sd_bus_default, sd_bus_default_user, sd_bus_default_system, sd_bus_open, sd_bus_open_user, sd_bus_open_system, sd_bus_open_system_remote, sd_bus_open_system_machine — Acquire a connection to a system or user bus
|const char *host|
|const char *machine|
sd_bus_default() acquires a bus
connection object to the user bus when invoked in user context, or
to the system bus otherwise. The connection object is associated
to the calling thread. Each time the function is invoked from the
same thread the same object is returned, but its reference count
is increased by one, as long as at least one reference is
kept. When the last reference to the connection is dropped (using
call), the connection is terminated. Note that the connection is
not automatically terminated when the associated thread ends. It
is important to drop the last reference to the bus connection
explicitly before the thread ends or otherwise the connection will
sd_bus_default_user() returns a user
bus connection object associated to the calling thread.
sd_bus_default_system() is similar, but
connects to the system bus. Note that
sd_bus_default() is identical to these two
calls, depending on the execution context.
sd_bus_open() creates a new,
independent bus connection to the user bus when invoked in user
context, or the system bus
sd_bus_open_user() is similar, but
connects only to the user bus.
sd_bus_open_system() does the same, but
connects to the system bus. In contrast to
sd_bus_default_system() these calls return
new, independent connection objects that are not associated with
the invoking thread and are not shared between multiple
invocations. It is recommended to share connections per thread to
efficiently make use the available resources. Thus, it is
recommended to use
sd_bus_default_system() to connect to the
user or system buses.
variable is set
it will be used as the address of the user bus. This variable can
contain multiple addresses separated by "
this variable is not set, a suitable default for the default user
D-Bus instance will be used.
environment variable is set, it will be used as the address of the
system bus. This variable uses the same syntax as
$DBUS_SESSION_BUS_ADDRESS. If this variable is
not set, a suitable default for the default system D-Bus instance
will be used.
sd_bus_open_system_remote() connects to
the system bus on the specified
consists of an optional user name followed by the
@" symbol, and the hostname.
to the system bus in the specified
machine is the name of a local
for more information about the "machine" concept. Note that
connections into local containers are only available to privileged
processes at this time.
These calls allocate a bus connection object and initiate the connection ot a well-known bus of some form. An alternative to using these high-level calls is to create an unconnected bus object with sd_bus_new(3) and to connect it with sd_bus_start(3).
On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code.
sd_bus_open_system_machine() return a new
object and the caller owns the sole reference. When not needed
anymore, this reference should be destroyed with
sd_bus_default_system() do not necessarily
create a new object, but increase the connection reference by
to drop the reference.
Returned errors may indicate the following problems:
In addition, any further connection-related errors may be by returned. See sd_bus_send(3).
sd_bus_open_user() and the other
functions described here are available as a shared library, which
can be compiled and linked to with the