Re: multiple users, one emacs - how?

[Pascal Bourguignon]

Joe Corneli <jcorneli@planetmath.org> writes:

> The closest I've found to an answer is the suggestion by Pascal
> in the thread "howto: 2 users interactively edit the same file ?",
>
> http://lists.gnu.org/archive/html/help-gnu-emacs/2005-10/msg00842.html 
>
> I haven't had a chance to try this -- but I am primarily interested in
> a solution that doesn't involve/require X (e.g. because me and my
> collaborators are typically editing files in cybercafes, where it is
> AFAIK impossible to determine an actual IP address for the computer --
> if I'm wrong about this, I'd be willing to accept an X windows
> solution).

Well, when you connect to a remote host, you can know the IP. But
you're right, you may be behind a NAT router. In that case, you can
send the X traffic thru ssh: ssh publishes a X display on a local port
on the remote that it forward back to the client, so you can have the
display on the local computer with: 
  ssh -X remote.host xclock -display localhost:10
for example.


> Ideally (at least for now) what I'd like would be to have a copy of
> emacs running on a computer somewhere where we'd log in via shell
> accounts, and then we'd e.g. fire up an emacsclient and all get access
> to that emacs's state.
>
> It seems to be insinuated that (or anyway I've imagined) emacsclient
> can actually do this.  (Cf. this thread:
> http://lists.gnu.org/archive/html/help-gnu-emacs/2005-08/msg00226.html)
>
> Is this the case?  Can emacsclient be used by multiple users to access
> the same emacs through a shell?  Or, if not emacsclient, can anyone
> suggest a good solution?

You have several options.

You could use the multitty branch of emacs, which allows to create new
tty frames as we can create new X frames.

In terminal 1:  emacs 
In terminal 2:  emacsclient --tty

You could also use: M-x make-frame-on-tty RET /dev/pts/NN RET xterm RET

But you'd need to ensure that your input in the xterm is not taken by
another program: run sleep 100000 for example!

xterm -display :0.0  -e bash -c 'ls -l /proc/$$/fd/;sleep 1000'

The advantage of multi-tty emacs is that you can have both X and
terminal frames.


You can also use screen, which would allow you to share terminals on
the same shell for any terminal application, including an emacs (even
a non multi-tty one):

screen -e^^^^ -d -m emacs -nw  # to launch an emacs
screen -r -x                   # to attach to the session
screen -r -x                   # to attach to the session from another terminal.


(with emacs, it's useful to use C-^ as screen escape instead of the
default C-a).

You can try it with:

screen -e^^^^ -d -m emacs -nw
xterm -e screen -r -x &
xterm -e screen -r -x &
xterm -e screen -r -x &


The advantage of screen is that you can easily detach from the session
and having it go on with no terminal.

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/

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