Index · Directives systemd 228


sd_bus_new, sd_bus_ref, sd_bus_unref — Create a new bus object and create or destroy references to it


#include <systemd/sd-bus.h>
int sd_bus_new(sd_bus **bus);
sd_bus *sd_bus_ref(sd_bus *bus);
sd_bus *sd_bus_unref(sd_bus *bus);


sd_bus_new() creates a new bus object. This object is reference-counted, and will be destroyed when all references are gone. Initially, the caller of this function owns the sole reference and the bus object will not be connected to any bus. To connect it to a bus, make sure to set an address with sd_bus_set_address(3) or a related call, and then start the connection with sd_bus_start(3).

In most cases, it is a better idea to invoke sd_bus_default_user(3), sd_bus_default_system(3) or related calls instead of the more low-level sd_bus_new() and sd_bus_start(). The higher-level calls not only allocate a bus object but also start the connection to a well-known bus in a single function invocation.

sd_bus_ref() creates a new reference to bus.

sd_bus_unref() destroys a reference to bus. Once the reference count has dropped to zero, bus cannot be used anymore, so further calls to sd_bus_ref() or sd_bus_unref() are illegal.

Return Value

On success, sd_bus_new() returns 0 or a positive integer. On failure, it returns a negative errno-style error code.

sd_bus_ref always returns the argument.

sd_bus_unref always returns NULL.


Returned errors may indicate the following problems:


Memory allocation failed.


sd_bus_new() and other functions described here are available 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_default_user(3), sd_bus_default_system(3), sd_bus_open_user(3), sd_bus_open_system(3)