Index · Directives systemd 250


sd_bus_set_connected_signal, sd_bus_get_connected_signal — Control emission of local connection establishment signal on bus connections


#include <systemd/sd-bus.h>
int sd_bus_set_connected_signal(sd_bus *bus,
 int b);
int sd_bus_get_connected_signal(sd_bus *bus);


sd_bus_set_connected_signal() may be used to control whether a local, synthetic Connected() signal message shall be generated and enqueued for dispatching when the connection is fully established. If the b parameter is zero the message is not generated (the default), otherwise it is generated.

sd_bus_get_connected_signal() may be used to query whether this feature is enabled. It returns zero if not, positive otherwise.

The Connected() signal message is generated from the "org.freedesktop.DBus.Local" service and interface, and "/org/freedesktop/DBus/Local" object path. Use sd_bus_match_signal_async(3) to match on this signal.

This message is particularly useful on slow transports where connections take a long time to be established. This is especially the case when sd_bus_set_watch_bind(3) is used. The signal is generated when the sd_bus_is_ready(3) returns positive for the first time.

The Connected() signal corresponds with the Disconnected() signal that is synthesized locally when the connection is terminated. The latter is generated unconditionally however, unlike the former which needs to be enabled explicitly before it is generated, with sd_bus_set_connected_signal().

Return Value

On success, these functions return 0 or a positive integer. On failure, they return a negative errno-style error code.


Returned errors may indicate the following problems:


The bus connection has been created in a different process.


These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.

See Also

systemd(1), sd-bus(3), sd_bus_match_signal_async(3), sd_bus_set_watch_bind(3), sd_bus_is_ready(3)