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Subject: Re: unable to type command into Cygwin after running 'tail'
From: Heath Kehoe <heath AT nozzala DOT net>
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Date: Thu, 2 Dec 2010 14:28:36 -0600
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On Dec 2, 2010, at 1:59 PM, Andy Koppe wrote:

> On 2 December 2010 18:40, Charles Wilson wrote:
>> On 12/2/2010 1:27 PM, David Rothenberger wrote:
>>> Illia Bobyr wrote:
>>>> On 12/1/2010 8:53 PM, David Rothenberger wrote:
>>>>> Try typing "reset" or "stty sane" (without the quotes) and pressing
>>>>> Enter. You won't see what you're typing, but after the shell should w=
ork
>>>>> again.
>>>>=20
>>>> Would you, please, elaborate on this a little bit?
>>>> Maybe a link or a reference that explains why this is happening?
>>>=20
>>> I'm sorry, I can't. I don't know why it is happening. I just know how to
>>> recover from it as a user.
>>=20
>> I've noticed that this misbehavior occurs more frequently these days:
>> ctrl-c'ing some tasks (tail, less, maybe a few others) ends up with the
>> terminal settings all scrogged up
>=20
> FWIW, I can't reproduce this, even if I kill the tail or less with
> SIGKILL, thus giving them no chance to do any cleanup. (I assume you
> use 'less -K' to allow it to be ctrl-c'ed?)
>=20
> Which shell do people who've seen the problem use? Is it an intermittent =
issue?
>=20

If you SIGKILL a 'less' while it has the tty set for raw/noecho then the tt=
y will stay in that mode. Bash apparently resets the tty to normal for you =
after the process is killed (actually, bash's readline normally runs the tt=
y in a psuedo-raw mode [-icanon min=3D1 -echo] as a matter of course). If y=
ou run 'less' from an 'ash' shell then SIGKILL it, the ash shell will need =
'stty sane' typed in.

Also, the OP said the problem was happening on pipelines like 'tail | grep'=
. Neither tail nor grep muck with tty settings (that I know of), so if the =
tty is ending up with echo disabled, it's got to be the shell leaving it th=
at way. Perhaps there's some kind of race condition in the shell's signal p=
rocessing? So again, we'll need to know which shell this is happening with =
and a way to reliably repro the issue to have any hope of fixing it.

-heath



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