QProcess / system call not working under linux. Why?

[jacek]

Try:

System_Call.start("dcmodify -m ...");
if( System_Call.waitForStarted() == false ) {
   std::cerr << "error" << std::endl;
}
else {
   System_Call.waitForFinished();
   QByteArray X = System_Call.readAllStandardOutput();
   std::cerr << X.constData() << std::endl;
}

System_Call.start("dcmodify -m ...");
if( System_Call.waitForStarted() == false ) {
   std::cerr << "error" << std::endl;
}
else {
   System_Call.waitForFinished();
   QByteArray X = System_Call.readAllStandardOutput();
   std::cerr << X.constData() << std::endl;
}

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[johnny_sparx]

I tried it, but got nothing on the console....
I still seem to get no results when I try to hard code even a single file (known to exist)... I tried startDetached and this seems to give *something* on the console... so it is a good start. Oddly enough, under linux, this does work for another section of code:

QString AcquisitionBrowserWidget::Get_DICOM_Information(QString File_Name, QString Key_String_Value)
{
    // Call 'dcmdump' from the DCMTK 3.5.4 toolkit (already in path), retrieve the result
    // from 'stdout'.  Do a search for the specified key using a regular expression.
    QDir Directory(Target_File_Path);
    QFileInfoList Files;
    QProcess System_Call(this);
 
    // Create the parameter list for the external call.  Check operating system.
    QStringList Parameters;
    #ifdef Q_WS_WIN
    Parameters<<("\""+Target_File_Path+"\\"+File_Name+"\"");
    #else
    Parameters<<(Target_File_Path+"/"+File_Name);
    #endif
 
    // Make the system call.  Wait until execution is complete, then retrieve 'stdout' in a buffer.
    System_Call.start("dcmdump",Parameters);
    QString Standard_Output_Buffer;
    System_Call.waitForFinished();
    Standard_Output_Buffer = System_Call.readAllStandardOutput();
 
    // Search the buffer for the key in the correct format.  The key is assumed to be UNIQUE.
    QString RegExp = "([(]"+Key_String_Value+"[)])( [A-Z]{2} )([[])([ \\w,.:-]*)([]])";
    QRegExp Key_Pattern(RegExp);
    if(Key_Pattern.indexIn(Standard_Output_Buffer,0)>-1)
        {
        // The key was found, return it from the fourth regular expression grouping.
        //(*Output)<<Key_Pattern.cap(4)<<endl;
        return Key_Pattern.cap(4);
        }
    else
        {
        // The key was not found.
        //(*Output)<<RegExp<<endl; // Keep the fourth regular expression grouping.
        return KEY_NOT_FOUND;
        }
}

QString AcquisitionBrowserWidget::Get_DICOM_Information(QString File_Name, QString Key_String_Value)
{
    // Call 'dcmdump' from the DCMTK 3.5.4 toolkit (already in path), retrieve the result
    // from 'stdout'.  Do a search for the specified key using a regular expression.
    QDir Directory(Target_File_Path);
    QFileInfoList Files;
    QProcess System_Call(this);

    // Create the parameter list for the external call.  Check operating system.
    QStringList Parameters;
    #ifdef Q_WS_WIN
    Parameters<<("\""+Target_File_Path+"\\"+File_Name+"\"");
    #else
    Parameters<<(Target_File_Path+"/"+File_Name);
    #endif

    // Make the system call.  Wait until execution is complete, then retrieve 'stdout' in a buffer.
    System_Call.start("dcmdump",Parameters);
    QString Standard_Output_Buffer;
    System_Call.waitForFinished();
    Standard_Output_Buffer = System_Call.readAllStandardOutput();

    // Search the buffer for the key in the correct format.  The key is assumed to be UNIQUE.
    QString RegExp = "([(]"+Key_String_Value+"[)])( [A-Z]{2} )([[])([ \\w,.:-]*)([]])";
    QRegExp Key_Pattern(RegExp);
    if(Key_Pattern.indexIn(Standard_Output_Buffer,0)>-1)
        {
        // The key was found, return it from the fourth regular expression grouping.
        //(*Output)<<Key_Pattern.cap(4)<<endl;
        return Key_Pattern.cap(4);
        }
    else
        {
        // The key was not found.
        //(*Output)<<RegExp<<endl; // Keep the fourth regular expression grouping.
        return KEY_NOT_FOUND;
        }
}

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Is voodo at work here? This is curious, and given the timing of this problem and my work deadline on monday... I am suspecting that dark forces are at work. This problem is very odd.

[jacek]

Does "std::cerr << "something" << std::endl;" writes something on the console?

[johnny_sparx]

Yes it does.

For a single file, no wildcard, when I use start() I get the following output to the console (there are multiple calls to this section of code):

roetgen 102% something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.

roetgen 102% something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.

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With startDetached(), I get this:

roetgen 104% something
something
something
something
 
something
 
 
Tsomething
 
 
There were 0 error(s)
 
 
There were 0 error(s)
here were 0 error(s)
 
There were 0 error(s)
 
 
 
 
error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/dicom-0000-muehlboeck_sebastien_20051126.085338_1_1.dcm
 
There were 1 error(s)
There were 0 error(s)

roetgen 104% something
something
something
something

something


Tsomething


There were 0 error(s)


There were 0 error(s)
here were 0 error(s)

There were 0 error(s)




error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/dicom-0000-muehlboeck_sebastien_20051126.085338_1_1.dcm

There were 1 error(s)
There were 0 error(s)

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A race condition is expected since repeated calls are happening on the same file.

I suspect that Bojan may be on to something with the wildcards. If I insert the wildcard back and repeat the same experiment above, I get first (start()):

roetgen 111% something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.

roetgen 111% something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.
something
QProcess object destroyed while process is still running.

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...and then for startDetached(), I get:

roetgen 108% something
something
something
 
 
error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*
 
There were 1 error(s)
something
something
something
 
 
error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*
 
There were 1 error(s)
 
 
error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*
 
There were 1 error(s)
 
 
error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*
 
There were 1 error(s)
 
 
 
error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*
 
There were 1 error(s)
 
error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*
 
There were 1 error(s)

roetgen 108% something
something
something


error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*

There were 1 error(s)
something
something
something


error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*

There were 1 error(s)


error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*

There were 1 error(s)


error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*

There were 1 error(s)



error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*

There were 1 error(s)

error: unable to load file /export/data/jsalik/DICOM_DB/PENDING/SEBASTIAN_HEAD_4/*.*

There were 1 error(s)

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The solution here has much to do with the way the operating systems deal with external processes and how they process wildcards as parameters. Does this sound reasonable?

JS

[jacek]

QProcess object destroyed while process is still running.

Maybe QProcess::waitForFinished() timeout is too small? What does QProcess::error() return?

The solution here has much to do with the way the operating systems deal with external processes and how they process wildcards as parameters. Does this sound reasonable?

Yes, under Unices wildcards won't be processed.