The title says it all. I've seen many solutions to execute the oposite operation but not this way.
I'm using Qt to create a temporary file. If I get its name it will be something on the likes of:
QTemporaryFile tempFile;
tempFile.open();
qDebug() << tempFile.fileName();
// C:/Users/USERNA~1/AppData/Local/Temp/qt_temp.Hp4264
I have tried some solutions such as using QFileInfo:
QFileInfo fileInfo(tempFile);
qDebug() << fileInfo.filePath()
And QDir:
QDir dir(tempFile.fileName());
qDebug() << dir.absolutePath();
Without success.
Is there any solution for this using purely Qt? I know I can navigate the directory tree to find the full name but I was trying to avoid this, especially because of the possibility of two folders with the same prefix.
the win32 function GetLongPathName is your answer.
QString shortPath = tempFile.fileName();
int length = GetLongPathNameW(shortPath.utf16(),0,0);
wchar_t* buffer = new wchar_t[length];
length = GetLongPathNameW(shortPath.utf16(), buffer, length);
QString fullpath = QString::fromUtf16(buffer, length);
delete[] buffer;
there is no pure Qt function for this because only windows does this (and Qt is meant to be portable)
Related
I've replicated this in two places in my code, one written by me and the one I'm posting an image of, that was written by someone else. I can't get the base64 to output to qDebug at all. I thought base64 was supposed to be readable. It has a size. But it won't print the entire qDebug line.
Thanks in advance for any help.
Here's the code. I'm on Qt Kit 5.12.1 64 bit mingw in release.
QFile* file = new QFile("C:\\Qr-Pic\\Poll_Directory\\IMG_00000001 - Copy (53).jpg");
file->open(QIODevice::ReadOnly);
QByteArray image = file->readAll();
int originalSize = image.length();
QString encoded = QString(image.toBase64());
int encodedSize = encoded.size();
qDebug() << "encodedSize=" << encodedSize;
qDebug() << "encode=" << encoded;
Output:
encodedSize= 34036
I would like to add text to a text file only if the text doesn't already exist in the text file. My implementation below adds text even if it already exists. How can I fix my implementation to only add new non-existent items?
My implementation so far:
WriteToFile::WriteToFile(QString data)
{
path += "C:/Data.txt";
QFile file(path);
if ( file.open(QFile::Append) )
{
QTextStream in (&file);
QString line;
do {
line = in.readAll();
qDebug() << in.readLine();
if (!line.contains(data)) {
QTextStream stream( &file );
data += "\r\n";
stream << data << endl;
}
} while (!line.isNull());
}
}
You will either have to:
parse the entire file and extract all paths from it or
keep track of all paths written to a file to avoid parsing it again and again
From there is it simple, just create a QSet<QString> writtenSoFar, and for every path, check if the set contains it, if so skip writing, if not, write it and append it to the set. In the first case, you will have to write the parsed paths into the set just to make a single check, wildly inefficient, just like the parsing itself. So better keep track of the paths as you go.
The set is important to give you good lookup performance. It is quite fast, since it is hash based, it is essentially a value-less QHash.
I need to find and replace some text in the text file. I've googled and found out that easiest way is to read all data from file to QStringList, find and replace exact line with text and then write all data back to my file. Is it the shortest way? Can you provide some example, please.
UPD1 my solution is:
QString autorun;
QStringList listAuto;
QFile fileAutorun("./autorun.sh");
if(fileAutorun.open(QFile::ReadWrite |QFile::Text))
{
while(!fileAutorun.atEnd())
{
autorun += fileAutorun.readLine();
}
listAuto = autorun.split("\n");
int indexAPP = listAuto.indexOf(QRegExp("*APPLICATION*",Qt::CaseSensitive,QRegExp::Wildcard)); //searching for string with *APPLICATION* wildcard
listAuto[indexAPP] = *(app); //replacing string on QString* app
autorun = "";
autorun = listAuto.join("\n"); // from QStringList to QString
fileAutorun.seek(0);
QTextStream out(&fileAutorun);
out << autorun; //writing to the same file
fileAutorun.close();
}
else
{
qDebug() << "cannot read the file!";
}
If the required change, for example is to replace the 'ou' with the american 'o' such that
"colour behaviour flavour neighbour" becomes "color behavior flavor neighbor", you could do something like this: -
QByteArray fileData;
QFile file(fileName);
file.open(stderr, QIODevice::ReadWrite); // open for read and write
fileData = file.readAll(); // read all the data into the byte array
QString text(fileData); // add to text string for easy string replace
text.replace(QString("ou"), QString("o")); // replace text in string
file.seek(0); // go to the beginning of the file
file.write(text.toUtf8()); // write the new text back to the file
file.close(); // close the file handle.
I haven't compiled this, so there may be errors in the code, but it gives you the outline and general idea of what you can do.
