pthread 예제프로그램이 컴파일이 안되네요.

 
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
 
void *thread_function(void *arg);
 
char message[] = " Sibal World ";
 
int main()
{
	int res;
	pthead_t a_thread;
	void *thread_result;
 
	res = pthread_create(&a_thread, NULL, thread_function, (void *)message);
	if( res !=0)
		{
			perror("Thread creation failed");
			exit(EXIT_FAILURE);
		}
 
	printf("Wating for thread to finish...\n");
	res = pthread_join(a_thread,&thread_result);
	if( res != 0 )
		{
			perror("Thread join failed");
			exit(EXIT_FAILURE);
		}
 
	printf("thread joined , it returned %s \n", (char *)thread_result);
	printf("message is now %s \n",message);
	exit(EXIT_SUCCESS);
}
 
void *thread_function(void *arg)
{
 
	printf("thread_function is running. Argument was %s \n", (char *)arg);
	sleep(3);
	strcpy(message,"Bye!");
	pthread_exit("Thank you for CPU time");
}