readdir的可重入函数readdir_r

readdir函数：      

struct dirent *readdir(DIR *dirp); 

       The  data  returned by readdir() may be overwritten by subsequent calls to readdir() for the same directory stream.

readdir函数为非线程安全函数；

解决方法：1、加锁；

    2、用局部变量保存数据；

readdir_r()就是采用局部变量保存数据；

int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);

The  readdir_r() function returns 0 on success.  On error, it returns apositive error number (listed under ERRORS).  If the end of the  directory  stream  is  reached,  readdir_r()  returns 0, and returns NULL in*result

例子：

int main()
{
  struct dirent *pStResult = NULL;
  struct dirent *pStEntry = NULL;
  int len = 0;

  DIR *pDir = opendir("/home/wzy/owner_lib");
  if(NULL == pDir)
  {
      printf("Opendir failed!\n");
      return 0;
  }

  len = offsetof(struct dirent, d_name) + pathconf("/home/wzy/owner_lib", _PC_NAME_MAX) + 1;
  pStEntry = (struct dirent*)malloc(len);
  while(! readdir_r(pDir, pStEntry, &pStResult) && pStResult != NULL)
  {
      printf("file'name is %s\n", pStEntry->d_name);
  }

  free(pStEntry);
  closedir(pDir);
  return 0;
}