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problem with System()

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system commandsystem
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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #2

    Hi,

    What does it have to do with Qt ?

    In any case, check the content of your command string.

    Note that you can use QProcess for that kind of task.

    Interested in AI ? www.idiap.ch
    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

    AlvaroSA 1 Reply Last reply
    2
    • SGaistS SGaist

      Hi,

      What does it have to do with Qt ?

      In any case, check the content of your command string.

      Note that you can use QProcess for that kind of task.

      AlvaroSA Offline
      AlvaroSA Offline
      AlvaroS
      wrote on last edited by
      #3

      @SGaist Yes, command string is right... but I do not why segmentation fault...
      I am going to check QProcess

      1 Reply Last reply
      0
      • AlvaroSA AlvaroS

        Hello everyone:

        First of all thanks a lot for reading this post and being able to help.
        I have a problem whit System command.

        if I write:

        sprintf(command, "%s %0.0f %0.0f 0 %0.0f %0.0f %s 0 0 +", princi,wps.front().x(), wps.front().y(),wps.back().x(),wps.back().y(),name_bmp);
        
        chdir("/home/"); //To change directory
        system(command);
        

        It give me segmentation fault when it runs system(command)

        However if I write:

        system("./princi 0 747.37 427.68 0 844.37 42.54 prueba_princi.bmp 0 0 +")
        
        

        it runs perfectly....

        What am I doing wrong?
        Thanks!

        Joel BodenmannJ Offline
        Joel BodenmannJ Offline
        Joel Bodenmann
        wrote on last edited by Joel Bodenmann
        #4

        This is not really an answer to your question but still related: You should consider using the QProcess class. This is not only a lot more flexible & portable than the system() function but also integrates well into the Qt framework (signal&slots, properties, ...).
        Usually you want to use Qt library components wherever possible.

        To still be somewhat useful: Did you check that command is large enough and that the string assembled by sprintf() is correct?

        Edit: @SGaist played ninja again....

        Industrial process automation software: https://simulton.com
        Embedded Graphics & GUI library: https://ugfx.io

        1 Reply Last reply
        2
        • mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by
          #5

          @AlvaroS said:

          sprintf(command, "%s %0.0f %0.0f 0 %0.0f %0.0f %s 0 0 +", princi,wps.front().x(), wps.front().y(),wps.back().x(),wps.back().y(),name_bmp)

          What types are
          princi
          name_bmp

          better not be QStrings :)

          AlvaroSA 1 Reply Last reply
          3
          • mrjjM mrjj

            @AlvaroS said:

            sprintf(command, "%s %0.0f %0.0f 0 %0.0f %0.0f %s 0 0 +", princi,wps.front().x(), wps.front().y(),wps.back().x(),wps.back().y(),name_bmp)

            What types are
            princi
            name_bmp

            better not be QStrings :)

            AlvaroSA Offline
            AlvaroSA Offline
            AlvaroS
            wrote on last edited by
            #6

            @mrjj Hello.
            They are const char* !

            1 Reply Last reply
            1
            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #7

              Then run your application through the debugger.

              Interested in AI ? www.idiap.ch
              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

              AlvaroSA 1 Reply Last reply
              0
              • SGaistS SGaist

                Then run your application through the debugger.

                AlvaroSA Offline
                AlvaroSA Offline
                AlvaroS
                wrote on last edited by
                #8

                @SGaist Now I do this:

                    QString program = "./home/princi";
                    QStringList arguments;
                
                    arguments << "0" << QString::number(wps.front().x()) << QString::number(wps.front().y()) << "0" << QString::number(wps.back().x()) << QString::number(wps.back().y()) << "prueba_princi.bmp" << "0 0 +" ;
                
                    QProcess myProcess;
                
                    myProcess.start(program,arguments);
                

                it compiles good but my application does not run...

                1 Reply Last reply
                0
                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #9

                  You call it with a path relative to where you main application is started.

                  ./home/princi is equivalent to $PWD/home/princi/ which is likely not what you want, is it ?

                  Interested in AI ? www.idiap.ch
                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                  AlvaroSA 2 Replies Last reply
                  2
                  • SGaistS SGaist

                    You call it with a path relative to where you main application is started.

                    ./home/princi is equivalent to $PWD/home/princi/ which is likely not what you want, is it ?

                    AlvaroSA Offline
                    AlvaroSA Offline
                    AlvaroS
                    wrote on last edited by
                    #10

                    @SGaist yes! but it does not run with that code..

                    1 Reply Last reply
                    0
                    • SGaistS SGaist

                      You call it with a path relative to where you main application is started.

                      ./home/princi is equivalent to $PWD/home/princi/ which is likely not what you want, is it ?

                      AlvaroSA Offline
                      AlvaroSA Offline
                      AlvaroS
                      wrote on last edited by
                      #11

                      @SGaist Now I do this and nothing as well..

