run a sh shell while clicking button in QML with QT5.15.0

[mrjj]

@lxy12345 said in run a sh shell while clicking button in QML with QT5.15.0:

onReadyRead

Hi
Its also for other things.
" QProcess emits readyRead() when data is available on the current read channel. It also emits readyReadStandardOutput() when new standard output data is available"

https://doc.qt.io/qt-5/qprocess.html
in the Communicating via Channels section

[lxy12345]

@jsulm when I tried the code ,
Text {
id: text
}

Process{
    id: process
     onReadyRead: text.text = readAll();
}
Timer {
     interval: 10
     repeat: true
     triggeredOnStart: true
     running: true
     onTriggered: process.start("/bin/cat", [ "/proc/uptime" ]);
 }

it outputs:
QProcess::start: Process is already running
QProcess::start: Process is already running
QProcess::start: Process is already running
QProcess::start: Process is already running
QProcess::start: Process is already running
QProcess::start: Process is already running
QProcess::start: Process is already running
QProcess::start: Process is already running

I think that the shell here is just "cat /proc/uptime", it should output some numbers.
Maybe I should read and understand Qprocess class first?

[JonB]

@lxy12345
I don't know anything about QML, but

QProcess::start: Process is already running

means that you have a QProcess instance where you have set of a start() but it has not yet completed and you have not waited for it, and now you're trying to set off a new start(). You either need to wait for completion of the process instance, or you need to use a new instance of QProcess each time. As I say, i don't know QML how to do that, but that's the cause/reason.

[mrjj]

Hi
Since you set the timer to repeat, it will start a new QProcess each time and
10 ms might be too short. try raising it so the other Qprocess gets change to finished.

Timer {
interval: 10
repeat: true

[JonB]

@mrjj
Really it ought have a handler for "process finished" signal, to be robust. I don't know how you do that from QML.

OP might have a go at the naughty:

     onTriggered: process.start("/bin/cat", [ "/proc/uptime" ]); process.waitForFinished();

with all the caveats. I don't know if that would work simpler.

[mrjj]

@JonB
Yes i agree as guessing on execution time is bound to fail in many other cases.

[lxy12345]

@mrjj finally, I found the reason. I should add console.log() to show output . The post is correct, thanks guys

[JonB]

@lxy12345 said in run a sh shell while clicking button in QML with QT5.15.0:

The post is correct

What post is correct?

[lxy12345]

@JonB http://71.254.128.33/qml/process.html This post.

[JonB]

@lxy12345
Ah, I see. Yes, that looks reasonable. However, it has no code for waiting for the QProcess::finished signal. I admitted earlier I do not know how QML works with regard to instances. But if it does not create new QProcess instances, and if you re-use the one instance before the cat OS command has completed, you will get the QProcess::start: Process is already running error you showed earlier. Since the /bin/cat /proc/uptime completes "quickly" you may get away with it for a while.

You may well be using this as just an example to play with QProcess, I don't know. But be aware that if you are really trying to do /bin/cat /proc/uptime , that is a waste of time! All that does is an OS command to read the contents of the file. You would be better doing this by just opening the file /proc/uptime and reading its content from QML, without any QProcess OS command at all.

[lxy12345]

@JonB thanks for replying me. The "cat /proc/uptime" cmd is just an example. I change the cmd in my project, I use this code to open a shell which controls some peripherals.

[foxoman]

Basically close/kill / terminate the process before running a new process
here an example I extracted from one of my projects as I keep "bash" process alive till closing the app itself.
so try to find where you wan to stop the process and close it.

cmd.h

#pragma once
#include <QProcess>
#include <QVariant>

class Process : public QProcess
{
    Q_OBJECT
public:
    explicit Process( QObject* parent = Q_NULLPTR ) : QProcess( parent )
    { }

     // If want to use Start with arguments
    Q_INVOKABLE void start( const QString& program, const QVariantList& arguments )
    {
        QStringList args;

        // convert QVariantList from QML to QStringList for QProcess
        for ( const auto& temp : arguments ) {
            args << temp.toString();
        }

