QFile doesn't detect read-only files

[Sucharek]

Hi @mchinand, the return value of copying is true, and I can remove the file, even when it's unwritable (with QFile::remove()).

[JonB]

@Sucharek
You claim QFile::exists() returns false. What does QFileInfo have to say about the file?

[Christian Ehrlicher]

This is working fine for me on a NTFS file system with Qt5.15.2 (assuming a read-only file named 'tmp1.txt' is in D:\

int main(int argc, char** argv)
{
    QCoreApplication app(argc, argv);
    QString filename = "tmp1.txt";
    QString mainPath = "D:/";
    QString rPath = "subdir/";
    if (!QDir().mkpath(mainPath + rPath)) {
        qDebug() << "Could not create path " << mainPath + rPath;
    }
    QFile move(mainPath + filename);
    bool system = move.isWritable();
    if (system == false) {
        move.copy(mainPath + rPath + filename);
        QFile check(mainPath + rPath + filename); //path of the moved file
        if (check.exists()) {
            qDebug() << "Copied file at " << check.fileName() << "exists - removing";
            move.remove();
        }
        else {
            qDebug() << "Copied file at " << check.fileName() << "does not exist";
            qDebug() << mainPath + rPath + filename;
            qDebug() << check.exists();
        }
    }
    else {
        qDebug() << "File is writeable";
    }
    return 0;
}

[mpergand]

I don't know on Windows but on Mac since the file is not open for writing, isWritable() return false

   QFile file(path);
   QTLog(<<"is writable"<<file.isWritable())       
       if(file.open(QIODevice::WriteOnly))
           { 
           QTLog(<<"is writable"<<file.isWritable())  
            ...

is writable false
is writable true

[mchinand]

The documentation says QIODevice::isWritable() checks the OpenMode, so seems like your finding isn't specific to Mac and QIODevice::isWritable() is only useful for open files. QFileInfo::isWritable() is what is needed here.

[mpergand]

@mchinand said in QFile doesn't detect read-only files:
so seems like your finding isn't specific to Mac

Yes I know ;)
All the topic makes no sense because there is a confusion between the open state of a file (read/write) and the permissions for a file.

[Sucharek]

Hi, thanks for all the replies, but none of them seem to work.
@JonB QFileInfo returned false.
@Christian-Ehrlicher your method doesn't work for me. Prints:
Copied file at "C:/Users/username/Downloads/Other/Spotify.lnk" does not exist
But it actually does exist.

[mchinand]

@Sucharek You may be having issues because your file is a .lnk file (shortcut) which I think is treated as a symbolic link, so keep that in mind when you are reading the documentation on various file manipulation methods. For copy(), the documentation says it copies the file that the .lnk file is referring to, not the .lnk file itself.

[Sucharek]

Hi @mchinand, thank you for your answer.
I guess that explains my issue.
Thanks

[JonB]

@Sucharek said in QFile doesn't detect read-only files:

Copied file at "C:/Users/username/Downloads/Other/Spotify.lnk" does not exist

This is a .lnk file. You never mentioned this, even though it behaves differently from all other file types under Windows. Did you not think that relevant? The QFile etc. documentation tells you how it handles .lnk files --- effectively, it always tells you about the file pointed to by the .lnk file, not the .lnk file itself. So, for example, when you say QFile::exists() reports it as not existing, it is telling you about the file the .lnk points to. Did that exist?

@JonB QFileInfo returned false

You were supposed to look through the various QFileInfo::is...() methods, not just QFileInfo::exists(), to see what the attributes of the file are. For instance, QFileInfo::isShortcut() under Windows would have told you/us what is relevant here.