Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. How we can run Linux command from qt code?
Forum Updated to NodeBB v4.3 + New Features

How we can run Linux command from qt code?

Scheduled Pinned Locked Moved Unsolved General and Desktop
21 Posts 4 Posters 2.5k Views
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • W Wasee
    5 Jan 2022, 06:58

    @jsulm thanks;
    kindly give me any suitable example QFile device read.
    thanks

    J Offline
    J Offline
    JonB
    wrote on 5 Jan 2022, 07:22 last edited by JonB 1 May 2022, 07:36
    #9

    @Wasee
    To answer your original question: the code you showed in your first example should do exactly what you say you want it to do --- provided you have first typed that command into a bash shell to verify it works correctly. So how do you know "it is not executing my command"? There is no need to run it startDetached() instead of plain start(). You could then capture any error and anything written to stdout/stderr ot check for anything unexpected. [Note: your literal string has \: in it. That is not right for C++. Either \\: or just simple :. Maybe that is why it had problems.]

    However, as @jsulm said this command simple writes a string to a file. So no need for a QProcess, what is wrong with:

    QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
    if (f.open(QIODevice::WriteOnly))
    {
        qint64 count = f.write("24250000");
        Q_ASSERT(count > 0);
        f.close();
    }
    
    W 2 Replies Last reply 5 Jan 2022, 09:41
    5
    • J JonB
      5 Jan 2022, 07:22

      @Wasee
      To answer your original question: the code you showed in your first example should do exactly what you say you want it to do --- provided you have first typed that command into a bash shell to verify it works correctly. So how do you know "it is not executing my command"? There is no need to run it startDetached() instead of plain start(). You could then capture any error and anything written to stdout/stderr ot check for anything unexpected. [Note: your literal string has \: in it. That is not right for C++. Either \\: or just simple :. Maybe that is why it had problems.]

      However, as @jsulm said this command simple writes a string to a file. So no need for a QProcess, what is wrong with:

      QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
      if (f.open(QIODevice::WriteOnly))
      {
          qint64 count = f.write("24250000");
          Q_ASSERT(count > 0);
          f.close();
      }
      
      W Offline
      W Offline
      Wasee
      wrote on 5 Jan 2022, 09:41 last edited by
      #10

      @JonB Hi;
      I coded as you suggested above but still not changing TX_LO_frequency value. why?
      thanks

      J J 3 Replies Last reply 5 Jan 2022, 09:44
      0
      • W Wasee
        5 Jan 2022, 09:41

        @JonB Hi;
        I coded as you suggested above but still not changing TX_LO_frequency value. why?
        thanks

        J Offline
        J Offline
        jsulm
        Lifetime Qt Champion
        wrote on 5 Jan 2022, 09:44 last edited by
        #11

        @Wasee Did you do what @JonB mentioned: "provided you have first typed that command into a bash shell to verify it works correctly"?
        So, does it work if you do it in terminal?

        1 Reply Last reply
        1
        • W Wasee
          5 Jan 2022, 09:41

          @JonB Hi;
          I coded as you suggested above but still not changing TX_LO_frequency value. why?
          thanks

          J Offline
          J Offline
          jsulm
          Lifetime Qt Champion
          wrote on 5 Jan 2022, 09:46 last edited by
          #12
          This post is deleted!
          1 Reply Last reply
          0
          • W Wasee
            5 Jan 2022, 09:41

            @JonB Hi;
            I coded as you suggested above but still not changing TX_LO_frequency value. why?
            thanks

            J Offline
            J Offline
            JonB
            wrote on 5 Jan 2022, 09:57 last edited by JonB 1 May 2022, 09:58
            #13

            @Wasee said in How we can run Linux command from qt code?:

            but still not changing TX_LO_frequency value. why?

            Did you even at least check the return result of the open() for yourself? For all I know you do not have permission to write to that file. This is part of what doing development involves....

            @jsulm

            Also I would not write a string but a number:

            That's fine, but it's not what the OP's echo 24250000 > out_altvoltage1_TX_LO_frequency would do (treat anything as a number), which I was trying to copy. In fact I think Linux echo will append a newline, so the OP may need to do that too.

            1 Reply Last reply
            2
            • W Offline
              W Offline
              Wasee
              wrote on 5 Jan 2022, 10:25 last edited by
              #14

              @JonB said in How we can run Linux command from qt code?:
              echo 24250000 > out_altvoltage1_TX_LO_frequency this command run in terminal and change the value on device. But not changing from qt code.

              J 1 Reply Last reply 5 Jan 2022, 10:27
              0
              • W Wasee
                5 Jan 2022, 10:25

                @JonB said in How we can run Linux command from qt code?:
                echo 24250000 > out_altvoltage1_TX_LO_frequency this command run in terminal and change the value on device. But not changing from qt code.

                J Offline
                J Offline
                jsulm
                Lifetime Qt Champion
                wrote on 5 Jan 2022, 10:27 last edited by
                #15

                @Wasee said in How we can run Linux command from qt code?:

                change the value on device

                Without sudo?

                Please add error handling to your code: print error message if f.open(...) fails.

                W 1 Reply Last reply 5 Jan 2022, 10:42
                0
                • J jsulm
                  5 Jan 2022, 10:27

                  @Wasee said in How we can run Linux command from qt code?:

                  change the value on device

                  Without sudo?

