# sd_bus_request_name

## 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.
    
               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.
    


## 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



           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.
    


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