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Old 05-21-2012, 10:28 PM
Eric Cooper
 
Default why does control-4 generate SIGQUIT in X?

I recently noticed that when I hold the control key and press '4', it
generates ^, i.e. SIGQUIT. This happens in both gnome-terminal and
xterm, and on two different kinds of physical keyboards. It doesn't
happen outside of X, on just a linux VT.

It's pretty annoying in mutt, because I often need to type shift-4 for
escape and typing control instead of shift kills the session.

What kind of X keyboard mapping determines this behavior, and how can
I change it?

(Please CC me since I'm not subscribed to this list.)

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Old 05-22-2012, 05:32 PM
Camaleón
 
Default why does control-4 generate SIGQUIT in X?

On Mon, 21 May 2012 18:28:55 -0400, Eric Cooper wrote:

> I recently noticed that when I hold the control key and press '4', it
> generates ^, i.e. SIGQUIT. This happens in both gnome-terminal and
> xterm, and on two different kinds of physical keyboards. It doesn't
> happen outside of X, on just a linux VT.

http://en.wikipedia.org/wiki/SIGQUIT
http://en.wikipedia.org/wiki/Unix_signal

Ah, curious...

> It's pretty annoying in mutt, because I often need to type shift-4 for
> escape and typing control instead of shift kills the session.
>
> What kind of X keyboard mapping determines this behavior, and how can I
> change it?

Mmm... someone will confirm (or provide a better solution) but Google
points to 'stty quit ""' to disable the key shortcut.
>
> (Please CC me since I'm not subscribed to this list.)

Sorry, I can't :-(

Greetings,

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Old 05-22-2012, 07:42 PM
Chris Bannister
 
Default why does control-4 generate SIGQUIT in X?

On Tue, May 22, 2012 at 05:32:10PM +0000, Camaleón wrote:
> On Mon, 21 May 2012 18:28:55 -0400, Eric Cooper wrote:
>
> > I recently noticed that when I hold the control key and press '4', it
> > generates ^, i.e. SIGQUIT. This happens in both gnome-terminal and
> > xterm, and on two different kinds of physical keyboards. It doesn't
> > happen outside of X, on just a linux VT.
>
> http://en.wikipedia.org/wiki/SIGQUIT
> http://en.wikipedia.org/wiki/Unix_signal
>
> Ah, curious...
>
> > It's pretty annoying in mutt, because I often need to type shift-4 for
> > escape and typing control instead of shift kills the session.
> >
> > What kind of X keyboard mapping determines this behavior, and how can I
> > change it?
>
> Mmm... someone will confirm (or provide a better solution) but Google
> points to 'stty quit ""' to disable the key shortcut.
> >
> > (Please CC me since I'm not subscribed to this list.)
>
> Sorry, I can't :-(

Huh? Well anyway, so that your post is not a waste of time.

Yes, stty quit "" works!!


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Old 05-22-2012, 09:02 PM
Eric Cooper
 
Default why does control-4 generate SIGQUIT in X?

On Wed, May 23, 2012 at 07:42:14AM +1200, Chris Bannister wrote:
> Yes, stty quit "" works!!

Unfortunately, I'd still like ^ to generate SIGQUIT, but
"stty quit ^" also enables ctrl-4 as an alias.

Thanks for the reference -- I'm surprised I never noticed this before.

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Old 05-22-2012, 09:57 PM
Chris Davies
 
Default why does control-4 generate SIGQUIT in X?

Chris Bannister <cbannister@slingshot.co.nz> wrote:
> Yes, stty quit "" works!!

That disables SIGQUIT capability from the keyboard entirely, so the more
usual ^ also no longer works.

CHris


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Old 05-23-2012, 12:16 PM
Vincent Lefevre
 
Default why does control-4 generate SIGQUIT in X?

On 2012-05-22 17:02:56 -0400, Eric Cooper wrote:
> On Wed, May 23, 2012 at 07:42:14AM +1200, Chris Bannister wrote:
> > Yes, stty quit "" works!!
>
> Unfortunately, I'd still like ^ to generate SIGQUIT, but
> "stty quit ^" also enables ctrl-4 as an alias.

