C创建稀疏文件，生成的文件在两次写入之间有为\0的位， 这些\0位被称做孔， 有孔的文件被称为稀疏文件。 稀疏文件的一个有趣特性是， 根据它们属于的文件系统， 孔可以不实际占有任何磁盘块（而有些系统要填孔）， 这正是为什么磁盘上所有文件的大小总和可以超出磁盘容量的原因。-AlphaC to create a sparse file, the generated files for the \ 0 bits between the two write, \ 0 is called a hole, a hole in the file is called a sparse file. An interesting feature of the sparse file, they belong to the file system, the hole can not actually occupy any disk blocks (and some system to fill the hole), which is why the total size of all files on the disk can exceed the disk capacity is due.