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how to echo directly from dynamic input

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  • MijazM Mijaz

    This code worked fine:

    system("cd /sys/bus/iio/devices/iio:device1/; echo 1111 > out_altvoltage1_TX_LO_frequency");
    QProcess process1;
    process1.start("cat /sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
    process1.waitForFinished(-1); // will wait forever until finished
    QString stdout1 = process1.readAllStandardOutput();
    qDebug() << stdout1;
    ui->lineEdit_3->setText(stdout1);
    

    // output display in lineEdit_3 : 1111 (this is correct)

    This code not working correctly:
    QString input = ui->lineEdit_1->text();
    // entered value 2222 to the lineEdit_1 in GUI
    ui->lineEdit_2->setText(input);
    // diplay lineEdit_2 : 2222 (this is correct)
    // I want to directly echo the input as given below but this not updating the (out_altvoltage1_TX_LO_frequency) register value.

    system("cd /sys/bus/iio/devices/iio:device1/; echo input > out_altvoltage1_TX_LO_frequency");   
    QProcess process1;
    process1.start("cat /sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
    process1.waitForFinished(-1); // will wait forever until finished
    QString stdout1 = process1.readAllStandardOutput();
    qDebug() << stdout1;
    ui->lineEdit_3->setText(stdout1);
    

    // output display in lineEdit_3 : 1111 (this is not correct)

    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by
    #2

    @Mijaz This looks really overcomplicated: why don't you simply use QFile to read from /sys/bus... instead of spawning a process for such a simple task? There is really no need to use cat in a process to read a file...

    https://forum.qt.io/topic/113070/qt-code-of-conduct

    MijazM 1 Reply Last reply
    2
    • jsulmJ jsulm

      @Mijaz This looks really overcomplicated: why don't you simply use QFile to read from /sys/bus... instead of spawning a process for such a simple task? There is really no need to use cat in a process to read a file...

      MijazM Offline
      MijazM Offline
      Mijaz
      wrote on last edited by
      #3

      Hi @jsulm yes, you are correct I can read from QFile also. But here main problem is
      echo input > out_altvoltage1_TX_LO_frequency;
      How can do this in qt;

      jsulmJ 1 Reply Last reply
      0
      • MijazM Mijaz

        Hi @jsulm yes, you are correct I can read from QFile also. But here main problem is
        echo input > out_altvoltage1_TX_LO_frequency;
        How can do this in qt;

        jsulmJ Offline
        jsulmJ Offline
        jsulm
        Lifetime Qt Champion
        wrote on last edited by
        #4

        @Mijaz said in how to echo directly from dynamic input:

        How can do this in qt;

        This writes into a file, you can do it also with QFile.

        https://forum.qt.io/topic/113070/qt-code-of-conduct

        MijazM 1 Reply Last reply
        1
        • jsulmJ jsulm

          @Mijaz said in how to echo directly from dynamic input:

          How can do this in qt;

          This writes into a file, you can do it also with QFile.

          MijazM Offline
          MijazM Offline
          Mijaz
          wrote on last edited by Mijaz
          #5

          @jsulm
          Do you mean like this?

          QFile f("echo /sys/bus/iio/devices/iio:device1/input > out_altvoltage1_TX_LO_frequency");
          if (f.open(QIODevice::ReadOnly | QIODevice::Text))
          {
          QByteArray ba = f.readAll();
          ui->lineEdit_3->setText(QString(ba));
          f.close();
          }
          Selection_022.png

          jsulmJ 2 Replies Last reply
          0
          • MijazM Mijaz

            @jsulm
            Do you mean like this?

            QFile f("echo /sys/bus/iio/devices/iio:device1/input > out_altvoltage1_TX_LO_frequency");
            if (f.open(QIODevice::ReadOnly | QIODevice::Text))
            {
            QByteArray ba = f.readAll();
            ui->lineEdit_3->setText(QString(ba));
            f.close();
            }
            Selection_022.png

            jsulmJ Offline
            jsulmJ Offline
            jsulm
            Lifetime Qt Champion
            wrote on last edited by
            #6

            @Mijaz said in how to echo directly from dynamic input:

            you mean like this?

