Can't see keyboard input after "killall python"

Question

I am working on an embedded Busybox system running Python 2.7.

Whenever I kill Python using

killall python

while I run an interactive python shell future instances of the interactive python shell break for that session.

So e.g. I have an ssh connection to the device that is currently running the python shell. Now I use "killall python" from another shell. The shell on the first ssh connection closes (as expected) with the message "Terminated". So far this is all expected.

Now I use the "python" command again in the same shell where I had the last python shell. Now I get abnormal behaviour in the sense that none of my input is displayed.

So e.g. if I normally enter "print('test')" I see this:

>>> print('test')
test
>>>

If I do the same after killing python I see this:

>>> test
>>>

So as you see, my input ("print('test')\n") is not displayed as expected. All outputs from the program are visible, though.

To fix this I have to close the connection (e.g. the ssh connection) and start it again. It only affects connections that had the python shell running while I used the killall-command. So if there are multiple ssh connections only the ones are affected that had python running at the time of the killall-command.

It doesn't matter if I use "killall" or just "kill [PID]", the result is the same.

Does anyone know what causes this and how to fix this?

Answer 1

"Local echo" -- printing input you type -- is a toggleable terminal setting. You're getting your terminal into a state where it's turned off. (This can easily happen if a program exits while prompting for password input, which is a particular circumstance where it's common to turn off local echo for security reasons).

To completely reset your terminal to a known-good state, run stty sane before restarting Python. To only enable local echo, run stty echo.