Linux 编译报错 undefined reference to `pthread_create'

在编译Linux下多线程程序的时候出现错误信息，

写好代码，进行编译时，出现如下错误提示信息： 

thread.c:(.text+0xae): undefined reference to `pthread_create'
thread.c:(.text+0xf3): undefined reference to `pthread_create'
thread.c:(.text+0x127): undefined reference to `pthread_join'
thread.c:(.text+0x13a): undefined reference to `pthread_join'
collect2: ld returned 1 exit status

linux下的多线程程序代码如下：

/* thread.c */
#include <stdio.h>
#include <pthread.h>

/* thread 1 */
void thread1(void)
{
  int i = 0;
  for (i=0; i<6; i++)
  {
    printf("This is a pthread1.\n");
    if (i == 2)
        pthread_exit(0);    
    sleep(1);
  }    
}

/* thread 2 */
void thread2(void)
{
  int i;
  for (i=0; i<3; i++)
      printf("This is a pthread2.\n");
  pthread_exit(0);    
}

int main(void)
{
  pthread_t id1, id2;
  int i, ret;
  
  /* Create Thread 1 */
  ret = pthread_create(&id1, NULL, (void *)thread1, NULL);
  if (ret != 0)
  {
    printf("Create pthread error!\n");
    exit(1);    
  }    
  
  /* Create Thread 2 */
  ret = pthread_create(&id2, NULL, (void *)thread2, NULL);
  if (ret != 0)
  {
    printf("Create pthread error!\n");    
    exit(1);
  }
  
  /* Wait Thread Terminate */
  pthread_join(id1, NULL);
  pthread_join(id2, NULL);
  
  exit(0);
}

错误原因： pthread 库不是 Linux 系统默认的库，连接时需要使用静态库 libpthread.a，所以在使用pthread_create()创建线程，以及调用 pthread_atfork()函数建立fork处理程序时，需要链接该库。

解决之道：在编译中要加 -lpthread参数，类似于在使用是的参数 -lm.

    gcc thread.c  -lpthread

    thread.c为源文件，不要忘了加上头文件#include

最后输出如下：

[root@MUPF-SST-A xudong]# ./a.out
This is a pthread1.
This is a pthread2.
This is a pthread2.
This is a pthread2.
This is a pthread1.
This is a pthread1.