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. why QProcess not show output of ls /dev/sd* command ?
Forum Updated to NodeBB v4.3 + New Features

why QProcess not show output of ls /dev/sd* command ?

Scheduled Pinned Locked Moved Solved General and Desktop
18 Posts 4 Posters 1.1k 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.
  • Q Qt embedded developer

    i have implemted below code to find usb device name to print but its not working .

    Actually this command working when execute on linux terminal.

     Command = "ls";
    
    args<<" /dev/sd*"
    
        OProcess.start(Command,args,QIODevice::ReadOnly); //Starts execution of command
        OProcess.waitForFinished();                       //Waits for execution to complete
    
        QString sFromDateTime = OProcess.readAllStandardOutput();  //Reads standard output
        QString StdError = OProcess.readAllStandardError();
    
        if(StdError.isEmpty())
        {
    
            qDebug() << "output : " << sFromDateTime;
    
                QStringList List;
                   List = sFromDateTime.split("\n");
                   List = List.filter("/dev");
                   foreach(QString item, List)
                          qDebug() << "List items = " << item;
        }
        else
        {
            qDebug() << "StdError:" << StdError;
        }
    
    
    jsulmJ Offline
    jsulmJ Offline
    jsulm
    Lifetime Qt Champion
    wrote on last edited by jsulm
    #2

    @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

    Command = "ls";

    Use whole path to ls instead of relative path.
    Also, always add error handling code (https://doc.qt.io/qt-6/qprocess.html#errorOccurred) to know what happens...
    "/dev/sd*" will NOT work with QProcess, because the shell is resolving *.

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

    Q 1 Reply Last reply
    0
    • jsulmJ jsulm

      @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

      Command = "ls";

      Use whole path to ls instead of relative path.
      Also, always add error handling code (https://doc.qt.io/qt-6/qprocess.html#errorOccurred) to know what happens...
      "/dev/sd*" will NOT work with QProcess, because the shell is resolving *.

      Q Offline
      Q Offline
      Qt embedded developer
      wrote on last edited by Qt embedded developer
      #3

      @jsulm said in why QProcess not show output of ls /dev/sd* command ?:

      shell is resolving *

      so what i need to do to execute it ?

      i think its not relative path this is absolute path. if not then can you let me know how i can get absolute path ?

      jsulmJ 2 Replies Last reply
      0
      • Q Qt embedded developer

        i have implemted below code to find usb device name to print but its not working .

        Actually this command working when execute on linux terminal.

         Command = "ls";
        
        args<<" /dev/sd*"
        
            OProcess.start(Command,args,QIODevice::ReadOnly); //Starts execution of command
            OProcess.waitForFinished();                       //Waits for execution to complete
        
            QString sFromDateTime = OProcess.readAllStandardOutput();  //Reads standard output
            QString StdError = OProcess.readAllStandardError();
        
            if(StdError.isEmpty())
            {
        
                qDebug() << "output : " << sFromDateTime;
        
                    QStringList List;
                       List = sFromDateTime.split("\n");
                       List = List.filter("/dev");
                       foreach(QString item, List)
                              qDebug() << "List items = " << item;
            }
            else
            {
                qDebug() << "StdError:" << StdError;
            }
        
        
        JonBJ Offline
        JonBJ Offline
        JonB
        wrote on last edited by JonB
        #4

        @Qt-embedded-developer
        Because your /dev/sd* has a * wildcard in it. ls (or any other Linux command) does not expand wildcards. Only a shell expands wildcards! If you want to do it this way you will need:

         Command = "/bin/sh";
        
        args << "-c" << "ls /dev/sd*";
        

        Note that running a command to expand a filepath like this is not "efficient". You could do the work from, say, Qt QDir on /dev and look through the child filenames yourself to see which start with sd. Or QFileInfoList QDir::entryInfoList(const QStringList &nameFilters, QDir::Filters filters = NoFilter, QDir::SortFlags sort = NoSort) const could be used to do the wildcard matching. This would also be a lot cleaner than your code trying to parse ls's output.

