<LI>실행방법 : % gcc -o thread2 thread2.c -lpthread
<LI>위에서 -lpthread가 무슨 의미인가 설명하시오.
<LI>위의 예제 프로그램 내에 있는 시스템호출 pthread_create(), pthread_join(), pthread_exit(), sleep()에 대하여 설명하시오, <LI>위의 프로그램의 내용을 설명하고, 실행결과에 대하여 논하시오.
<PRE>#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include <string.h>

void* thread_function1(void*);
void* thread_function2(void*);

char msg[] = "Hello World";

int main() {
        int res;
        pthread_t a_thread;
        pthread_t b_thread;
        void* thread_result;

        res = pthread_create(&a_thread, NULL, thread_function1, (void*)msg);
        if(res != 0) {
                perror("Thread1 creation failed\n");
                exit(EXIT_FAILURE);
        }
        res = pthread_create(&b_thread, NULL, thread_function2, (void*)msg);
        if(res != 0) {
                perror("Thread2 creation failed\n");
                exit(EXIT_FAILURE);
        }

        printf("Waiting for thread1 to finish...\n");
        res = pthread_join(a_thread, &thread_result);
        if(res != 0) {
                perror("Thread1 join failed\n");
                exit(EXIT_FAILURE);
        }

        printf("Thread1 joined, it returend %s\n", (char*)thread_result);
        printf("Message is now %s\n", msg);

        printf("Waiting for thread2 to finish...\n");
        res = pthread_join(b_thread, &thread_result);
        if(res != 0) {
                perror("Thread2 join failed\n");
                exit(EXIT_FAILURE);
        }
        printf("Thread2 joined, it returend %s\n", (char*)thread_result);
        printf("Message is now %s\n", msg);

        exit(EXIT_SUCCESS);
}

void* thread_function1(void* arg) {
        int i,j;
        printf("thread_function1 is running. Argument was %s\n", (char*)arg);
        sleep(1);
        for(j=1;j<1000;j++)
        {
                printf("1 ");
                for(i=1;i<100000;i++);
        }
        printf("\n");
        strcpy(msg, "Bye thread1!");
        pthread_exit("Thank you Thread1 for the CPU time!");
}
void* thread_function2(void* arg) {
        int i,j;
        printf("thread_function2 is running. Argument was %s\n", (char*)arg);
        sleep(1);
        for(j=1;j<1000;j++)
        {
                printf("2 ");
                for(i=1;i<100000;i++);
        }
        printf("\n");
        strcpy(msg, "Bye thread2!");
        pthread_exit("Thank you Thread2 for the CPU time!");
}
</PRE>