Writing commands on linux terminal using Qt

Question

I'm trying to get Qt creator to print a user input by using a push button on an UI into the terminal. As of now, the code is executable on the terminal via human input. Here is the code:

  void MainWindow::on_pushButton_clicked()
{
    QProcess::execute("/catkin_ws/devel/lib/submodbus");

    system("cd catkin_ws/devel/lib/submodbus");
    system("./submodbus_node");

}

Current output when using the code

Output via human input

The versions i'm running on are: -Ubuntu 16.04 -QT Creator 3.5.1

change cd catkin_ws/devel/lib/submodbus to cd /full_path/of/catkin_ws/devel/lib/submodbus — eyllanesc
– eyllanesc, Commented Dec 10, 2018 at 3:03
remove system("cd catkin_ws/devel/lib/submodbus"); system("./submodbus_node"); and change QProcess::execute("/catkin_ws/devel/lib/submodbus"); to QProcess::execute("/full/path/of/catkin_ws/devel/lib/submodbus/submodbus_node"); — eyllanesc
– eyllanesc, Commented Dec 10, 2018 at 3:57
This exe file is for a robot operation and I am currently using the executable file named submodbus_node from here link but trying to open it directly from here does not do anything, i have to source its location and type ./submodbus node into the console to actually run this exe file. I have tried what you suggested above but there were no results — Avrem Tan
– Avrem Tan, Commented Dec 10, 2018 at 4:33
Are you trying to change the working directory first then execute the program? — JustWe
– JustWe, Commented Dec 10, 2018 at 5:00

JustWe · Accepted Answer · 2018-12-10 07:19:00Z

3

system can't change the current directory globally. but could use like this:

system("cd /catkin_ws/devel/lib/submodbus && ./submodbus_node");

or using QProcess::setProgram with QProcess::setWorkingDirectory

QProcess p;
p.setProgram("submodbus_node");
//p.setArguments(QStringList()<<args); // if you need
p.setWorkingDirectory("/catkin_ws/devel/lib/submodbus");
p.start();

or QDir::setCurrent

QDir::setCurrent("/catkin_ws/devel/lib/submodbus");
QProcess::startDetached("submodbus_node");

Test demo, create three files in the parent directory:

#include <QApplication>
#include <QProcess>
#include <QDir>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    system("cd ../ && touch test1.txt");

    QProcess p;
    p.setProgram("touch");
    p.setArguments(QStringList()<<"test2.txt");
    p.setWorkingDirectory("../");
    p.start();

    QDir::setCurrent("../");
    QProcess::startDetached("touch test3.txt");

    return a.exec();
}

edited Dec 10, 2018 at 7:19

answered Dec 10, 2018 at 5:07

JustWe

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15 Comments

Avrem Tan Over a year ago

Hi thanks for the reply, I tried your second method and found out that there is no member called setProgram in QProcess

JustWe Over a year ago

@AvremTan What's the Qt version? (not QtCreator). the second one requires Qt 5.1.

Avrem Tan Over a year ago

I'm running it on Qt version 5.5.1

JustWe Over a year ago

@AvremTan umm...that's weird. I am using the environment exactly same as you. What's the error message?

JustWe Over a year ago

@AvremTan Could you post the line where you invoke the function?

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