stop python program when ssh pipe is broken

Question

I'm writing a python script with an infinite while loop that I am running over ssh. I would like the script to terminate when someone kills ssh. For example:

The script (script.py):

while True:
    # do something

Will be run as:

ssh foo ./script.py

When I kill the ssh process, I would like the script on the other end to stop running.

I have tried looking for a closed stdout:

while not sys.stdout.closed:
    # do something

but this didn't work.

How do I achieve this?

Edit:

The remote machine is a Mac which opens the program in a csh:

502 29352 ??         0:00.01 tcsh -c python test.py
502 29354 ??         0:00.04 python test.py

I'm opening the ssh process from a python script like so:

p = Popen(['ssh','foo','./script.py'],stdout=PIPE)

while True:
    line = p.stdout.readline()
    # etc

EDIT

Proposed Solutions:

1. Run the script with while os.getppid() != 1

This seems to work on Linux systems, but does not work when the remote machine is running OSX. The problem is that the command is launched in a csh (see above) and so the csh has its parent process id set to 1, but not the script.

1. Periodically log to stderr

This works, but the script is also run locally, and I don't want to print a heartbeat to stderr.

1. Run the script in a pseduo tty with ssh -tt.

This does work, but has some weird consequences. Consider the following:

remote_script:

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

while True:
    print time.time()
    sys.stdout.flush()
    time.sleep(1)

local_script:

#!/usr/bin/env python
from subprocess import Popen, PIPE
import time

p = Popen(['ssh','-tt','user@foo','remote_script'],stdout=PIPE)

while True:
    line = p.stdout.readline().strip()
    if line:
        print line
    else:
        break
    time.sleep(10)

First of all, the output is really weird, it seems to keep adding tabs or something:

[user@local ~]$ local_script 
1393608642.7
            1393608643.71
                         1393608644.71
                                      Connection to foo closed.

Second of all, the program does not quit the first time it receives a SIGINT, i.e. I have to hit Ctrl-C twice in order to kill the local_script.

Answer 1

Have you tried

ssh -tt foo ./script.py

Answer 2

When the terminal connection is lost, the application is supposed to receive SIGHUP signal, so all you have to do is to register a special handler using signal module.

import signal
def MyHandler(self, signum, stackFrame):
    errorMessage = "I was stopped by %s" % signum
    raise Exception(errorMessage)

# somewhere in the beginning of the __main__:
# registering the handler
signal.signal(signal.SIGHUP, MyHandler)

Note that most likely you'll have to handle some other signals. You can do it in absolutely the same way.