Bash print gets messed up after running script

bashterminalUbuntu

My bash terminal in Ubuntu gets messed up after running a Python script. I have no clue why but after that, I can't use it again and need to close the shell and open a new one.

I am attaching a picture for you to see. Maybe someone can point out what could be a reason for this to happen.

Best Answer

This usually happens when the script uses some commands to change terminal settings and fails to reset them back to their default before it ends.

For instance, you can simulate a situation such as this with this command:

stty -echo

(I expect it will look like what you're experimenting.)

You can typically get back to "normal" with the reset command, so try pressing Ctrl+C or Return to make sure you're at the start of a new prompt, then type "reset" (you won't see anything) and Return and things might get back to normal:

reset

It's hard to tell what checkpoint_ps.py is doing that's leaving the terminal in a weird state... Though disabling terminal "echo" might be that... It's a common thing to do while asking for a password (so the password doesn't show up.) It looks from the output like "sudo" is getting involved, so I wouldn't expect checkpoint_ps.py would be messing with the terminal itself... But who knows, it's possible. If you find something in there that might be related to that, maybe ask a separate question about it so we can help you figure that out too.

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If you are using bash, check if "checkwinsize" option is activated in your session using

shopt | grep checkwinsize

If you don't get

checkwinsize    on

then activate it with

shopt -s checkwinsize

Bash documentation says for "checkwinsize" attribute :

"If set, Bash checks the window size after each command and, if necessary, updates the values of LINES and COLUMNS."

If you like the setting, you could activate checkwinsize in your ~/.bashrc.

To activate: shopt -s checkwinsize
To deactivate: shopt -u checkwinsize

Ubuntu – How to test UPSTART feature of ubuntu to see the script gets restarted automatically if it gets killed

Just run:

sudo status testing

that gives you the status of the running upstart service.

And with tail -f /var/log/syslog you can see if it is respawning.

The "Hello World" goes is I think going nowhere.

I recommend testing with:

#!/usr/bin/python
import time
import os

with open('/var/tmp/testing.log', 'a') as fp:
    try:
        while True:
            print >> fp, "Hello World", os.getpid()
            fp.flush()
            time.sleep(5)
    except Exception as e:
        print >> fp, 'exception', e
        fp.flush()
        raise

and run tail -f /var/tmp/testing.log in an other window.

Best Answer

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