python subprocess.Popen and ssh port forwarding in

Question

I need to have functionality that would essentially emulate user creating a port forwrding with ssh. So, essentially that should work like that: - execute ssh -f -N -L 10000:gateway:11000 localhost - if there is an output from that command, show to the user and pump user's input as a response - finish The code I came up with below, almost does what I need:

    ssh_proc = Popen(['ssh', '-f', '-N', '-L', '10000:gateway:11000', 'localhost'], stdin=PIPE, stdout=PIPE)
stdoutdata, stderrdata = ssh_proc.communicate()

But the problem is it never finishes. I see the command is executed and forwarding tunnel is created but communicate() is still stuck. I can break out of that with Ctrl+C and get this:

    ^CTraceback (most recent call last):
  File "sshman.py", line 278, in <module>
    add(args.remote_host, args.remote_port, args.local_port, args.local_host)
  File "sshman.py", line 125, in add
    stdoutdata, stderrdata = ssh_proc.communicate()
  File "/usr/lib64/python2.7/subprocess.py", line 740, in communicate
    return self._communicate(input)
  File "/usr/lib64/python2.7/subprocess.py", line 1256, in _communicate
    stdout, stderr = self._communicate_with_poll(input)
  File "/usr/lib64/python2.7/subprocess.py", line 1310, in _communicate_with_poll
    ready = poller.poll()
KeyboardInterrupt

Since i use -f with ssh command, it should fork the connection. Is there a way to interrupt communicate() when it is done or is there more elegant solution?

Thank you in advance for any advices/suggestions/comments.

Answer 1

I guess the solution was pretty easy

ssh_proc = Popen(['ssh', '-f', '-N', '-L', '10000:gateway:11000', 'localhost'], stdin=PIPE, stdout=PIPE)
stat = ssh_proc.poll()
while stat == None:
    stat = ssh_proc.poll()