有问题，找男人。
用man这么久了，以前从没注意到它有几个很有用的选项。
-a 查看所有,-k 查找相关.
以前只知道前面加数字是查找相应的区，却不知道它具体有哪些区，原来有这些：
1 Executable programs or shell commands
2 System calls (functions provided by the kernel)
3 Library calls (functions within program libraries)
4 Special files (usually found in /dev)
5 File formats and conventions eg /etc/passwd
6 Games
7 Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
8 System administration commands (usually only for root)
9 Kernel routines [Non standard]
早知道有这个 -a和 -k我就不用一个区一个区的试了。