                          QString program = "princi";
                          QStringList arguments;
                      
                          arguments << "0" << QString::number(wps.front().x()) << QString::number(wps.front().y()) << "0" << QString::number(wps.back().x()) << QString::number(wps.back().y()) << "prueba_princi.bmp" << "0 0 +" ;
                      
                          QString folder = "/home/";
                      
                          QProcess *myProcess = new QProcess(this);
                      
                          myProcess->setWorkingDirectory(folder);
                      
                          myProcess->start(program,arguments);
                      
                      1 Reply Last reply
                      0
                      • SGaistS Offline
                        SGaistS Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on last edited by
                        #12

                        What is the full path to princi ? And what is the full path to your application ?

                        Interested in AI ? www.idiap.ch
                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                        AlvaroSA 1 Reply Last reply
                        0
                        • SGaistS SGaist

                          What is the full path to princi ? And what is the full path to your application ?

                          AlvaroSA Offline
                          AlvaroSA Offline
                          AlvaroS
                          wrote on last edited by
                          #13

                          @SGaist Full path of princi (which is the executable) is /home/
                          and full path of my QT aplication is /home/workspace

                          1 Reply Last reply
                          0
                          • jsulmJ Online
                            jsulmJ Online
                            jsulm
                            Lifetime Qt Champion
                            wrote on last edited by
                            #14

                            /home is not the full path to your application except it is called home and is located in the root directory.
                            So, you can start the program in a shell with /home/princi?
                            Did you try it?
                            This is quite strange path: in /home you usually have a directory for each user and /home is not writable by normal user.

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

                            AlvaroSA 1 Reply Last reply
                            2
                            • jsulmJ jsulm

                              /home is not the full path to your application except it is called home and is located in the root directory.
                              So, you can start the program in a shell with /home/princi?
                              Did you try it?
                              This is quite strange path: in /home you usually have a directory for each user and /home is not writable by normal user.

                              AlvaroSA Offline
                              AlvaroSA Offline
                              AlvaroS
                              wrote on last edited by
                              #15

                              @jsulm sorry yes, it is in /home/user1/ but it does not run as well...

                              1 Reply Last reply
                              0
                              • mrjjM Offline
                                mrjjM Offline
                                mrjj
                                Lifetime Qt Champion
                                wrote on last edited by
                                #16

                                @AlvaroS said:

                                QString program = "princi";

                                should be

                                QString program = "/home/user1/princi";

                                ?

                                AlvaroSA 1 Reply Last reply
                                1
                                • mrjjM mrjj

                                  @AlvaroS said:

                                  QString program = "princi";

                                  should be

                                  QString program = "/home/user1/princi";

                                  ?

                                  AlvaroSA Offline
                                  AlvaroSA Offline
                                  AlvaroS
                                  wrote on last edited by
                                  #17

                                  @mrjj It works in the same way... :(

                                  jsulmJ mrjjM 2 Replies Last reply
                                  0
                                  • AlvaroSA AlvaroS

                                    @mrjj It works in the same way... :(

                                    jsulmJ Online
                                    jsulmJ Online
                                    jsulm
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #18

                                    @AlvaroS So, if you enter /home/user1/princi in a terminal window and press enter it does not start? What happens? Any error message?

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

                                    AlvaroSA 1 Reply Last reply
                                    1
                                    • AlvaroSA AlvaroS

                                      @mrjj It works in the same way... :(

                                      mrjjM Offline
                                      mrjjM Offline
                                      mrjj
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #19

                                      @AlvaroS

                                      Ok, you must debug then
                                      try to use
                                      http://doc.qt.io/qt-5/qprocess.html#error
                                      to see what it thinks.

                                      AlvaroSA 1 Reply Last reply
                                      2
                                      • jsulmJ jsulm

                                        @AlvaroS So, if you enter /home/user1/princi in a terminal window and press enter it does not start? What happens? Any error message?

                                        AlvaroSA Offline
                                        AlvaroSA Offline
                                        AlvaroS
                                        wrote on last edited by
                                        #20

                                        @jsulm In a terminal if I write

                                        ./princi 0 747.37 427.68 0 844.37 42.54 prueba_princi.bmp 0 0 +
                                        

                                        in /home/user1/ directory it runs good

                                        jsulmJ AlvaroSA 2 Replies Last reply
                                        0
                                        • AlvaroSA AlvaroS

                                          @jsulm In a terminal if I write

                                          ./princi 0 747.37 427.68 0 844.37 42.54 prueba_princi.bmp 0 0 +
                                          

                                          in /home/user1/ directory it runs good

                                          jsulmJ Online
                                          jsulmJ Online
                                          jsulm
                                          Lifetime Qt Champion
                                          wrote on last edited by jsulm
                                          #21

                                          @AlvaroS Then try what @mrjj suggested

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

                                          1 Reply Last reply
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