On Dec 11, 11:11 am, "[EMAIL PROTECTED]"
<[EMAIL PROTECTED]> wrote:
> On Dec 10, 11:05 am, cthoday <[EMAIL PROTECTED]> wrote:
>
.
> > There is a Smart Terminal that allows interactive shells to operate
> > within a wx.TextCtrl. On Unix such programs need to be connected to a
> > pseudo terminal if they are to operate in interactive rather than
> > batch mode. However, the easy way to connect a Python program to
> > another process is by pipes. I have solved this by writing a small C
> > program to copy to and from the subprocess via the pseudo terminal.
>
> ddd and Emacs typically work this way - using a subprocess via a
> pseudo terminal.
>
Python has a pseudo tty module but I could not get it to do what I
wanted. The basic problem is that the shell thinks it is controlling a
VDU terminal but the application program cannot find out what mode the
shell is working in. If it is working in canonical mode then the line
is composed in the application before being sent to the shell. In raw
mode the application must send individual characters and compose the
line from the responses it gets. There may be no response if the input
was a password. Some responses do not work as might be expected. For
example the response to Backspace is Backspace, Space, Backspace. The
first Backspace moves the cursor to the left, the Space replaces the
character to be erased (provided it is not in Insert mode) and the
second Backspace move back over the Space.
There is no means for the application program to determine whether or
not the shell is waiting for input. The shell assumes that the
terminal has displayed the prompt but it may be waiting in a buffer.
If it assumed that no buffering is used then multiple lines of output
from the program running in the shell may be painfully slow to display
in the application. The solution uses three processes: one copies from
the pipe to the tty, another copies from the tty to the pipe and the
third runs the shell. This works well except that it sometimes leaves
zombie processes if a process terminates abnormally.
Shells that use GNU readline operate in raw mode but those that do not
have this facility provide a very poor experience for the user. In
this case I implement some basic line editing so that the user can at
least correct mistakes with Backspace. Shells that do not have line
editing include PHP and OCaml but, in the latter case, the shell comes
with the "ledit" command which solves the problem.
