QTemporaryFile Class

Member Function Documentation

QTemporaryFile::QTemporaryFile()

Constructs a QTemporaryFile.

The default file name template is determined from the application name as returned by QCoreApplication::applicationName() (or "qt_temp" if the application name is empty), followed by ".XXXXXX". The file is stored in the system's temporary directory, as returned by QDir::tempPath().

See also setFileTemplate(), fileTemplate(), fileName(), and QDir::tempPath().

[explicit] QTemporaryFile::QTemporaryFile(QObject *parent)

Constructs a QTemporaryFile with the given parent.

The default file name template is determined from the application name as returned by QCoreApplication::applicationName() (or "qt_temp" if the application name is empty), followed by ".XXXXXX". The file is stored in the system's temporary directory, as returned by QDir::tempPath().

See also setFileTemplate().

[explicit] QTemporaryFile::QTemporaryFile(const QString &templateName)

Constructs a QTemporaryFile with templateName as the file name template.

Upon opening the temporary file, templateName will be used to create a unique filename.

If the file name (the part after the last directory path separator in templateName) doesn't contain "XXXXXX", it will be added automatically.

"XXXXXX" will be replaced with the dynamic part of the file name, which is calculated to be unique.

If templateName is a relative path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct templateName if you want use the system's temporary directory.

It is important to specify the correct directory if the rename() function will be called, as QTemporaryFile can only rename files within the same volume / filesystem as the temporary file itself was created on.

See also open() and fileTemplate().

QTemporaryFile::QTemporaryFile(const QString &templateName, QObject *parent)

Constructs a QTemporaryFile with the specified parent, and templateName as the file name template.

Upon opening the temporary file, templateName will be used to create a unique filename.

If the file name (the part after the last directory path separator in templateName) doesn't contain "XXXXXX", it will be added automatically.

"XXXXXX" will be replaced with the dynamic part of the file name, which is calculated to be unique.

If templateName is a relative path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct templateName if you want use the system's temporary directory. It is important to specify the correct directory if the rename() function will be called, as QTemporaryFile can only rename files within the same volume / filesystem as the temporary file itself was created on.

See also open() and fileTemplate().

[explicit, since 6.7] QTemporaryFile::QTemporaryFile(const std::filesystem::path &templateName, QObject *parent = nullptr)

This is an overloaded function.

This function was introduced in Qt 6.7.

[virtual noexcept] QTemporaryFile::~QTemporaryFile()

Destroys the temporary file object, the file is automatically closed if necessary and if in auto remove mode it will automatically delete the file.

See also autoRemove().

bool QTemporaryFile::autoRemove() const

Returns true if the QTemporaryFile is in auto remove mode. Auto-remove mode will automatically delete the filename from disk upon destruction. This makes it very easy to create your QTemporaryFile object on the stack, fill it with data, read from it, and finally on function return it will automatically clean up after itself.

Auto-remove is on by default.

See also setAutoRemove() and remove().

[static] QTemporaryFile *QTemporaryFile::createNativeFile(QFile &file)

If file is not already a native file, then a QTemporaryFile is created in QDir::tempPath(), the contents of file is copied into it, and a pointer to the temporary file is returned. Does nothing and returns 0 if file is already a native file.

For example:

  QFile f(":/resources/file.txt");
  QTemporaryFile::createNativeFile(f); // Returns a pointer to a temporary file

  QFile f("/users/qt/file.txt");
  QTemporaryFile::createNativeFile(f); // Returns 0

See also QFileInfo::isNativePath().

[static] QTemporaryFile *QTemporaryFile::createNativeFile(const QString &fileName)

This is an overloaded function.

Works on the given fileName rather than an existing QFile object.

[static, since 6.7] QTemporaryFile *QTemporaryFile::createNativeFile(const std::filesystem::path &fileName)

This is an overloaded function.

This function was introduced in Qt 6.7.

