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syncrw.c

+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <pthread.h>
+#include <semaphore.h>
+
+#define THREAD_SIZE 3
+#define ITER_PER_THREAD 4
+
+void *reader(void *arg);
+void *writer(void *arg);
+
+int num = 0;
+sem_t mutex;
+
+int main(void)
+{
+    pthread_t w[THREAD_SIZE];
+    pthread_t r[THREAD_SIZE];
+
+    sem_init(&mutex, 0, 1); 
+
+    printf("Start program\n\n");
+
+    for(int i = 0; i < 3; i++){
+
+        int w_thread = pthread_create(&w[i], NULL, (void *)writer, (void*)&i);
+
+        if(w_thread < 0){
+            perror("thread create error : ");
+            exit(0);
+        }    
+
+        int r_thread = pthread_create(&r[i], NULL, (void *)reader, (void*)&i);
+
+        if(r_thread < 0){
+            perror("thread create error : ");
+            exit(0);
+        }
+
+    }
+
+    for(int i = 0; i < 3; i++)
+    {
+        pthread_join(w[i],NULL);
+        pthread_join(r[i],NULL);
+    }
+
+    printf("\nEnd of program\n");
+
+    return 0;
+}
+
+void *reader(void *arg)
+{
+    bool readable;
+
+    for(int i = 0; i < ITER_PER_THREAD; i++)
+    {        
+        sem_wait(&mutex);
+
+        printf("Read current number: %d\n", num);
+
+        sem_post(&mutex);
+    }
+
+    sleep(1);
+}
+
+void *writer(void *arg)
+{
+    for(int i=0; i<5; i++)
+    {
+        sem_wait(&mutex);
+
+        num = rand() % 10;
+        printf("Write random number: %d\n", num);
+
+        sem_post(&mutex);
+    }
+
+    sleep(1);
+}
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