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

[Princy K. V.]

Hi,
 Thanks forum..
Information in the following link solved my issues..
http://lists.trolltech.com/qt-interest/2004-08/thread00314-0.html

Thanks chandrasekar wagmare for all ur suggestions..


Thanks
Princy





    Re: About QProcess :How to read stdoutput realtime?
      (chandrasekar wagmare)


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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The company/sender cannot be responsible for any unauthorized alterations or modifications made to the contents. If you require any form of confirmation of the contents, please contact the company/sender. The company/sender is not liable for any errors or omissions in the content of this message.