        QProcess::setProcessChannelMode( QProcess::MergedChannels );
        QProcess::start( program, args );
    }

    // If wan to start without arguments for Qt > 5.14
    Q_INVOKABLE void start( const QString& program )
    {

        QProcess::setProcessChannelMode( QProcess::MergedChannels );
        QProcess::setProgram( program );
        QProcess::start();
        QProcess::open( QProcess::ReadWrite );
    }

    Q_INVOKABLE QByteArray readAll() { return QProcess::readAll(); }
    Q_INVOKABLE QByteArray readLine() { return QProcess::readLine(); }

     // if you want to write to an active process, not fully tested!
    Q_INVOKABLE qint64 write( const QString& data )
    {
        return QProcess::write( qPrintable( data ) );
    }

private:
    Q_DISABLE_COPY( Process )
};

In main.h

qmlRegisterType<Process>( "Process", 1, 0, "Process" );

In main.qml

import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQuick.Layouts 1.15
import Qt.labs.platform 1.1
import Process 1.0

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    Component.onCompleted: {
        py.start("bash")
    }

    // use py.close() or py.kill(0 or py.terminate() to kill the process
    Component.onDestruction: py.close()

    Process {
        id: py

        property string output: ""

        onStarted: print("Started")
        onFinished: print("Closed")

        onErrorOccurred: console.log("Error Ocuured: ", error)

        onReadyReadStandardOutput: {
            output = py.readAll()
            term.text += output
        }
    }

    Page {

        anchors.fill: parent

        ScrollView {
            id: view
            anchors.fill: parent

            TextArea {
                id: term
                textFormat: TextArea.RichText
            }
        }

        footer: RowLayout {
            Layout.fillWidth: true

            TextField {
                id: input
                Layout.fillWidth: true
            }
            Button {
                text: "Send!"
                property string command: input.text.trim() + "\n"
                onClicked: {
                    py.write(command)
                    term.text += ("<br /><b>" + command + " : </b>")
                }
            }
        }
    }
}

I have run cat /proc/uptime as one program command.

[foxoman]

Here is an update to run multiple process as a replay to reddit QA

import QtQuick 2.15
import QtQuick.Controls 2.15
import Process 1.0

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: "Run a sh file in CMD!"

    // prcoess to run and read .sh file
    Process {
        id: cmd

        property string output: ""

        onStarted: print("Started")

        // Once reading the .sh finish we will run another process to run the notify-send!
        onFinished: notify.start("notify-send",
                                 ["-t", "4000", "Reading .sh file Completed!"])

        onErrorOccurred: console.log("Error Ocuured: ", error)

        onReadyReadStandardOutput: {
            output = cmd.readAll()
            txt.text += output
        }
    }

    // process to run firefox
    Process {
        id: fireFox

        property string output: ""

        // start notify process once we run firefox!
        onStarted: notify.start("notify-send",
                                ["-t", "4000", "Starting FireFox!"])
        onFinished: print("Closed")

        onErrorOccurred: console.log("Error Ocuured: ", error)

        onReadyReadStandardOutput: {
            output = cmd.readAll()
            console.log("READING CONSOLE: ", output)
        }
    }

    // process to run notify-osd !!
    Process {
        id: notify

        property string output: ""

        onStarted: print("Started")
        onFinished: print("Closed")

        onErrorOccurred: console.log("Error Ocuured: ", error)

        onReadyReadStandardOutput: {
            output = cmd.readAll()
            console.log("READING CONSOLE: ", output)
        }
    }

    Column {
        anchors.centerIn: parent
        TextArea {
            id: txt
            text: ""
        }

        Row {
            Button {
                text: "Run SH!"
                onClicked: cmd.start("/home/foxoman/file.sh")
            }
            Button {
                text: "Run FireFox!"
                onClicked: fireFox.start("firefox")
            }
            Button {
                text: "Run Notify"
                onClicked: notify.start(
                               "notify-send",
                               ["-t", "4000", "OSD Notify From Command Line!"])
            }
        }
    }
}