man -h
man,version 1.6c
usage: man [-adfhktwW] [section] [-M path] [-P pager] [-S list]
[-m system] [-p string] name ...
其中的(1)，指其中的可选参数[section]。
在系统中，有些系统命令/系统调用/程序库会重名，这种情况下直接问男人，男人猜不透你想要问他的是哪个?
于是把这些手册分成了8类:
Section Description
1 General commands
2 System calls
3 Library functions, covering in particular the C standard library
4 Special files (usually devices, those found in /dev) and drivers
5 File formats and conventions
6 Games and screensavers
7 Miscellanea
8 System administration commands and daemons
参考文献：
[1] http://en.wikipedia.org/wiki/Man_page
[2] 转自知乎网友回答www.zhihu.com/question/20219623
