How To Read a Text File Contents Located on a FTP Server

rezaMSLM

I have written a program to login to my ftp account:
Here
Now i want to read a text file Located on my FTP server and search for some special strings in it; if there is do something if not do another.
how can I do this?

mrjj

Hi
Since you are using the QFtp class then the old samples can be useful.
This list and downloads files from ftp
http://doc.qt.io/archives/qt-4.8/qt-network-qftp-example.html

Overall the process is.

// connect finished signal
  ftp = new QFtp(this);
    connect(ftp, SIGNAL(commandFinished(int,bool)),   this, SLOT(ftpCommandFinished(int,bool)));
// login etc
// ask for file
 ftp->get(filename, file);

The void FtpWindow::downloadFile() should be what you need.

aha_1980

Hi @rezaMSLM,

the short recipe is:

download the file by FTP with QFtp
store the file in a temp folder (make sure to override existing files or give them unique names): QTemporaryFile
open the file and search for your strings: QFile, QTextStream

Regards

Edit: @mrjj was faster once again ;)

rezaMSLM

when using QFtp::get() method to download a file from server where is the file stored?

aha_1980

@rezaMSLM said in How To Read a Text File Contents Located on a FTP Server:

when using QFtp::get() method to download a file from server where is the file stored?

You provide a pointer to a QFile as second parameter of get(). So it's up to you where the file lands.

Just have a deep look the the Example that was recommended you by @mrjj already.

rezaMSLM

@aha_1980 said in How To Read a Text File Contents Located on a FTP Server:

Just have a deep look the the Example that was recommended you by @mrjj already.

I tried reading that example and some other codes on the internet But I'm a beginer and the examples were Confusing for me !
for first step I just want to download a text file located on FTP server into my desktop.
would any one please write a sample code for me doing that? thinking on simple sample codes will help me much.

jsulm

@rezaMSLM @mrjj already provided simple example code

rezaMSLM

@jsulm
I Didn't got it

jsulm

@rezaMSLM What exactly you didn't get?

rezaMSLM

@jsulm
how to specify download directory

jsulm

@rezaMSLM It is up to you where to store the file. You can use http://doc.qt.io/qt-5/qstandardpaths.html#locate to get a directory (for example the temp directory).

rezaMSLM

@jsulm
I want a sample Code not an english Link
I understand C++ much better than English

rezaMSLM

Where i am wrong?

MainWindow::MainWindow(...)
{
my_file=new QFile("Qt_Test.txt");//create new file named Qt_Test.txt
QTemporaryFile(QDir::tempPath());//store that file in temp path
.
.
}

void MainWindow::on_pushButton_Download_clicked()
{
    ftp->get("Qt_Test.txt",my_file,QFtp::Ascii);//download Qt_Test.txt which is located on server 
}

I Receive no error but no file is downloaded to temp folder

jsulm

@rezaMSLM Did you check the example? http://doc.qt.io/archives/qt-4.8/qt-network-qftp-example.html

MainWindow::MainWindow(...)
{
}

void MainWindow::on_pushButton_Download_clicked()
{
    QString path = QDir::tempPath() + '/' + "Qt_Test.txt";
    my_file=new QFile(path);
    my_file->open(QIODevice::WriteOnly);
    ftp->get("Qt_Test.txt",my_file,QFtp::Ascii);//download Qt_Test.txt which is located on server 
}

rezaMSLM

@jsulm

@jsulm said in How To Read a Text File Contents Located on a FTP Server:

Did you check the example? http://doc.qt.io/archives/qt-4.8/qt-network-qftp-example.html

yes

the file is created but is empty while the program is open!

JonB

@rezaMSLM
I could be wrong, but in @jsulm's code immediately after the ftp->get() line I would add line:

my_file->close()

I see that the example in the docs does not do that. Which seems a bit surprising, but the docs may know better than I do. However, assuming the file close is needed, you would get exactly the behaviour you describe (empty till exit program) if you do not close it. So I would give it a try and see....

EDIT My assumption here was wrong, see further post below.

rezaMSLM

@JonB
I tried it but didn"t worked

JonB

@rezaMSLM
Hang on, I've just read more in the docs, as follows:

On the other hand, if you only want to work with the complete data, you can connect to the commandFinished() signal and read the data when the get() command is finished.

The function does not block and returns immediately. The command is scheduled, and its execution is performed asynchronously. The function returns a unique identifier which is passed by commandStarted() and commandFinished().

When the command is started the commandStarted() signal is emitted. When it is finished the commandFinished() signal is emitted.

So if I understand right, the get() merely initiates the transfer. I believe you need to write a commandFinished slot, and close the file there.

Ah yes, the example page goes on to show that. The example code has:

    if (ftp->currentCommand() == QFtp::Get) {
        if (error) {
            statusLabel->setText(tr("Canceled download of %1.")
                                 .arg(file->fileName()));
            file->close();
            file->remove();
        } else {
            statusLabel->setText(tr("Downloaded %1 to current directory.")
                                 .arg(file->fileName()));
            file->close();
        }

When a Get command is finished, a file has finished downloading (or an error occurred during the download).

I do believe the reason your file is empty is that it must be closed, at the correct time, before you will see contents.

I think you have to follow the whole example code, or perhaps download the source files from there and p,lay with the whole project if you want to see how to use it fully.

hskoglund

Hi, also you could check that the FTP username and password are correct.

JonB

@hskoglund
Yes, but isn't username/password checking performed/errored much earlier than when he gets to issuing the get()? It's performed during FTP connection open.

The behaviour he describes --- file content not "visible" till exit application, then correct --- is explained exactly by failure to close output file, at least under Windows, which has a habit of marking files to be 0 length till closed by writer.