To complete the accepted answer, here is a tested code. It is needed to use QByteArray instead of QString.
QFile file(fileName);
file.open(QIODevice::ReadWrite);
QByteArray text = file.readAll();
text.replace(QByteArray("ou"), QByteArray("o"));
file.seek(0);
file.write(text);
file.close();
I've being used regexp with batch-file and sed.exe (from gnuWin32, http://gnuwin32.sourceforge.net/). Its good enough for replace one-single text.
btw, there is not a simple regexp syntax there. let me know If you want to get some example of script.
I just started learning C++ in Qt and I was wondering how can I put a variables result in a string? I'm trying to use this for a simple application where someone puts their name in a text field then presses a button and it displays there name in a sentence. I know in objective-c it would be like,
NSString *name = [NSString stringWithFormatting:#"Hello, %#", [nameField stringValue]];
[nameField setStringValue:name];
How would I go about doing something like this with C++? Thanks for the help
I assume we're talking about Qt's QString class here. In this case, you can use the arg method:
int i; // current file's number
long total; // number of files to process
QString fileName; // current file's name
QString status = QString("Processing file %1 of %2: %3")
.arg(i).arg(total).arg(fileName);
See the QString documentation for more details about the many overloads of the arg method.
You don´t mention what type your string is. If you are using the standard library then it would be something along the lines of
std::string name = "Hello, " + nameField;
That works for concatenating strings, if you want to insert other complex types you can use a stringstream like this:
std::ostringstream stream;
stream << "Hello, " << nameField;
stream << ", here is an int " << 7;
std::string text = stream.str();
Qt probably has its own string types, which should work in a similar fashion.
I would use a stringstream but I'm not 100% sure how that fits into your NSString case...
stringstream ss (stringstream::in);
ss << "hello my name is " << nameField;
I think QString has some nifty helpers that might do the same thing...
QString hello("hello ");
QString message = hello % nameField;
You could use QString::sprintf. I haven't found a good example of it's use yet, though. (If someone else finds one, feel free to edit it in to this answer).
You might be interested in seeing information about the difference between QString::sprintf and QString::arg.
I've tried the following short example to find out about a bug in a bigger program I am working on. It looks like QFile doesn't support unix (or the shell's) notation for the home directory:
#include <QFile>
#include <QDebug>
int main()
{
QFile f("~/.vimrc");
if (f.open(QIODevice::ReadOnly))
{
qDebug() << f.readAll();
f.close();
}
else
{
qDebug() << f.error();
}
}
As soon as I replace the "~" with my real home directory path, it works. Is there an easy workaround - some setting to enable? Or do I have to go the "ugly" way and ask QDir for the home directory of the current user and prepend that manually to each path?
Addendum: It's clear that usually the shell performs the tilde expansion so programs would never see that. Still it is so convenient in unix shells that I hoped the Qt implementation for file access would have that expansion included.
You can just create a helper function to do this for you, something like:
QString morphFile(QString s) {
if ((s == "~") || (s.startsWith("~/"))) {
s.replace (0, 1, QDir::homePath());
}
return s;
}
:
QFile vimRc(morphFile("~/.vimrc"));
QFile homeDir(morphFile("~"));
A more complete solution, allowing for home directories of other users as well, may be:
QString morphFile(QString fspec) {
// Leave strings alone unless starting with tilde.
if (! fspec.startsWith("~")) return fspec;
// Special case for current user.
if ((fspec == "~") || (fspec.startsWith("~/"))) {
fspec.replace(0, 1, QDir::homePath());
return fspec;
}
// General case for any user. Get user name and length of it.
QString name (fspec);
name.replace(0, 1, ""); // Remove leading '~'.
int len = name.indexOf('/'); // Get name (up to first '/').
len = (len == -1)
? name.length()
: len - 1;
name = name.left(idx);
// Find that user in the password file, replace with home
// directory if found, then return it. You can also add a
// Windows-specific variant if needed.
struct passwd *pwent = getpwnam(name.toAscii().constData());
if (pwent != NULL)
fspec.replace(0, len+1, pwent->pw_dir);
return fspec;
}
Just one thing to keep in mind, the current solution is not portable to Windows (as per the comments in the code). I suspect this is okay for the immediate question since .vimrc indicates that's not the platform you're running on (it's _vimrc on Windows).
Tailoring the solution to that platform is possible, and indeed shows that the helper-function solution is a good fit since you'll only have to change one piece of code to add that.
It has nothing to do with not supporting UNIX; the expansion of tildes to the user's home directory is a substitution performed by the shell, so yes, you will have to manually replace them.
Please submit a suggestion to the Qt bugtracker.
https://bugreports.qt.io/
Take a look at the C library function glob, which will do tilde expansion (and possibly wildcard expansion and various other functions too).