$ echo -n , | 9p write acme/2/addr

$ echo dot=addr | 9p write acme/2/ctl

I see the entire text of the window get selected.

I had assumed that if I then read addr that I would

get back two numbers, 0 and the final byte offset

of the file (it is a non-zero length file).

However, I get back two zeros:

$ 9p read acme/2/addr

          0           0