获取u盘设备的大小

unsigned long long usb_dev_get_free(char *dir)
{
 struct statfs diskInfo;
 unsigned long long totalBlocks;
 unsigned long long totalSize;
 unsigned long long freeDisk;

 if( statfs(dir,&diskInfo) == 0 )
 {
  totalBlocks = diskInfo.f_bsize;
  totalSize = totalBlocks * diskInfo.f_blocks;
     printf("TOTAL_SIZE == %lld MB\n",totalSize>>20);

     freeDisk = diskInfo.f_bfree*totalBlocks;
     printf("DISK_FREE == %lld MB\n",freeDisk>>20);

  return freeDisk;
 }

 return 0; 
}