[ale] how to redirect fds through telnet session in QNX?

[Christopher Fowler]

On Sat, 2007-03-24 at 15:48 -0400, Step wrote:
> Since the instrument is often mounted on lifts, walls, or otherwise
> relatively inaccessible locations, I was hoping to just push over a
> script or some code with our next embedded software update, that I can
> then run through telnet to duplicate or somehow send debug information
> to file.  Barring that, I want to understand why that won't work

If the output is sent to a tty then you just can't grab that output.
There were products on the market that I used years ago that would do
this.  One product was named Double Vision.  It ran on SCO,AIX, and
other UNIX systems.  It included a kernel driver.  It would allow you to
run a program and attach to the TTY of what you wanted to control.  We
used it to connect to IBM3151, Wyse50, and Tiny Term terminals.  We
could then run programs and detach or must likely we would be training
people over the phone.  We took control of their serial terminal and
walked them through the software.  That would be a good solution but I
can think of any way that the Linux kernel is going to just allow you to
take join a TTY like that.  I did at one time see a similar program
which included no driver but on inspection it used the same concept of
what I just done in PERL.  It would run programs on pseudos and then you
would use a client to connect to the main daemon.  You could then decide
which session you would like to attach to.  Not a bad solution but not
the way that DV did things.  It was a user space solution.  Who wrote it
decided to solve the problem in user space using the tools provided.

In my example I use a pseudo and that may be over kill.  If your program
requires a tty, isatty(3), then you would need a pseudo.  If you wanted
to interface via a curses like GUI then you would need a pseudo.
Otherwise pipe(2) would work great.  The only reason I used a pseudo it
because you mentioned a pseudo and I'm not sure what your app does or
needs in the way of input and output.  Pseudos do their best to emulate
a tty with minor limitations.  They are just fancy pipes.

If you want to use the pipe then look at Jame's response in regard to
netcat.  You'll have to compile to run on QNX though.