How to redirect stdout/etc of detached QProcess
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wrote on 8 Mar 2021, 04:28 last edited by
out of curiosity, do you connect the file descriptor signals BEFORE starting the process?
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@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
How can I properly redirect this?
Don't start the process as detached...
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Hey
I think I've tried everything but still no luck.
I start my app as
QProcess *s = new QProcess() s->setProgram("Path") s->setArguments({"-arg=lala"} s->setProcessChannelMode(QProcess::ForwardedChannels); s->startDetached()and I connect signals to >
readyReadStandardError readyReadStandardOutputBut no matter which setProcessChannelMode I pick, everything always goes in to my main application std out and not my functions/signal/slots. How can I properly redirect this?
TIA!
wrote on 8 Mar 2021, 08:37 last edited by JonB 3 Aug 2021, 08:44@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
s->startDetached()
You are choosing to use bool QProcess::startDetached(qint64 *pid = nullptr). As a result
s->setProcessChannelMode(QProcess::ForwardedChannels);has no effect, and the signals will not be raised. The documentation page covers this.By far the easiest thing you can do is not use
startDetached(), as @Christian-Ehrlicher says, and usestart()instead. Why do you need to usestartDetached()? "Detached" means detached from the calling process so that it is not the child process's parent, and hence cannot access stiff like child's stdout/stderr, yet that seems to be exactly what you do want to access.... -
wrote on 8 Mar 2021, 09:03 last edited by
Hey
Yeh found it few hours latter. I ended up spawning QThread and running the process in that thread & spawning as ->start() instead. The startDetaching make sense, kinda wish id had more "backend" logic to handle streams/etc. I cant even disable stdout stream using the detached mode.
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@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I cant even disable stdout stream using the detached mode.
That's why it's called 'detached' ...
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Hey
Yeh found it few hours latter. I ended up spawning QThread and running the process in that thread & spawning as ->start() instead. The startDetaching make sense, kinda wish id had more "backend" logic to handle streams/etc. I cant even disable stdout stream using the detached mode.
wrote on 8 Mar 2021, 09:20 last edited by@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I ended up spawning QThread and running the process in that thread & spawning as ->start() instead.
That sounds quite wrong. There is no need for any thread here,
QProcess::start()and all the signals are asynchronous, what do you want any thread for?? -
@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I ended up spawning QThread and running the process in that thread & spawning as ->start() instead.
That sounds quite wrong. There is no need for any thread here,
QProcess::start()and all the signals are asynchronous, what do you want any thread for??wrote on 8 Mar 2021, 12:22 last edited by@JonB said in How to Re-dirrect stdout/etc of Detached QProcess:
@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I ended up spawning QThread and running the process in that thread & spawning as ->start() instead.
That sounds quite wrong. There is no need for any thread here,
QProcess::start()and all the signals are asynchronous, what do you want any thread for??I don't want to block the main thread.
I want to run the app and then manage it from my GUI while it runs. -
@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I don't want to block the main thread.
QProcess is async as @JonB already said so why do you block the main thread when you run a QProcess there?
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@JonB said in How to Re-dirrect stdout/etc of Detached QProcess:
@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I ended up spawning QThread and running the process in that thread & spawning as ->start() instead.
That sounds quite wrong. There is no need for any thread here,
QProcess::start()and all the signals are asynchronous, what do you want any thread for??I don't want to block the main thread.
I want to run the app and then manage it from my GUI while it runs.wrote on 8 Mar 2021, 12:57 last edited by JonB 3 Aug 2021, 12:58@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I don't want to block the main thread.
And? I know that. Like I said,
QProcess::start/startDetached()do not block anything. As I wrote, they are already asynchronous, and there is no need for any threading of your own. -
@Dariusz said in How to Re-dirrect stdout/etc of Detached QProcess:
I don't want to block the main thread.
And? I know that. Like I said,
QProcess::start/startDetached()do not block anything. As I wrote, they are already asynchronous, and there is no need for any threading of your own.
11/11