(3)、 简单的多线程示例
一个简单的Linux多线程示例如下：
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void *thread_function(void *arg);
char message[] = "Hello World";
int main()
{
int res;
pthread_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("Waiting for thread to finish.../n");
res = pthread_join(a_thread, &thread_result);
if (res != 0)
{
perror("Thread join failed!/n");
exit(EXIT_FAILURE);
}
printf("Thread joined, it returned %s/n", (char *)thread_result);
printf("Message is now %s/n", message);
exit(EXIT_FAILURE);
}
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 your CPU time!");
}
编译语句如下：
gcc –lpthread thread1.c -o thread1
输出结果是：
$./thread1[输出]：
thread_function is running. Argument was Hello World
Waiting for thread to finish...
Thread joined, it returned Thank you for your CPU time!
Message is now Bye!
在这个例子中，pthread_exit(void *retval)本身返回的就是指向某个对象的指
针，因此，pthread_join(pthread_t th, void **thread_return);中的thread_return
是二级指针，指向线程返回值的指针。可以看到，我们创建的新线程修改的数组
message的值，而原先的线程也可以访问该数组。如果我们调用的是fork而不是
pthread_create，就不会有这样的效果了。因为fork创建子进程之后，子进程会拷贝
父进程，两者分离，相互不干扰，而线程之间则是共享进程的相关资源。
<4>、多线程实例
(1)、创建新文件1.Multithreading.c：
/*1.Multithreading.c ：c multiple thread programming in linux */
#include "pthread.h"
#include <stdio.h>
#include <sys/time.h>
#include <string.h>
#include <time.h>
#define MAX 10
pthread_t thread[2];
pthread_mutex_t mut;
int number=0, i;
void *thread1()
{
printf ("thread1 : I'm thread 1\n");
system("ls -l");
pthread_exit(NULL);
}
void *thread2()
{
int j;
printf ("thread1 : I'm thread 2\n");
for(j = 0; j < 5; j++)
{
sleep(1);
printf("%dS\n",j + 1);
}
pthread_exit(NULL);
}
void thread_create(void)
{
int temp;
memset(&thread, 0, sizeof(thread)); //comment1
/*创建线程*/
if((temp = pthread_create(&thread[0], NULL, thread1, NULL)) != 0)
//comment2
printf("线程1创建失败\n");
else
printf("线程1被创建\n");
if((temp = pthread_create(&thread[1], NULL, thread2, NULL)) != 0)
//comment3
printf("线程2创建失败\n");
else
printf("线程2被创建\n");
}
void thread_wait(void)
{
/*等待线程结束*/
if(thread[0] !=0)
{ //comment4
pthread_join(thread[0],NULL);
printf("线程1已经结束\n");
}
if(thread[1] ==0)
{
// pthread_join(thread[1],NULL);
printf("线程2已经结束\n");
}
}
int main()
{
/*用默认属性初始化互斥锁*/
pthread_mutex_init(&mut,NULL);
printf("我是主函数\n");
thread_create();
printf("我是主函数，正在等待线程完成任务\n");
thread_wait();
return 0;
}
(2)、进行编译运行：
sudo gcc 1.Multithreading.c -o 1.Multithreading -lpthread
./ 1.Multithreading
