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

local_script:

#!/usr/bin/env python
from subprocess import Popen, PIPE
import timep = Popen(['ssh','-tt','user@foo','remote_script'],stdout=PIPE)while True:line = p.stdout.readline().strip()if line:print lineelse:breaktime.sleep(10)

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

[user@local ~]$ local_script 
1393608642.71393608643.711393608644.71Connection 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.

Okay, I have a solution for you

When the ssh connection closes, the parent process id will change from the pid of the ssh-deamon (the fork that handles your connection) to 1.

Thus the following solves your problem.

#!/usr/local/bin/pythonfrom time import sleep
import os#os.getppid() returns parent pid
while (os.getppid() != 1):sleep(1)pass

Can you confirm this is working in your end too :)

edit

I saw you update.

This is not tested, but to get this idea working on OSX, you may be able to detect if the process of the csh changes. The code below only illustrates an idea and has not been tested. That said i think it would work, but it would not be the most elegant solution. If a cross platform solution using signals could be found, it would be preferred.

def do_stuff():sleep(1)if sys.platform == 'darwin':tcsh_pid = os.getppid()sshfork_pid = psutil.Process(tcsh_pid).ppidwhile (sshfork_pid == psutil.Process(tcsh_pid).ppid)do_stuff()elif sys.platform == 'linux':while (os.getppid() != 1):sleep(1)
else:raise Exception("platform not supported")sys.exit(1)