open-nandra

For liqrf project we would like to add some gui so I start thinking about possibility to have controlled existing liqrf console appliaction via some nice gui (be honest not all users like command line ). In this how to I’ll try to show how easily use Qprocess class for this purpose.

For Qt development I’m using Qt Creator which is freely available and combine designer and editor to one complex program.

First simple program which print some data to standard output.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(void)
{
    unsigned i = 0;

    for ( ; ; ) {
        fprintf(stdout,"Value = %X\n", i++);
        fflush(stdout);
        sleep(2);
    }
    return 0;
}

For compiling use :

gcc -o test test.c

For reading stdout we use Qt signal readyStandardOutput() which is triggered when something is written to stdout.

In Qt Creator just create default Qt4 application.

Add to mainwindow.h:

private:
    Ui::MainWindowClass *ui;
    QProcess *process;

Methods and slot in mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QProcess>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent), ui(new Ui::MainWindowClass)
{
    ui->setupUi(this);
    process = new QProcess(this);
    process->setReadChannel(QProcess::StandardOutput);
    connect(process, SIGNAL(readyReadStandardOutput()), this, SLOT(updateOutput()));
    process->start("./test");

}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow :: updateOutput(void)
{
    QByteArray bytes = process->readAllStandardOutput();
    ui->textEdit->insertPlainText(bytes);
}

That’s all. When you run Qt application you should see all stdout in textEdit.
Complete project here:  ext_process.tar

Marek

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