Send arguments to LinuX Terminal with QProcess



  • Hi
    I want to send arguments to Linux terminal with Qprocess in Qt, like below:

    //my code
        QProcess *Process = new QProcess();
        QString exec = "konsole";
        QStringList params;
        params <<"ls";
        Process->start(exec,params,QIODevice::ReadWrite);
        Process->waitForFinished(-1);
        QString p_stdout = Process->readAllStandardOutput();
        qDebug()<<p_stdout;
    

    The konsole ran but QProcess did not send any arguments and finally I can not read any Output ! can some body help me, How can i run terminal of Linux in background , Send argument to that and receive the Output?


  • Moderators

    @Alexanov If you do not need any console window you can just use /bin/sh instead of konsole.
    For konsole you probably need to pass some parameter to tell it to execute the command you want (check its man page or other doc).



  • Hi @Alexanov

    You will have to connect to readyReadStandardOutput, readyReadStandardError. Start the linux command with process->start(...), collect the stdout- and stderr-output in the slots you connected with, and wait for the finished signal. I would put this all into a class of its own.

    -Michael.



  • @jsulm
    Hi thanks for your Reply , I knew that for run Konsole without Gui I have to use "sh" in proc.start(program,argument) command , program section.
    for send executable command to Konsole I knew that before send command I have to send "-c" like below , but how can i know that this properties (like -c for executable commadn)?I did not see any of argument properties in QProcess help link in Qt.

        QProcess proc;
        proc.start("sh", QStringList() << "-c" << "ls");
    
        proc.waitForFinished();
        QByteArray output = proc.readAll();
    

  • Moderators

    @Alexanov You will not find it in the QProcess documentation because it is completely unrelated to QProcess. Those are parameters for commands which you want to execute. So, if you want to execute sh you need to read sh documentation. If you want to execute konsole then read its documentation. QProcess just starts an executable in a process and passes the parameter you provide, it does not care what executable is started and which parameters it supports.



  • @jsulm Thanks , I will read konsole documentation ...
    My problem solved but i have little question that remained , if i want to send multiple executable commands and then see outputs ... how can i do that?(sequentially send and read output and go to next command )


  • Moderators

    @Alexanov You can write to the process using QProcess. There is an example here http://doc.qt.io/qt-5/qprocess.html



  • @Alexanov Hi Alexanov , are you able to sequentially send and read output ?? if yes, please attach a code snippet .
    i tied this ,using write command but after one write command i had to use "closewriteterminal()" command in order to read standardoutput or standarderror. And next time , i cant send the write command since write terminal is closed. So i have to again use the start command to start my process. following is code snippet:

    QProcess myprocess ;
    myprocess.start("python");
    myprocess.write("print("hello")");
    myprocess.waitForFinished();
    myprocess.closeWriteChannel();
    while(myprocess.waitForFinished())
    {
    qDebug()<<myprocess.readAll();
    }

    // again i have to start the process
    myprocess.start("python");

    //and then the next write command
    myprocess.write("print("world")");

    can anybody tell better method to do it using Qprocess or any other . All solutions are welcom :)


  • Qt Champions 2017

    Hi and welcome to the forums.
    You start python in interactive mode so process never terminates.
    maybe you can make it quit with
    myprocess.write("exit()");



  • @mrjj Thanks for your suggestios. My worry is not about how to close python session. But how to send 2 write commands without starting again the python. Which means that one time only i will open the qPROCESS as python and then sequentially i write some command to python and read the output of python.


  • Qt Champions 2017

    @Rajesh-Bhau
    Ok so you want it to be interactive ?
    see
    https://forum.qt.io/topic/90904/how-do-i-run-docker-using-qprocess/8
    i start python there and its interactive.
    But its only for windows.



  • @mrjj Thanks for the answer, i want to make Qtextedit to mimic like python console. So i am trying to open python as qprocess in background and then input from Qtextedit will got to Python.exe to process and based on that the standard output will get printed back to Qtextedit.
    i tried using Qprocess its working fine except that i cant do sequential input\output as i told i have to close the write terminal and start it again.


  • Qt Champions 2017

    @Rajesh-Bhau
    Yeah and for that to work, at least on windows, the process must be interactive for that to work.
    it will just run command and exit. ( i think)
    Looking at your code it seems to do that. so after print, it does terminate ?


  • Qt Champions 2017

    @Rajesh-Bhau
    Oh maybe -i will help
    python -i foo.py
    do not quit
    https://www.johnny-lin.com/cdat_tips/tips_pylang/keep_open.html
    forget about the interactive shell. you dont want to type so that should not be needed.


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