Hi there,
I'm the author of jpathwatch [1], a Java library that provides
directory watching capability to Java programs. The library is
cross-platform and supports Linux as well as Windows, OSX and FreeBSD.
The library implements JDK7's WatchService API, but can also be used
in JDK5 and JDK6 programs.
For the API I'm providing (which I cannot really change), I need to
distinguish between files that are renamed within the same directory
('local' renames), and files that are moved into and out of the
watched directory ('foreign' renames). Local and foreign renames map
to different events:
* local renames show up as such, as RENAME_FROM and RENAME_TO events
* foreign renames show up as CREATE and DELETE events.
The problem I'm now having is that from an IN_MOVE_FROM event alone I
cannot tell whether it is a local or a foreign rename. One (bad)
solution in userland would be to wait for a matching IN_MOVE_TO. In
case of a foreign rename this event will never happen, so I'd have to
hold back the IN_MOVE_FROM until some timeout and then send send it as
DELETE; for local renames I'd receive IN_MOVE_TO and would send
RENAME_FROM and RENAME_TO.
But obviously that solution is poor, so I'm wondering if some
enhancement in inotify that indicates foreign renames in events could
help (or if I'm missing something obvious here and am just typing
gibberish :)
So in conclusion:
* Am I missing something? Is there really no way to tell local from
foreign renames in inotify?
* If I'm not, I propose to add a flag mask bit to indicate this
situation, similar to the IN_ISDIR flag in the mask field - let's call
it IN_ISFOREIGN. Whenever this bit is set on an IN_MOVE_FROM event,
the user program knows that it won't have to look for a matching
IN_MOVE_TO in the same directory. Same could be done for IN_MOVE_TO
(although it's not entirely necessary, but it would make sense just
for symmetry)
Cheers,
Uwe Pachler
[1] http://jpathwatch.wordpress.com/
P.S.: Sorry for the wonky email address; I'm SPAM paranoid
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