How to use the command qdbus (with examples)

Qdbus is an Inter-Process Communication (IPC) and Remote Procedure Calling (RPC) mechanism originally developed for Linux. It allows communication between different processes and enables method invocations, signal handling, and property access.

Use case 1: List available service names

Code:

qdbus

Motivation: The motivation for this use case is to retrieve a list of available service names that can be accessed using qdbus.

Explanation: The qdbus command without any arguments lists all the available service names. It provides a comprehensive list of all the services running on the system.

Example output:

com.canonical.Unity
org.freedesktop.DBus
org.kde.ActivityManager
org.kde.akonadi.AgentBase
org.kde.Akonadi.AkonadiControl
org.kde.Akonadi.AgentServer
...

Use case 2: List object paths for a specific service

Code:

qdbus service_name

Motivation: This use case allows users to obtain a list of object paths associated with a specific service.

Explanation: The qdbus command followed by the service name as an argument lists the object paths associated with that particular service. Object paths represent the hierarchy of objects available under a service.

Example output:

/org/freedesktop/DBus
/org/
/org/freedesktop/DBus/Local
/org/gnome/Nautilus
...

Use case 3: List methods, signals, and properties available on a specific object

Code:

qdbus service_name /path/to/object

Motivation: The motivation for this use case is to retrieve information about the methods, signals, and properties available on a specific object.

Explanation: By providing the service name and the object path as arguments to the qdbus command, a list of methods, signals, and properties associated with that object can be obtained.

Example output:

method int org.freedesktop.DBus.Introspectable.Introspect() const
method void org.freedesktop.DBus.Peer.Ping()
method QString org.freedesktop.DBus.Properties.Get(QString interface_name, QString property_name)
method QStringList org.freedesktop.DBus.Properties.GetAll(QString interface_name)
signal void org.freedesktop.DBus.Properties.PropertiesChanged(QString interface_name, QVariantMap changed_properties, QStringList invalidated_properties)
...

Use case 4: Execute a specific method passing arguments and display the returned value

Code:

qdbus service_name /path/to/object method_name argument1 argument2

Motivation: This use case allows the execution of a specific method available on an object, along with passing arguments and displaying the returned value.

Explanation: By providing the service name, object path, method name, and necessary arguments, the qdbus command can execute the specified method and display the returned value.

Example output:

42

Use case 5: Display the current brightness value in a KDE Plasma session

Code:

qdbus org.kde.Solid.PowerManagement /org/kde/Solid/PowerManagement/Actions/BrightnessControl org.kde.Solid.PowerManagement.Actions.BrightnessControl.brightness

Motivation: The motivation for this use case is to retrieve the current brightness value of a KDE Plasma session.

Explanation: By using the qdbus command with the appropriate service name, object path, and method, the current brightness value of a KDE Plasma session can be obtained.

Example output:

75

Use case 6: Set a specific brightness to a KDE Plasma session

Code:

qdbus org.kde.Solid.PowerManagement /org/kde/Solid/PowerManagement/Actions/BrightnessControl org.kde.Solid.PowerManagement.Actions.BrightnessControl.setBrightness 5000

Motivation: This use case allows users to set a specific brightness level in a KDE Plasma session.

Explanation: By using the qdbus command with the necessary arguments, including the service name, object path, method, and the desired brightness value, the brightness level can be set.

Example output:

Use case 7: Invoke volume up shortcut in a KDE Plasma session

Code:

qdbus org.kde.kglobalaccel /component/kmix invokeShortcut "increase_volume"

Motivation: The motivation for this use case is to trigger the volume up action in a KDE Plasma session.

Explanation: By using the qdbus command with the appropriate service name, object path, and method, the volume up shortcut can be invoked.

Example output:

Use case 8: Gracefully log out and then do nothing, reboot, or shut down

Code:

qdbus org.kde.Shutdown /Shutdown logout|logoutAndReboot|logoutAndShutdown

Motivation: This use case provides the ability to perform different actions related to logout, reboot, or shut down in a KDE Plasma session.

Explanation: By using the qdbus command with the necessary arguments, including the service name, object path, and method, the desired action can be performed, such as logging out, rebooting, or shutting down.

Example output:

Conclusion:

The qdbus command is a powerful tool for interacting with various services and objects in a Linux system. It allows users to retrieve information, execute methods, and control different aspects of the system. By utilizing the provided examples, users can effectively utilize the qdbus command to streamline their workflow and perform various tasks efficiently.