            No, I don't.
            Just open the file using QFile and read/write from/to it:

            QFile f("/sys/bus/iio/devices/iio:device1/input");
            if (f.open(QIODevice::ReadOnly | QIODevice::Text)) {
                QByteArray ba = f.readAll();
                ui->lineEdit_3->setText(QString(ba));
                f.close();
            }
            

            Be careful with QIODevice::Text: don't use it if file contains binary data.

            https://forum.qt.io/topic/113070/qt-code-of-conduct

            MijazM 1 Reply Last reply
            0
            • MijazM Mijaz

              @jsulm
              Do you mean like this?

              QFile f("echo /sys/bus/iio/devices/iio:device1/input > out_altvoltage1_TX_LO_frequency");
              if (f.open(QIODevice::ReadOnly | QIODevice::Text))
              {
              QByteArray ba = f.readAll();
              ui->lineEdit_3->setText(QString(ba));
              f.close();
              }
              Selection_022.png

              jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by jsulm
              #7

              @Mijaz The line where you get that error does not make any sense.
              I don't know what you are trying to do there...

              https://forum.qt.io/topic/113070/qt-code-of-conduct

              MijazM 1 Reply Last reply
              1
              • jsulmJ jsulm

                @Mijaz said in how to echo directly from dynamic input:

                you mean like this?

                No, I don't.
                Just open the file using QFile and read/write from/to it:

                QFile f("/sys/bus/iio/devices/iio:device1/input");
                if (f.open(QIODevice::ReadOnly | QIODevice::Text)) {
                    QByteArray ba = f.readAll();
                    ui->lineEdit_3->setText(QString(ba));
                    f.close();
                }
                

                Be careful with QIODevice::Text: don't use it if file contains binary data.

                MijazM Offline
                MijazM Offline
                Mijaz
                wrote on last edited by
                #8

                @jsulm
                QFile f("/sys/bus/iio/devices/iio:device1/input");
                if (f.open(QIODevice::ReadOnly | QIODevice::Text)) {
                QByteArray ba = f.readAll();
                ui->lineEdit_3->setText(QString(ba));
                f.close();
                }

                I executed above your code, no any output display.

                jsulmJ 1 Reply Last reply
                0
                • MijazM Mijaz

                  @jsulm
                  QFile f("/sys/bus/iio/devices/iio:device1/input");
                  if (f.open(QIODevice::ReadOnly | QIODevice::Text)) {
                  QByteArray ba = f.readAll();
                  ui->lineEdit_3->setText(QString(ba));
                  f.close();
                  }

                  I executed above your code, no any output display.

                  jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #9

                  @Mijaz said in how to echo directly from dynamic input:

                  /sys/bus/iio/devices/iio:device1/input

                  Is this a valid path?
                  Did you check return value of open()?
                  Did you check what https://doc.qt.io/qt-5/qiodevice.html#errorString returns?
                  Does /sys/bus/iio/devices/iio:device1/input contain text or binary data?

                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                  1 Reply Last reply
                  1
                  • jsulmJ jsulm

                    @Mijaz The line where you get that error does not make any sense.
                    I don't know what you are trying to do there...

                    MijazM Offline
                    MijazM Offline
                    Mijaz
                    wrote on last edited by
                    #10

                    @jsulm
                    I want to update register (out_altvoltage1_TX_LO_frequency) with the new value;
                    In real time when I will enter new value to lineEdit_1 then it should be display in lineEdit_2 as well as update the register (out_altvoltage1_TX_LO_frequency) which will recheck in lineEdit_3.

                    QString input = ui->lineEdit_1->text();
                    ui->lineEdit_2->setText(input);
                    QFile f("/sys/bus/iio/devices/iio:device1/input");
                    if (f.open(QIODevice::ReadOnly | QIODevice::Text))
                    {
                    QByteArray ba = f.readAll();
                    ui->lineEdit_3->setText(QString(ba));
                    f.close();
                    }

                    jsulmJ 1 Reply Last reply
                    0
                    • MijazM Mijaz

                      @jsulm
                      I want to update register (out_altvoltage1_TX_LO_frequency) with the new value;
                      In real time when I will enter new value to lineEdit_1 then it should be display in lineEdit_2 as well as update the register (out_altvoltage1_TX_LO_frequency) which will recheck in lineEdit_3.

