Problem with reading from file

Hi,

I am trying to read from a file using readLine function. This is my code.

QFile file("tempfile");
if (!file.open(QIODevice::ReadOnly ))
{
return;
}
while (!file.atEnd())
{

QString line = file.readLine();
qWarning(line.toAscii());
}

But some characters in the read line is not printing like " ' " as it is . For example if the actual file content is this

str_cpy.c: In function ‘str_cpy’:

It is read and printed as

In function ‘str_cpy’:

What can I do to print these lines like the file content itself. What am I missing here.

Jayanth.S

have a look at QTextStream, using it you can set needed encoding.

Thanks spirit for the quick reply. I tried QTextStream::setCodec() function to change to different character coding schemes. But none of them is working. I think characters like " ' " is causing the problem. Which is the encoding scheme that supports these characters.

Jayanth.S

Quote:

---

Originally Posted by iamjayanth

I think characters like " ' " is causing the problem. Which is the encoding scheme that supports these characters

---

Everyone! What encoding has your file. Make sure you use the same. Under Linux you can type under console

Code:

---

$ file yourfile.txt

---

to get the encoding. And please show us, how you have used QTextStream.

QFile file("tempfile");
if (!file.open(QIODevice::ReadOnly ))
{
return;
}
QTextStream out(stdout);
out.setCodec("UTF-8");
while (!file.atEnd())
{
QString line = file.readLine();
line.remove(0,len);
if(line.contains("error",Qt::CaseSensitive)!=0)
{
out<<line;
list->addItem(line.toAscii());
}
else if(line.contains("warning",Qt::CaseSensitive)!=0)
{
out<<line;
list->addItem(line.toAscii().data());
}
else
{
out<<line;
list->addItem(line.toAscii().data());
}
}

This is how I used QText stream to read from a file ' tempfile ' and write the content to stdout and also to a list widget (list) . I tried file command in console for tempfile

$ file tempfile
tempfile: UTF-8 Unicode text

That is the reason I chose UTF-8 as codec for QTextStream. How to fix that problem.

QFile file("tempfile");
if (!file.open(QIODevice::ReadOnly ))
{
return;
}
QTextStream out(stdout);
out.setCodec("UTF-8");
while (!file.atEnd())
{
QString line = file.readLine();
line.remove(0,len);
if(line.contains("error",Qt::CaseSensitive)!=0)
{
out<<line;
list->addItem(line.toAscii());
}
else if(line.contains("warning",Qt::CaseSensitive)!=0)
{
out<<line;
list->addItem(line.toAscii().data());
}
else
{
out<<line;
list->addItem(line.toAscii().data());
}
}

This is how I used QText stream to read from a file ' tempfile ' and write the content to stdout and also to a list widget (list) . I tried file command in console for tempfile

$ file tempfile
tempfile: UTF-8 Unicode text

That is the reason I chose UTF-8 as codec for QTextStream. Still when I print the content of the file into stdout and listwidget some characters are not printing (" ' " for example).Thanks for the reply

Use QTextStream for reading the file not only for giving the wrong read text out!

Edit: From the QFile documentation

Code:

---

QFile file("in.txt");
     if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
         return;
 
     QTextStream in(&file);
     while (!in.atEnd()) {
         QString line = in.readLine();
         process_line(line);
     }

---

Hi,

Now I am able to print to stdout correctly. But when I try to insert the line into QListWidget problem persists. Below given my code.

QFile file("tempfile");
if (!file.open(QIODevice::ReadOnly ))
{
return;
}
QTextStream in(&file);
QTextStream out(stdout);
in.setCodec("UTF-8");
while (!in.atEnd())
{
QString line = in.readLine();
out<<line<<'\n';
list->addItem(line.toAscii().data());
}

When I add the line to listwidget I am still getting problems. This time " ' " is printing as " ? ".

Qt internally uses UTF-16.

Then how can I display the contents read from file in the listwidget as it is .

try this

Code:

---

QByteArray encodedString = "...";
QTextCodec *codec = QTextCodec::codecForName("UTF-8");
QString string = codec->toUnicode(encodedString);

---

read more about QTextCodec.

I think I have corrected the problem.... I used setUtf16() function to convert UTF-8 to UTF-16. I dont know if this is the correct way. But it worked.

Code:

---

list->addItem(line.setUtf16(0,line.length()));

---

Thanks spirit and lykurg for your valuable time. I am now reading QTextCodec to check for any better ways... Thanks again.

Quote:

---

while (!in.atEnd())
{
QString line = in.readLine();
out<<line<<'\n';
list->addItem(line.toAscii().data());
}

---

Please use the [ CODE ] tags and simply write:

Code:

---

while (!in.atEnd()) 
{
  QString line = in.readLine();
  out<<line<<'\n';
  list->addItem(line); // <--
}

---

There is no need to transform the QString. And by using toAscii() - as you could expect - it is destroying the UTF-8 by converting to ascii...

hi,

So lykurg, you are saying the encoding was UTF-8 from the start. I just need to pass it onto listwidget. I think i have done the same earlear but didnt worked . But now it is working. The only difference is that I used normal file reading methods in the first time and QTextStream now. What is the difference in using QTextStream.

Quote:

---

Originally Posted by iamjayanth

So lykurg, you are saying the encoding was UTF-8 from the start. I just need to pass it onto listwidget. I think i have done the same earlear but didnt worked .

---

No you haven't. You have used the readLine directly on the QFile. And how the docs says: This function reads a line of ASCII characters from the device... So you tried to read UTF8 with a ASCII reader which leads to garbage in your QString. And setting garbage via your QString to the table widget won't heal the content.

Quote:

---

But now it is working. The only difference is that I used normal file reading methods in the first time and QTextStream now. What is the difference in using QTextStream.

---

In QTextStream there is the difference. QTextStream respects the encoding of a file and do perform conversions on the bytes which it reads. So you get the right data in your QString.

Thanks Lykurg....That cleared it all....Thank you very much....