QFileInfo Class

On Unix (including macOS and iOS), the property getter functions in this class return the properties such as times and size of the target, not the symlink, because Unix handles symlinks transparently. Opening a symlink using QFile effectively opens the link's target. For example:

#ifdef Q_OS_UNIX

QFileInfo info1("/home/bob/bin/untabify");
info1.isSymLink();          // returns true
info1.absoluteFilePath();   // returns "/home/bob/bin/untabify"
info1.size();               // returns 56201
info1.symLinkTarget();      // returns "/opt/pretty++/bin/untabify"

QFileInfo info2(info1.symLinkTarget());
info2.isSymLink();          // returns false
info2.absoluteFilePath();   // returns "/opt/pretty++/bin/untabify"
info2.size();               // returns 56201

#endif

On Windows, shortcuts (.lnk files) are currently treated as symlinks. As on Unix systems, the property getters return the size of the target, not the .lnk file itself. This behavior is deprecated and will likely be removed in a future version of Qt, after which .lnk files will be treated as regular files.

#ifdef Q_OS_WIN

QFileInfo info1("C:\\Users\\Bob\\untabify.lnk");
info1.isSymLink();          // returns true
info1.absoluteFilePath();   // returns "C:/Users/Bob/untabify.lnk"
info1.size();               // returns 63942
info1.symLinkTarget();      // returns "C:/Pretty++/untabify"

QFileInfo info2(info1.symLinkTarget());
info2.isSymLink();          // returns false
info2.absoluteFilePath();   // returns "C:/Pretty++/untabify"
info2.size();               // returns 63942

#endif

On NTFS file systems, ownership and permissions checking is disabled by default for performance reasons. To enable it, include the following line:

extern Q_CORE_EXPORT int qt_ntfs_permission_lookup;

Permission checking is then turned on and off by incrementing and decrementing qt_ntfs_permission_lookup by 1.

qt_ntfs_permission_lookup++; // turn checking on
qt_ntfs_permission_lookup--; // turn it off again

The safe and easy way to manage permission checks is to use the RAII class QNtfsPermissionCheckGuard.

void complexFunction()
{
    QNtfsPermissionCheckGuard permissionGuard;  // check is enabled

    // do complex things here that need permission check enabled

}   // as the guard goes out of scope the check is disabled

If you need more fine-grained control, it is possible to manage the permission with the following functions instead:

qAreNtfsPermissionChecksEnabled();   // check status
qEnableNtfsPermissionChecks();       // turn checking on
qDisableNtfsPermissionChecks();      // turn it off again

Some of QFileInfo's functions have to query the file system, but for performance reasons, some functions only operate on the path string. For example: To return the absolute path of a relative entry's path, absolutePath() has to query the file system. The path() function, however, can work on the file name directly, and so it is faster.

QFileInfo also caches information about the file system entry it refers to. Because the file system can be changed by other users or programs, or even by other parts of the same program, there is a function that refreshes the information stored in QFileInfo, namely refresh(). To switch off a QFileInfo's caching (that is, force it to query the underlying file system every time you request information from it), call setCaching(false).

Fetching information from the file system is typically done by calling (possibly) expensive system functions, so QFileInfo (depending on the implementation) might not fetch all the information from the file system at construction. To make sure that all information is read from the file system immediately, use the stat() member function.

birthTime(), fileTime(), lastModified(), lastRead(), and metadataChangeTime() return times in local time by default. Since native file system API typically uses UTC, this requires a conversion. If you don't actually need the local time, you can avoid this by requesting the time in QTimeZone::UTC directly.

On Android, some limitations apply when dealing with content URIs:

• Access permissions might be needed by prompting the user through the QFileDialog which implements Android's native file picker.

• Aim to follow the Scoped storage guidelines, such as using app specific directories instead of other public external directories. For more information, also see storage best practices.

• Due to the design of Qt APIs (e.g. QFile), it's not possible to fully integrate the latter APIs with Android's MediaStore APIs.

See also QDir, QFile

Constructs an empty QFileInfo object that doesn't refer to any file system entry.

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Constructs a QFileInfo that gives information about a file system entry located at path that can be absolute or relative.

If path is relative, the QFileInfo will also have a relative path.

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Constructs a new QFileInfo that gives information about file file.

If the file has a relative path, the QFileInfo will also have a relative path.

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Constructs a new QFileInfo that gives information about the given file system entry path that is relative to the directory dir.

If dir has a relative path, the QFileInfo will also have a relative path.

If path is absolute, then the directory specified by dir will be disregarded.

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Constructs a new QFileInfo that gives information about the given file.

This function was introduced in Qt 6.0.

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Constructs a new QFileInfo that gives information about the file system entry at path that is relative to the directory dir.

If dir has a relative path, the QFileInfo will also have a relative path.

If path is absolute, then the directory specified by dir will be disregarded.

This function was introduced in Qt 6.0.

Constructs a new QFileInfo that is a copy of the given fileinfo.

Destroys the QFileInfo and frees its resources.

Returns a QDir object representing the absolute path of the parent directory of the file system entry that this QFileInfo refers to.

// Given a current working directory of "/home/user/Documents/memos/"
QFileInfo info1(u"relativeFile"_s);
qDebug() << info1.absolutePath(); // "/home/user/Documents/memos/"
qDebug() << info1.baseName(); // "relativeFile"
qDebug() << info1.absoluteDir(); // QDir(u"/home/user/Documents/memos"_s)
qDebug() << info1.absoluteDir().path(); // "/home/user/Documents/memos"

// A QFileInfo on a dir
QFileInfo info2(u"/home/user/Documents/memos"_s);
qDebug() << info2.absolutePath(); // "/home/user/Documents"
qDebug() << info2.baseName(); // "memos"
qDebug() << info2.absoluteDir(); // QDir(u"/home/user/Documents"_s)
qDebug() << info2.absoluteDir().path(); // "/home/user/Documents"

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Returns the absolute full path to the file system entry this QFileInfo refers to, including the entry's name.

On Unix, absolute paths begin with the directory separator '/'. On Windows, absolute paths begin with a drive specification (for example, D:/).

On Windows, the paths of network shares that are not mapped to a drive letter begin with //sharename/. QFileInfo will uppercase drive letters. Note that QDir does not do this. The code snippet below shows this.

    QFileInfo fi("c:/temp/foo"); => fi.absoluteFilePath() => "C:/temp/foo"

This function returns the same as filePath(), unless isRelative() is true. In contrast to canonicalFilePath(), symbolic links or redundant "." or ".." elements are not necessarily removed.

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Returns the absolute path of the file system entry this QFileInfo refers to, excluding the entry's name.

On Unix, absolute paths begin with the directory separator '/'. On Windows, absolute paths begin with a drive specification (for example, D:/).

On Windows, the paths of network shares that are not mapped to a drive letter begin with //sharename/.

In contrast to canonicalPath() symbolic links or redundant "." or ".." elements are not necessarily removed.

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Returns the base name of the file without the path.

The base name consists of all characters in the file up to (but not including) the first '.' character.

Example:

QFileInfo fi("/tmp/archive.tar.gz");
QString base = fi.baseName();  // base = "archive"

The base name of a file is computed equally on all platforms, independent of file naming conventions (e.g., ".bashrc" on Unix has an empty base name, and the suffix is "bashrc").

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