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[Solved]QT widget doesnt work due to open a file in a QProcess

  • Hi all,
    i have here a nice problem.
    I wrote a small gui for starting a perlscript. This script prints out the stuff which is defined in my gui.After that i write a file with the variables and start thru a QProcess a perlscript to process the data.

    The problem is, that the perl script isnt working. If i comment out the open file, in the perlscript everything is ok.

    Thanks for some hints..


    Below see my files.

    void MainWindow::on_commandLinkButton_clicked()
    //input variables
    QString Variant = ui->inputVariant->text();
    QString Load = ui->inputLoad->text();

    //write file
    QFile inputfile("/fs1/PerlQt/QtCreator/test/variables.inp");|QFile::Truncate|QFile::Text);
    QTextStream str(&inputfile);
    QStringList list;
    list << Variant << Load ;
    foreach(const QString &s, list)
    str << s << endl;

    //start perlscript
    QProcess perl;
    QString p_stdout = perl.readAllStandardOutput(&#41;;
    QString p_stderr = perl.readAllStandardError();
    //output in textwindow


    sub print_var()
    print "Name \n\n"; #print name
    print "=> $files[0] \n"; #print the first entry in array files
    open incl, 'variables.inp' or die "Datei nicht gefunden $!"; # open the file variables.inp
    @files = <incl>; #read in file and fill a array @files
    close(incl); #close file
    print "agghagh \n\n"; #print stupid stuff
    print_var(); #print the stuff which is in sub print_var@

  • Hmm, Your code is almost unreadable! Place it in the code box please!!

  • Lifetime Qt Champion

    At first sight, you try to open a file with perl that is still opened by QFile (the data might be still in a buffer and not yet on the disk).

    What happens if you close inputFile before calling your perl script ?

  • tried and the same. no output.

  • Lifetime Qt Champion

    Just in case, did you saw that your inputFile is "/fs1/PerlQt/QtCreator/test/variables.inp" and your script is "./fs1/PerlQt/QtCreator/test/" <= There's a dot in front here.

  • Moderators

    By default QProcess is started with a working directory of the calling process. Since you have a relative path in your perl script it is looking for input file in the directory of your executable, not where the script file is. Use QProcess::setWorkingDirectory() to change that.

  • @SGaist: ./ is for start the script here. This is normal linux stuff, but thanks for the hint.
    @krzysztof: i catch stderr, so ishould get an error,file not found and the perlscript should print the first aggah and then i shold get errormessage, because the file is processed after the print command. Setting the file to an absolut path didnt work as well.

    but anyway thanks to u guys.
    Hope we will find the error, any others thoughts....

  • Moderators

    Ok, this might be stupid because I know little about linux and how QProcess behaves there, but maybe this would work?
    perl.start("perl ./fs1/PerlQt/QtCreator/test/");

  • as well no output.

  • Lifetime Qt Champion

    That's why i suggested you to double check the use of "./" since your inputFile path is an absolute path but your perl script path is relative. That might be the culprit.

  • Hi,

    i changed everything to absolute paths and started the perl with

    perl.start("perl /fs1/PerlQt/QtCreator/test/");

    Thats not the problem. there is still no output.

  • Lifetime Qt Champion

    Did you check the working directory of your perl script ?
    Besides that, make it print the content of the current directory, that might give your some clues

  • For all whoo are interessted in.
    The problem was the following code in perl, which wasnt correctly compiled due QT.

    @open incl, 'variables.inp' or die "Datei nicht gefunden $!"; # open the file variables.inp@

    This line open a file and if the file not exists the applikation die and print file not found.
    I found out, that without the booleen or die everything is ok and worked.

    Thanks for all your post and the help.


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