#include <stdio.h> 
#include <stdlib.h> 
#include <sys/types.h> 
#include <sys/ipc.h> 
#include <sys/sem.h> 
#include <sys/stat.h> 
#include <fcntl.h> 
#include <semaphore.h>
#include <unistd.h>

union semun 
{ 
    int val; 
    struct semid_ds *buf; 
    unsigned short int *array; 
    struct seminfo *__buf; 
}; 

void *childThread(void* args);

int value;
int rc = 0;
sem_t test_semaphore;

int main(void) 
{ 
    int i = 0; 
    sem_init(&test_semaphore, 1, 0);
    sem_getvalue(&test_semaphore, &value);
    printf("The value of semaphore is %d\n", value);

    pthread_t tid;
    pthread_create(&tid,NULL,childThread,NULL);

    while (i < 5) { 
        sem_post(&test_semaphore);  
        sem_getvalue(&test_semaphore, &value);
        i++;
        sleep(1);
    } 
 
    return 0; 
} 


void *childThread(void* args){

    while(1){
        sem_wait(&test_semaphore);
        printf("I am the child thread. \n");
    }

}
 

上面就是一個簡單的執行緒間同步操作。