QProcess doesn´t emit finished() when done

SGaist

Hi,

Did you check the output of the QProcess::error method ?

You should also check the standard error and output content. That should give you more clues about what is happening.

LogiSch17

Hi,
i got

QObject::connect(copy, SIGNAL(errorOccurred(QProcess::ProcessError)), this, SLOT(errorFound(QProcess::ProcessError)));

copy is my Qprocess.
which was also never emmited. Is there any more error methods i could read?

This is how my code looks like.

header:

#ifndef UPDATE_HANDLER_H
#define UPDATE_HANDLER_H

#include <QtCore/QObject>
#include <QProcess>
#include <QFile>
#include <QStringList>
#include <QProcess>

class UpdateHandler : public QObject
{
    Q_OBJECT

    public:
        UpdateHandler(QObject* parent = nullptr);


    signals:
        void updateSuccess();
        void updateFailed();

    private slots:
        void fileSearch();
        void fileCopied(int);

    private:
        QFile* file;
        QFile* updEnc;
        QStringList cpscript;
        QProcess* copy;
        QString filename;
        QFile log;

};

#endif // UPDATE_HANDLER_H

UpdateHandler::UpdateHandler(QObject* parent)
    :QObject(parent)
{
    updEnc = new QFile("/media/upStick/update.enc");
    cpscript <<"/usr/bin/cpupdt.sh";
    file = new QFile("/usr/update.enc");
    copy  = new QProcess(this);
    QObject::connect(copy, SIGNAL(finished(int)), this, SLOT(fileCopied(int)));
    QObject::connect(copy, SIGNAL(errorOccurred(QProcess::ProcessError)), this, SLOT(errorFound(QProcess::ProcessError)));
}
void UpdateHandler::fileSearch(){
    if(updEnc->exists()){
        qDebug()<< "Updatefile found on Stick";
        qDebug()<< "copying file to /usr";
        copy->start("/bin/sh", cpscript);
        }else{
        qWarning()<< "no update found at UpdateStick/or no Stick insert";
        emit updateFailed();
    }
}
void UpdateHandler::fileCopied(int status){
    qWarning()<< copy->errorString();
    copy->close();
    if(status==0){
        if(file->exists())
        {
            qDebug()<< "sucess",
            emit updateSuccess();

        }else{
            qWarning()<< "no update.enc found in /usr";
            emit updateFailed();
        }
    }else{
        qWarning()<< "/usr/bin/cpupdt.sh crashed ";
        emit updateFailed();

    }
}
void UpdateHandler::errorFound(QProcess::ProcessError e){
    QString filename="/var/ziesel/update.txt";
    QFile log( filename);
    qDebug()<< "Error during Update: "<< e ;
    if ( log.open(QIODevice::WriteOnly | QIODevice::Append | QIODevice::Unbuffered | QIODevice::Text) )
    {
        QTextStream stream(&log);
        stream << "Error:" << e << endl;
        log.close();
    }
}

I know i have only finished(int) , instead of finished(int, QProcess::ExitStatus);
But i have qt 5.6 on my device and i wasn´t sure which to use, but i tried both.

LogiSch17

So for everyone who is interrested. I found what was causing the missbehavoir
I had a Qprocess in a constructer of a other class. Which makes the handshake for a CAN controller.
This here:

QProcess * canup;
canup = new QProcess(this);
QStringList args;
args << "can0" << "up";
canup->start("ifconfig", args);

When i comment this out everything works.
But i don´t know why this is happening.

SGaist

I guess it's not likely but does your copy script depends on the can bus interface to be up ?

ambershark

@LogiSch17 said in QProcess doesn´t emit finished() when done:

So for everyone who is interrested. I found what was causing the missbehavoir
I had a Qprocess in a constructer of a other class. Which makes the handshake for a CAN controller.
This here:

QProcess * canup;
canup = new QProcess(this);
QStringList args;
args << "can0" << "up";
can0->start("ifconfig", args);

When i comment this out everything works.
But i don´t know why this is happening.

That's interesting... Does your canup finish and get cleaned up properly before you are trying with the next QProcess? Just curious, it's not like you can't have multiple QProcesses at any given time.

Are these QProcesses in different threads?

Do you get the signals from the canup process properly?

LogiSch17

Hi, sry have been sick.

First, no the copy script doesm´t depend on the can bus interface.
And second:
For the can up , i have never tried to get the finished signal. But i tried
canup->wait ForFinished();
Which seems to work cause there is no delay during the can initialisation.
And yes the QProcesses are in different threads, or in different QObjects.

SGaist

So if you ensure can0 is finished before starting the next QProcess, everything is running fine ?

ambershark

@LogiSch17 So what if after you start your process you immediately do copy->waitForFinished(). Will that ever return?

LogiSch17

@SGaist No even if i wait i have the can0-> waitForFinished(), all the following QProcesses are not returning.
do i have to close something?

@ambershark I allready tried but, it stays for the default 30000msecs, but afterwards nothing has been returned.

SGaist

Did you check the content of the standard error and standard output of all your QProcess ? There might be a clue there to what is happening.

LogiSch17

yes i did. got nothing.
Currently i removed the ifconfig QProccess from my code and run it as script in init.d before running my programm.
Now everything works fine.
Look´s like QProccess has problems with the ifconfig command.

SGaist

Can you provide a minimal code sample that triggers that ?

LogiSch17

i got something like

    QStringList arguments;
    arguments << "can0" << "up";
    QProcess::execute("ifconfig",  arguments );

but i had it allready with finished() and errorOccured() signals conected to slots -> same result.
I would say my buildroot generated OS makes the problem.

SGaist

Really surprising. If you call any other command, do you have the same problem ?

LogiSch17

No never seen the problem before , and i have a lot of qproccess in my code. From shutdown , reboot, mv , cp to a lot of scripts .

SGaist

Is it only on your device or can you reproduce that on your desktop machine ?

LogiSch17

On my desktop machine it works fine. But i have no CAN device their.
So i returns that can0 device not exists and goes on normaly. But the the other proccesses are working afterwards.

SGaist

Since the can bus is a network device, did you try calling ifconfig up on another device ? That might help narrow down the problem.

LogiSch17

No didn´t tried yet. I have it fixed now by running a startup script . Which does exatly the same.
But i will have a look at this problem again when i have some more time. I will let you know if i find out something.

bisou

@LogiSch17 I had a similar problem in that no QProcess::finished() signals were being emitted. The problem was SOLVED by not catching the Unix signal SIGCHLD, which implies that this signal is being used by QProcess to communicate between parent and child processes. Maybe this was your problem too.