Recursively iterate over all the files in a directory and its subdirectories in Qt

Question

I want to recursively scan a directory and all its sub-directories for files with a given extension - for example, all *.jpg files. How can you do that in Qt?

Answer 1

I suggest you have a look at QDirIterator.

QDirIterator it(dir, QStringList() << "*.jpg", QDir::Files, QDirIterator::Subdirectories);
while (it.hasNext())
    qDebug() << it.next();

You could simply use QDir::entryList() recursively, but QDirIterator is simpler. Also, if you happen to have directories with a huge amount of files, you'd get pretty large lists from QDir::entryList(), which may not be good on small embedded devices.

Example (dir is QDir::currentPath()):

luca @ ~/it_test - [] $ tree
.
├── dir1
│   ├── image2.jpg
│   └── image3.jpg
├── dir2
│   └── image4.png
├── dir3
│   └── image5.jpg
└── image1.jpg

3 directories, 5 files
luca @ ~/it_test - [] $ /path/to/app
"/home/luca/it_test/image1.jpg"
"/home/luca/it_test/dir3/image5.jpg"
"/home/luca/it_test/dir1/image2.jpg"
"/home/luca/it_test/dir1/image3.jpg"

Answer 2

This should work :

void scanDir(QDir dir)
{
    dir.setNameFilters(QStringList("*.nut"));
    dir.setFilter(QDir::Files | QDir::NoDotAndDotDot | QDir::NoSymLinks);

    qDebug() << "Scanning: " << dir.path();

    QStringList fileList = dir.entryList();
    for (int i=0; i<fileList.count(); i++)
    {
        if(fileList[i] != "main.nut" &&
           fileList[i] != "info.nut")
        {
            qDebug() << "Found file: " << fileList[i];
        }
    }

    dir.setFilter(QDir::AllDirs | QDir::NoDotAndDotDot | QDir::NoSymLinks);
    QStringList dirList = dir.entryList();
    for (int i=0; i<dirList.size(); ++i)
    {
        QString newPath = QString("%1/%2").arg(dir.absolutePath()).arg(dirList.at(i));
        scanDir(QDir(newPath));
    }
}

The differences from your code are the following:

• Breadth first search instead of depth first search (no reason for it, I just prefer it)
• More filters in order to avoid sym links
• EntryList instead of EntryInfoList. You don t need if you just want the name of the file.

I tested it and it works correctly, but notice the following:

• This may take a lot of time, so consider running it from thread
• If there is deep recursion you may have problem with your stack

Answer 3

I used QDirIterator.

Here's how I do it and how simple it was to find all XML absolute file paths recursively very fast (Qt4.8.1):

// used to store the file paths
filesStack = new QStack<QString>();

// I use a file dialog to let the user choose the root folder to search in
if (fileDialog->exec() == QFileDialog::Accepted) {
    QDir selectedDir(fileDialog->selectedFiles().first());
    selectedDir.setFilter(QDir::Files |
                          QDir::Dirs | QDir::NoDot | QDir::NoDotDot);
    QStringList qsl; qsl.append("*.xml"); // I only want XML files
    selectedDir.setNameFilters(qsl);
    findFilesRecursively(selectedDir);
}

// this function stores the absolute paths of each file in a QVector
void findFilesRecursively(QDir rootDir) {
    QDirIterator it(rootDir, QDirIterator::Subdirectories);
    while(it.hasNext()) {
        filesStack->push(it.next());
    }
}

Thanks to everyone for the hints.

EDIT: I may have omitted some declarations, beware.