QDir::exists returns false on applications private directory

[H0LL0]

On a Symbian Device i have the following problem:

qDebug() << QDir("C:/DATA").exists(); // true
qDebug() << QDir(QApplication::applicationDirPath()).exists(); // false
qDebug() << QFile::exists(QApplication::applicationDirPath() + "/version.txt"); // true

what am i doing wrong? the directory doesnt exist but a file in it does.

The only Explanation I have is that I'm using Qt 4.6.3 instead of 4.7 is that the problem?

[kkrish]

what QApplication::applicationDirPath() is returning ?

[kamalakshan]

Just check if you have to convert from Symbian dir separator format to Qt format.

[savaj]

Yes, it is correct behavior of application. In Qt (for Symbian) this function will return the application private directory, not the path to executable itself. So if you are not creating it at installation time (by pasting some file in it) just create it right before its first use...

For "qDebug() << QFile::exists(QApplication::applicationDirPath() + "/version.txt"); // true" i guess QApplication::applicationDirPath() returning NULL but you have "/version.txt" somewhere, where the QFile::exists is looking for.

Provide some more input. like are you testing on device or simulator? and location of your version.txt file.

[laa-laa]

It's because the \private directory itself is not accessible (without AllFilles capability) while \private\youruid is.

[ltomuta]

Running virtually the same code:

    qDebug() << "App dir: " << QApplication::applicationDirPath();
    qDebug() << "Exists: " << QDir(QApplication::applicationDirPath()).exists(); // false

I get:

Executable file: 9972 2011-04-19T14:40:09 C:\QtSDK\Symbian\SDKs\Symbian3Qt473\epoc32\release\armv5\udeb\TestAppDir.exe
Starting application...
Application running with pid 836.
[Qt Message] App dir: "C:/Private/e07ccd81"
[Qt Message] Exists: true

So the behaviour of the APIs is correct, although:
a) the directory may or may not exist and that may or may not be relevant
b) if the directory does not exists, you may have to create it
c) it would appeat that Qt does create that directory for one reason or another when the application is first started. That does not mean that you should also use it, for example you may want to use e:/Private/e07ccd81, a directory which is equaly valid but very likely not to exist by default if the app is installed on C:\

[H0LL0]

The directory returned by QApplication::applicationDirPath() definetly DOES exist on application creation. (it is C:\private\<uid>) i can write files in it. i can read files from it. i can NOT create directories in it.

The dir seperator is "\\" as it should be. (although that doesnt matter, since qt corrects wrong seperators on file access)

the version.txt is shipped with the application and is included correctly in the .sis file. the target is !:\private\<uid>\version.txt and the application is installed to C: and as i said i can read that file.

i work on a nokia e66 (s60 3rd FP1)

[ltomuta]

That is not what you have asked for in the previous post. Anyway, creating a subdirectory works and exist() returns true when executed on it later.

[H0LL0]

ok, i tested a little again and to make my point clear here is my code:

	QDir appDir(QApplication::applicationDirPath());
	QString fileName = QApplication::applicationDirPath() + "/version.txt";
	QFile testFile(fileName);

	qDebug() << "App dir:" << QApplication::applicationDirPath();
	qDebug() << "AppDir Exists:" << appDir.exists();
	qDebug() << "File:" << fileName;
	qDebug() << "File Exists:" << QFile::exists(fileName);
	qDebug() << "Copy:" << testFile.copy(QApplication::applicationDirPath() + "/test.txt");
	qDebug() << "Copy in Subdir:" << testFile.copy(QApplication::applicationDirPath() + "/test/test.txt");
	qDebug() << "Subdir Exists:" << QDir(QApplication::applicationDirPath() + "/test").exists();
	qDebug() << "mkpath Subdir" << QDir().mkpath(QApplication::applicationDirPath() + "/test");
	qDebug() << "mkdir Subdir:" << appDir.mkdir("test");
	qDebug() << "Subdir Exists:" << QDir(QApplication::applicationDirPath() + "/test").exists();
	qDebug() << "Copy in Subdir:" << testFile.copy(QApplication::applicationDirPath() + "/test/test.txt");

Output:

[Qt Message] App dir: "C:/Private/e68fb921"
[Qt Message] AppDir Exists: false
[Qt Message] File: "C:/Private/e68fb921/version.txt"
[Qt Message] File Exists: true
[Qt Message] Copy: true
[Qt Message] Copy in Subdir: false
[Qt Message] Subdir Exists: false
[Qt Message] mkpath Subdir false
[Qt Message] mkdir Subdir: true
[Qt Message] Subdir Exists: true
[Qt Message] Copy in Subdir: true

Unexpected behaviour: not working mkpath and not working exists() function on the path. still looks like a qt bug to me.

[H0LL0]

I tested it on Qt 4.7.3 now it doesnt work either.

[laa-laa]

It's a feature of Symbian and not really a bug. The reason is already there in post #5: \private directory itself is not accessible (without AllFilles capability) while \private\youruid is. Checking for file or dir existence requires access to the directory where the file or subdir resides.

[ltomuta]

Testing on the application directory and its content should work just fine. Well, not just should, it actually does. This is what I get running the same code on E7

[Qt Message] App dir: "C:/Private/e07ccd81" 
[Qt Message] AppDir Exists: true 
[Qt Message] File: "C:/Private/e07ccd81/version.txt" 
[Qt Message] File Exists: false 
[Qt Message] Copy: false 
[Qt Message] Copy in Subdir: false 
[Qt Message] Subdir Exists: false 
[Qt Message] mkpath Subdir true 
[Qt Message] mkdir Subdir: false 
[Qt Message] Subdir Exists: true 
[Qt Message] Copy in Subdir: false

It is strange that you are getting false there. What phone are you using for testing?

The rest of the results also appear to be correct as you are doing a lot of operations with testFile, a file which does not exist and is never created.
Then makepath succeeds while mkdir, called to create an existing subdirectory, fails.

[H0LL0]

Hmm ok. So it seems to be a Symbian Security issue. It is trange that Qt behaves different on different Symbian platforms, though. I develop on a Nokia E66 (S60 3rd FP1).

[ltomuta]

If Qt really behaves differently then it is a bug and you should report it at http://bugreports.qt.nokia.com
I'll see if I can find a 3.1 device where I can test it, but that's unlikely, so please do create a bug report based on your current findings.

[H0LL0]

http://bugreports.qt.nokia.com/browse/QTBUG-18944

i hope to get my hands on another 3.1 device soon, too.