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#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
/* Global variables */
int x = 0;
sem_t sync;
/* Thread function */
void *my_func(void *arg)
{
/* wait for signal from main thread */
sem_wait(&sync);
printf("X = %d\n", x);
}
void main ()
{
pthread_t thread;
/* semaphore sync should be initialized by 0 */
if (sem_init(&sync, 0, 0) == -1) {
perror("Could not initialize mylock semaphore");
exit(2);
}
if (pthread_create(&thread, NULL, my_func, NULL) < 0) {
perror("Error: thread cannot be created");
exit(1);
}
/* perform some operation(s) */
x = 55;
/* send signal to the created thread */
sem_post(&sync);
/* wait for created thread to terminate */
pthread_join(thread, NULL);
/* destroy semaphore sync */
sem_destroy(&sync);
exit(0);
}