Using QProcess from a QTcpServer based class [SOLVED]

[xtingray]

Hi,
I am trying to use a QProcess object from a QTcpServer based class, but when I try to detect the moment a process is done, it seems the signal finished() never is called. Here is a little piece of the code I am using:

void InternetService::directoryContent(const QString &path)
{
    process = new QProcess(this);
    process->start("/bin/ls", QStringList() << path);
    connect(process, SIGNAL(finished(int, QProcess::ExitStatus)), 
    this, SLOT(printDirectoryContent(int, QProcess::ExitStatus)));
}

void InternetService::printDirectoryContent(int exitCode, QProcess::ExitStatus exitStatus)
{
    qDebug() << "Tracing this slot...";
}

Any suggestion about how to make it work? Thanks!

[mcosta]

Hi,

if there's some problem string the process QProcess emits the error() signal; you can connect a slot to it to understand what happens

[SGaist]

Hi,

To add to @mcosta, you should connect everything before calling start.

Also, you have a "memory leak" here, since every time you call directoryContent, you create new QProcess

[xtingray]

Thank you!
Using the error() signal I could trace the problem.

connect(process, SIGNAL(error(QProcess::ProcessError)), this, SLOT(processError(QProcess::ProcessError)));

But, now I have a new question: How can I capture the output of the process in an accurate way? I was trying to use the readLine() method but all I get is a NULL pointer exception:

        char *data = NULL;
        int size = process->readLine(data, 4);

Any suggestion? Any small example to understand how to do it correctly? Thanks.

[mcosta]

Hi,

if you need to read the standard output after the process finished, the simplest way is to use QProcess: readAllStandardOutput()

[xtingray]

It worked perfect! Thanks! :)

[Pablo J. Rogina]

Even when the issue seems [SOLVED], if you're using 'ls' as the actual process to run (and not just as a simple example of how to use the QProcess() class) I would like to suggest you please consider using QDir and QFileInfo to deal with directories and files in a portable and platform independant way. See example [1] which may benefit your application in the future.

[1] http://doc.qt.io/qt-5.4/qdir.html#details