Getting hold of a remote PID through Paramiko

By means of this article, I would like to share with you a little trick so as to obtain the PID of a remote process run through Paramiko. That is, figure for a moment that you launch an application on a remote system by using Paramiko, and you would like to kill that process after a certain timeout.

To be able to do that, you will have to grab the PID of that process after running it, and if you do not want to use "grep" or other kind of filters like this, the shell provides a curious mechanism which consists in executing that process in a new shell and afterwards, reading the PID of that process which has just been run.

Let's see an example.

import paramiko

if __name__ == "__main__":
    
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    ssh.connect("ubuntu-server.local", username="javi", password="xxxxxx")
    
    _, stdout, _ = ssh.exec_command("echo $$ ; exec python test.py")
    pid = stdout.readline()
    print "PID of the remote process: " + pid
    
    _, stdout, _ = ssh.exec_command("ps -eo pid,command | grep %s" % pid)
    print "Looking for the process:\n" + stdout.read()
    
    ssh.exec_command("kill -s SIGINT %s" % pid)
    ssh.close()

As you can see above, I am running on a remote server a straightforward script called test.py with the following lines.

while True:
    pass

Before executing the script through exec (replaces the current process image with a new one), I have put the order "echo $$", and in this way, I will be able to dump the PID of that process. Finally, I am using that PID to search for that process by means of ps and kill it. Let's run the module.

$ python remote_pid.py 
PID of the remote process: 6020

Looking for the process:
 6020 python test.py
 6021 bash -c ps -eo pid,command | grep 6020 
 6023 grep 6020