Kill a process and its children

[deleted471]

@hbatalha Try Detach

[JonB]

@APM0X400
Why do you think that will help? Worth a try I guess, but I would not have thought so.

[SGaist]

@hbatalha beside the good points of @JonB, what exactly are you using to pilot ffmpeg ?

[hbatalha]

@JonB said in Kill a process and its children:

Why does it not exit normally after doing whatever it is you ask it to do?

It does exit normally after completing its task. But I want to give the user the option to cancel whatever it is doing any time. I can't stop ffmpeg with QProcess because it is a child process of the process QProcess

But you chose not to answer.

Sorry, I must have missed it. Yes I can go in the task manager and kill with no problem, that's what I have been doing.

@SGaist said in Kill a process and its children:

what exactly are you using to pilot ffmpeg ?

I am using yt-dlp which in turn uses ffmpeg to do some file conversions. Those conversion usually takes a long time, that's why I want to give the user the ability to cancel it anytime.

[jsulm]

@hbatalha What about https://doc.qt.io/qt-5/qprocess.html#kill ?

[SGaist]

If the QProcess::kill suggested by @jsulm does not work as expected (which I think should), then try sending the SIGINT signal to the process.

[JonB]

@hbatalha said in Kill a process and its children:

Yes I can go in the task manager and kill with no problem, that's what I have been doing

You can try @SGaist's attempt to send the parent process a SIGINT and hope that might interrupt its child, I don't know how that all works on Windows.

To get at the ffmpeg process to kill it: you should be able to use EnumProcesses function (psapi.h) to enumerate all running processes and look at their names, and kill the desired one. I came across https://social.msdn.microsoft.com/Forums/en-US/67331e20-a30b-417d-85e5-f9350fef908d/do-we-need-to-use-enumprocesses-and-enumprocessmodules-when-terminating-the-process-in-c?forum=vcgeneral or https://stackoverflow.com/questions/1916574/how-to-effectively-kill-a-process-in-c-win32 you might want to read through. Or Google windows enumprocesses kill process to get going.

[JoeCFD]

@JonB said in Kill a process and its children:

ffmpeg

https://stackoverflow.com/questions/9722624/how-to-stop-ffmpeg-remotely

[JoeCFD]

You send out ctrl + C to exit cleanly
kill( m_process->processId(), SIGINT );

[hbatalha]

I thank everyone's reply here, I was able to find a solution for windows by, as suggested in the replies, sending SIGNT signal to the parent process.

I found the solution in @JonB referenced SO post in this answer and translated it into Qt code:

QProcess::execute("taskkill", {"/pid", QString::number(process->processId()), "/t", "/f"});

I am yet to test the QProcess::kill behavior in Linux. It would be a bonus if someone who knows telling me.

[JoeCFD]

@hbatalha kill( m_process->processId(), SIGINT ); is same as Ctrl + C.
will work on both Windows and Linux. kill() is c code. You do not need taskkill pid on Windows and kill -9 pid on Linux.

[hbatalha]

@JoeCFD in which header will I find the kill function?

[JoeCFD]

@hbatalha #include <signal.h>

[hbatalha]

@JoeCFD said in Kill a process and its children:

@hbatalha #include <signal.h>

I am still getting undeclared identifier 'kill' error after including <signal.h>

[JoeCFD]

@hbatalha https://man7.org/linux/man-pages/man2/kill.2.html

[hbatalha]

@JoeCFD that's for linux, I was asking for MingW equivalent

[jeremy_k]

kill() is a posix API. It isn't part of standard C or C++.

[JoeCFD]

@hbatalha Sorry. My bad. It is not for Windows. I thought it is standard C code.
You may try kill -9 pid on MingW.

[hbatalha]

@JoeCFD what about taskkill that I am currently using?

[JoeCFD]

@hbatalha if it works, it should be ok. Ctrl+C is cleaner, I believe.

https://stackoverflow.com/questions/813086/can-i-send-a-ctrl-c-sigint-to-an-application-on-windows