[SOLVED] Problem with cmd process

Cimmy

First of all, sorry for my bad english.
I have a .exe called "rtosim_ik_from_file" which want 3 arguments (model, tracing and taskset) and i run this from the cmd.exe with this command "rtosim_ik_from_file --model OpenSim_Example_3/arm8mark32scaled.osim --trc OpenSim_Example_3/irio/os_irio_11042019.trc --task-set OpenSim_Example_3/irio/ik_taskset.xml -v". Then, it shows a 3d simulation of inverse kinematics.

Now, i'm building a script which shows a windows with 4 lines: general directory, model's directory, tracing's directory and taskset's directory. By clicking a button, the script has to run the .exe:

void MainWindow::on_submitpath_clicked()
{
QString directory = ui->linepath->text() ;
QString model = ui->linemodel->text();
QString tracing = ui->linetracing->text();
QString taskset = ui->linetaskset->text();
QString sndstring="rtosim_ik_from_file --model ";
sndstring.append(model);
sndstring.append(" --trc ");
sndstring.append(tracing);
sndstring.append(" --task-set ");
sndstring.append(taskset);
sndstring.append(" -v");
QStringList params = QStringList() << "/k"<< sndstring;
qDebug()<<params;
QString command = "C:/Windows/System32/cmd.exe";
QProcess process;
process.setWorkingDirectory(directory);
process.start(command, params);
process.waitForFinished(-1);
}

But the window freezes and it doesn't work. Any suggestions?
Thank you in advance.

artwaw

Hi.
You are running the cmd. Your exe that does the work is just a parameter - my guess would be that exe has done the job but cmd is still running. Can you verify this?

Cimmy

Right.
Usually, i run cmd.exe, i set another directory ("cd C:\OpenSimLib\rtosim_install\bin") and i write that command "rtosim_ik_from_file --model OpenSim_Example_3/arm8mark32scaled.osim --trc OpenSim_Example_3/irio/os_irio_11042019.trc --task-set OpenSim_Example_3/irio/ik_taskset.xml -v". And it works.

Now i want to do this thing with a qt process. How?

artwaw

@Cimmy On Windows .cmd files are run by the system using command line. I'd suggest creating temporary file (.bat, .cmd, whatever works for you really) and starting that directly.
On a separate note: have you tried to run that .exe directly? It's been a while since I used command line on Windows, but don't it recognize the .exe format and runs it in cmd as it is?

artwaw

@Cimmy Also, parameters there seem to be two spaces distant, not one. Not sure if that is an issue but have you tried to copy/paste the debug formatted list to check if it works?

jsulm

@Cimmy said in Problem with cmd process:

process.waitForFinished(-1);

Why do you wait for it to finish? This is why your app freezes.
Simply add QProcess member to your class and use it to execute the process without waiting.

Cimmy

First try: use cmd, use rtosim_ik_from_file.exe as parameters. Message "destroyed while process is still running" and nothing happen

Second try: run directly rtosim_ik_from_file.exe with parameters (model, trc ect) but nothing happen. NO "destroyed while [...]" message.

Any other suggestions?
Don't know how to create a batch file. I will try...

mrjj

Hi
-Don't know how to create a batch file. I will try...
Its just a text file and then you rename it to filename.bat and then its a bat file.

Regarding the code.
You are using the parameters in an odd way since you add to a string and then add to that string to the param list.
Normally you would do like

 QString program = "./path/to/Qt/examples/widgets/analogclock";
 QStringList arguments;
 arguments << "-style" << "fusion";

so each param and value are differnt indexs in the list.
In your sample, it seems to be one big string

Cimmy

I'm trying to create a batch file. How can i set the path of this file?

mrjj

@Cimmy
Hi Do you mean by the path ?
You can place it the same place as the .exe if you wish.

