CODEWITHSUNDEEP
c++qtqtcore
punksta
punksta

Reputation: 2808

QFile does not open file

QLabel* codeLabel = new Qlabel;

QFile file("C:\index.txt");
file.open(stderr, QIODevice::WriteOnly);
QByteArray data;
data = file.readAll();

codeLabel->setText("test"+QString(data));
file.close();

Then there is only "test" in QLabel. Help, Please

Upvotes: 2

Views: 2152

Answers (4)

paxdiablo
paxdiablo

Reputation: 881093

Aside from the fact you should escape backslashes within C-style strings (c:\\index.txt), you have a problem with the following sequence:

//                           vvvvvvvvv
file.open(stderr, QIODevice::WriteOnly);
:
data = file.readAll();
//          ^^^^

What exactly did you think was going to happen when you opened the file write-only, then tried to read it? You need to open it for reading such as with QIODevice::ReadOnly or QIODevice::ReadWrite.

On top of that, you should check the return code of all functions that fail by giving you a return code. You currently have no idea whether the file.open() worked or not.

I'm also not convinced that you should be opening stderr (which is really an ouput "device") for input. You'll almost certainly never get any actual data coming in on that file descriptor, which is probably why your input is empty.

You need to step back and ask what you're trying to acheive. For example, are you trying to capture everything your process sends to standard error? If so, it's not going to work that way.

If you're just trying to read the index.txt file, you're using the wrong overload. Remove the stderr parameter altogether:

file.open (QIODevice::ReadOnly);

If it's something else you're trying to do, add that to the question.

Upvotes: 4

fjardon
fjardon

Reputation: 7996

QFile file("C:\index.txt");

Here you try to open a file called: C:index.txt because '\i' is converted to i. You want to double you backslash:

QFile file("C:\\index.txt");

Upvotes: 2

ratchet freak
ratchet freak

Reputation: 48176

file.open(stderr, QIODevice::WriteOnly);

this closes the file again and reopens with the stderr stream in write only mode

you'll want to change that to 

file.open(QIODevice::ReadOnly);

Upvotes: 2

Some programmer dude
Some programmer dude

Reputation: 409136

Because you read from a file you opened write-only.

Upvotes: 0

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