The file is opened  in  append  mode.  Before  each
write, the file pointer is positioned at the end of
the file, as if with lseek.  O_APPEND may  lead  to
corrupted  files  on  NFS file systems if more than
one process appends data to a file at  once.   This
is  because  NFS  does  not  support appending to a
file, so the client  kernel  has  to  simulate  it,
which can't be done without a race condition