[C++]多线程: 教你写第一个线程

原文：http://blog.csdn.net/cn_wk/article/details/62236057

hello thread!

1. 声明线程A的端口号

   
   #include <pthread.h>
   
   pthread_t tid;

2. 定义线程运行函数

   void thread_function(void *args)
   {
       printf("thread_function is called!
   ");
       //注意区别 cout << "thread_function is called! << endl; 和上一行
   }

3. 创建线程

   pthread_create(&tid, NULL, &thread_function, NULL);

4. (optional)阻塞: 挂起当前线程，直到tid线程结束

   pthread_join(tid, NULL);

好了，这样就可以启一个线程了，完整代码如下：

#include<unistd.h>
#include<stdio.h>
#include<cstring>
#define MAX_THREAD 2

pthread_t thread[MAX_THREAD];
pthread_mutex_t mut;

int num = 0;
void* thread1(void *args)
{
    printf("hi, I am thread1
");
    for(int i=0; i < 6; i++){
        pthread_mutex_lock(&mut);
        printf("[thread1]num=%d, i=%d
", num, i);
            num ++;
        pthread_mutex_unlock(&mut);
        sleep(2);
    }
    pthread_exit(NULL);
}

void* thread2(void *args)
{
    printf("hi, I am thread2
");
    for(int i = 0; i < 10; i++)
    {
        pthread_mutex_lock(&mut);
        printf("[thread2]num=%d, i=%d
", num, i);
            num ++;
        pthread_mutex_unlock(&mut);
        sleep(3);
    }
    pthread_exit(NULL);
}

void thread_create()
{
    memset(&thread, 0, sizeof(thread));
    if( 0!=pthread_create(&thread[0], NULL, thread1, NULL))
        printf("thread1 create faild
");
    else
            printf("thread1 established
");

    if( 0 != pthread_create(&thread[1], NULL, thread2, NULL))
        printf("thread2 create faild
");
    else
        printf("thread2 established
");

}

void thread_wait()
{
    if(0 != thread[0])
    {
        pthread_join(thread[0], NULL);
        printf("thread 1 is over
");
    }

    if(0 != thread[1])
    {
        pthread_join(thread[1], NULL);
        printf("thread 2 is over
");
    }
}

int main()
{
    pthread_mutex_init(&mut, NULL);
    printf("main thread: creating threads...
");
    thread_create();
    printf("main thread: waiting threads to accomplish task...
");
    thread_wait();
    return 0;
}

代码，得到结果:

tmain thread: creating threads… 
thread1 established 
hi, I am thread1 
[thread1]num=0, i=0 
thread2 established 
main thread: waiting threads to accomplish task… 
hi, I am thread2 
[thread2]num=1, i=0 
[thread1]num=2, i=1 
[thread2]num=3, i=1 
[thread1]num=4, i=2 
[thread2]num=5, i=2 
[thread1]num=6, i=3 
[thread1]num=7, i=4 
[thread2]num=8, i=3 
[thread1]num=9, i=5 
[thread2]num=10, i=4 
thread 1 is over 
[thread2]num=11, i=5 
[thread2]num=12, i=6 
[thread2]num=13, i=7 
[thread2]num=14, i=8 
[thread2]num=15, i=9 
thread 2 is over

OK，现在说一下pthread_create方法的原型

pthread_create方法

作用

• 创建线程

原型

```
int pthread_create(pthread_t *restrict tidp,const pthread_attr_t *restrict_attr,void*（*start_rtn)(void*),void *restrict arg);
```

参数

• 第一个参数是指向线程标识符的指针
• 第二个参数用来设置线程的属性
• 第三个参数是线程运行函数的首地址
• 第四个参数是线程运行函数的参数

返回值

• 若成功，则返回0；否则，返回错误编号。

pthread_join方法

作用

• 这个函数是一个线程阻塞的函数
• 等待线程结束再继续往下执行，要不然主进程和下面的线程并行执行

原型

extern int pthread_join __P ((pthread_t __th, void **__thread_return))

参数

• 第一个参数是被等待线程的标识符
• 第二个参数是用户自定义的指针。用来存储被等待线程的返回值