nbd_aio_opt_info - Man Page

request the server for information about an export


 #include <libnbd.h>

 typedef struct {
   int (*callback) (void *user_data, int *error);
   void *user_data;
   void (*free) (void *user_data);
 } nbd_completion_callback;

 int nbd_aio_opt_info (struct nbd_handle *h,
                       nbd_completion_callback completion_callback);


Request that the server supply information about the export name previously specified by the most recent nbd_set_export_name(3) or nbd_connect_uri(3).  This can only be used if nbd_set_opt_mode(3) enabled option mode.

To determine when the request completes, wait for nbd_aio_is_connecting(3) to return false.  Or supply the optional completion_callback which will be invoked as described in “Completion callbacks” in libnbd(3), except that it is automatically retired regardless of return value.  Note that detecting whether the server returns an error (as is done by the return value of the synchronous counterpart) is only possible with a completion callback.

Return Value

If the call is successful the function returns 0.


On error -1 is returned.

Refer to “ERROR HANDLING” in libnbd(3) for how to get further details of the error.

Handle State

The handle must be negotiating, otherwise this call will return an error.


This function first appeared in libnbd 1.4.

If you need to test if this function is available at compile time check if the following macro is defined:


See Also

nbd_aio_is_connecting(3), nbd_connect_uri(3), nbd_create(3), nbd_is_read_only(3), nbd_opt_info(3), nbd_set_export_name(3), nbd_set_opt_mode(3), libnbd(3).


Eric Blake

Richard W.M. Jones


This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

Referenced By

libnbd(3), libnbd-release-notes-1.4(1), nbd_opt_info(3).

2020-10-05 libnbd-1.5.4