unable to type command into Cygwin after running 'tail'

Heath Kehoe heath@nozzala.net
Thu Dec 2 20:28:00 GMT 2010

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 work
>>>>> again.
>>>> Would you, please, elaborate on this a little bit?
>>>> Maybe a link or a reference that explains why this is happening?
>>> 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.
>> 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
> 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?)
> Which shell do people who've seen the problem use? Is it an intermittent issue?

If you SIGKILL a 'less' while it has the tty set for raw/noecho then the tty 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 tty in a psuedo-raw mode [-icanon min=1 -echo] as a matter of course). If you 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 that way. Perhaps there's some kind of race condition in the shell's signal processing? 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.


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