                      QString input = ui->lineEdit_1->text();
                      ui->lineEdit_2->setText(input);
                      QFile f("/sys/bus/iio/devices/iio:device1/input");
                      if (f.open(QIODevice::ReadOnly | QIODevice::Text))
                      {
                      QByteArray ba = f.readAll();
                      ui->lineEdit_3->setText(QString(ba));
                      f.close();
                      }

                      jsulmJ Offline
                      jsulmJ Offline
                      jsulm
                      Lifetime Qt Champion
                      wrote on last edited by
                      #11

                      @Mijaz You did not answer my questions from my previous post.
                      Do you mean you want to update out_altvoltage1_TX_LO_frequency inside /sys/bus/iio/devices/iio:device1/input ?
                      Because this:

                      echo /sys/bus/iio/devices/iio:device1/input > out_altvoltage1_TX_LO_frequency
                      

                      would write the content of /sys/bus/iio/devices/iio:device1/input into file out_altvoltage1_TX_LO_frequency in current working directory.

                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                      MijazM 1 Reply Last reply
                      0
                      • jsulmJ jsulm

                        @Mijaz You did not answer my questions from my previous post.
                        Do you mean you want to update out_altvoltage1_TX_LO_frequency inside /sys/bus/iio/devices/iio:device1/input ?
                        Because this:

                        echo /sys/bus/iio/devices/iio:device1/input > out_altvoltage1_TX_LO_frequency
                        

                        would write the content of /sys/bus/iio/devices/iio:device1/input into file out_altvoltage1_TX_LO_frequency in current working directory.

                        MijazM Offline
                        MijazM Offline
                        Mijaz
                        wrote on last edited by
                        #12

                        @jsulm
                        No input is not a directory it is the string in which I have stored value in about command like this:

                        QString input = ui->lineEdit_1->text();
                        ui->lineEdit_2->setText(input);
                        Now I want to use this "input" in which I already stored value to update my out_altvoltage1_TX_LO_frequency.
                        //
                        Detail explenation of my work:
                        Step 1:
                        I firstly executed following commands on my board where I am deploying my project like this:

                        cd /sys/bus/iio/devices/iio:device1/
                        echo 111111 > out_altvoltage1_TX_LO_frequency
                        This worked fine;
                        Step 2:
                        I create project on my PC using following commands and GUI.

                        system("cd /sys/bus/iio/devices/iio:device1/; echo 222222 > out_altvoltage1_TX_LO_frequency");
                        QProcess process1;
                        process1.start("cat /sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                        process1.waitForFinished(-1); // will wait forever until finished
                        QString stdout1 = process1.readAllStandardOutput();
                        qDebug() << stdout1;
                        ui->lineEdit_3->setText(stdout1);
                        This also work correctly.
                        Step 3:
                        Now, because it is my task requirement that I need update register (out_altvoltage1_TX_LO_frequency) value at real-time, depends on the situation not remained fixed like (222222), therefore I update code like this:

                        QString input = ui->lineEdit_1->text();
                        ui->lineEdit_2->setText(input);
                        QFile f("/sys/bus/iio/devices/iio:device1/input");
                        if (f.open(QIODevice::ReadOnly | QIODevice::Text))
                        {
                        QByteArray ba = f.readAll();
                        ui->lineEdit_3->setText(QString(ba));
                        f.close();
                        }

                        whenever I will enter a new value to lineEdit_1 that should update register (out_altvoltage1_TX_LO_frequency) immediately,

                        this code not working as my requirements.

                        jsulmJ 1 Reply Last reply
                        0
                        • MijazM Mijaz

                          @jsulm
                          No input is not a directory it is the string in which I have stored value in about command like this:

                          QString input = ui->lineEdit_1->text();
                          ui->lineEdit_2->setText(input);
                          Now I want to use this "input" in which I already stored value to update my out_altvoltage1_TX_LO_frequency.
                          //
                          Detail explenation of my work:
                          Step 1:
                          I firstly executed following commands on my board where I am deploying my project like this:

                          cd /sys/bus/iio/devices/iio:device1/
                          echo 111111 > out_altvoltage1_TX_LO_frequency
                          This worked fine;
                          Step 2:
                          I create project on my PC using following commands and GUI.

