sd_bus_request_name, sd_bus_request_name_async, sd_bus_release_name, sd_bus_release_name_async — Request or release a well-known service name on a bus
|const char *name,|
|const char *name,|
|const char *name|
|const char *name,|
sd_bus_request_name() requests a well-known service name on a bus. It takes a bus
connection, a valid bus name and a flags parameter. The flags parameter is a combination of the following
After acquiring the name successfully, permit other peers to take over the name when they try
to acquire it with the
SD_BUS_NAME_REPLACE_EXISTING flag set. If
SD_BUS_NAME_ALLOW_REPLACEMENT is not set on the original request, such a request by other
peers will be denied.
Take over the name if it is already acquired by another peer, and that other peer has permitted
takeover by setting
SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring it.
Queue the acquisition of the name when the name is already taken.
sd_bus_request_name() operates in a synchronous fashion: a message requesting the name
is sent to the bus broker, and the call waits until the broker responds.
sd_bus_request_name_async() is an asynchronous version of
sd_bus_release_name(). Instead of waiting for the request to complete, the request message is
enqueued. The specified
callback will be called when the broker's response is received. If
the parameter is specified as
NULL a default implementation is used instead which will
terminate the connection when the name cannot be acquired. The function returns a slot object in its
slot parameter — if it is passed as non-
NULL — which may be used as a
reference to the name request operation. Use
sd_bus_slot_unref(3) to destroy
this reference. Note that destroying the reference will not unregister the name, but simply ensure the specified
callback is no longer called.
sd_bus_release_name() releases an acquired well-known name. It takes a bus connection
and a valid bus name as parameters. This function operates synchronously, sending a release request message to the
bus broker and waiting for it to reply.
sd_bus_release_name_async() is an asynchronous version of
sd_bus_release_name(). The specified
callback function is called when
the name has been released successfully. If specified as
NULL a generic implementation is used
that ignores the result of the operation. As above, the
NULL) is set to an object that may be used to reference the operation.
These functions are supported only on bus connections, i.e. connections to a bus broker and not on direct connections.
On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code.
SD_BUS_NAME_QUEUE is specified,
sd_bus_request_name() will return
0 when the name is already taken by another peer and the client has been added to the queue for the name. In that
case, the caller can subscribe to "
NameOwnerChanged" signals to be notified when the name is
sd_bus_request_name() returns > 0 when the name has immediately
been acquired successfully.
Returned errors may indicate the following problems:
The caller already is the owner of the specified name.
The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the name.
It was attempted to release a name that is currently not registered on the bus.
It was attempted to release a name that is owned by a different peer on the bus.
A specified parameter is invalid. This is also generated when the requested name is a special service name reserved by the D-Bus specification, or when the operation is requested on a connection that does not refer to a bus.
The bus connection has been disconnected.
The bus connection has been created in a different process than the current one.
sd_bus_acquire_name() and the other interfaces described here are available as a
shared library, which can be compiled and linked to with the
libsystemd pkg-config(1) file.