Python check if another script is running and stop it

Question

I have several python scripts that turn my TV on and off. Sometimes the TV does not respond the first time so I use a while loop to continue sending the command until the "success" response is sent. Up to 10 times.

I need to check if one of these programs are running when any of them are started and kill the first process.

This answer uses domain locks and I think this could work but I dont really understand whats happening there: https://stackoverflow.com/a/7758075/2005444

What I dont know is what the process_name would be. The scripts are titles tvon.py, tvoff.py, and tvtoggle.py. Is it just the title? Would it include the extension? How do I get the pid so I can kill the process?

This is running on Ubuntu 14.04.1

EDIT: all I really need is to search for any of these running scripts first. Also, instead of killing the process maybe I could just wait for it to finish. I could just do a loop and break it if none of those processes are running.

The reason I need to do this is if the tv is off and the off script is run it will never succeed. The TV wont respond if it is already off. Which is why I built in the limit of 10 commands. It never really takes over 4 so 10 is overkill. The problem is if the off command is trying to run and I turn the TV on using the tvon script the TV will turn on and back off. Although the TV limits how often commands can be accepted, which reduces the chance of this happening I still want the to be as cleanly working as possible.

EDIT: I found that I can not kill the process because it can lock the tty port up which requires a manual restart. So I think the smarter way is to have the second process wait until the first is done. Or find a way to tell the first process to stop at a specific point in the loop so I know its not transmitting.

Answer 1

If you have a socket, use it. Sockets provide full-blown bidirectional communication. Just write your script to kill itself if it receives anything on the socket. This can be most easily done by creating a separate thread which tries to do a socket.recv() (for SOCK_DGRAM ) or socket.accept() (for SOCK_STREAM / SOCK_SEQPACKET ), and then calls sys.exit() once that succeeds.

You can then use socket.send() ( SOCK_DGRAM ) or socket.connect() ( SOCK_STREAM / SOCK_SEQPACKET ) from the second script instance to ask the first instance to exit.

Answer 2

This function can kill a python script by name on *nix systems. It looks through a list of running processes, finds the PID of the one associated with your script, and issues a kill command.

import subprocess
def killScript(scriptName):
        # get running processes with the ps aux command
        res = subprocess.check_output(["ps","aux"], stderr=subprocess.STDOUT)

        for line in res.split("\n"):
                # if one of the lines lists our process
                if line.find(scriptName) != -1:
                        info = []

                        # split the information into info[]
                        for part in line.split(" "):
                                if part.strip() != "":
                                        info.append(part)

                        # the PID is in the second slot
                        PID = info[1]

                        #kill the PID
                        subprocess.check_output(["kill",PID], stderr=subprocess.STDOUT)

At the beginning of your tv script you could run something like:

killList = ["tvon.py", "tvoff.py", "tvtoggle.py"]
for script in killList:
        killScript(script)