On Thursday 03 April 2008 16:11:59 Mel wrote:
On Thursday 03 April 2008 12:25:55 John Conover wrote:
Does freebsd support the F_NOTIFY, (i.e., File and directory change
notification,) in fcntl(2)?
I get that it doesn't, but its an old 5X version, and I might have to
upgrade.
Nope, this is a GNU extension to fcntl. File change notifications are done
with EVFILT_VNODE using kqueue(2). Directory changes have no interface that
I know of. You might wanna take a look at how devel/gamin handles this,
specifically the kqueue implementation.
Figured I'd give an example of how it can be done (as in: works for me for
file deletion/creation and renames). Doesn't work for utimes(2) operations on
a file, as in touch /tmp/this_file_exists will not fire.
Code inlined below sig.
--
Mel
#include sys/types.h
#include sys/event.h
#include sys/time.h
#include sysexits.h
#include err.h
#include stdio.h
#include sys/stat.h
#include time.h
#include fcntl.h
int main(int argc, char **argv)
{
int kq, fd;
struct kevent changes, events;
time_t *mtime;
struct stat sb;
if( -1 == (fd = open(/tmp/., O_RDONLY)) )
err(EX_OSERR, Cannot open dir /tmp);
if( NULL == (mtime = malloc(sizeof(time_t))) )
err(EX_OSERR, Failed to allocate %d bytes, sizeof(time_t));
if( -1 == fstat(fd, sb) )
err(EX_OSERR, Cannot stat fd %u, fd);
*mtime = sb.st_mtime;
if( -1 == (kq = kqueue()) )
err(EX_OSERR, Cannot get a kqueue);
EV_SET(changes, fd, EVFILT_TIMER, EV_ADD|EV_ENABLE, 0, 500,
(void *)mtime);
for( ;; )
{
/* we can only get one event, really. */
if( -1 == kevent(kq, changes, 1, events, 1, NULL) )
err(EX_OSERR, kevent);
if( events.flags EV_ERROR )
errc(EX_OSERR, events.data, Event error);
/* secretly, our timer is an fd, we probably should use udata for this
* though.
*/
if( -1 == fstat(events.ident, sb) )
{
warn(Failed to stat fd %u, events.ident);
break;
}
else
{
if( *mtime *mtime != sb.st_mtime )
printf(Mtime changed: %u = %u\n, *mtime, sb.st_mtime);
else
printf(Mtime unchanged: %u\n, *mtime);
*mtime = sb.st_mtime;
}
}
close(kq);
return 0;
}
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