.\" The "BSD-New" License
.\" 
.\" Copyright (c) 2013, NLnet Labs, Verisign, Inc.
.\" All rights reserved.
.\" 
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions are met:
.\" * Redistributions of source code must retain the above copyright
.\"   notice, this list of conditions and the following disclaimer.
.\" * Redistributions in binary form must reproduce the above copyright
.\"   notice, this list of conditions and the following disclaimer in the
.\"   documentation and/or other materials provided with the distribution.
.\" * Neither the names of the copyright holders nor the
.\"   names of its contributors may be used to endorse or promote products
.\"   derived from this software without specific prior written permission.
.\" 
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL Verisign, Inc. BE LIABLE FOR ANY
.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
.\" ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
.\" SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\" 

.TH getdns_context_set_context_update_callback 3 "December 2015" "getdns 1.7.3" getdns
.SH NAME
.B getdns_context_set_context_update_callback 
-- get informed on getdns context updates

.SH LIBRARY
DNS Resolver library (libgetdns, \-lgetdns)

.SH SYNOPSIS
#include <getdns.h>

getdns_return_t
.br
.B getdns_context_set_context_update_callback
(getdns_context ** context,
.RS 3
.br
void (*cbfun)(getdns_context *context, getdns_context_code_t changed_item)
.RE

.SH DESCRIPTION

.LP
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
.B
cbfun

.HP 3
.I context
a previously initialized context

.HP 3
.I 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.

.HP
.SH "RETURN VALUES"

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

.LP
.B GETDNS_RETURN_GENERIC_ERROR
memory allocation failed or some other untoward thing happened 

.LP
.B GETDNS_RETURN_BAD_CONTEXT 
if the context pointer is invalid

.SH EXAMPLES

TBD

.SH SEE ALSO
.BR libgetdns (3),
.BR getdns_context_create (3),
.BR getdns_context_set (3),
.BR getdns_context_set_context_update_callback (3),