I Need help in C Script in unix enviroment

I want to Implement a Synchronisation primitive such as a semaphore
that will ensure mutual exclusion, prevent deadlock when concurrent
request are made from the clients. C scripts in the UNIX environment
in the below script

I ma just trying to stop two clients accessing the same server file at
the same time



Any help would greatly help

I am willing to do any thing in the return even pay