Problems with QProcess
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Hi.
Sorry, if i doublepost this question, just point me to the solution, i didnt find any.So to my problem. I made a simple application in which the user can chose an ID for a IPTV(InternetTelevision) and then press a start button. This button should start a programm(it downloads the tv-stream) that run in a console and doesnt give it free. There are reasons that this programm occupies the console, so i use QProcess to detach this process so it doesnt bother me and let the GUI accessible. Now at some point when the user wants to change the channel, i have to kill the running process and start it with a different channel_id.
So now im strugling with the killing part. At the moment i create and start the new process in my void on_StartButton_clicked(); in my qmainwindow , but somehow i cant access it from the StopButton, to terminate it. Do i have to call and create the new process some other way oder do i need a different approach? Any suggestions would be helpful.PS: If its important, im using Qt 5.5 on win7.
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Hi and welcome to devnet,
Are you really required to kill the application ? Can't you send it a command ?
In any case, can you show the code you are using with QProcess ?
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I can, but i donk know if its going to be helpful. I try to describe what i am doing in words first, and when its not enough, ill post the code.
So the main task i want to achieve is grabing a videostream from the server and save it. I do it with WGET ( a commandline downloadmanager). I manage to do so by login to server, getting cookies, then asking for a streamlink i want to watch and grabbing it. The stream is a live-TV program. The stream can abruptly end and i have no means to pick it up where it ends. So what i do now i write something like
system("wget blablabla to file.ts.001");
system("wget blablabla to file.ts.002");
...so like 3-4 more times...
(this i do in my separate c++prog.exe and then starting this program in Qt on click)
Im starting WGET in a console-occupying manner so when the stream breaks, it automatically pick it up shortly after by going to ne next system() command. I watch the stream already while its being downloaded and the VLC-Player does play that without interruption and even allow me to to navigate throughout the stream even its separated in several files.Since the program is mainly for privat use, i thought this would be ok and i just need to start and kill this program as separated process by click in my QtGUI-App.
Now i actually wanted to write all i do in my c++prog.exe inside a Qt function(or class). For example i can start WGET in background from the commandline arguments. It spits out a processID that it have in windows and start as a separate process. Problem is, i dont know when the process is going to end, so i have to start another one to pick up stream. I could of course let my GUI-App asking windows frequently if processID of my wget is still running, but ithoughti just could start and stop the exe with a click in my app.
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@Maser
Hello,
QProcess::waitForFinished might be what you're after. Although I suggest capturing the stream directly from your Qt program instead of relying on an external program. Here's a simple example. -
@kshegunov
Hi.
See, my problem is, id have to make a thread and within the thread a new(oder several new) process for every calling of WGET. The thread would then be waiting for every WGET fo finish. But i need to kill the thread instantly, when im going to change the channel. Can i do that? QTread man says i can cancel a loop in a thread, and if there is no loop, it wont do nothing. -
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@kshegunov
Well, because i do need to kill the running WGET when i want to go to another channel. Actually that was my initial question, how i can start a detached process and then kill it instantly(or almost instantly) on click. -
@Maser
You use either QProcess::kill or QProcess::terminate, as for starting you do that by QProcess::start. When using QProcess processes by default are started as detached -
@kshegunov
"You use either QProcess::kill or QProcess::terminate"
Yes, i know. But i dont know how to get it running. Can you draft me an example how can i start a process by clicking on a StartButton and kill/terminate it on StopButton? -
@Maser
This should suffice, assuming your buttons are available as objects:QProcess * wget = new QProcess; wget->setProgram("wget"); QStringList arguments; arguments << "some argument you want to pass to wget" << "another argument" << ...; wget->setArguments(arguments); // Connect your stop button to stop the process QObject::connect(stopButton, SIGNAL(clicked()), wget, SLOT(terminate())); // Connect to clean up the QProcess instance when the process has finished QObject::connect(wget, SIGNAL(finished(int, QProcess::ExitStatus)), wget, SLOT(deleteLater())); // Start the process wget->start();
