man
man [选项] [命令名称]
man目录：[root@node203 /]# ls /usr/share/man
man init
man -k keyword
man -f keyword
man -a keyword
man -n keyword //不存在的参数，直接显示man的参数
Help
可以用来查找Shell命令的用法
ll --help
info
info mknod
whereis
查找命令所在的位置
whereis ls
OPTIONS
-b Search only for binaries.只查找二进制文件
-m Search only for manual sections. //查找主要文件
-s Search only for sources.//查找来源
-u Search for unusual entries. A file is said to be unusual if it
does not have one entry of each requested type. Thus
‘whereis -m -u *’ asks for those files in the current direc-
tory which have no documentation. //查找不常用的记录文件
-B Change or otherwise limit the places where whereis searches for
binaries.
-M Change or otherwise limit the places where whereis searches for
manual sections.
-S Change or otherwise limit the places where whereis searches for
sources.
-f Terminate the last directory list and signals the start of file
names, and must be used when any of the -B, -M, or -S options
are used.
