I think you want to create some kind of redirected handle to the ctl file first, then start a new block in rc.  I believe this is how network programming in rc can be accomplished in Inferno as well.  Is this not allowed in p9p?  I've honestly not used the 9p commands too often.

On Fri, Mar 5, 2010 at 7:37 PM, Micah Stetson <micah@stetsonnet.org> wrote:
I think this may apply to all versions of acme, but I'm running into
it on p9p.  First, acme(4) claims that a read on a window's addr file
returns the current address as a pair of character offsets m and n, in
'#m,#n' format or just '#m' if m and n are equal.  It looks like it
really returns m and n as two space-padded integer values.

But that's just a documentation bug.  What's really bothering me is
that I can't seem to get the value of dot.  I've tried this:

% echo -n 'addr=dot' | 9p write acme/70/ctl
% 9p read acme/70/addr
         0           0 %

Window 70's dot is somewhere on line 16.  Thinking maybe the ctl file
had to stay open, I tried this:

% {echo 'addr=dot'; 9p read acme/70/addr >[1=2]} | 9p write acme/70/ctl
         0           0 %

No help.  Am I doing something wrong?

Micah