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Name

sd_bus_request_name, sd_bus_release_name — Request or release a well-known name on a bus

Synopsis

#include <systemd/sd-bus.h>
int sd_bus_request_name(sd_bus *bus,
 const char *name,
 uint64_t flags);
 
int sd_bus_release_name(sd_bus *bus,
 const char *name);
 

Description

sd_bus_request_name() requests a well-known 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 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 is 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_release_name() releases an acquired well-known name. It takes a bus connection and a valid bus name as parameters.

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.

-ENOTCONN

The bus connection has been disconnected.

-ECHILD

The bus connection has been created in a different process than the current one.

Notes

The sd_bus_acquire_name() and sd_bus_release_name() interfaces are available 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)