Create a system command line with QT

QT practical tutorial:

Source address: [QT] Implementing a command line through QProcess
After understanding QProcessthe power, you can implement a system command line.

Create a new QT project, then drag one lineEditto rename lineCode; drag one textBrowserto rename txtRecv. Right click lineEditto go to the slot and add an returnPressed()action to it.

Its code is

void MainWindow::on_lineCode_returnPressed()
{
    
    
    QProcess cmd;
    QString codes = ui->lineCode->text();
    QStringList para = codes.split(" ");
    cmd.start(para.first(),para.sliced(1));
    cmd.waitForStarted();
    cmd.waitForFinished();
    ui->lineCode->setText("");
    ui->txtRecv->append(codes);
    ui->txtRecv->append(cmd.readAllStandardOutput());
}

The effect is

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There is a problem with this, that is, the error cannot be displayed. Obviously, the last input is qnmdnot a command, but there is no prompt, so it needs to print the error. So pull a new one txtcontent, then change the code to

void MainWindow::on_lineCode_returnPressed()
{
    
    
    QProcess cmd;
    QString codes = ui->lineCode->text();
    QStringList para = codes.split(" ");
    cmd.start(para.first(),para.sliced(1));
    cmd.waitForStarted();
    cmd.waitForFinished();
    ui->lineCode->setText("");
    QString output = cmd.readAllStandardOutput();
    if(!output.isEmpty()){
    
    
        ui->txtRecv->append(codes);
        ui->txtRecv->append(output);
    }
    QString err = cmd.readAllStandardError();
    if(!err.isEmpty()){
    
    
        ui->txtError->append(codes);
        ui->txtError->append(err);
    }
}

The effect is

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But this does not actually solve the problem of wrong instructions. Since qnmdit is not a valid instruction, there is neither standard output nor standard error.

In order to identify this situation, a member function can be called error(), and its return value is an enumeration type. When the return value 0is, it means that the startup program failed.

The effect is

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just waitForFinished();insert below

if(cmd.error()==0)
  ui->txtError->append(codes+" error!!!\n请输入正确的指令");

The error()returned enumeration type is as follows

`QProcess::`	value	describe
FailedToStart	0	process failed to start
Crashed	1	Crash after process succeeds
Timedout	2	The last call to waitFor...() function timed out. At this point, the state of QProcess remains unchanged, and functions of type waitFor...() can be called again
WriteError	3	There was an error writing data to the process. If the process has not started, or the input channel is closed.
ReadError	4	Error reading data from process. If the process has not started
UnknownError	5	Default return value, unknown or no error.

In the end, I still feel that something is wrong. The main reason is that the current position will be given in the command line. This is not difficult, just use

QString path = QCoreApplication::applicationDirPath();
codes = path + ">" + codes;

Then you can see

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Create a system command line with QT

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