nbd_set_debug_callback - set the debug callback


 #include <libnbd.h>

 typedef struct {
   int (*callback) (void *user_data, const char *context,
                    const char *msg);
   void *user_data;
   void (*free) (void *user_data);
 } nbd_debug_callback;

 int nbd_set_debug_callback (
       struct nbd_handle *h,
       nbd_debug_callback debug_callback


Set the debug callback. This function is called when the library emits debug messages, when debugging is enabled on a handle. The callback parameters are user_data passed to this function, the name of the libnbd function emitting the debug message (context), and the message itself (msg). If no debug callback is set on a handle then messages are printed on stderr.

The callback should not call nbd_* APIs on the same handle since it can be called while holding the handle lock and will cause a deadlock.


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.

The following parameters must not be NULL: h. For more information see "Non-NULL parameters" in libnbd(3).


This function first appeared in libnbd 1.0.

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



nbd_create(3), libnbd(3).


Eric Blake

Richard W.M. Jones


Copyright Red Hat


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.

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