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(* Example showing how to enable debugging, and capture it into any
* custom logging system.
*)
(* Events we are interested in. This bitmask covers all trace and
* debug messages.
*)
let event_bitmask = [
Guestfs.EVENT_LIBRARY;
Guestfs.EVENT_WARNING;
Guestfs.EVENT_APPLIANCE;
Guestfs.EVENT_TRACE
]
let rec main () =
let g = new Guestfs.guestfs () in
(* By default, debugging information is printed on stderr. To
* capture it somewhere else you have to set up an event handler
* which will be called back as debug messages are generated. To do
* this use the event API.
*
* For more information see EVENTS in guestfs(3).
*)
ignore (g#set_event_callback message_callback event_bitmask);
(* This is how debugging is enabled:
*
* Setting the 'trace' flag in the handle means that each libguestfs
* call is logged (name, parameters, return). This flag is useful
* to see how libguestfs is being used by a program.
*
* Setting the 'verbose' flag enables a great deal of extra
* debugging throughout the system. This is useful if there is a
* libguestfs error which you don't understand.
*
* Note that you should set the flags early on after creating the
* handle. In particular if you set the verbose flag after launch
* then you won't see all messages.
*
* For more information see:
* http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs
*
* Error messages raised by APIs are *not* debugging information,
* and they are not affected by any of this. You may have to log
* them separately.
*)
g#set_trace true;
g#set_verbose true;
(* Do some operations which will generate plenty of trace and debug
* messages.
*)
g#add_drive "/dev/null";
g#launch ();
g#close ()
(* This function is called back by libguestfs whenever a trace or
* debug message is generated.
*
* For the classes of events we have registered above, 'array' and
* 'array_len' will not be meaningful. Only 'buf' and 'buf_len' will
* be interesting and these will contain the trace or debug message.
*
* This example simply redirects these messages to syslog, but
* obviously you could do something more advanced here.
*)
and message_callback event event_handle buf array =
if String.length buf > 0 then (
let event_name = Guestfs.event_to_string [event] in
Printf.printf "[%s] %S\n%!" event_name buf
)
let () = main ()
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