How to make a program close it's currently running instance upon startup?

Question

I have a command line program which I'd like to keep running until I open it again, so basically a program which first checks if there's currently any already running instance of itself and kill it.

I tried os.system('TASKKILL /F /IM program.exe') but it turned out to be stupid because it also kills itself.

`taskkill` will make it depend on Windows platform so I suggest to use `psutils` library instead. — David Ferenczy Rogožan, Sep 20 '18 at 10:30
Or do you mean `program.exe` itself should check if there's any instance of it already running and kill it/them? — David Ferenczy Rogožan, Sep 20 '18 at 10:34
Please don't forget to mark any answer which solved your problem as an accepted. It'll help other people looking for a solution to find the answer. — David Ferenczy Rogožan, Sep 20 '18 at 11:09
@DawidFerenczy Look at my answer to myself... thanks for your solution though — Yaniv K., Sep 23 '18 at 06:43

Lie Ryan · Answer 1 · 2018-09-20T10:53:10.237

The most reliable way to make sure there's only one instance of your application is to create a pid file in a known (fixed) location. This location will usually be in your application data folder or in the temporary directory. At startup, you should check if the pid file exists and if the pid contained there still exists and refers to your target process. If it exists, send a kill signal to it, then overwrite the file with your current pid before starting the rest of the application.

For extra safetiness, you may want to wait until the previous process have completely terminated. This can be done by either waiting/polling to check if the process with that pid still exists, or by polling for the killed process to delete its own pid file. The latter may be necessary if process shutdown are very lengthy and you want to allow the current process to already start working while the old process is shutting down.

David Ferenczy Rogožan · Answer 2 · 2018-09-20T11:05:12.163

1

You can use the psutil library. It simply iterates through all running processes, filter processes with a specific filename and if they have a different PID than the current process, then it kills them. It will also run on any platform, considering you have a right process filename.

import psutil

process_to_kill = "program.exe"

# get PID of the current process
my_pid = os.getpid()

# iterate through all running processes
for p in psutil.process_iter():
    # if it's process we're looking for...
    if p.name() == process_to_kill:
        # and if the process has a different PID than the current process, kill it
        if not p.pid == my_pid:
            p.terminate()

If just the program filename is not unique enough, you may use the method Process.exe() instead which is returning the full path of the process image:

process_to_kill = "c:\some\path\program.exe"

for p in psutil.process_iter():
    if p.exe() == process_to_kill:
         # ...

edited Sep 20 '18 at 11:05

answered Sep 20 '18 at 10:39

David Ferenczy Rogožan

23,966
9
79
68

Be careful if you are using p.name() to identify processes, as it may be possible for unrelated processes to have the same name. It may be safer to use p.exe() to match the executable path instead. – Lie Ryan Sep 20 '18 at 11:01
Check my answer, I'm suggesting to use the `cmdline()` method. – David Ferenczy Rogožan Sep 20 '18 at 11:02
OK, the `exe` method looks more suitable, thanks for the suggestion! – David Ferenczy Rogožan Sep 20 '18 at 11:05

Yaniv K. · Accepted Answer · 2018-09-24T11:58:47.883

Because my working stations don't have access to internet and installing packages is a mess, I ended up coming up with this solution:

import os

os.system('tasklist > location/tasks.txt')
with open('location/tasks.txt', 'r') as pslist:
    for line in pslist:
        if line.startswith('python.exe'):
            if line.split()[1] != str(os.getpid()):
                os.system(f'TASKKILL /F /PID {line.split()[1]}')
                break
os.remove('location/tasks.txt')

It prints the output of the tasklist command to a file and then checks the file to see if there's a runnig python process with a different PID from it's own.

edit: Figured out I can do it with popen so it's shorter and there are no files involved:

import os

for line in os.popen('tasklist').readlines():
    if line.startswith('python.exe'):
        if line.split()[1] != str(os.getpid()):
            os.system(f'taskkill /F /PID {line.split()[1]}')
            break

But this way you'll kill any running Python interpreter, even if it's executing a different script. Maybe you're fine with it, you just should be aware of that. — David Ferenczy Rogožan, Sep 25 '18 at 10:25
Ye I know. I'm not expecting to run multiple scripts anytime soon but if in the future I'll want to, I'll just expose the PID of the first instance to a file and then check with that file. — Yaniv K., Sep 26 '18 at 11:24

score -1 · Answer 4 · answered Sep 20 '18 at 10:25

-1

You can use the process id of already running instance.

import os
os.system("taskkill /pid <ProcessID>")

answered Sep 20 '18 at 10:25

Dhnesh Dhingra

301
1
7

How to find it's PID? – Yaniv K. Sep 20 '18 at 10:29
you can use psutil to get pid by process name – Dhnesh Dhingra Sep 20 '18 at 10:52

How to make a program close it's currently running instance upon startup?

4 Answers4