用标准c的I/O库函数实现对一个文本文档的逆序- C using standard I/O library functions to achieve the reverse of a text document

调用mmap函数对文件进行逆序操作。熟悉并使用mmap来减少系统调用和拷贝的次数。- Calls mmap function on a file in reverse operation. Familiar with and use mmap to reduce the number of system calls and copying.

使用unix的I/O函数：open/read/write，对指定文件进行逆序操作。-example：./unix test.txt 4 time ./unix test.txt 4 strace ./unix test.txt 4