Get output of cmd command in real time in Qt

Question

Im using this code in Qt to get output of a cmd commend

     QProcess c_output;
     c_output.start("some-exe", QStringList() << "param1" << "param2" << "param3...");
     if (!c_output.waitForStarted())
         std::cout << false;

     c_output.write("...");
     c_output.closeWriteChannel();

     if (!c_output.waitForFinished())
         std::cout << false;

its work just good.
with this code i can access output with c_output.readAll(), but problem is this code wait until cmd finish exec ... and then give all output in c_output.readAll(), i want to get output in realtime and show them in gui of my program
my mean is my commend print multiply lines after exec, i want to show all of them one by one in my program and not wait for it to finish.

like in another thread? – ΦXocę 웃 Пepeúpa ツ Sep 16 '20 at 17:34 — ΦXocę 웃 Пepeúpa ツ, Sep 16 '20 at 17:34
@ΦXocę웃Пepeúpaツ you talk about what thread? – sanab3343 Sep 16 '20 at 17:38 — sanab3343, Sep 16 '20 at 17:38

zgyarmati · Accepted Answer · 2020-09-16T17:58:43.717

2

You can use waitForReadyRead instead of the waitForFinished , see at https://doc.qt.io/qt-5/qprocess.html#waitForReadyRead

Here is a simple example with the usage:

#include <QCoreApplication>
#include <QFile>
#include <QTextStream>
#include <QProcess>
#include <QDebug>

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

    QCoreApplication app(argc, argv);
    QProcess c_output;
    c_output.setProcessChannelMode(QProcess::MergedChannels);
     c_output.start("dmesg", QStringList() << "-w");
     if (!c_output.waitForStarted()){
         qDebug() << "Failed to start";
        return -1;
     }

     c_output.write("...");
     c_output.closeWriteChannel();

     while (c_output.state() != QProcess::NotRunning)
     {
        qDebug() << ".";
        if (c_output.waitForReadyRead())
         qDebug() << "c_output" << c_output.readAllStandardOutput();
     }


    return app.exec();
}

edited Sep 16 '20 at 17:58

answered Sep 16 '20 at 17:42

zgyarmati

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after that how can i use c_output.readAll() to read the output? – sanab3343 Sep 16 '20 at 17:53
thanks for good example, can you please show example for showing in gui? i mean append output in exiting text – sanab3343 Sep 16 '20 at 18:33
1

I think this is out of scope for this question. See for example this SO answer: https://stackoverflow.com/questions/13559990/how-to-append-text-to-qplaintextedit-without-adding-newline-and-keep-scroll-at or state a separated question with your exact issue. – zgyarmati Sep 16 '20 at 18:35
a problem i found in your code is it show \r\n and its also some time merge line – sanab3343 Sep 16 '20 at 18:38
i think its because im in the window and i think its use \r\n for going to next line – sanab3343 Sep 16 '20 at 18:44
1

This also depends on the format of the output of the executable, so i can't guide you with a specific example, but you can try to use the combination of `canReadLine() ` and `readLine()` methods as well to get separated lines. – zgyarmati Sep 16 '20 at 18:48

Get output of cmd command in real time in Qt

1 Answers1