QProcess: start a compiled c program and output to textBrowser in Linux
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wrote on 15 Dec 2017, 15:53 last edited by
Hi, welcome to the forum. Check the ProcessError to get a hint on what went wrong. Also, add a call to waitForStarted and see if it hangs. Judging by the pathname, your
a.outis owned by the userroot. I assume you're not logged in as root so you probably don't have the sufficient access rights to run that executable. -
Hi
Besides what @Wieland suggests
did you try open a shell and just type
/root/Desktop/a.outand see if it can run ?
in some cases it wants
chmod +x a.outto even be allowed to run.
(normally the compiler / linker does that for you) -
I have search and looked at other examples but nothing seems to work.
Here are where I've referred to:
http://www.qtforum.org/article/3079/howto-start-an-external-program-from-a-qt-application.html
http://doc.qt.io/qt-5/qprocess.html
and a few othersHere's what I have in my project:
mainwindow.h#ifndef MAINWINDOW_H #define MAINWINDOW_H #include <QMainWindow> namespace Ui { class MainWindow; } class MainWindow : public QMainWindow { Q_OBJECT public: explicit MainWindow(QWidget *parent = 0); ~MainWindow(); private slots: void on_pushButton_clicked(); private: Ui::MainWindow *ui; }; #endif // MAINWINDOW_Hmain.cpp
#include "mainwindow.h" #include <QApplication> #include <QPushButton> int main(int argc, char *argv[]) { QApplication a(argc, argv); MainWindow w; w.show(); return a.exec(); }mainwindow.cpp
#include "mainwindow.h" #include "ui_mainwindow.h" #include <QProcess> MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow) { ui->setupUi(this); } MainWindow::~MainWindow() { delete ui; } void MainWindow::on_pushButton_clicked() { QProcess proc; proc.start("/root/Desktop/a.out"); proc.waitForFinished(); QString output = proc.readAllStandardOutput(); ui->textBrowser->setText(output); }mainwindow.ui
<?xml version="1.0" encoding="UTF-8"?> <ui version="4.0"> <class>MainWindow</class> <widget class="QMainWindow" name="MainWindow"> <property name="geometry"> <rect> <x>0</x> <y>0</y> <width>683</width> <height>519</height> </rect> </property> <property name="maximumSize"> <size> <width>1112</width> <height>625</height> </size> </property> <property name="windowTitle"> <string>MainWindow</string> </property> <widget class="QWidget" name="centralWidget"> <widget class="QTextBrowser" name="textBrowser"> <property name="geometry"> <rect> <x>20</x> <y>50</y> <width>631</width> <height>191</height> </rect> </property> </widget> <widget class="QWidget" name="layoutWidget"> <property name="geometry"> <rect> <x>20</x> <y>10</y> <width>631</width> <height>30</height> </rect> </property> <layout class="QHBoxLayout" name="horizontalLayout"> <item> <widget class="QPushButton" name="pushButton"> <property name="text"> <string>Start pcap (100p)</string> </property> </widget> </item> <item> <spacer name="horizontalSpacer"> <property name="orientation"> <enum>Qt::Horizontal</enum> </property> <property name="sizeHint" stdset="0"> <size> <width>200</width> <height>20</height> </size> </property> </spacer> </item> </layout> </widget> </widget> <widget class="QMenuBar" name="menuBar"> <property name="geometry"> <rect> <x>0</x> <y>0</y> <width>683</width> <height>25</height> </rect> </property> </widget> <widget class="QToolBar" name="mainToolBar"> <attribute name="toolBarArea"> <enum>TopToolBarArea</enum> </attribute> <attribute name="toolBarBreak"> <bool>false</bool> </attribute> </widget> <widget class="QStatusBar" name="statusBar"/> </widget> <layoutdefault spacing="6" margin="11"/> <resources/> <connections/> </ui>When I clicked the pushButton nothing happens but if I tried using Linux system's command in the QProcess such as
QProcess proc; proc.start("ls -al"); proc.waitForFinished(); QString output = proc.readAllStandardOutput(); ui->textBrowser->setText(output);It works where in the textBrowser it will list files/folders in the home directory.
I've also tried with sh -c but still doesn't work.proc.start("sh", QStringList() << "-c" << "/root/Desktop/a.out");Is there way to execute a compiled c program using QProcess?
I'm at lostwrote on 15 Dec 2017, 19:14 last edited by@Naim , @mrjj
If you like trivia (you probably don't...), you can actually execute it without the execute bit set via the accepted answer to https://superuser.com/questions/341439/can-i-execute-a-linux-binary-without-the-execute-permission-bit-being-set :) -
@Naim , @mrjj
If you like trivia (you probably don't...), you can actually execute it without the execute bit set via the accepted answer to https://superuser.com/questions/341439/can-i-execute-a-linux-binary-without-the-execute-permission-bit-being-set :)@JNBarchan
But does it set the bit ?
chmod a-x /tmp/ls -
Hi, welcome to the forum. Check the ProcessError to get a hint on what went wrong. Also, add a call to waitForStarted and see if it hangs. Judging by the pathname, your
a.outis owned by the userroot. I assume you're not logged in as root so you probably don't have the sufficient access rights to run that executable. -
@Wieland Yes I'm using root. As for ProcessError and waitForStarted I'll reply that later
@mrjj I compiled a.out as the root user@Naim
Ok, so you are logged in as root. so its not just rights issue.
Hopefully ProcessError tells you why it cant run :) -
@Naim
Ok, so you are logged in as root. so its not just rights issue.
Hopefully ProcessError tells you why it cant run :) -
@mrjj said in QProcess: start a compiled c program and output to textBrowser in Linux:
@JNBarchan
But does it set the bit ?
chmod a-x /tmp/lschmod a-x /tmp/lsclears the executable bit ;) -
@mrjj said in QProcess: start a compiled c program and output to textBrowser in Linux:
@JNBarchan
But does it set the bit ?
chmod a-x /tmp/lschmod a-x /tmp/lsclears the executable bit ;)@aha_1980
ahh of course its -x :)
my brain said a TO x (facepalm)
So it can run without it using LD and some magic. Cool. -
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@aha_1980 Yes I can run it in shell with ./root/Desktop/a.out. I'm using the root user on a virtual machine.
wrote on 18 Dec 2017, 02:39 last edited byI may have find the problem here. My C program a.out runs indefinitely and textBrowser only shows the output once my program have finished executing. I've tried to run another C program that accepts command line input to loop how many times. Its output shows up in textBrowser after it has done looping.
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I may have find the problem here. My C program a.out runs indefinitely and textBrowser only shows the output once my program have finished executing. I've tried to run another C program that accepts command line input to loop how many times. Its output shows up in textBrowser after it has done looping.
@Naim Use http://doc.qt.io/qt-5/qprocess.html#readyReadStandardOutput and http://doc.qt.io/qt-5/qprocess.html#readyReadStandardError to get notifications each time the process writes something to stdout or stderr and read it using http://doc.qt.io/qt-5/qprocess.html#readAllStandardOutput and http://doc.qt.io/qt-5/qprocess.html#readAllStandardError. Do not call waitForFinished, just make sure your proc does not go out of scope (make it class member).
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