帮助与手册

man

man - an interface to the on-line reference manuals

$ man <section> <subject>
 
# 查看 <subject> 有多(少) man
$ man -f <subject>
 
# 在命令名及摘要中按关键词查找
$ man -k <keyword>

sections
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]

* 常用