I am working in Qt 4.7, and I have a program that needs to use a QProcess to output the result of running a Windows PowerShell command. For the purposes of this question, let's say all that needs to be supported is use of the "-Command" option. Right now I have this:
QString path = "C:/windows/system32/WindowsPowerShell/v1.0/powershell.exe";
QStringList command;
command.append("-Command");
command.append(/*Whatever test command I want to use...*/);
process = new QProcess(); //Note: QProcess *process is a member of this class
connect(process, SIGNAL(error(QProcess::ProcessError)), this, SLOT(/*slot to print qprocess errors...*/);
connect(process, SIGNAL(readyReadStandardOutput()), this, SLOT(/*slot to display PowerShell output...*/);
process->start(path, command);
The slot to print the PowerShell output is simply as follows:
std::cout << "RESULT: " << QString(process->readAllStandardOutput()).toStdString() << std::endl;
This works perfectly with correct PowerShell commands. For example, I tested it with the command "Get-ChildItem C:\", and it printed the correct data. It also works fine if there is a QProcess error. What I need to know how to do is, how can I have it print a PowerShell error message? For example, if I try to use the command "Get-ChildIte" (missing the m at the end) directly in PowerShell I get an error message. But with my code, it just doesn't print anything. I need it to print that error message. If anyone knows of a way this could be done, I'd really appreciate it. Thanks!
Ok, you posted your answer 7 seconds ago. I just wanted to confirm, and give a link to reference for you that may help troubleshoot this in the future.
QProcess Class
Yes, you want the readAllStandardError() function of QProcess.
So, about a minute after I posted this I discovered QProcess's signal readyReadStandardError(), which operates identically to readyReadStandardOutput except that it is emitted when whatever the QProcess is running has an error. I connected this to a slot identical to what I have above but instead printing QString(process->readAllStandardError()).toStdString() and it worked.
Related
I'm new using QT, I need to execute a CMD command on windows and get the output of this command as a string to later process and get specific data. The following code works well (it seems to work well). The only problem is that I get the following warning: "start is deprecated", I think this warning message is because the start method needs an arguments list as parameter.
QString command = "tasklist /FI \"IMAGENAME eq notepad.exe\"";
QProcess *executeCommand = new QProcess();
executeCommand->start(command);
executeCommand->waitForFinished(-1);
QString output = executeCommand->readAllStandardOutput();
executeCommand->terminate();
qDebug() << commandOutput;
how can I remove this warning message?
Also I found in the web that I can use system() to execute a CMD command, but I'm not able to catch the output as string.
Another question: which of the above options is better to achieve what I'm trying to do, the QProcess or System (if is possible to get the output as QString)?
Thanks in advance!
There is an answer read QProcess output to string recommending static method QProcess::readAllStandardOutput() returning QByteArray. Then just instantiate QString from QByteArray implicitly.
If you are working on Qt application, it is better to stay inside Qt API to keep the code more or less portable.
I want to backup my database with qprocess in QT program, the code is as follows, but 0kb occurs when backing up and when I look at the error Qprocess: Destroyed while process("mysqldump.exe") is still runnuing.
QProcess dump(this);
QStringlist args;
QString path="C:/Users/mahmut/Desktop/dbbackupfile/deneme.sql";
args<<"-uroot"<<"-proot"<<"kopuz"<<">";
dump.setStandardOutputFile(path);
dump.start("mysqldump.exe",args);
if(!dump.waitForStarted(1000))
{
qDebug()<<dump.errorString();
}
Can you help to me? ı do not understand this error and okb back up file.
Your program terminates before process finished, you need to either use static bool QProcess::startDetached(program, arguments, workingDirectory) or add dump.waitForFinished(); to the end.
Also, you dont need to add ">" to arguments. You already redirected output with dump.setStandardOutputFile(path), ">" does not work with process as it requires shell to execute command, QProcess does not use shell it just runs one process not shell expression.
In my QT widget application I am attempting to run a shellscript that opens a C++ program and provides inputs to the program as well. The program starts a command prompt that requires the users input to start. Once the program is started the output of the program is redirected via the standard output to a text file. I am attempting to use QProcess to open and run this shellscript, then read the standard output that is being used to print the result of the C++ program to the text file. The shell script only runs this process and does not terminate it. This is because I need to continuously read this output into the GUI as the program is running. It will not be sufficient to wait until the program is finished to read this information. I am fairly new to QT and C++ programming. I was hoping that someone could help me with my implementation of this.
QProcess process;
process.start("/home/pi/Desktop/ShellScripts/RunTutorial3.sh");
QString output =process.readAllStandardOutput();
qDebug() << output;
QString err = process.readAllStandardError();
qDebug() << err;
I have experimented with using other read function such as readline and also trying to start the process as a detatched process. I have not had success with any of my experimentations. Is it possible to do what I am attempting in QT. I just need the program to run continuously and for QT to read this output every so often.
Shell script:
#!/bin/bash
cd
cd Desktop
cd tutorial3App
cd bin
echo "start" | ./tutorial3
C++ code: I need the meanTOE value to be captured in standard output to use in my GUI.