Ctrl-4 generating ^ is a keyboard configuration setting that can
be seen with xev:

KeyPress event, serial 40, synthetic NO, window 0x3200001,
root 0x2b4, subw 0x0, time 87345747, (114,90), root1719,110),
state 0x4, keycode 13 (keysym 0x34, 4), same_screen YES,
XLookupString gives 1 bytes: (1c) ""
XmbLookupString gives 1 bytes: (1c) ""
XFilterEvent returns: False

Byte 1c (= 28 in decimal) is ^.

FYI, Ctrl-3 to Ctrl-7 respectively generate 1b to 1f, and Ctrl-8
generates 7f (DEL).

Since this happens just under X, I'd say that it is related to XKB.
However the XKB keyboard description generated with

xkbcomp $DISPLAY xkb.dump

doesn't show anything related to this behavior.

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Old 05-23-2012, 12:29 PM
Vincent Lefevre
 
Default why does control-4 generate SIGQUIT in X?

On 2012-05-22 17:02:56 -0400, Eric Cooper wrote:
> Unfortunately, I'd still like ^ to generate SIGQUIT, but
> "stty quit ^" also enables ctrl-4 as an alias.
>
> Thanks for the reference -- I'm surprised I never noticed this before.

I wonder whether this is recent. One of the side effects is recent
under Ubuntu:

https://bugs.launchpad.net/ubuntu/+source/unity/+bug/961056

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Old 05-23-2012, 03:40 PM
Camaleón
 
Default why does control-4 generate SIGQUIT in X?

On Tue, 22 May 2012 17:02:56 -0400, Eric Cooper wrote:

> On Wed, May 23, 2012 at 07:42:14AM +1200, Chris Bannister wrote:
>> Yes, stty quit "" works!!
>
> Unfortunately, I'd still like ^ to generate SIGQUIT, but "stty quit ^"
> also enables ctrl-4 as an alias.

The above command completely disables the quit signal combo(s) so you can
call it when launching Mutt, that way it won't survive when you close the
terminal.

Greetings,

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Old 05-23-2012, 04:05 PM
Chris Bannister
 
Default why does control-4 generate SIGQUIT in X?

On Tue, May 22, 2012 at 10:57:34PM +0100, Chris Davies wrote:
> Chris Bannister <cbannister@slingshot.co.nz> wrote:
> > Yes, stty quit "" works!!
>
> That disables SIGQUIT capability from the keyboard entirely, so the more
> usual ^ also no longer works.

Where are you setting it?

Short version.
--------------
start an xterm, type
stty quit ""<return>
stty -a shows quit as "<UNDEF>"
start another xterm
stty -a shows quit as "^"

but ctrl-f4 is buggered up entirely
see Vincent's post, I think that is what he is referring to.
also see below, for an attempt at describing it.

Slightly longer version.
------------------------
Curiouser and Curiouser

I use startx (no DE, just barebones FVWM)
and in my .xsessionrc I have:

---
xterm -fn 10x20 -xrm "XTerm.vt100.background: #CCA8AA" -xrm
"XTerm.vt100.foreground: blue" -geom 50x25 &
---
Once X starts, and I type stty quit ""<return> then mutt, ctrl-f4 just
beeps. If I invoke *another* xterm from the menu and just type mutt,
ctrl-f4 quits el pronto.

If I then type stty quit ""<return> in that other xterm then mutt,
ctrl-f4 just beeps as expected. If I then invoke another xterm from
the menu, ctrl-f4 just beeps.

I think this is what Vincent, was referring to; its now buggered up
ctrl-f4. Even a cold restart doesn't bring ctrl-f4 back to quitting.

(If I can clear the setting, for ctrl-f4 I can mess around a bit more,
because I can't see the logic in my above test. I'd like to confirm it)

BUT quit is reset back to ctrl-, on the start of a new xterm

using "stty -a" shows the settings.

--
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who are being oppressed, and loving the people who are doing the
oppressing." --- Malcolm X


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Old 05-24-2012, 02:59 PM
Chris Davies
 
Default why does control-4 generate SIGQUIT in X?

Chris Bannister <cbannister@slingshot.co.nz> wrote:
> start an xterm, type
> stty quit ""<return>
> stty -a shows quit as "<UNDEF>"

Exactly my point. So ^ no longer works at all (in that xterm).
Chris


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