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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS_REQUEST_NAME(3) sd_bus_request_name SD_BUS_REQUEST_NAME(3)
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
#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);
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.
Added in version 209.
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.
SD_BUS_NAME_QUEUE
Queue the acquisition of the name when the name is already
taken.
Added in version 209.
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.
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.
Functions described here are available as a shared library, which
can be compiled against and linked to with the
libsystemd pkg-config(1) file.
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.
sd_bus_request_name() and sd_bus_release_name() were added in
version 209.
sd_bus_request_name_async() and sd_bus_release_name_async() were
added in version 237.
systemd(1), sd-bus(3), sd_bus_new(3), sd_bus_slot_unref(3)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel SD_BUS_REQUEST_NAME(3)
Pages that refer to this page: sd-bus(3), sd_bus_set_watch_bind(3), systemd.directives(7), systemd.index(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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