ios 获取指定路径文件大小

-(long long) fileSizeAtPath:(NSString*) filePath{  
  NSFileManager* manager = [NSFileManager defaultManager];  
  if ([manager fileExistsAtPath:filePath]){  
    return [[manager attributesOfItemAtPath:filePath error:nil] fileSize];  
  }  
  return 0;  
}