getdns_context_set_context_update_callback -- get informed on getdns context updates

       Changes to the context such as in response to system files that affect the contet (/etc/resolv.conf etc.)
       trigger a call to the callback function specified as cbfuncontext a previously initialized context

       cbfun  callback  function  to  invoked when the specified context changes.  If this argument is NULL then
          updates to the context will not invoke a callback.

       TBD

       DNS Resolver library (libgetdns, -lgetdns)

getdns_context_set_context_update_callback -- get informed on getdns context updates

       Upon successful completion each of these functions return GETDNS_RETURN_GOOD ,  otherwise  the  following
       error values are returned:

       GETDNS_RETURN_GENERIC_ERROR memory allocation failed or some other untoward thing happened

       GETDNS_RETURN_BAD_CONTEXT if the context pointer is invalid

libgetdns(3),                       getdns_context_create(3),                      getdns_context_set(3),
       getdns_context_set_context_update_callback(3),

getdns 1.6.0                                      December 2015    getdns_context_set_context_update_callback(3)

       #include <getdns.h>

       getdns_return_t
       getdns_context_set_context_update_callback (getdns_context ** context,
          void (*cbfun)(getdns_context *context, getdns_context_code_t changed_item)