        Q 1 Reply Last reply
        1
        • Q Qt embedded developer

          @jsulm said in why QProcess not show output of ls /dev/sd* command ?:

          shell is resolving *

          so what i need to do to execute it ?

          i think its not relative path this is absolute path. if not then can you let me know how i can get absolute path ?

          jsulmJ Offline
          jsulmJ Offline
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #5

          @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

          i think its not relative path this is absolute path

          How is ls an absolute path?!
          On my Ubuntu machine the absolute path to ls is /usr/bin/ls

          I'm wondering why you need QProcess for such a task at all? You can simply use https://doc.qt.io/qt-6/qdir.html

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

          Q 1 Reply Last reply
          0
          • Q Qt embedded developer

            @jsulm said in why QProcess not show output of ls /dev/sd* command ?:

            shell is resolving *

            so what i need to do to execute it ?

            i think its not relative path this is absolute path. if not then can you let me know how i can get absolute path ?

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

            @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

            can you let me know how i can get absolute path ?

            Execute the bellow command:
            which ls

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

            JonBJ 1 Reply Last reply
            1
            • jsulmJ jsulm

              @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

              can you let me know how i can get absolute path ?

              Execute the bellow command:
              which ls

              JonBJ Offline
              JonBJ Offline
              JonB
              wrote on last edited by JonB
              #7

              @jsulm said in why QProcess not show output of ls /dev/sd* command ?:

              which ls

              Observation: if which finds ls then there is no need to use a full path to it. And if it's not on your path which won't find it! :)

              1 Reply Last reply
              1
              • jsulmJ jsulm

                @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

                i think its not relative path this is absolute path

                How is ls an absolute path?!
                On my Ubuntu machine the absolute path to ls is /usr/bin/ls

                I'm wondering why you need QProcess for such a task at all? You can simply use https://doc.qt.io/qt-6/qdir.html

                Q Offline
                Q Offline
                Qt embedded developer
                wrote on last edited by
                #8

                @jsulm means i just need to check there is file name start with sd is there on not int /dev directory

                jsulmJ 1 Reply Last reply
                0
                • JonBJ JonB

                  @Qt-embedded-developer
                  Because your /dev/sd* has a * wildcard in it. ls (or any other Linux command) does not expand wildcards. Only a shell expands wildcards! If you want to do it this way you will need:

                   Command = "/bin/sh";
                  
                  args << "-c" << "ls /dev/sd*";
                  

                  Note that running a command to expand a filepath like this is not "efficient". You could do the work from, say, Qt QDir on /dev and look through the child filenames yourself to see which start with sd. Or QFileInfoList QDir::entryInfoList(const QStringList &nameFilters, QDir::Filters filters = NoFilter, QDir::SortFlags sort = NoSort) const could be used to do the wildcard matching. This would also be a lot cleaner than your code trying to parse ls's output.

                  Q Offline
                  Q Offline
                  Qt embedded developer
                  wrote on last edited by
                  #9

                  @JonB said in why QProcess not show output of ls /dev/sd* command ?:

                  QFileInfoList QDir::entryInfoList(const QStringList &nameFilters, QDir::Filters filters = NoFilter, QDir::SortFlags sort = NoSort) const

                  as per my case what i need to write in above ?

                  jsulmJ 1 Reply Last reply
                  0
                  • Q Qt embedded developer

                    @jsulm means i just need to check there is file name start with sd is there on not int /dev directory

                    jsulmJ Offline
                    jsulmJ Offline
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #10

                    @Qt-embedded-developer Yes, get entries in /dev folder using QDir::entryInfoList and filter all entries starting with sd (you can pass file name filter directly to QDir::entryInfoList).

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

                    1 Reply Last reply
                    0
                    • Q Qt embedded developer

                      @JonB said in why QProcess not show output of ls /dev/sd* command ?:

                      QFileInfoList QDir::entryInfoList(const QStringList &nameFilters, QDir::Filters filters = NoFilter, QDir::SortFlags sort = NoSort) const

                      as per my case what i need to write in above ?

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

                      @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

                      as per my case what i need to write in above ?

                      What exactly is not clear?

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

                      Q 1 Reply Last reply
                      1
                      • jsulmJ jsulm

                        @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

                        as per my case what i need to write in above ?