                          system("cd /sys/bus/iio/devices/iio:device1/; echo 222222 > out_altvoltage1_TX_LO_frequency");
                          QProcess process1;
                          process1.start("cat /sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                          process1.waitForFinished(-1); // will wait forever until finished
                          QString stdout1 = process1.readAllStandardOutput();
                          qDebug() << stdout1;
                          ui->lineEdit_3->setText(stdout1);
                          This also work correctly.
                          Step 3:
                          Now, because it is my task requirement that I need update register (out_altvoltage1_TX_LO_frequency) value at real-time, depends on the situation not remained fixed like (222222), therefore I update code like this:

                          QString input = ui->lineEdit_1->text();
                          ui->lineEdit_2->setText(input);
                          QFile f("/sys/bus/iio/devices/iio:device1/input");
                          if (f.open(QIODevice::ReadOnly | QIODevice::Text))
                          {
                          QByteArray ba = f.readAll();
                          ui->lineEdit_3->setText(QString(ba));
                          f.close();
                          }

                          whenever I will enter a new value to lineEdit_1 that should update register (out_altvoltage1_TX_LO_frequency) immediately,

                          this code not working as my requirements.

                          jsulmJ Offline
                          jsulmJ Offline
                          jsulm
                          Lifetime Qt Champion
                          wrote on last edited by
                          #13

                          @Mijaz OK, that means you want to write to /sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency file, because

                          cd /sys/bus/iio/devices/iio:device1/
                          echo 111111 > out_altvoltage1_TX_LO_frequency
                          

                          does exactly that.
                          Then simply use QFile to write:

                          QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                          if (f.open(QIODevice::WriteOnly | QIODevice::Text)) {
                              f.write(ui->lineEdit_2->text().toLatin1());
                              f.close();
                          }
                          

                          https://forum.qt.io/topic/113070/qt-code-of-conduct

                          MijazM 2 Replies Last reply
                          1
                          • jsulmJ jsulm

                            @Mijaz OK, that means you want to write to /sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency file, because

                            cd /sys/bus/iio/devices/iio:device1/
                            echo 111111 > out_altvoltage1_TX_LO_frequency
                            

                            does exactly that.
                            Then simply use QFile to write:

                            QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                            if (f.open(QIODevice::WriteOnly | QIODevice::Text)) {
                                f.write(ui->lineEdit_2->text().toLatin1());
                                f.close();
                            }
                            
                            MijazM Offline
                            MijazM Offline
                            Mijaz
                            wrote on last edited by
                            #14

                            @jsulm

                            QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                            if (f.open(QIODevice::WriteOnly | QIODevice::Text))
                            {
                            f.write(ui->lineEdit_2->text().toLatin1());
                            f.close();
                            }

                            this still not updating register ( out_altvoltage1_TX_LO_frequency) value.

                            jsulmJ 1 Reply Last reply
                            0
                            • MijazM Mijaz

                              @jsulm

                              QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                              if (f.open(QIODevice::WriteOnly | QIODevice::Text))
                              {
                              f.write(ui->lineEdit_2->text().toLatin1());
                              f.close();
                              }

                              this still not updating register ( out_altvoltage1_TX_LO_frequency) value.

                              jsulmJ Offline
                              jsulmJ Offline
                              jsulm
                              Lifetime Qt Champion
                              wrote on last edited by
                              #15

                              @Mijaz You still did not answer any of my previous questions?
                              Did you check what happens? Please use debugger and see whether your if block was executed at all.
                              Did you check return value of open()?
                              Did you check what https://doc.qt.io/qt-5/qiodevice.html#errorString returns?

                              https://forum.qt.io/topic/113070/qt-code-of-conduct

                              JonBJ MijazM 2 Replies Last reply
                              2
                              • jsulmJ jsulm

                                @Mijaz You still did not answer any of my previous questions?
                                Did you check what happens? Please use debugger and see whether your if block was executed at all.
                                Did you check return value of open()?
                                Did you check what https://doc.qt.io/qt-5/qiodevice.html#errorString returns?

