How to close the subroutine of the program started by qprocess?

JonB

My program runs on Ubuntu

And so? As I & @Christian-Ehrlicher have said, you cannot use this to kill a "sub-sub-process". You don't know the PID of the process you want to kill.

Can you please take the time to address what @Christian-Ehrlicher wrote earlier:

Then fix A so it properly shuts down B

[Under Linux you could try using pkill to kill all B processes, but I really wouldn't recommend it....]

jiaming

I forgot to say that if A is opened in a terminal, B will also be closed when using Ctrl+C to close. What I am looking for is a method similar to sending a Ctrl+C signal.

JonB

@jiaming
Use Linux man 2 kill call: kill(pid_of_A, SIGINT). But I doubt it will work from here.

It's nice to see that you ignore every suggestion we make.... Best of luck.

jiaming

The main reason is that I didn't write A and B programs. They have formed a good system. It's troublesome for me to change them. It's better to have a simpler method.

I found that PPID of B is 1......

I'm sorry for the trouble.

jsulm

@jiaming said in How to close the subroutine of the program started by qprocess?:

I found that PPID of B is 1

You need PID if you want to kill it...

jsulm

@jiaming You could try to get PID from B using PID from A, see https://stackoverflow.com/questions/17743879/how-to-get-child-process-from-parent-process

JonB

@jiaming said in How to close the subroutine of the program started by qprocess?:

I found that PPID of B is 1......

Which is why I said I do not think that sending a SIGINT to the parent (A) will have any effect on B...!

A process ID value of 1 indicates that there is no parent process associated with the [...] process."

JoeCFD

@jiaming kill( m_process->pid(), SIGINT ); <==this does what you need. You need somehow to find the pid of B.
std::string pid_str = exec( "pidof B" ); exec is defined in the post above and "pidof" is a linux command to find process id.
if( !pid_str.empty() ) {
int pid = std::stoi( pid_str );
kill( pid, SIGINT );
}

JonB

@JoeCFD said in How to close the subroutine of the program started by qprocess?:

You need somehow to find the pid of B.

But he doesn't know the PID of B.

JoeCFD

Be aware that Control + C ( kill( pid, SIGINT ); ) may not kill your process all the time.
exec( "kill -9 pid" ) will be very clean.

Kent-Dorfman

Nothing original to add, but I recommend all participants in this thread read http://morningcoffee.io/killing-a-process-and-all-of-its-descendants.html as he does a fair job explaining the relationships in POSIX environments.

JoeCFD

@Kent-Dorfman thanks for sharing.