Communicating with program for GUI input

[d_stranz]

if it is possible for QT to access a variable in a C++ program that is not included in the QTCreator IDE.

Do you have the source code to this C++ program? If you do, you might be able to adapt it so that it runs as part of a Qt GUI-based program. If not, the simplest option for you is probably to just read from the file after the external program has updated it.

[ghaas123]

The source code is a rather large project, I am unsure as to how to adapt it to a Qt GUI application as I did not write the external project, just the GUI. The way that the external program writes the output that I need to a text file is by redirecting the standard output to a file. Is there any QT Class and functions that you could point me towards that would allow me to read the standard output of the program into the QT GUI without changing the source code that is sending this output to a text file? Any help is greatly appreciated.

[d_stranz]

You might be able to run the external program in a QProcess and redirect its stdout into stdin of your Qt program. See QProcess::setProcessChannelMode()

Here's some code from a stackoverflow accepted answer to a similar question:

QProcess p;
p.start( /* whatever your command is, see the doc for param types */ );
p.waitForFinished(-1);
 
QString p_stdout = p.readAllStandardOutput();

QProcess p;
p.start( /* whatever your command is, see the doc for param types */ );
p.waitForFinished(-1);

QString p_stdout = p.readAllStandardOutput();

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This, however, blocks your Qt app while the external process is running. You could also connect slots to QProcess signals (finished(), readyReadStandardOutput) and not use waitForFinished. See this other stackoverflow answer.