Cimmy

void MainWindow::on_submitpath_clicked()
{
QString directory = ui->linepath->text() ;
QString model = ui->linemodel->text();
QString tracing = ui->linetracing->text();
QString taskset = ui->linetaskset->text();
QString sndstring="rtosim_ik_from_file --model ";
sndstring.append(model);
sndstring.append(" --trc ");
sndstring.append(tracing);
sndstring.append(" --task-set ");
sndstring.append(taskset);
sndstring.append(" -v");
QString filenew = directory;
filenew.append("/Filenew.bat");
QFile file(filenew);
if ( file.open(QIODevice::ReadWrite) )
{
QTextStream stream(&file);
stream << sndstring <<endl;
}
QStringList arguments;
arguments << "/c" << "Filenew.bat";
QProcess *exec = new QProcess();
exec->setWorkingDirectory(directory);
exec->start("cmd.exe", arguments);
}

SOLVED!! Thanks to all!!

jsulm

@Cimmy You're creating local QProcess instance on the stack! It is deleted when the slot finishes!
I wrote before: "Simply add QProcess member to your class".

jsulm

@Cimmy said in Problem with cmd process:

SOLVED!! Thanks to all!!

Not really - you leak memory (exec is never deleted). As I wrote already add exec to your class as member, or pointer to QProcess to be able to delete it when you're done.

Cimmy

QProcess exec;
exec.setWorkingDirectory(directory);
exec.start("cmd.exe",arguments);

right?

JonB

@Cimmy
You need to make the

QProcess exec;

a member of your class (MainWindow), not a local variable in function on_submitpath_clicked.

jsulm

@Cimmy said in Problem with cmd process:

right?

wrong. Then you will again have same issue: QProcess going out of scope and deleted.
I write it now for the third time: "I wrote before: "Simply add QProcess member to your class"." (as @JonB suggested also).

JonB

@Cimmy
If you are interested (as I am!) as to why you have things this way. Here is what @jsulm has been telling you:

The issue is the QProcess destructor:

Destructs the QProcess object, i.e., killing the process.

Note that this function will not return until the process is terminated.

So if a QProcess gets destructed it will kill the process if it's still running. The problem is your code is only going to start() the sub-process running. It can/will continue running for a while. If your code were waiting for it to finish (e.g. QProcess::execute() or QProcess::waitForFinished()), there wouldn't be a problem, after that you could allow the QProcess to get destroyed.

If your QProcess is a local variable on the stack in a function like you propose, as soon as the function exits (variable goes "out of scope") the destructor would get called. So you can either:

Move QProcess exec variable to a member of your class, not destructed till class instance destructed; or
Use QProcess *exec = new QProcess(), allocated on the heap. Not destructed till delete exec. But then you need somewhere to save that pointer so that you can later delete it, no use as a local variable, so equally needs moving to class scope.

@jsulm
I have musing over this. If you want simple to start a sub-process and "forget" about it (yes, I know about "zombie" processes), this ~QProcess() behaviour is a bit problematic. I don't think startDetached() in itself would help here, it doesn't say that the destructor will not kill the process in this case:

If the calling process exits, the detached process will continue to run unaffected.

Yes, but if ~QProcess() called on exit it will still kill it, unless the docs are a bit vague here. Perhaps actually it does not? I wonder if QProcess() could do with a setNoKillOrWaitOnDestruct() flag, if startDetached() does not do that?

So.... I guess in this case the only safe thing to do would be to go new QProcess and deliberately not delete on exit? C++ doesn't go through everything you've newed and delete prior to exit, does it?! So accept that your program "leaks" prior to exit (e.g. a memory checker) and put up with it?

jsulm

@JonB "If the calling process exits, the detached process will continue to run unaffected." - https://doc.qt.io/qt-5/qprocess.html#startDetached
So, the QProcess destructor will not terminate the detached process as it is detached.
"this ~QProcess() behaviour is a bit problematic" - in what way? If you use startDetached() then the destructor doesn't matter. If you use exec() then I don't see why ~QProcess() terminating process is a problem? At the end it's your job as developer to select the right approach.

JonB

@jsulm

"If the calling process exits, the detached process will continue to run unaffected."

That describes what happens if the calling process exits. It does not state it countermands what I quoted from ~QProcess(), which states it kills & waits. The question (my question) is what happens, which "wins", if you do not use new but have a "global" scoped QProcess globProc variable (not *globProc), initiate glocProc.startDetached(), and then exit your program. To me the docs are unclear....

Can I try this myself? No, because I'm stinky Python, and there are no variables, only heap pointers....

jsulm

@JonB And there are static methods in QProcess to execute a process without even creating a QProcess instance.

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[SOLVED] Problem with cmd process