                  Please add error handling to your code: print error message if f.open(...) fails.

                  W Offline
                  W Offline
                  Wasee
                  wrote on 5 Jan 2022, 10:42 last edited by
                  #16

                  @jsulm Hi;
                  Yes without sudo in terminal its changing value. No error of device open its not returning.
                  thanks

                  J 1 Reply Last reply 5 Jan 2022, 10:53
                  0
                  • W Wasee
                    5 Jan 2022, 10:42

                    @jsulm Hi;
                    Yes without sudo in terminal its changing value. No error of device open its not returning.
                    thanks

                    J Offline
                    J Offline
                    JonB
                    wrote on 5 Jan 2022, 10:53 last edited by
                    #17

                    @Wasee

                    • Did you add the error checking code I advised?
                    • Did you try appending the newline I advised?
                    1 Reply Last reply
                    0
                    • J JonB
                      5 Jan 2022, 07:22

                      @Wasee
                      To answer your original question: the code you showed in your first example should do exactly what you say you want it to do --- provided you have first typed that command into a bash shell to verify it works correctly. So how do you know "it is not executing my command"? There is no need to run it startDetached() instead of plain start(). You could then capture any error and anything written to stdout/stderr ot check for anything unexpected. [Note: your literal string has \: in it. That is not right for C++. Either \\: or just simple :. Maybe that is why it had problems.]

                      However, as @jsulm said this command simple writes a string to a file. So no need for a QProcess, what is wrong with:

                      QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                      if (f.open(QIODevice::WriteOnly))
                      {
                          qint64 count = f.write("24250000");
                          Q_ASSERT(count > 0);
                          f.close();
                      }
                      
                      W Offline
                      W Offline
                      Wasee
                      wrote on 6 Jan 2022, 04:53 last edited by
                      #18

                      @JonB said in How we can run Linux command from qt code?:

                      QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                      if (f.open(QIODevice::WriteOnly))
                      {
                      qint64 count = f.write("24250000");
                      Q_ASSERT(count > 0);
                      f.close();
                      }

                      how I can pass variable instead of 24250000.

                      1 Reply Last reply
                      0
                      • W Offline
                        W Offline
                        Wasee
                        wrote on 6 Jan 2022, 05:18 last edited by
                        #19

                        @JonB Thanks for your appreciated help!
                        Your suggestion of QFile is working fine now.

                        QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                        if (f.open(QIODevice::WriteOnly))
                        {
                            qint64 count = f.write("2425000000");
                            Q_ASSERT(count > 0);
                            f.close();
                        }
                        

                        The value 2425000000 is coming from a variable which can be change any time. I need to pass this value as a variable instead of constant 2425000000.
                        thanks

                        K J 2 Replies Last reply 6 Jan 2022, 08:13
                        0
                        • W Wasee
                          6 Jan 2022, 05:18

                          @JonB Thanks for your appreciated help!
                          Your suggestion of QFile is working fine now.

                          QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                          if (f.open(QIODevice::WriteOnly))
                          {
                              qint64 count = f.write("2425000000");
                              Q_ASSERT(count > 0);
                              f.close();
                          }
                          

                          The value 2425000000 is coming from a variable which can be change any time. I need to pass this value as a variable instead of constant 2425000000.
                          thanks

                          K Offline
                          K Offline
                          KroMignon
                          wrote on 6 Jan 2022, 08:13 last edited by
                          #20

                          @Wasee said in How we can run Linux command from qt code?:

                          The value 2425000000 is coming from a variable which can be change any time. I need to pass this value as a variable instead of constant 2425000000.
                          thanks

                          Are you joking???
                          Do you really don't have any idea how to do this simple stuff?
                          It is so complicated to create a string and write it to a file?
                          What did you try to do?

                          It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                          1 Reply Last reply
                          0
                          • W Wasee
                            6 Jan 2022, 05:18

                            @JonB Thanks for your appreciated help!
                            Your suggestion of QFile is working fine now.

                            QFile f("/sys/bus/iio/devices/iio:device1/out_altvoltage1_TX_LO_frequency");
                            if (f.open(QIODevice::WriteOnly))
                            {
                                qint64 count = f.write("2425000000");
                                Q_ASSERT(count > 0);
                                f.close();
                            }
                            

                            The value 2425000000 is coming from a variable which can be change any time. I need to pass this value as a variable instead of constant 2425000000.
                            thanks

                            J Offline
                            J Offline
                            JonB
                            wrote on 6 Jan 2022, 08:18 last edited by
                            #21

                            @Wasee
                            You must convert your (integer) variable to a string. QIODevice::write() accepts either a const char * or a const QByteArray & for the string to write. You can use either QString::number() or QByteArray::number() to convert a number to a string/byte array to pass to write(), as you please.

                            1 Reply Last reply
                            1

                            18/21

                            6 Jan 2022, 04:53

                            • Login

                            • Login or register to search.
                            18 out of 21
                            • First post
                              18/21
                              Last post
                            0
                            • Categories
                            • Recent
                            • Tags
                            • Popular
                            • Users
                            • Groups
                            • Search
                            • Get Qt Extensions
                            • Unsolved