[override virtual] QString QTemporaryFile::fileName() const

Reimplements: QFile::fileName() const.

Returns the complete unique filename backing the QTemporaryFile object. This string is null before the QTemporaryFile is opened, afterwards it will contain the fileTemplate() plus additional characters to make it unique.

The file name returned by this method is relative or absolute depending on the file name template used to construct this object (or passed to setFileTemplate()) being relative or absolute, respectively.

See also fileTemplate().

QString QTemporaryFile::fileTemplate() const

Returns the file name template.

The file name template returned by this method, will be relative or absolute depending on the file name template used to construct this object (or passed to setFileTemplate()) being relative or absolute, respectively.

See also setFileTemplate(), fileName(), and Default File Name Template.

bool QTemporaryFile::open()

Opens a unique temporary file in the file system in QIODeviceBase::ReadWrite mode. Returns true if the file was successfully opened, or was already open. Otherwise returns false.

If called for the first time, open() will create a unique file name based on fileTemplate(). The file is guaranteed to have been created by this function (that is, it has never existed before).

If a file is reopened after calling close(), the same file will be opened again.

See also setFileTemplate() and QT_USE_NODISCARD_FILE_OPEN.

[override virtual protected] bool QTemporaryFile::open(QIODeviceBase::OpenMode mode)

Reimplements: QFile::open(QIODeviceBase::OpenMode mode).

Opens a unique temporary file in the file system with mode flags. Returns true if the file was successfully opened, or was already open. Otherwise returns false.

If called for the first time, open() will create a unique file name based on fileTemplate(), and open it with mode flags. The file is guaranteed to have been created by this function (that is, it has never existed before).

If a file is reopened after calling close(), the same file will be opened again with mode flags.

See also setFileTemplate() and QT_USE_NODISCARD_FILE_OPEN.

bool QTemporaryFile::rename(const QString &newName)

Renames the current temporary file to newName and returns true if it succeeded.

This function has an important difference compared to QFile::rename(): it will not perform a copy+delete if the low-level system call to rename the file fails, something that could happen if newName specifies a file in a different volume or filesystem than the temporary file was created on. In other words, QTemporaryFile only supports atomic file renaming.

This functionality is intended to support materializing the destination file with all contents already present, so another process cannot see an incomplete file in the process of being written. The QSaveFile class can be used for a similar purpose too, particularly if the destination file is not temporary.

See also QSaveFile, QSaveFile::commit(), and QFile::rename().

[since 6.7] bool QTemporaryFile::rename(const std::filesystem::path &newName)

This is an overloaded function.

This function was introduced in Qt 6.7.

void QTemporaryFile::setAutoRemove(bool b)

Sets the QTemporaryFile into auto-remove mode if b is true.

Auto-remove is on by default.

If you set this property to false, ensure the application provides a way to remove the file once it is no longer needed, including passing the responsibility on to another process. Always use the fileName() function to obtain the name and never try to guess the name that QTemporaryFile has generated.

On some systems, if fileName() is not called before closing the file, the temporary file may be removed regardless of the state of this property. This behavior should not be relied upon, so application code should either call fileName() or leave the auto removal functionality enabled.

See also autoRemove() and remove().

void QTemporaryFile::setFileTemplate(const QString &templateName)

Sets the file name template to templateName.

If the file name (the part after the last directory path separator in templateName) doesn't contain "XXXXXX", it will be added automatically.

"XXXXXX" will be replaced with the dynamic part of the file name, which is calculated to be unique.

If templateName is a relative path, the path will be relative to the current working directory. You can use QDir::tempPath() to construct templateName if you want use the system's temporary directory. It is important to specify the correct directory if the rename() function will be called, as QTemporaryFile can only rename files within the same volume / filesystem as the temporary file itself was created on.

See also fileTemplate() and fileName().

[since 6.7] void QTemporaryFile::setFileTemplate(const std::filesystem::path &name)

This is an overloaded function.

This function was introduced in Qt 6.7.