[Qt-interest] newbie: application locks up

[john doe]

On Fri, May 1, 2009 at 3:07 PM, john doe <thebiggestbangtheory at gmail.com>wrote:

>
>
> On Fri, May 1, 2009 at 2:56 PM, john doe <thebiggestbangtheory at gmail.com>wrote:
>
>>
>>
>> On Fri, May 1, 2009 at 1:12 PM, john doe <thebiggestbangtheory at gmail.com>wrote:
>>
>>>
>>>
>>> On Fri, May 1, 2009 at 2:47 AM, chandrasekar wagmare <
>>> sekarwagmare at gmail.com> wrote:
>>>
>>>>
>>>> use this two signals in QProcess() :
>>>>  void readyReadStandardOutput();     //when a stdoutput is available
>>>>
>>>>  void readyReadStandardError();         //when a stderror is available
>>>>
>>>> and use  QByteArray readAllStandardOutput(); and readAllStandardError()
>>>> ; to read the std output or error of the external process in a QString and
>>>> display it in the box;
>>>>
>>>>
>>> This is great! thanks a ton!
>>>
>>>
>>>>
>>>> ay 1, 2009 at 1:19 PM, john doe <thebiggestbangtheory at gmail.com> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Fri, May 1, 2009 at 12:46 AM, chandrasekar wagmare <
>>>>> sekarwagmare at gmail.com> wrote:
>>>>>
>>>>>>
>>>>>> u have two ways, invoking an external program using QProcess()
>>>>>> and if u dont want the gui part freeze use QThread() .
>>>>>>
>>>>>
>>>>> awesome! I will look them up.. and since we are on the topic how can I
>>>>> set up a 2-way communication with the external program to display any error
>>>>> msgs in a text box or something?
>>>>>
>>>>> Thanks again
>>>>>
>>>>>
>>>>>> On Fri, May 1, 2009 at 1:08 PM, john doe <
>>>>>> thebiggestbangtheory at gmail.com> wrote:
>>>>>>
>>>>>>> Hello all,
>>>>>>>              Still relative newbie with Qt. I have made my first form
>>>>>>> containing combo buttons, lineedits and whatnot :-). I am facing a problem
>>>>>>> though regarding calling an external program from within the C++ Qt code.
>>>>>>>
>>>>>>> I have a ubuntu system and want to invoke a shell script which does
>>>>>>> some string manipulations on a large file. I used system() within the C++
>>>>>>> code to do it and it runs. The problem is that when I press a button to
>>>>>>> start the external program, if it takes 10 minutes to finish, the button
>>>>>>> seems to be depressed for this duraion. Basically, like waiting for the
>>>>>>> program to finish. How can I make the button not be depressed for this
>>>>>>> complete duration so that I can possibly start another instance of the
>>>>>>> external program by pressing a button on the main form.
>>>>>>>
>>>>>>> I am not an expert programmer, but I think this smells of
>>>>>>> asynchronous calls..right? Any insight would be greatly appreciated :-).
>>>>>>>
>>>>>>> I did try using a & at the end of the external program I am invoking
>>>>>>> but that does not help. Nothing runs. I am using kdesudo to start the
>>>>>>> external program as it requires certain privileges.
>>>>>>>
>>>>>>> Also I tried to use a progress bar with minimum and max set to 0 to
>>>>>>> continuosly work while the external program is running and it does not seem
>>>>>>> to work. Any pointers to threads/articles?
>>>>>>>
>>>>>>> Thanks in  advance.
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Qt-interest mailing list
>>>>>>> Qt-interest at trolltech.com
>>>>>>> http://lists.trolltech.com/mailman/listinfo/qt-interest
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> WAGMARE
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> WAGMARE
>>>>
>>>
>>> Thanks everyone for helping out. I used the suggestions to write up some
>> code..which unfortunately does not work.. its probably some easy thing that
>> I am not identifying!
>>
>> I am using Qt 4.4.3, on Ubuntu 8.10 and am using QDevelop as an IDE. I
>> have 3 files dialogimpl.h, min.cpp and dialogimpl.cpp. The code follows
>> below.
>>
>> dialogimpl.h
>> [code]
>>
>> #ifndef DIALOGIMPL_H
>>
>> #define DIALOGIMPL_H
>>
>> //
>>
>> #include <QDialog>
>>
>> #include "ui_dialog.h"
