reader writer problem using semaphore under unix

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C

i can't reach a solution for this problem :
i want to design and implement a programming solution to the reader-writer problem
using semaphores in C language under UNIX.
We assume that we have three readers and two writers processes that would run concurrently.
A writer is to update (write) into one memory location (let’s say a variable of type integer named
temp initialized to 0). In the other hand, a reader is to read the content of temp and display its
content on the screen in a formatted output. One writer can access the shared data exclusively
without the presence of other writer or any reader, whereas, a reader may access the shared
memory for reading with the presence of other readers (but not writers).