Suppose you have the executable
      fcntlother
Then you can run it with the command
      fcntlother self i
where self is an integer you use to represent this process
and i is a lock on the file mylock (the index of the byte being locked)

If you run on a machine the command
      fcntlother 1 1 &
      fcntlother 2 2 &
and on a second machine sharing the file mylock 
with the previous machine you run
      fcntlother 3 1 &
      fcntlother 4 2 &
you will see messages on the two systems that indicate that
the locks are working properly, i.e. processes 1 and 3 are mutually
exclusive as are processes 2 and 4, while processes 1 and 3 can
execute concurrently with processes 2 and 4.