stty in 5.0 and 4.1

[Rick Stevenson]

jonas at lkbpyr.UUCP (Jonas Heyman) writes:
>I have a problem concerning stty in the "att" universe.
>I recently uppgraded from 4.1 to 5.0 on a 9820 Pyramid.
>On this machine I tried to do following:

>    stty < /dev/tty104          (shows 300 baud)
>    stty 9600 < /dev/tty104     (trying to change to 9600 baud)
>    stty < /dev/tty104          (still 300 baud ?)

>When I do the following on a machine with OS 4.1 it works fine,is there
>something I'm doing wrong ? or is there a difference between the OS versions.
>(The port tty104 is marked "off" in inittab).

The behaviour you are seeing on OSx 5.0 is what I would have expected. The
default baud rate for a tty device is 300 baud, and when you open a tty
that is not already open the baud rate will be reset. Changing the speed with
stty will only "stick" while the tty is kept open. Try this and see if it works:

  sleep 120 > /dev/ttyi04 &	(keep tty device open for a while)
  stty 9600 < /dev/ttyi04
  stty < /dev/ttyi04

The device will be reset to 300 baud again if you open it after the
sleep has completed.

I'm not sure why see different behaviour on 4.1. I suspect that the
difference is not directly related to the OS version (perhaps there is
a spooler or something which holds the device open on the 4.1 machine?).
The 4.1 kernel should behave as described above, but I can't
guarantee it - 4.1 was before my time.

Rick.
--
      -m-------   Rick Stevenson
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-------mmmmmmm-   Gold Coast, Q 4229, AUSTRALIA	     rick at ptcburp.ptcbu.oz.au