I am trying to detect when Dropbox is busy updating a file in a user's Dropbox in Mac OS X. By running stat(1) or stat(2) on a file, I see that the user defined flags for file (st_flags) are normally 0x40, but while Dropbox is updating the file they change to 0x00 for a couple seconds.
Poking around my Desktop and other folders, I see that ~95% of files have flags value 0x00 but about 5% have value 0x40. So it may be not just a Dropbox implementation detail. I cannot discern any pattern for predicting which files have 0x40 flags. Does anyone know what these values mean? Who is the "user" that is defining them?
The flags can be set with the chflags command line tool or the chflags() system call (see man 2 chflags). The values can be found in "/usr/include/sys/stat.h".
UF_TRACKED seems to be a bit special. It is documented in "sys/stat.h"
#define UF_TRACKED 0x00000040 /* file renames and deletes are tracked */
but not in the "chflags" man-page.
Unfortunately, I cannot tell you what "tracked" precisely means, but perhaps this helps already to find more information.