Well, technically, the POSIX standard specifies that "After a write() to a regular file has successfully returned: ... Any successful read() from each byte posi

Well, technically, the POSIX standard specifies that "After a write() to a regular file has successfully returned: ... Any successful read() from each byte position in the file that was modified by that write shall return the data specified by the write() for that position until such byte positions are again modified." How well any given operating system implements this and whether it properly considers all the aspects of multiple processes writing/reading to the same file is anybody's guess. Linux /should/ do it correctly, but as I recall, SQLite had some related issues with shared files on OS X a few years ago.