| SD_BUS_REQUEST_NAME(3) | sd_bus_request_name | SD_BUS_REQUEST_NAME(3) |
.SH "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
.SH "SYNOPSIS"
#include <systemd/sd-bus.h>
.HP 960u typedef int
(*sd_bus_message_handler_t)(sd_bus_message *m,
void *userdata,
sd_bus_error *ret_error);
.HP 576u int sd_bus_request_name(sd_bus *bus,
const char *name,
uint64_t flags);
.HP 720u 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);
.HP 576u int sd_bus_release_name(sd_bus *bus,
const char *name);
.HP 720u int sd_bus_release_name_async(sd_bus *bus,
sd_bus_slot **slot,
const char *name,
sd_bus_message_handler_t callback,
void *userdata);
.SH "DESCRIPTION"
.PP 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:
.PP 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.
Added in version 209.
.RE
.PP 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.
Added in version 209.
.RE
.PP SD_BUS_NAME_QUEUE
Queue the acquisition of the name when the name is already taken.
Added in version 209.
.RE
.PP 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.
.PP 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.
.PP 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.
.PP 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.
.PP These functions are supported only on bus connections, i.e. connections
to a bus broker and not on direct connections.
.SH "RETURN VALUE"
.PP On success, these calls return 0 or a positive integer. On failure, these
calls return a negative errno-style error code.
.PP 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.
.SS "Errors"
.PP Returned errors may indicate the following problems:
.PP -EALREADY
The caller already is the owner of the specified name.
.RE
.PP -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.
.RE
.PP -ESRCH
It was attempted to release a name that is currently not registered on the
bus.
.RE
.PP -EADDRINUSE
It was attempted to release a name that is owned by a different peer on the
bus.
.RE
.PP -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.
.RE
.PP -ENOTCONN
The bus connection has been disconnected.
.RE
.PP -ECHILD
The bus connection has been created in a different process than the current
one.
.RE
.SH "NOTES"
.PP Functions described here are available as a shared library, which can be
compiled against and linked to with the
libsystemd pkg-config(1) file.
.PP All functions listed here are thread-agnostic and only a single thread
may operate on a given object at any given time. Different threads may
access the same object at different times. Multiple independent objects may
be used from different threads in parallel.
.PP The code described here uses getenv(3), which is declared to be
not multi-thread-safe. This means that the code calling the functions
described here must not call setenv(3) from a parallel thread. It is
recommended to only do calls to setenv() from an early phase of the
program when no other threads have been started.
.SH "HISTORY"
.PP sd_bus_request_name() and sd_bus_release_name() were added
in version 209.
.PP sd_bus_request_name_async() and sd_bus_release_name_async()
were added in version 237.
.SH "SEE ALSO"
.PP systemd(1), sd-bus(3), sd_bus_new(3),
sd_bus_slot_unref(3)
| systemd 262.2 |