Problem with qprocess

[jacek]

m_process->setProcessChannelMode(QProcess::MergedChannels) ;

Shouldn't you use QProcess::SeparateChannels here (i.e. the default mode)?

What do the "out" and "err" files contain after you do the following?

$ echo "3" > in # or whatever command is for "do nothing and exit"
$ thatcmd < in > out 2> err

[resal]

Shouldn't you use QProcess::SeparateChannels here (i.e. the default mode)?

I tried separate channels first, but to make stdout unbuffered, I used merged channel too. no success in both.

What do the "out" and "err" files contain after you do the following?

what that they expected to have. stderr messages in err file, and stdout menu in out file.[ My fault: when I said no success in getting those lines in redirections, I meant that I couldn't have those lines BEFORE writing to stdin. The problem is to have menu then providing input based on this menu.]

[resal]

Do you know any (not-very-complicated) (especially in Qt4) application with similar functionality? I mean an application which is a GUI that runs some commands AND communicates with those commands while they are still running(i.e. it doesn't wait for commands to finish and then gets the output; rather it gets the messages of commands during execution, displays the messages to user and then writes user options to command stdin). I reviewed konsole code, but got lost in (kde-related) classes....

thanks

[jacek]

what that they expected to have. stderr messages in err file, and stdout menu in out file.

OK, so at least that application isn't playing any tricks by detecting whether the input comes from a file or a terminal.

There is no way to control the buffers through QProcess, but maybe reimplementing QProcess::setupChildProcess() will help. You might try to alter the buffer size with setbuf, but I'm not sure if it's going to work (I think I've tried it to solve a similar problem, but without a success).

Do you know any (not-very-complicated) (especially in Qt4) application with similar functionality?

Unfortunately, I don't.

I reviewed konsole code, but got lost in (kde-related) classes....

kconsole doesn't use pure QProcess, but a K3Process subclass. The most important difference is that KDE allows you to use a pty device to communicate with the child process.

Here are the relevant sources:
http://websvn.kde.org/trunk/KDE/kdeb....h?view=markup
http://websvn.kde.org/trunk/KDE/kdeb...pp?view=markup
http://api.kde.org/4.0-api/kdelibs-a...rocess_8h.html
http://api.kde.org/4.0-api/kdelibs-a...classKPty.html

[resal]

Thank you jacek.

Here are the relevant sources:
http://websvn.kde.org/trunk/KDE/kdeb....h?view=markup
http://websvn.kde.org/trunk/KDE/kdeb...pp?view=markup
http://api.kde.org/4.0-api/kdelibs-a...rocess_8h.html
http://api.kde.org/4.0-api/kdelibs-a...classKPty.html

I have reviewed them before. As you said the trick in konsole is using kpty device.

There is no way to control the buffers through QProcess, but maybe reimplementing QProcess::setupChildProcess() will help. You might try to alter the buffer size with setbuf, but I'm not sure if it's going to work (I think I've tried it to solve a similar problem, but without a success).

I think this is the case. I 've played with setupChild Process() but I couldn't figured it out how to use it. I found these links though :
http://labs.trolltech.com/blogs/2006...with-qprocess/
http://www.koders.com/default.aspx?s...arch&la=*&li=*
http://www.koders.com/cpp/fidCB4E6B7...upchildprocess

The first one, I think, is the solution. I tried to find some example of its usage, so I search koders, which didn't help me a lot.

Can anyone write an example code about how to use the method that first link suggest?

Thanks in advance.

[jacek]

I think this is the case. I 've played with setupChild Process() but I couldn't figured it out how to use it.

You have to create a QProcess subclass and use that new class instead.

class UnbufferedProcess : public QProcess
{
   protected:
      void setupChildProcess()
      {
         ::setbuf( stdout, 0 );
      }
};

class UnbufferedProcess : public QProcess
{
   protected:
      void setupChildProcess()
      {
         ::setbuf( stdout, 0 );
      }
};

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But as I said, I'm not sure if it's going to help.

The first one, I think, is the solution. I tried to find some example of its usage, so I search koders, which didn't help me a lot.

You use it just like QProcess, but I'm not sure if it solves your problem. I think that this class is useful if the process you want to start insists on reading from the terminal. Nevertheless, try it.