Hi, the open(2) man page says:

       O_EXCL When  used with O_CREAT, if the file already exists
              it is an error and the open will fail.   O_EXCL  is
              broken  on NFS file systems, programs which rely on
              it for performing locking tasks will contain a race
              condition.  The solution for performing atomic file
              locking using a lockfile is to create a unique file
              on  the  same  fs (e.g., incorporating hostname and
              pid), use link(2) to make a link to  the  lockfile.
              If  link() returns 0, the lock is successful.  Oth­
              erwise, use stat(2) on the unique file to check  if
              its  link  count  has increased to 2, in which case
              the lock is also successful.

I coded this up and tried it here on a cluster of different operating
systems (Linux 2.4.5 server, linux, freebsd, solaris, aix, hpux, irix
clients) and it doesn't work.

2 questions:

a) is it the belief of folks here that this should work?

b) if performance isn't a big issue, is there any portable way to do
   locking over NFS with just files?