Directly executing a batch through clicked function in qt

Question

So I'm trying to have my "button" directly execute a Batch file, important here is that I don't want it to show me a dialogue and make me chose the path, which is the problem I'm having right now with the following code

  void MainWindow::on_pushButton_clicked()
    {

      QString filename=QFileDialog::getOpenFileName(
      this,
      tr("Open File"),
      "C://",
      "All files (*.*);;Text File (*.txt);;Music file (*.mp3)");
    }

I think this is probably really simple, but i can't get it, I'm not even learning c++ at the moment but my boss asked me to create something out of my scope (wants me to create a GUI for a batch file and have them interact) and I thought of this approach, which is just creating a GUI that executes it.

I've looked at this question: asked to execute an external program with Qt

but they don't talk about how the file path can directly be added into the code, or if I should even be using Qprocess and how, and if I can pass it through "clicked" function.

I'm really inexperienced, all of the code above I got with the help of the internet, but I really don't know how to program using c++ so could someone please be kind enough to show me how a file path can be added to the code, assuming it's in C:\Users\name_goes_here\Downloads

I'd really appreciate it :D

Answer 1

I'd recommend using QProcess for anything "execute external program" with Qt.

You could do it like this:

void MainWindow::on_pushButton_clicked()
{
    QProcess process;
    process.start("C:/Users/name_goes_here/Downloads/yourfile.bat");
    process.waitForFinished(); // Assuming that you do want to wait for it to finish before the code execution resumes
}

Note the "/" in the path. Only Windows uses the messed up "\" for path separation, which would require you to write "C:\\Users\\.." in any string in C++ as "\" needs to be escaped.
Luckily, Qt uses "/" as the universal separator and translates it to whatever the OS needs as required. So you should just use "/" whenever working with Qt.

This is from the Qt documentation:

Qt uses "/" as a universal directory separator in the same way that "/" is used as a path separator in URLs. If you always use "/" as a directory separator, Qt will translate your paths to conform to the underlying operating system.

And finally, if you don't know how to code in C++, shouldn't you be learning that first instead of trying to execute batch files from within a library as complex as Qt? Sounds like you're trying to do too many new things at once.

Answer 2

This is fairly simple merging your source and the one you linked:

void MainWindow::on_pushButton_clicked()
{
  QProcess::execute(
    QString::fromLatin1(
      "cmd.exe /c C:\\Users\\name_goes_here\\Downloads\\file.bat"));
}

Notes:

1. I used QProcess::execute() instead of QProcess::start() to make things even simpler.

2. To achieve execution of the batch file, I pass it to cmd32.exe as this is the interpreter which is responsible.

---

As MCVE testQProcessBatch.cc:

// Qt header:
#include <QtWidgets>

void on_pushButton_clicked()
{
#if 0 // WORKS:
  QProcess::execute(
    QString::fromUtf8("cmd.exe /c C:\\Users\\Scheff\\Downloads\\testBatch.bat"));
#else // WORKS AS WELL:
  QProcess::execute(
    QString::fromUtf8("C:\\Users\\Scheff\\Downloads\\testBatch.bat"));
#endif // 0
}

int main(int argc, char **argv)
{
  qDebug() << "Version:" << QT_VERSION_STR;
  // main application
  QApplication app(argc, argv);
  QMainWindow qWin;
  QPushButton qBtn(QString::fromLatin1("Start cmd"));
  qWin.setCentralWidget(&qBtn);
  qWin.show();
  QObject::connect(&qBtn, &QPushButton::clicked,
    &on_pushButton_clicked);
  // run application
  return app.exec();
}

and the test batch file testBatch.bat:

echo "This is testBatch.bat"
pause

Tested with VS2013 on Windows 10:

Answer 3

Thanks for contributing guys!

I tried using the QProcess method but I think I'm too inexperienced when it comes to figuring out problems associated with it (which I did face when using this method). the CMD route is probably good but I also thought it was too difficult and both of these methods didn't work for me.

Here's what I have now (thanks to Detonar and ymoreau) and and it seems to be doing the job, this might not be the most optimal approach, but it worked for me!

I included QDesktopServices and QUrl

void MainWindow::on_pushButton_clicked()
 {
      QString filename="C:\\Users\\Name_goes_here\\Downloads\\test.bat";(
      this);

      hide();  //optional

      QDesktopServices::openUrl(QUrl("file:///"+filename,QUrl::TolerantMode));
        }