make stty settings permanent

Posted on 2002-06-04
Last Modified: 2008-02-01
 I am able to set the xon xoff settings on a serial port (rh linux 7.2), but unable to make them permanent. The settings toggle back to "defaults" when the port changes state (respawn to off, etc). I am actually using the ditty command which is a stty interface from digiboard. Is there a way to make the changes permanent?
Question by:medent
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LVL 51

Expert Comment

ID: 7054063
respawn ditty, so I assume that it is specified in /etc/inittab, there you can place all options which can be passed to ditty. You need to read the docs about ditty which options you need.

Author Comment

ID: 7056006
Not sure I understand- Please clarify. I know the ditty command syntax to set the xon xoff state, thats not my problem. I want to know how to make stty settings stick. I have put in inittab as "once" to run once, but that will change if a port is toggled (occasionally done to "reset" a stuck terminal,etc). I'm not sure if respawn ditty is valid (which appears to be your idea), because it would continually restart the process after terminated (great for login bad for ditty). Thank You.
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Expert Comment

ID: 7056315
even if it is once in inittab, you should set the parameters there (if ditty has some)
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Author Comment

ID: 7056353
The question remains how to preserve the stty settings or protect them from changing during runtime. Thank You.
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Accepted Solution

ahoffmann earned 400 total points
ID: 7056416
to restrict changes during runtime, you need to remove permissions to stty and/or corresponding libraries for the user using this tty.

> .. preserve settings ..
you mean for next start of dtty? then see my previous comments

Author Comment

ID: 7056530
This is not an intention user change. The stty defaults as a side effect of when status of the port in the inittab changes (respawn to off, or vice versa).
I do not understand why the stty goes to default when the inittab changes in that way, or even why a reboot defaults all you stty settings, but I would like to at least preserve the settings during runtime. Disabling stty will probably trade problems for problems...

Expert Comment

ID: 9089025
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Author Comment

ID: 9089259
stty or ditty are not directly issued from within the inittab,  "agetty" is (generates a login)
 so the problem seems to be when agetty respawns, it changes the port state (flow control in particular), then I have to fix it by usuing the ditty command.

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Expert Comment

ID: 9655884
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