I used a QProcess to launch xterm and try to get tty. And I used this:

proc=new QProcess(this);
QStringList args;
proc->start("xterm", args, QIODevice::ReadWrite);
proc->waitForStarted();
qDebug()<<proc->write("tty\r\n");
qDebug()<<QString(proc->readAllStandardOutput());

But when it's running, it just launch a xterm without doing anything. But write() returns 5. I've e tried ubuntu terminal. It seems works the same as xterm. Other command line tools works well, like GDB or GCC. This must be a bug of QProcess. Or is there something I didn't notice?