check for new BBoard messages in an asynchronous fashion:
using the \pgm{CShell} variable \file{\$mail} and running the \pgm{useto}
program.

\subsubsection{Asynchronous Checking with the CShell}
The \pgm{CShell} has a variable called \file{\$mail}.
This variable can contain one or more words.
Each word should be a filename where the shell should check for new mail.
The check is performed after a specified time interval has elapsed just
before the shell would prompt the user.

If the first word of \file{\$mail} is a number,
then this number specifies a different checking interval, in seconds,
than the default, which is 10 minutes.

Whenever the time interval elapses and the shell is ready to prompt the user,
the shell looks at the file and decides if new messages have arrived.
If so, it says \example You have new mail.\endexample
if only one file is present in \file{\$mail}.
Otherwise,
if more than one file is present in \file{\$mail},
then the shell says \example New mail in foo.\endexample whenever there is new
mail in the file called \eg{foo}.

To find out what file is associated with a BBoard, say \eg{info-unix},
the \MH/ user types \example bbc\ -topics\ -verbose\ info-unix\endexample
Usually the local file for a BBoard has an extension of \file{.mbox}.

\subsubsection{Asynchronous Checking with Useto}
In contrast to using the \file{\$mail} variable in the \pgm{CShell},
the \MH/ user might employ \pgm{useto} instead.%
\nfootnote{Not all sites have \pgm{useto};
contact the same people who supplied \MH/ to get a copy.}
The \pgm{useto} program is a continuous update display that prints information
on the status line of your terminal.
Needless to say,
your terminal must support a status line in order to run \pgm{useto}.
Not all terminals have this capability,
but for those that do it's usually well worth the effort to run \pgm{useto}.

For example, users of \MH/  could put
\example
    useto\ -bepf\ \'tcp-ip\ sftp\'\ %
	\'\%D\ \%M\ \%d\ \%h:\%m\%z\%b\ \%n.tty\%t:\%l1\'%
\endexample
in their \file{\$HOME/.login} file.
This command line to \pgm{useto} says to inform the user of
\smallskip
{\advance\leftskip by\parindent
\item{$\bullet$} the current date and time
\item{$\bullet$} new mail for the user
\item{$\bullet$} new messages for the BBoards \eg{tcp-ip} and \eg{sftp}
\item{$\bullet$} the name of the host and tty that the user is logged in on
\item{$\bullet$} the 5--minute load average of that host
\smallskip}

The \pgm{useto} program is really quite amusing and useful.%
\nfootnote{To be honest,
the author considers computing environments without \pgm{useto}
to be less than adequate.}

\subsection{BBoard reading}
If \pgm{bbc} is not given either the \switch{check} or \switch{topics} option,
the \pgm{bbc} program reads BBoard messages.
For each BBoard listed in the \MH/ user's profile entry for \eg{bboards:},
\pgm{bbc} checks to see if there is unread mail.
If so, \pgm{bbc} starts \pgm{msh} on the BBoard,
telling \pgm{msh} which messages haven't been seen.%
\nfootnote{If the \switch{verbose} option is given to \pgm{bbc},
then \pgm{bbc} will start \pgm{msh} on the BBoard regardless of whether there
are unseen messages there.}

When \pgm{msh} starts it identifies the BBoard being read and indicates how
many messages are present and how many the user has read.
Usually, in the user's \MH/ profile,
the user has the entry \example msh:\ -scan\endexample
This says that when \pgm{msh} starts,
it should print a {\it scan listing} of the messages which the user
hasn't seen yet.

The \pgm{msh} program now prompts the user for \MH/ commands.
The user may type most of the normal \MH/ command.
The syntax and semantics of the commands typed to \pgm{msh} are identical
to their \MH/ counterparts.
For example, to reply to a message on the BBoard,
the \MH/ user types \eg{repl};
other \MH/ commands likewise may be applied to BBoard messages.
In cases where the nature of \pgm{msh} would be inconsistent
(e.g., specifying a \arg{+folder} with some commands),
\pgm{msh} will duly inform the user.
In addition to supporting most \MH/ commands,
\pgm{msh} also has a \eg{help} command which gives a brief overview.

The only command that behaves entirely differently in \pgm{msh} is the
\eg{mark} command when given no arguments.
The \pgm{msh} program maintains a special sequence, \eg{unseen},
which it uses to keep track of the messages you've seen.
If the \eg{mark} command is given without any arguments,
then \pgm{msh} will interpret it as
\example mark\ -sequence\ unseen\ -delete\ -nozero\ all\endexample
Hence, to discard all of the messages in the current BBoard being read,
the \MH/ user types \eg{mark} which says to remove all messages from sequence
called \eg{unseen}.

To leave \pgm{msh} use the \eg{quit} command.
This tells \pgm{msh} to terminate and \pgm{bbc} to go to the next BBoard.
Instead, if the user types EOT (usually CTRL-D),
then \pgm{bbc} will exit as well,
updating whatever information was appropriate.

