I have a QTextBrowser in which I display the output contents of an external binary using QProcess in Linux. All is GOOD! But most of the contents are just boxes, so now it's the character encoding UTF-8 is missing and I need to tell this to the QTextBrowser. Is there any way for that?
The code:
....
processRAM = new QProcess();
processRAM->start("memtester", QStringList() << "1" << "1");
.....
connect(processRAM, SIGNAL(readyRead()),this,SLOT(displayRAMTestOutput()));
......
void MainWindow::displayRAMTestOutput()
{
textBrowserData->append(Qtring::fromUtf8(processRAM->readAllStandardOutput())));
}
I added the char encoding UTF-8 and still I see only boxes. What am I missing here?
You can set content of QTextBrowser in this way:
textBrowser->setText(QString::fromUtf8(processOutput)));
EDIT:
Your problem with "boxes" isn't connected with UTF8 encoding. Symbols which you see are control characters which are used by memtester when it displays text to console. If you don't want to display such characters in textBrowser, you can filter output:
while(!processRAM->atEnd())
{
QString out = QString::fromAscii(processRAM->readLine());
if(!out.contains("\b"))
textBrowser->append(out);}
}
\b means backspace which is displayed in you textBrowser as boxes.
Related
I want to read and parse contents of the /proc/PID/status file on a linux machine, but the QTextStream.atEnd is always returning true when starting to read. The code:
QString procDirectory = "/proc/";
procDirectory.append(QString::number(PID));
procDirectory.append("/status");
QFile inputFile(procDirectory);
if (inputFile.open(QIODevice::ReadOnly))
{
QTextStream in(&inputFile);
QString line;
while (!in.atEnd())
{
line = in.readLine();
File exists and if I read lines manually without the while expression, the files are read normally.
Did I miss something obvious?
(Debian 8 x64, QT 5.4.1 x64, gcc 4.9.2)
Nevermind found out I needed to read one line before the while clause, now it works.
The preferred way oft looping over these streams is with a do/while loop. This is for allowing the stream to detect Unicode correctly before any queries (like atEnd) are made.
QTextStream stream(stdin);
QString line;
do {
line = stream.readLine();
} while (!line.isNull());
I try to show a persian string in Qt:
QMessageBox msg;
QString str = "یا حسین";
msg.setText(QString::fromUtf8(str));
msg.exec();
but it shows the following error :
/home/msi/Desktop/VoMail
Project/Project/VoMail-build-desktop-Qt_4_8_1_in_PATH__System__Release/../VoMail/mainwindow.cpp:40:
error: no matching function for call to 'QString::fromUtf8(QString&)'
I want to use a string variable, and not a string directly.
How can I convert a QString variable to Utf8?
As seen here, QString::fromUtf8() does not accept an argument of type QString. You must give it a const char *, so you could rewrite it like this:
QMessageBox msg;
QString str = QString::fromUtf8("یا حسین");
msg.setText(str);
msg.exec();
its not good idea write like that
using this must be better
QString str(tr("ya hossein");
and use linguist and add persian translation file to your project http://qt-project.org/doc/qt-4.8/linguist-translators.html
and if you dont want use this, you must be sure your IDE or code editor (like qtcreator) use utf8 for saving files and just use
QString str("یا حسین");
it must be ok, i tested that so many times
How can i find a specific character in a QFile which has a text in it?
for example i have ' $5000 ' written somewhere in my file. in want to find the "$" sign so i will realize that I've reached the number.
I tried using QString QTextStream::read(qint64 maxlen) by putting 1 as the maxlen :
QFile myfile("myfile.txt");
myfile.open(QIODevice::ReadWrite | QIODevice::Text);
QTextStream myfile_stream(&myfile);
while(! myfile_stream.atEnd())
{
if( myfile_stream.read(1) == '$')
{
qDebug()<<"found";
break;
}
}
and i get "error: invalid conversion from 'char' to 'const char* "
i also tried using the operator[] but apparently it can't be used for files.
Read in a line at a time and search the text that you've read in
QTextStream stream(&myFile);
QString line;
do
{
line = stream.readLine();
if(line.contains("$"))
{
qDebug()<<"found";
break;
}
} while (!line.isNull());
The error message you've posted doesn't match the issue in your code. Possibly the error was caused by something else.
QTextStream::read returns QString. You can't compare QString and const char* directly, but operator[] can help:
QString s = stream.read(1);
if (s.count() == 1) {
if (s[0] == '$') {
//...
}
}
However reading a file by too small pieces will be very slow. If your file is small enough, you can read it all at once:
QString s = stream.readAll();
int index = s.indexOf('$');
If your file is large, it's better to read file by small chunks (1024 bytes for example) and calculate the index of found character using indexOf result and count of already read chunks.
a single char could be read with
QTextStream myfile_stream(&myfile);
QChar c;
while (!myfile_stream.atEnd())
myfile_stream >> c;
if (c == '$') {
...
}
myfile_stream.read(1) - this is not good practice, you should not read from file one byte at a time. Either read the entire file, or buffered/line by line if there is a risk for the file to be too big to fit in memory.
