QProcess start, correct way to pass arguments with > piping to an output file.

jonndoe47

Trying to pipe output of an executable to a file. Code is:

	QString p = QString::fromStdString(param);
	QStringList arguments;
	arguments << p;

	proc->start(path, arguments);

The values of the vars at run time are:

+		p	-listxml > mame.dat	QString
+		param	"-listxml > mame.dat"	std::string
+		path	C:\mame\mame64.exe	QString

Now the weird thing.... The debug output:

>> Started ok
"Error: unknown option: -listxml > mame.dat\r\n"
>>>>> Exit Code: QProcess::NormalExit
Program ran successfully

Where did the "\r\n" come from ? And how do I actually pass a arg to an exe to tell it to pipe in QProcess? And yes, that command via dos works fine. Can 't use a batch file before you ask because this programme will be put up on github and free to use, including source, so that means the end user won't have a batch file there. Hmmm

Christian Ehrlicher

Piping is a bash feature. So either start a bash shell or read the data from stdout and write it to your second process.

JonB

@jonndoe47
As @Christian-Ehrlicher says, except that I doubt you'll have bash as you have a .exe so are probably under Windows :) It always helps to state OS when asking QProcess questions....

The shortest, dirtiest answer is you need to go

process->start("cmd", QStringList() << "/c" << "C:\\mame\\mame64.exe -listxml > mame.dat")

Nicer here would be to use QProcess::setStandardOutputFile on mame.dat which you have previously opened for output as a QFile yourself in caller. Then you can go back to running "C:\\mame\\mame64.exe" as the executable (and pass -listxml argument). But that's more lines of code (only a couple, you can do that can't you?).

jonndoe47

Done it all, i forgot > is part of command shell not program.... Doh! All ok now thank you all.