Re: RE: [Expectperl-discuss] errors when installing io::tty under cyg win

[Roland G. <RGi...@a1...>]

>  I note that the new IO::Tty is "based on ideas from openssh and 
> Xemacs."Any ideas from Libes' original Expect in there?  Have the 
> openssh and Xemacs
> guys figured out a better way than he did or did they just borrow 
> from his method?  How do all these different approaches compare?
> 
>  I'm just eaten up with curiosity. :)

Then you need a speedy answer! :-)

For pty allocation, I used ideas from openssh and Xemacs as they have a 
more modern approach.  A lot of systems have incorporated some kind of 
cloning device in the meantime that weren't there when Tcl/Expect was 
developed.  I concentrated on an idea from Xemacs, namely just figuring 
out what possibilities (libs/devices) are there and then trying all of 
them in order until one succeeds, the last one being the standard BSD-
style technique of opening all /dev/pty*s one after another until an 
open succeeds.

I collected several methods of allocating a pty from several sources. 
These are:

  openpty()
  _getpty()
  getpt()
  /dev/ptmx
  /dev/ptym/clone
  /dev/ptc
  /dev/ptmx_bsd

If anybody knows about other methods, please let me know.

Now what could be a problem is the pty setup: I use grantpt() and 
unlockpt() and push appropriate stream modules via ioctl, but there 
could be others necessary, esp. on older systems.  The problem is that 
I can only rely on information in manpages etc. that I look up via 
Google, so I'm flying by instruments, pestering clients to get test 
results.  

What I used from Tcl/Expect was the method how spawn() works, namely 
using pipes to synchronize the parent with the forked child until the 
child has set up the pty, passing up a possible exec() error on the 
fly. Quite nifty!

Any more questions?

Roland
--
RGi...@cp...