The error you get is because you compare a QString for equality with a character literal - needless to say that is not going to work as expected. A string is a string even if there is only one character in it. As advised - use either the [] operator or better off for reading - QString::at() const which is guaranteed to create no extra copy. You don't use it on the QFile, nor on the QTextStream, but on the QString that is returned from the read() method of the text stream targeted at the file.
Once you have the text in memory, you can either use the regular QString methods like indexOf() to search for the index of a contained character.
in want to find the "$" sign so i will realize that I've reached the
number.
It sounds to me that you're searching for the '$' symbol because you're more interested in the dollar value that follows it. In this case, I suggest reading the files line by line and running them through a QRegExp to extract any values you're looking for.
QRegExp dollarFind("\\$(\\d+)");
while(!myfile_stream.atEnd()){
QString line = myfile_stream.readLine();
if (dollarFind.exactMatch(line)){
QStringList dollars = dollarFind.capturedTexts();
qDebug() << "Dollar values found: " << dollars.join(", ");
}
}
I'm looking to overwrite data in a text file but all I can seem to do is append to it
mFile.open(QFile::ReadWrite)
QTextStream in(&mFile);
QString first = in.readLine(); //discard the headers
QString dataLine = in.readLine(); //headers
QStringList sql_row = dataLine.split("\t"); //first row (sake of proj only 1 row)
if(sql_row[1].isEmpty()) //no user name registered
{
QByteArray user= getenv("USERNAME"); //for windows
if(user.isEmpty())
{
user = getenv("USER"); ///for MAc or Linux
}
dataLine = dataLine.insert(dataLine.indexOf("\t")+ 1,user);
in << first << endl << dataLine << endl;
mFile.flush();
mFile.close();
Change
mFile.open(QFile::ReadWrite);
to
mFile.open(QIODevice::ReadWrite | QIODevice::Truncate | QIODevice::Text);
The QIODevice vs QFile distinction isn't necessary, but I personally favor using the base class. The Truncate flag will overwrite (i.e., delete) an existing file.
Alternatively, you can follow the other suggestion and open your text file directly using one of QTextStream's constructors. The same QIODevice::OpenMode conventions apply. This only works if mFile is a FILE object and not a QFile, which isn't the case in your example.
A couple additional notes for beginners.
Related Note 1
You didn't ask about this, but I also added the QIODevice::Text flag to ensure that newline characters get translated to/from the local encoding (plain \n vs. \r\n) when you use endl.
A really common mistake is to use \r\n AND QIODevice::Text, which results in text files with double-returns \r\r\n on Windows. Just use QIODevice::Text when opening and simply \n or endl and you'll never have this problem.
Related Note 2
Using QTextStream::endl will automatically call flush() each time. If your loop is large, use "\n" instead to prevent a slowdown unless you actually need to flush every line. The stream will automatically write to disk as its buffer gets full, or when it's closed.
QFile::close() also calls flush(), which makes your mFile.flush() at the end redundant.
Use an overloaded constructor of QTextStream:
QTextStream in(&mFile, QIODevice::ReadWrite | QIODevice::Truncate);
The QIODevice::Truncate will remove all the previous content of the file, and QIODevice::ReadWrite will open it for read and write access.
The following code somehow fails to notice any files with non-ASCII characters in their names (Cyrillic characters, specifically):
for (int path = 1; path < argc; path++) {
QFileInfo fi(argv[path]);
if (fi.isDir()) {
QDir dir(argv[path], "", QDir::LocaleAware, QDir::AllEntries);
qDebug() << dir.entryList();
QDirIterator it(QString(argv[path]), QDirIterator::Subdirectories);
while (it.hasNext()) {
it.next();
qDebug() << it.fileInfo().absoluteFilePath();
/* Processing; irrelevant in the context of the question */
}
}
}
What exactly am I doing wrong here? How should I handle QDir and QDirIterator to make them aware of Cyrillic filenames?
The system locale is en_US.UTF-8.
Update: On Windows, everything works correctly.
Get cmd line parameters out of QApplication itself.
So
QApplication app(argc, argv);
QStringList args = app.arguments();
for(...)
Qt will handle encoding properly. But that will only fix problems with unicode on cmd line. Not sure if that is your main problem though.
EDIT:
fromLocal8Bit() probably doesn't work because it wasn't local encoding, but utf8. So fromUtf8() would work on linux and osx (but it won't work on windows). On *nuxes it depends on some environment variables (LS_LANG or something). I guess Qt takes everything into account and converts it properly. You can look at the constructor code for QApplication if you want to know exactly what they do.
Which part is failing? Reading the initial directory specified argv[path] or the iterator? If it's the former, you should convert byte strings to QString for file processing using QFile::decodeName. The default char* => QString conversion uses Latin-1, which is not what you want for file names.
Don't use argv[path] just like that when constructing the QStrings. This will treat the string as a latin1 string (which doesn't care about cyrillic characters). Try using
const QString dirName = QString::fromLocal8Bit( argv[path] );
at the top of your loop and then use dirName everywhere instead of argv[path].