Until now, we have spoken about the system and the session buses,
which are the default buses to be connected to. However, it is
possible to connect to any bus, from which the address is known. This
is a UNIX domain or TCP/IP socket. Everywhere, where a bus is
mentioned as argument of a function (the symbol
:system or the
:session), this address can be used instead. The
connection to this bus must be initialized first.
Establish the connection to D-Bus bus.
bus can be either the symbol
:system or the symbol
:session, or it can be a string denoting the address of the
corresponding bus. For the system and session buses, this function
is called when loading dbus.el, there is no need to call it
The function returns a number, which counts the connections this Emacs
session has established to the bus under the same unique name
dbus-get-unique-name). It depends on the libraries Emacs
is linked with, and on the environment Emacs is running. For example,
if Emacs is linked with the gtk toolkit, and it runs in a GTK-aware
environment like Gnome, another connection might already be
When private is non-
nil, a new connection is established
instead of reusing an existing one. It results in a new unique name
at the bus. This can be used, if it is necessary to distinguish from
another connection used in the same Emacs process, like the one
established by GTK+. It should be used with care for at least the
:session buses, because other Emacs Lisp
packages might already use this connection to those buses.
Example: You initialize a connection to the AT-SPI bus on your host:
(setq my-bus (dbus-call-method :session "org.a11y.Bus" "/org/a11y/bus" "org.a11y.Bus" "GetAddress")) ⇒ "unix:abstract=/tmp/dbus-2yzWHOCdSD,guid=a490dd26625870ca1298b6e10000fd7f" ;; If Emacs is built with gtk support, and you run in a GTK enabled ;; environment (like a GNOME session), the initialization reuses the ;; connection established by GTK's atk bindings. (dbus-init-bus my-bus) ⇒ 2 (dbus-get-unique-name my-bus) ⇒ ":1.19" ;; Open a new connection to the same bus. This obsoletes the ;; previous one. (dbus-init-bus my-bus 'private) ⇒ 1 (dbus-get-unique-name my-bus) ⇒ ":1.20"
D-Bus addresses can specify different transport. A possible address could be based on TCP/IP sockets, see next example. However, it depends on the bus daemon configuration, which transport is supported.
Set the value of the bus environment variable variable to value.
bus is either a Lisp symbol,
or a string denoting the bus address. Both variable and
value should be strings.
Normally, services inherit the environment of the bus daemon. This function adds to or modifies that environment when activating services.
Some bus instances, such as
:system, may disable setting the
environment. In such cases, or if this feature is not available in
older D-Bus versions, a
dbus-error error is raised.
As an example, it might be desirable to start X11 enabled services on a remote host’s bus on the same X11 server the local Emacs is running. This could be achieved by
(setq my-bus "unix:host=example.gnu.org,port=4711") ⇒ "unix:host=example.gnu.org,port=4711" (dbus-init-bus my-bus) ⇒ 1 (dbus-setenv my-bus "DISPLAY" (getenv "DISPLAY")) ⇒ nil