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QDBusUnixFileDescriptor Class

The QDBusUnixFileDescriptor class holds one Unix file descriptor. More...

Header: #include <QDBusUnixFileDescriptor>
qmake: QT += dbus
Since: Qt 4.8

Public Functions

QDBusUnixFileDescriptor(int fileDescriptor)
QDBusUnixFileDescriptor(const QDBusUnixFileDescriptor &other)
int fileDescriptor() const
void giveFileDescriptor(int fileDescriptor)
bool isValid() const
void setFileDescriptor(int fileDescriptor)
void swap(QDBusUnixFileDescriptor &other)
int takeFileDescriptor()
QDBusUnixFileDescriptor & operator=(QDBusUnixFileDescriptor &&other)
QDBusUnixFileDescriptor & operator=(const QDBusUnixFileDescriptor &other)

Static Public Members

bool isSupported()

Detailed Description

The QDBusUnixFileDescriptor class holds one Unix file descriptor.

The QDBusUnixFileDescriptor class is used to hold one Unix file descriptor for use with the Qt D-Bus module. This allows applications to send and receive Unix file descriptors over the D-Bus connection, mapping automatically to the D-Bus type 'h'.

Objects of type QDBusUnixFileDescriptors can be used also as parameters in signals and slots that get exported to D-Bus by registering with QDBusConnection::registerObject.

QDBusUnixFileDescriptor does not take ownership of the file descriptor. Instead, it will use the Unix system call dup(2) to make a copy of the file descriptor. This file descriptor belongs to the QDBusUnixFileDescriptor object and should not be stored or closed by the user. Instead, you should make your own copy if you need that.


Unix file descriptor passing is not available in all D-Bus connections. This feature is present with D-Bus library and bus daemon version 1.4 and upwards on Unix systems. Qt D-Bus automatically enables the feature if such a version was found at compile-time and run-time.

To verify that your connection does support passing file descriptors, check if the QDBusConnection::UnixFileDescriptorPassing capability is set with QDBusConnection::connectionCapabilities(). If the flag is not active, then you will not be able to make calls to methods that have QDBusUnixFileDescriptor as arguments or even embed such a type in a variant. You will also not receive calls containing that type.

Note also that remote applications may not have support for Unix file descriptor passing. If you make a D-Bus to a remote application that cannot receive such a type, you will receive an error reply. If you try to send a signal containing a D-Bus file descriptor or return one from a method call, the message will be silently dropped.

Even if the feature is not available, QDBusUnixFileDescriptor will continue to operate, so code need not have compile-time checks for the availability of this feature.

On non-Unix systems, QDBusUnixFileDescriptor will always report an invalid state and QDBusUnixFileDescriptor::isSupported() will return false.

See also QDBusConnection::ConnectionCapabilities and QDBusConnection::connectionCapabilities().

Member Function Documentation


Default constructs an instance of QDBusUnixFileDescriptor.

QDBusUnixFileDescriptor::QDBusUnixFileDescriptor(int fileDescriptor)

Default constructs an instance of QDBusUnixFileDescriptor.

QDBusUnixFileDescriptor::QDBusUnixFileDescriptor(const QDBusUnixFileDescriptor &other)

Default constructs an instance of QDBusUnixFileDescriptor.


Destroys the instance of QDBusUnixFileDescriptor.

int QDBusUnixFileDescriptor::fileDescriptor() const

See also setFileDescriptor().

void QDBusUnixFileDescriptor::giveFileDescriptor(int fileDescriptor)

[static] bool QDBusUnixFileDescriptor::isSupported()

bool QDBusUnixFileDescriptor::isValid() const

void QDBusUnixFileDescriptor::setFileDescriptor(int fileDescriptor)

See also fileDescriptor().

void QDBusUnixFileDescriptor::swap(QDBusUnixFileDescriptor &other)

Swaps this file descriptor instance with other. This function is very fast and never fails.

This function was introduced in Qt 5.0.

int QDBusUnixFileDescriptor::takeFileDescriptor()

QDBusUnixFileDescriptor &QDBusUnixFileDescriptor::operator=(QDBusUnixFileDescriptor &&other)

Move-assigns other to this QDBusUnixFileDescriptor.

QDBusUnixFileDescriptor &QDBusUnixFileDescriptor::operator=(const QDBusUnixFileDescriptor &other)

Copy-assignment operator.

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