[Qt-interest] About QProcess :How to read stdoutput

Tue May 5 13:22:42 CEST 2009

i am not familiar with windows but i can predict that the problem is with
the external program u are trying to start with QProcess ...

On Tue, May 5, 2009 at 4:45 PM, Princy K. V. <princy.kv at nestgroup.net>wrote:

> Thanks for that information...
> My app is running in windows..
>
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>   1. Re: About QProcess :How to read stdoutput realtime?
>      (chandrasekar wagmare)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 5 May 2009 16:36:28 +0530
> From: chandrasekar wagmare <sekarwagmare at gmail.com>
> Subject: Re: [Qt-interest] About QProcess :How to read stdoutput
>        realtime?
> To: "qt-interest at trolltech.com" <qt-interest at trolltech.com>
> Message-ID:
>        <3bba330b0905050406y569c8b04ge912d9bcd13d5c15 at mail.gmail.com>
> Content-Type: text/plain; charset="windows-1252"
>
> no not to flush your Qt code .. check the output of  the external
> program u
> try to run from QProcess ... ex: if u are trying to run application
> "a.out"
> ..
>  in "a.out"  there may be any problem with stdout ...
>
> are u using linux .. if so
> run the application with this command
>      *a.out | less*
>
> and check if it is printing the output in regular interval ...
> On Tue, May 5, 2009 at 4:30 PM, Princy K. V.
> <princy.kv at nestgroup.net>wrote:
>
> >  Hi,
> >
> >  Sorry to interrupt  again..
> >
> > I modified code ..but Start slot never invoked? Why is it so??
> >
> >
> >
> > connect(process , SIGNAL(readyRead()) , process, SLOT(Start()));
> >
> >
> >
> > void CMainWindow::Start()
> >
> > {
> >
> > QByteArray byteArray;
> >
> > byteArray.resize(2000);
> >
> > byteArray.clear();
> >
> > fflush(stdout);
> >
> > byteArray=process->readAllStandardOutput();
> >
> > ui->plainTextEdit->appendPlainText(byteArray);
> >
> > }
> >
> >
> >
> > Thanks..
> >  ------------------------------
> >
> > *From:* chandrasekar wagmare [mailto:sekarwagmare at gmail.com]
> > *Sent:* Tuesday, May 05, 2009 3:33 PM
> > *To:* Princy K. V.
> > *Subject:* Re: [Qt-interest] About QProcess :How to read stdoutput
> > realtime?
> >
> >
> >
> > it's a problem of an incorrectly setup buffering method... and
> >
> > you won't be able to solve this from within your calling program.
> > Either "patch" the program you are calling to use line buffering --
> > setlinebuf(stdout) -- or use fflush(stdout) every now and then in this
> > program. If you can't do this, then there's no way to solve it.
> >
> > It's NOT a problem of QProcess or anything you could solve by any
> trickery
> > here... I have similar issues with some of the programs that I call
> from
> > some
> > of my apps and there's no way around it (at least no platform
> independent
> > one).
> > ex: i am using linux to run an external system call glxgears in
> QProcess
> > and i get output after ten minutes only or when the buffer filled
> completly
> > ..
> >         i try this one "glxgears | less" and find the problem in
> buffer
> > flush
> >
> > On Tue, May 5, 2009 at 2:43 PM, Princy K. V. <princy.kv at nestgroup.net>
> > wrote:
> >
> > Hi,
> >
> > Thanks for ur reply.
> >
> > But slot is not invoked when I used these signals
> *readyReadStandardError
> > * <http://qprocess.html#readyReadStandardError> () & *
> > readyReadStandardOutput*
> <http://qprocess.html#readyReadStandardOutput> (
> >
> > ..so I used following code snippets, this consumes lot of
> time..sometimes
> > not getting desired output..
> >
> >
> >
> > void CMainWindow::Run()
> >
> > {
> >
> > QByteArray byteArray;
> >
> > byteArray.resize(2000);
> >
> > byteArray.clear();
> >
> > ui->plainTextEdit->setEnabled(true);
> >
> > ui->plainTextEdit->clear();
> >
> > while(!Start())
> >
> > {
> >
> > //progress->hide();
> >
> > byteArray.clear();
> >
> > byteArray=process->readAllStandardOutput();
> >
> > ui->plainTextEdit->appendPlainText(byteArray);
> >
> > }
> >
> > }
> >
> >
> >
> > void CMainWindow::Start()
> >
> > {
> >
> > ??.
> >
> > process->start("xx.exe" ,arguments);
> >
> > if (!process->waitForStarted())
> >
> > return false;
> >
> > // ui->statusBar->addPermanentWidget(progress , 0);
> >
> > if(!process->waitForFinished())
> >
> > {
> >
> > //progress->setMinimum(0);
> >
> > //progress->setMaximum(0);
> >
> > //progress->show();
> >
> > return false;
> >
> > }
> >
> > ??
> >
> > return true;
> >
> > }
> >
> >
> >
> >
> >
> >
> >  ------------------------------
> >
> >
> >
> > u are using this signals right ,
> >
> > void
> *readyReadStandardError*<http://qprocess.html#readyReadStandardError>()
> >
> > void
> *readyReadStandardOutput*<http://qprocess.html#readyReadStandardOutput>(
> )
> >
> >
> >
> > On Tue, May 5, 2009 at 1:04 PM, Princy K. V. <princy.kv at nestgroup.net>
> > wrote:
> >
> > Hi,
> >  I m new to Qt.I want to display datas that are written on stdoutput
> by
> > an external process on my gui. I have started external process using
> > Qprocess. I can display all stdoutput data by calling,
> > byteArray=process->readAllStandardOutput();
> > ui->plainTextEdit->appendPlainText(byteArray);
> > But my reqiurment is to display data(line by line) same time it is
> > written on stdoutput.i have tried many methods.so far didn't get
> > required output..
> > Please suggest me some solutions..
> > Thanks..
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