The pseudo code implementation would be something like this. Get the semaphore ID in the child process using same key, either using ftok or hardcoded key, then obtain the current value of semaphore then perform appropriate operations.
struct shma{readindex,writeindex,buf_max,char buf[5],used_count};
main()
{
struct shma* shm;
shmid = shmget();
shm = shmat(shmid);
init_shma(0,0,5,0);
sembuf[3]; semun u1; values[] = {5,1,0}; // Sem Numbers 1,2,3
semid = semget(3 semaphores);
semctl(SETALL,values);
while(i++<2)
{
ret = fork();
if(ret > 0 )
continue;
if(ret ==0 )
{
if(i==0)
{
char value;
sembuf[3]; semun u1; values[];
semid = semget(3 semaphores);
while(1)
{
getValuefromuser(&value);
decrement(1);
decrement(2); // Critical section
*copy value to shared memory*
increment(2);
increment(3); // used count
}
}
if(i==1)
{
char value;
sembuf[3]; semun u1; values[];
while(1)
{
getValuefromuser(&value);
decrement(3); // Used Count
decrement(2); // Critical Section
read and print(&value); // From Shared Memory
increment(2);
increment(1); // free slots
}
}
}
}//while
Cleanup Code.
}//main