NAME
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 busSYNOPSIS
#include <systemd/sd-bus.h>
typedef
int (*sd_bus_message_handler_t)(sd_bus_message *m,
void *userdata,
sd_bus_error *ret_error);
int
sd_bus_request_name(sd_bus *bus,
const char *name,
uint64_t flags);
int
sd_bus_request_name_async(sd_bus *bus,
sd_bus_slot **slot,
const char *name,
uint64_t flags,
sd_bus_message_handler_t callback,
void *userdata);
int
sd_bus_release_name(sd_bus *bus,
const char *name);
int
sd_bus_release_name_async(sd_bus *bus,
sd_bus_slot **slot,
const char *name,
sd_bus_message_handler_t callback,
void *userdata);
DESCRIPTION
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 zero or more of the following flags: SD_BUS_NAME_ALLOW_REPLACEMENTAfter 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.
SD_BUS_NAME_REPLACE_EXISTING
Take over the name if it was already acquired
by another peer, and that other peer has permitted takeover by setting
SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring it.
SD_BUS_NAME_QUEUE
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_request_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 slot (if non- 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.
RETURN VALUE
On success, these calls return 0 or a positive integer. On failure, these calls return a negative errno-style error code. If 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 successfully acquired. sd_bus_request_name() returns > 0 when the name has immediately been acquired successfully.Errors
Returned errors may indicate the following problems: -EALREADYThe caller already is the owner of the
specified name.
-EEXIST
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.
-ESRCH
It was attempted to release a name that is
currently not registered on the bus.
-EADDRINUSE
It was attempted to release a name that is
owned by a different peer on the bus.
-EINVAL
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.
-ENOTCONN
The bus connection has been
disconnected.
-ECHILD
The bus connection has been created in a
different process than the current one.
NOTES
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_new(3), sd_bus_slot_unref(3)systemd 252 |