Yanyan Jiang wrote:
> If at this time, the system crashes (or later at write), the data is gone forever (or have a suffering recovery). Should we warn users of this, or add special treatment with this case (write a temp file and rename it)?

Thanks for reporting the issue. Writing to a temp file and renaming would have 
problems, as it might change the file's ownership or permissions or etc., and 
also won't behave as the user expects if the file has multiple hard links. We 
should at least warn users about the problem in the documentation, though, so I 
installed the attached patch on Savannah at:

http://git.savannah.gnu.org/cgit/coreutils.git/commit/?id=4c1995f1b673b0e1eae73a9db4e28016b86dee9e