>>
>> //
>>
>> class DialogImpl : public QDialog, public Ui::mygui
>>
>> {
>>
>> Q_OBJECT
>>
>> public:
>>
>> DialogImpl( QWidget * parent = 0, Qt::WFlags f = 0 );
>>
>> public slots:
>>
>> void getPathdir();
>>
>> void getPathsisterfile();
>>
>> void startjob();
>>
>> void readstdoutput();
>>
>> };
>>
>> #endif
>> [/code]
>>
>> main.cpp contains
>> [code]
>>
>> #include <QApplication>
>>
>> #include "dialogimpl.h"
>>
>> //
>>
>> int main(int argc, char ** argv)
>>
>> {
>>
>> QApplication app( argc, argv );
>>
>> DialogImpl win;
>>
>> win.show();
>>
>> app.connect( &app, SIGNAL( lastWindowClosed() ), &app, SLOT( quit() ) );
>>
>> return app.exec();
>>
>> }
>>
>> [/code]
>>
>> and finally dialogimpl.cpp contains
>> [code]
>>
>> #include <QtGui>
>>
>> #include "dialogimpl.h"
>>
>> #include <stdio.h>
>>
>> #include <stdlib.h>
>>
>> #include <iostream>
>>
>> #include <fstream>
>>
>> #include <QThread>
>>
>> using namespace std;
>>
>> //code still being tested
>>
>> QObject *parent;
>>
>> QString program;
>>
>> QProcess *myProcess = new QProcess(parent);
>>
>> QStringList arguments;
>>
>>  //
>>
>> DialogImpl::DialogImpl( QWidget * parent, Qt::WFlags f)
>>
>> : QDialog(parent, f)
>>
>> {
>>
>> setupUi(this);
>>
>>  // signals/slots mechanism in action
>>
>> connect( startjobpushButton, SIGNAL( clicked() ), this, SLOT( startjob() )
>> );
>>
>> connect( pushButton_browse_1, SIGNAL( clicked() ), this, SLOT(
>> getPathdir() ) );
>>
>> connect( pushButton_browse_2, SIGNAL( clicked() ), this, SLOT(
>> getPathsisterfile() ) );
>>
>> connect(myProcess, SIGNAL(readyReadStandardOutput()), this,
>> SLOT(readstdoutput()));
>>
>> }
>>
>>
>> //This function makes does something
>>
>> void DialogImpl::startjob()
>>
>> {
>>
>> //declare vars
>>
>> ....
>>
>> //make a config file
>>
>>  QFile file("/home/temporary-file.txt");
>>
>> QString line;
>>
>> if ( file.open(QIODevice::WriteOnly) ) {
>>
>>  // file opened successfully
>>
>> // use a text stream
>>
>> QTextStream out( &file );
>>
>> out << "Target=" << Target << endl;
>>
>>  // Close the file
>>
>> file.close();
>>
>>  //start the job
>>
>>  program="echo";
>>
>> arguments << "hello";
>>
>> myProcess->start(program, arguments);
>>
>>          //remove the file
>>
>> file.remove();
>>
>> }
>>
>> else
>>
>> {
>>
>> //failed to open file
>>
>> textEdit_output->insertPlainText("ERROR: Failed to create temporary
>> file");
>>
>> }
>>
>>  }
>>
>> //This function allows for the user to
>>
>> //read std output
>>
>> void DialogImpl::readstdoutput()
>>
>> {
>>
>> QString output;
>>
>>  output=myProcess->readAllStandardOutput();
>>
>>
> I should have read it in QByteArray as suggested..god! ... seems to work
> now.
>
>
Things are working if I try to execute a simple command like Echo hello.

I need to run a script to do some stuff and it also asks for sudo passwd. I
can't figure out what to do now!! I tried using kdesudo as a helper program
but nothing really happens. I use kdesudo as the program ( for a QProcess )
I want to invoke and -c, <myscript.sh>,<param1> as arguments to the program.

Things work however if I employ the system() command with kdesudo -c
<myscript.sh> <param1> .. I see a pop up box and on entering the passwd
stuff happens. This way the form gets locked for the duration of the shell
script processing and I can't show output in the text box :-(.

Any suggestions from Qt gurus? :-)

>
> textEdit_output->insertPlainText("ERROR: test msg to be displayed in text
>> box");
>>
>> textEdit_output->append(output);
>>
>> }
>>
>> [/code]
>>
>> What I want to do is when I click startjobpushbutton, a process should be
>> invoked, which does "echo hello" and I should be able to see "hello" in the
>> textEdit_ouput text box. Currently, when I click the button nothing happens.
>> Can someone please provide a little insight.
>>
>> Thanks in advance.
>>
>
>
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