How to get output system command in Qt C++?

[tadamo]

Hello,

I have a "test.exe" that I can use from the command line with the DOS console from Windows 10.
Example:
test.exe blue

returns a return code of 1
Otherwise, it returns 0.

I would like to use this "test.exe" by using command line in C ++ Qt and get the output from this command line, but I searched on the internet and I can't find any simple code for it.
For example, I found:

QProcess process;
process.start("test.exe blue");
process.waitForFinished(-1); // will wait forever until finished

QString stdout = process.readAllStandardOutput();
QString stderr = process.readAllStandardError();

But the last two lines are bad and don't work.

Do you have a good example to use command line in C++ Qt and get the value of this command line, please?

Thanks.

[SGaist]

Hi and welcome to devnet,

You should add error checking. The application you are calling with QProcess may have not started properly or triggered an error.

[tadamo]

Can you show me an example of code, please?

[Christian Ehrlicher]

@tadamo said in How to get output system command in Qt C++?:

Can you show me an example of code, please?

It's all in the doc: https://doc.qt.io/qt-5/qprocess.html#details

And if you want the return code you should take a look at QProcess::exitCode()

[tadamo]

Thanks, but I can't get the value of exitcode. Here is my code:

QString program = "test\\test.exe";
QStringList arguments;
arguments << "blue";

QProcess *myProcess = new QProcess(this);
myProcess->start(program, arguments);
int res = myProcess->exitCode();

I retrieve each time 0 in the varaible res whereas it should be 1.
Could you fix my code please?

Thanks.

[Bonnie]

@tadamo
You need to get the exit code AFTER the process finished.

Asynchronous (non-blocking) way:

QProcess *myProcess = new QProcess(this);
connect(myProcess, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), this,
     [=](int exitCode, QProcess::ExitStatus exitStatus){
    //use exitCode here directly
});
myProcess->start(program, arguments);

Synchronous (blocking) way:

myProcess->start(program, arguments);
myProcess->waitForFinished();
int res = myProcess->exitCode();

Note: you may also need to handle FailedToStart error when "start" or timeout when "waitForFinished"