询问grep中如何查询'-n'类似这样的内容？

[Shark Wang <sharkwang@gmail.com>]

我用 man netstat | grep -i '-n' ，系统告诉我错误！

Usage: grep [OPTION]... PATTERN [FILE]...
Try `grep --help' for more information.
Reformatting netstat(8), please wait...