pthread_create & pthread_join & pthread_exit 基本用法

#include <stdio.h>
#include <unistd.h>
#include <pthread.h>

int ret = 1234;

void* show_message(void* ptr)
{
    char* message;
    int x = 5;

    message = (char*) ptr;

    for (x = 5 ; x > 0 ; --x) {
        printf("%s \n", message);
        usleep(300);
    }

    pthread_exit((void*)&ret);
}

int main() {
    pthread_t thread1;
    pthread_t thread2;
    int *ret1 = NULL;
    int *ret2 = NULL;

    pthread_create(&thread1, NULL , show_message , (void*) "Thread 1");
    pthread_create(&thread2, NULL , show_message , (void*) "Thread 2");
    pthread_join( thread1, (void**)&ret1);
    pthread_join( thread2, (void**)&ret2);
    printf("return value from thread1 = %d\n", *ret1);
    printf("return value from thread2 = %d\n", *ret2);

    return 0;
}

gcc -o pthread pthread.c -lpthread