thanks, i think i get it.

2013/1/30 <Valdis.Kletnieks@vt.edu>

On Tue, 29 Jan 2013 20:16:26 +0100, you said:

> Actually my question is :
> Does POSIX specifies  the fact that we need to use "lockf" to be able to do
> read/write operation in different offset ? Is'n the kernel supposed to
> ensure this ?

If you have non-overlapping writes, the kernel will eventually sort it out
for you.  If your writes overlap, you'll have to provide your own locking
via lockf() or similar, and synchronization via other methods.