                                JonBJ Offline
                                JonBJ Offline
                                JonB
                                wrote on last edited by JonB
                                #16

                                @jsulm
                                Do you realise this thread is just a rehash of @Mijaz's own https://forum.qt.io/topic/107974/system-vs-process-command/ ? He asks exactly the same question there. You will see the same questions about the cat command and the same answers about using QFile, the same issue about the current directory and paths, .... I tried to help, but he chose not to supply the necessary information, and is just going through the same stuff again. It gets so frustrating here when people choose not to follow through the advice they are given when they do not like it, and instead create a new thread to get the information all over again...

                                jsulmJ 1 Reply Last reply
                                0
                                • JonBJ JonB

                                  @jsulm
                                  Do you realise this thread is just a rehash of @Mijaz's own https://forum.qt.io/topic/107974/system-vs-process-command/ ? He asks exactly the same question there. You will see the same questions about the cat command and the same answers about using QFile, the same issue about the current directory and paths, .... I tried to help, but he chose not to supply the necessary information, and is just going through the same stuff again. It gets so frustrating here when people choose not to follow through the advice they are given when they do not like it, and instead create a new thread to get the information all over again...

                                  jsulmJ Offline
                                  jsulmJ Offline
                                  jsulm
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #17

                                  @JonB Yes, I saw that thread and I agree that it is very frustrating if people do not answer questions and do not follow advices - what's the point to ask then in a forum? But it is how it is...

                                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  1 Reply Last reply
                                  0
                                  • jsulmJ jsulm

                                    @Mijaz You still did not answer any of my previous questions?
                                    Did you check what happens? Please use debugger and see whether your if block was executed at all.
                                    Did you check return value of open()?
                                    Did you check what https://doc.qt.io/qt-5/qiodevice.html#errorString returns?

                                    MijazM Offline
                                    MijazM Offline
                                    Mijaz
                                    wrote on last edited by
                                    #18

                                    @jsulm
                                    Thank you so much for your kind help to find a proper solution.

                                    jsulmJ 1 Reply Last reply
                                    1
                                    • MijazM Mijaz

                                      @jsulm
                                      Thank you so much for your kind help to find a proper solution.

                                      jsulmJ Offline
                                      jsulmJ Offline
                                      jsulm
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #19

                                      @Mijaz Does it work now?

                                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                                      MijazM 1 Reply Last reply
                                      0
                                      • jsulmJ jsulm

                                        @Mijaz Does it work now?

                                        MijazM Offline
                                        MijazM Offline
                                        Mijaz
                                        wrote on last edited by
                                        #20

                                        @jsulm
                                        yes, it is working correctly.

                                        1 Reply Last reply
                                        0
                                        • jsulmJ jsulm

                                          @Mijaz OK, that means you want to write to /sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency file, because

                                          cd /sys/bus/iio/devices/iio:device1/
                                          echo 111111 > out_altvoltage1_TX_LO_frequency
                                          

                                          does exactly that.
                                          Then simply use QFile to write:

                                          QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                                          if (f.open(QIODevice::WriteOnly | QIODevice::Text)) {
                                              f.write(ui->lineEdit_2->text().toLatin1());
                                              f.close();
                                          }
                                          
                                          MijazM Offline
                                          MijazM Offline
                                          Mijaz
                                          wrote on last edited by Mijaz
                                          #21

                                          @jsulm
                                          Now, If I want to update two different register (out_altvoltage0_TX_LO_frequency and out_altvoltage1_TX_LO_frequency ) with same value.
                                          The how can execute code using single QFile .
                                          I tried like follows but not worked:

                                          QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage0_TX_LO_frequency | out_altvoltage1_TX_LO_frequency");
                                          if (f.open(QIODevice::WriteOnly | QIODevice::Text)) {
                                          f.write(ui->lineEdit_2->text().toLatin1());
                                          f.close();
                                          }

                                          1 Reply Last reply
                                          0

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