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posix_sem_shm.c
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posix_sem_shm.c
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#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
int count = 0;
int limit = 5;
struct monitored_value
{
sem_t sem_read, sem_write;
int value;
};
int main(int argc, char *argv[])
{
int shm_ID;
struct monitored_value *my_shared_value;
shm_ID = shmget(ftok("mysharedmem", 4), getpagesize(), IPC_CREAT | 0600);
my_shared_value = (struct monitored_value *)
shmat(shm_ID, NULL, 0);
sem_init(&(my_shared_value->sem_read), 1, 0);
sem_init(&(my_shared_value->sem_write), 1, 0);
my_shared_value->value = count;
while(count < limit)
{
sem_wait(&(my_shared_value->sem_write));
printf("Reader Process: %dth Loop\n", count+1);
my_shared_value->value = count;
sem_post(&(my_shared_value->sem_read));
count++;
}
sem_destroy(&(my_shared_value->sem_write));
sem_destroy(&(my_shared_value->sem_read));
shmdt((void*) my_shared_value);
shmctl(shm_ID, IPC_RMID, NULL);
_exit(0);
}