/ Calculate average time to end of discharge
double meanToE = std::accumulate(ToESamples.begin(), ToESamples.end(), 0.0)/ToESamples.size();
file << ": EOL in " << meanToE << " s" << std::endl;
As I said in my comments one of the main problems is that when you run tutorial3 that process is separated so you can not get the output. Therefore, I recommend executing it directly, and QProcess is probably a local variable, eliminating after printing an empty text, a possible solution is to create a pointer. Another improvement would be to use the readyReadStandardOutput and readyReadStandardError signals since the impressions are not automatic.
QProcess *process = new QProcess(this);
connect(process, &QProcess::readyReadStandardOutput, [process, this](){
QString output =process->readAllStandardOutput();
qDebug() << "output: "<< output;
});
connect(process, &QProcess::readyReadStandardError, [process](){
QString err = process->readAllStandardError();
qDebug() << "error: "<<err;
});
process->setWorkingDirectory("/home/pi/Desktop/tutorial3App/bin/")
process->start("tutorial3", QStringList() << "start");
I think you have to read about signals and slots in Qt. QProcess has got a signal readyReadStandardOutput. So you have to connect to this signal and in your slot you should use QProcess function readAllStandardOutput. In other words when your shell programm outputs something you catch it in your slot and dump it or whatever you want.
Check the answer on this question. It might help you.
reading and writing to QProcess in Qt Console Application
I start rsync in QProcess. My process runs fine (in its own terminal) if I use QProcess::startDetached() but nothing happens if I start it with QProcess:start(). The problem seems to be that QProcess can't apparently read messages from rsync and write it to the output window.
I have connect this signal in constructor.
MainWindow::~MainWindow()
{
process = new QProcess(this);
connect( process, SIGNAL(readyReadStandardOutput()), this, SLOT(onReadyReadStandardOutput() ) );
}
Later on button clicked I call:
void MainWindow::onButton1Clicked()
{
process->start("rsync -a root#10.0.0.1:/path/ /rsync_folder");
//process->start("ping 10.0.0.01"); // this works for testing and I see output but not the above.
}
When rsync starts, it prints a message and ask for password..none of it is received by my QProcess but the ping message are received..what could be possibly wrong here?
The above grieving line also works directly on windows 7 command line but it just doesn't seem to show any progress in QProcess.
Update
Here is how I displaying the output.
void MainWindow::onReadyReadStandardOutput()
{
qDebug() << process->readAllStandardOutput();
}
http://doc.qt.io/qt-5/qprocess.html#communicating-via-channels
Did you remember to link to and check the standard error channel?
http://doc.qt.io/qt-5/qprocess.html#readAllStandardError
That has fixed it for me in the past for some QProcesses I have started.
Another way I've done it, is to use QProcess::startDetached();
Hope that helps.
My research shows that rsync probably behaves like scp which accordingly this answer doesn't generate output when it is redirected.
Ok, so I am executing a program ./led.sh present in my SBC6845, from my host system using a qt-C++ program. This program basically connects my SBC to my host system. It is the equivalent of "hyperterminal" or "Minicom". I obtained this program (the example code) "uartassistant" inside "qextserialport-1.2rc.zip" from http://code.google.com/p/qextserialport/ .
I came across this link: Running shell command in QT c++ in ubuntu , while searching how to execute a shell command from inside the qt program. I tried and succeeded in executing ./led.sh. Thanks to the link.
I declared
void someaction(); // in the dialog.h
then in dialog.cpp I add this
connect(ui->pushButton, SIGNAL(clicked()), SLOT(someaction()));
and this
void Dialog::someaction()
{
QString command = "sh ./led.sh\r\n"; const char* command2;
command2 = command.toLocal8Bit().data();
port->write(command2);
I was able to do the ledflash in my SBC.
But the problem occurs when I try to stop ./led.sh, I am unable to do so in the uartassistant (bugs, need modification, still working).
But for the time being I am trying to make another pushbutton_1 and put something like "Ctrl+Z" inside and ask ./led.sh to stop.
I came across some other links which I am unable to put due to low reputation points.
I have no idea how to use SIGTERM / kill option[from other links] inside qt app and execute on pushbutton click.
Say if I used kill how would I determine the pidof of multiple such pushbutton actions and assign whom to kill.
Also I would like to add that my SBC has ash [Almquist shell]. So it being low memory clone of Bourne shell, I don't know if it would support normal commands for exiting led.sh.
I have no idea how to use SIGTERM / kill option[from other links]
inside qt app and execute on pushbutton click.
As with so much, Qt gives you an intuitive abstraction that allows you to not have to worry about any of this, namely QProcess. In your case you'd want something like this:
QProcess proc;
proc.start("led.sh");
...
//handle Ctrl-Z event
proc.close();
The first answer here has several other techniques for executing more complicated shell commands.
I have found a temporary solution for my problem. I am yet to try the qprocess action.
In dialog.h I added another function:
void someotheraction();
then in dialog.cpp I did this:
connect(ui->pushButton_2,SIGNAL(clicked()), SLOT(someotheraction()));
and this:
void Dialog::someotheraction()
{
QString command = "\x001a \r\n"; const char* command2; // Ctrl-Z = \x001a
command2 = command.toLocal8Bit().data();
port->write(command2);}
The fifth reply here gave me the idea. I don't know how, but it did the job maybe some one can explain it better.