                        What exactly is not clear?

                        Q Offline
                        Q Offline
                        Qt embedded developer
                        wrote on last edited by Qt embedded developer
                        #12

                        @jsulm sorry its clear. i have to try. but if possible can you give example so it can help better.

                        Christian EhrlicherC 1 Reply Last reply
                        0
                        • Q Qt embedded developer

                          @jsulm sorry its clear. i have to try. but if possible can you give example so it can help better.

                          Christian EhrlicherC Offline
                          Christian EhrlicherC Offline
                          Christian Ehrlicher
                          Lifetime Qt Champion
                          wrote on last edited by
                          #13

                          @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

                          but if possible can you give example so it can help better.

                          Maybe reading the answers would help - it was already given...

                          Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                          Visit the Qt Academy at https://academy.qt.io/catalog

                          Q 1 Reply Last reply
                          0
                          • Christian EhrlicherC Christian Ehrlicher

                            @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

                            but if possible can you give example so it can help better.

                            Maybe reading the answers would help - it was already given...

                            Q Offline
                            Q Offline
                            Qt embedded developer
                            wrote on last edited by Qt embedded developer
                            #14

                            @Christian-Ehrlicher i have tried like below but i am getting empty list from fileinfolist

                            QString myPath="/dev";
                                    QDir dir;
                                    dir.setPath(myPath);
                                    QStringList filters;
                                    filters<<"sd";
                                    dir.setFilter( QDir::AllEntries | QDir::System);
                                    dir.setNameFilters(filters);
                                    dir.setSorting(QDir::Name );
                                    QFileInfoList list = dir.entryInfoList();
                            
                            

                            why my list is not giving file name what is expected ?

                            JonBJ 1 Reply Last reply
                            0
                            • Christian EhrlicherC Offline
                              Christian EhrlicherC Offline
                              Christian Ehrlicher
                              Lifetime Qt Champion
                              wrote on last edited by
                              #15

                              Because there is no /dev/sd in your directory. Please read the documentation...

                              Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                              Visit the Qt Academy at https://academy.qt.io/catalog

                              Q 1 Reply Last reply
                              0
                              • Christian EhrlicherC Christian Ehrlicher

                                Because there is no /dev/sd in your directory. Please read the documentation...

                                Q Offline
                                Q Offline
                                Qt embedded developer
                                wrote on last edited by
                                #16

                                @Christian-Ehrlicher actually above code i written to find name that start with sd .

                                Christian EhrlicherC 1 Reply Last reply
                                0
                                • Q Qt embedded developer

                                  @Christian-Ehrlicher actually above code i written to find name that start with sd .

                                  Christian EhrlicherC Offline
                                  Christian EhrlicherC Offline
                                  Christian Ehrlicher
                                  Lifetime Qt Champion
                                  wrote on last edited by Christian Ehrlicher
                                  #17

                                  @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

                                  actually above code i written to find name that start with sd .

                                  No, RTFM!

                                  Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                                  Visit the Qt Academy at https://academy.qt.io/catalog

                                  1 Reply Last reply
                                  0
                                  • Q Qt embedded developer

                                    @Christian-Ehrlicher i have tried like below but i am getting empty list from fileinfolist

                                    QString myPath="/dev";
                                            QDir dir;
                                            dir.setPath(myPath);
                                            QStringList filters;
                                            filters<<"sd";
                                            dir.setFilter( QDir::AllEntries | QDir::System);
                                            dir.setNameFilters(filters);
                                            dir.setSorting(QDir::Name );
                                            QFileInfoList list = dir.entryInfoList();
                                    
                                    

                                    why my list is not giving file name what is expected ?

                                    JonBJ Offline
                                    JonBJ Offline
                                    JonB
                                    wrote on last edited by
                                    #18

                                    @Qt-embedded-developer said in why QProcess not show output of ls /dev/sd* command ?:

                                    filters<<"sd";

                                    void QDir::setNameFilters(const QStringList &nameFilters)

                                    Each name filter is a wildcard (globbing) filter that understands * and ? wildcards. See QRegularExpression::fromWildcard().

                                    1 Reply Last reply
                                    0

                                    • Login

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