\section{Current BBoards}
There are many, many active interest groups.
Consult the BBoard called \eg{list-of-lists} for a comprehensive description.
Here are a few of the more popular:
\smallskip
{\advance\leftskip by\parindent
\item{\tx system}
Important announcements for the local system are posted here.

\item{\tx mh-users}
A discussion group for users of \MH/.

\item{\tx arpanet-bboards}
Redistribution address for all known BBoards on the ARPAnet.

\item{\tx editor-people}
Discussion of topics related to computerized text editing, display editors, 
and human factors in man/machine interaction.
The theoretical discussion is catholic,
but practical discussion focuses particularly on \tops20/ and \unix/.

\item{\tx franz-friends}
Discusses the Franz Lisp language.

\item{\tx header-people}
Interest specifically in the format of message headers and related issues 
such as inter-network mail formats/standards, etc.

\item{\tx human-nets}
{\sf Human-Nets} has discussed many topics,
all of them related in some way to the theme of a world-wide computer and
telecommunications network usually called WorldNet.
The topics have ranged very widely, from something like tutorials,
to state of the art discussions,
to rampant speculation about technology and its impact.

\item{\tx info-micro}
Information/discussion list on the general interest topic of microcomputers.

\item{\tx info-unix}
{\sf Info-UNIX} is intended for question/answer discussion,
where ``novice'' system administrators can pose questions.

\item{\tx msggroup}
Interest in electronic mail, message formats, message systems, and the 
sociological implications of the above.

\item{\tx poli-sci}
A permanent distributed political ``bull'' session.

\item{\tx sf-lovers}
Science Fiction lovers.
{\sf SF-Lovers} has discussed many topics,
all of them related in some way to the theme of science fiction or fantasy.  

\item{\tx space}
Discussions (daily digest) on space-related topics.

\item{\tx telecom}
A broad spectrum moderated-digest-format discussion on telecommunictions 
technology: the telephone system, modems, and other more technical aspects 
of telecommunications systems.  

\item{\tx unix-emacs}
Used for new release announcements and general discussions of Gosling's
\EMACS/.

\item{\tx unix-wizards}
Distribution list for people maintaining machines running the \unix/ operating
system.
\medskip}
\noindent
As discussed earlier,
to find out about all of the BBoards that the local host subscribes to,
the \MH/ users types \example bbc\ -topics\endexample

\section{More on BBoards}
Finally, here are a few more operational details:

\subsection{Creating a BBoard}
Contact the PostMaster at your host to have a BBoard created.
Be sure to indicate its status (public or private)
and scope (where distribution should occur).

\subsection{Subscribing to a BBoard}
If your local host already receives an interest group,
then simply add the name of the BBoard to the \eg{bboards:} entry in your
\MH/ profile.
If not, ask the PostMaster to create the BBoard and contact the global
request address for you.

\subsection{BBoard Archives}
BBoard messages are automatically archived on a weekly basis.
Usually, this results in messages older than 12 days being moved to an
{\it archive} area.
To read the archives for a BBoard, the \switch{archive} option is used.
For example, \example bbc\ -archive\ telecom\endexample
tells \pgm{bbc} to invoke \pgm{msh} on the archives for the \eg{telecom}
BBoard.

Note that the archives may not be present for all BBoards on a given host;
also note that the archives may be periodically moved to tape and expunged
from the system.
Contact your local PostMaster for the details.

\subsection{BBoard Addresses}
Each BBoard has associated with it 4 addresses
(for example, in the case of the mythical BBoard \eg{foo\/}):
\smallskip
{\advance\leftskip by\parindent
\item{\tx foo} The global distribution list\hbreak
If you post a message addressed to {\tx foo} then the message is distributed
to everyone who subscribes to \eg{foo}.

\item{\tx dist-foo} The local distribution list\hbreak
If you post a message addressed to {\tx dist-foo} then the message is
distributed to the local BBoard for \eg{foo}
and to any sites which the local system distributes to.

\item{\tx foo-request} The global moderator\hbreak
If you post a message addressed to {\tx foo-request} then the message is
sent to the moderator for the entire interest group called \eg{foo}.

\item{\tx local-foo-request} The local moderator\hbreak
If you post a message addressed to {\tx local-foo-request} then the message is
sent to the person responsible for the BBoard \eg{foo} on the local system.
\medskip}
\noindent
These addresses are defined by the \MH/ alias facility.
Users of the BBoards facility who do not use \MH/ may not be able to make use
of them.

\subsection{Leading a BBoard}
Except for special circumstances, this task is wholly automated.
For more information though,
see the manual entries for \man bbl(1) and \man bbleaders(8).

\section{Extra for Experts}
Some clever \MH/ users might ask why BBoards aren't kept as folders instead
of \pgm{pack}'d files.
This is a good question.
Perhaps some future release of \MH/ and the UCI BBoards facility will treat
BBoards as a variant of read-only folders.

The problem with \pgm{msh}, of course, is that it's a monolithic program,
and although it does support input/output redirection and a few other
primitive shell-like properties, it's still not the \pgm{CShell}.