[SOLVED] Problem with cmd process
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@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. -
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... -
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 likeQString 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 -
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!!
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@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.
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@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). -
@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 tostart()
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()
orQProcess::waitForFinished()
), there wouldn't be a problem, after that you could allow theQProcess
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 tilldelete 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 thinkstartDetached()
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 ifQProcess()
could do with asetNoKillOrWaitOnDestruct()
flag, ifstartDetached()
does not do that?So.... I guess in this case the only safe thing to do would be to go
new QProcess
and deliberately notdelete
on exit? C++ doesn't go through everything you'venew
ed anddelete
prior to exit, does it?! So accept that your program "leaks" prior to exit (e.g. a memory checker) and put up with it? -
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@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. -
"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 usenew
but have a "global" scopedQProcess globProc
variable (not*globProc
), initiateglocProc.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....
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@JonB said in Problem with cmd process:
That describes what happens if the calling process exits
Yes, and if an application exits ~QProcess() will be called (at least if it exits normally)...
It's the whole point of startDetached() - it detaches the QProcess instance from the started process. Just try. -
@jsulm
Ah!! (And you don't think those create an instance internally?). OK, so if I usestatic QProcess::startDetached()
that really should not call~QProcess
, even on program exit?It's the whole point of startDetached() - it detaches the QProcess instance from the started process.
Just because a process is detached that does not mean you cannot wait on or kill it, does it? It just means things like it's in its own session.
But it should not matter as the process is detached and the destructor should NOT terminate it.
OK, but I don't get that from the docs! Maybe we read them differently. I'm also having a deeper think about C++
static
, too long now of having to do Python... :(Time for me to have a play....
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@JonB said in Problem with cmd process:
And you don't think those create an instance internally?
I don't know. But it should not matter as the process is detached and the destructor should NOT terminate it.
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@jsulm
Just to confirm your interpretation.From Python/PySide2, from a terminal if I run an interactive
python3
and do>>> from PySide2.QtCore import QProcess >>> p = QProcess(); p.start("./script")
and then exit the python session (python will auto-delete everything created), I get a message
QProcess: Destroyed while process ("./script") is still running.
But if I use
>>> p = QProcess(); p.startDetached("./script") # or >>> QProcess.startDetached("./script")
no message, and I continue to see
./script
's output after the python session has exited.