SD_BUS_REQUEST_NAME(3) sd_bus_request_name SD_BUS_REQUEST_NAME(3)
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 bus
SYNOPSIS
#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_REPLACEMENT
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.
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:
-EALREADY
The 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 SD_BUS_REQUEST_NAME(3)
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