1.1 whatis：简述命令的作用
whatis： 简述命令的作用
root@Eternal:~# whatis whatis
whatis (1) - display one-line manual page descriptions
1.2 info：查看命令详细的说明文档
root@Eternal:~# info whatis
WHATIS(1) Manual pager utils WHATIS(1)
NAME
whatis - display one-line manual page descriptions
SYNOPSIS
whatis [-dlv?V] [-r|-w] [-s list] [-m system[,...]] [-M path] [-L
locale] [-C file] name ...
DESCRIPTION
Each manual page has a short description available within it. whatis
searches the manual page names and displays the manual page descrip‐
tions of any name matched.
name may contain wildcards (-w) or be a regular expression (-r). Using
these options, it may be necessary to quote the name or escape (\) the
special characters to stop the shell from interpreting them.
......
1.3 man：查看命令的说明文档
root@Eternal:~# man locate
locate(1) General Commands Manual locate(1)
NAME
locate - find files by name
SYNOPSIS
locate [OPTION]... PATTERN...
DESCRIPTION
locate reads one or more databases prepared by updatedb(8) and writes
file names matching at least one of the PATTERNs to standard output,
one per line.
If --regex is not specified, PATTERNs can contain globbing characters.
If any PATTERN contains no globbing characters, locate behaves as if
the pattern were *PATTERN*.
By default, locate does not check whether files found in database still
exist (but it does require all parent directories to exist if the data‐
base was built with --require-visibility no). locate can never report
files created after the most recent update of the relevant database.
......
man分类标示：
1）用户可以操作的命令或者是可执行文件
2)）系统核心可调用的函数与工具等
3)）一些常用的函数与数据库
4）设备文件的说明
5）设置文件或者某些文件的格式
6）游戏
7）惯例与协议等。例如Linux标准文件系统、网络协议、ASCⅡ，码等说明内容
8）系统管理员可用的管理条令
9）与内核有关的文件
用法：
root@Eternal:~# man 3 printf
1.4 which：查看可执行文件的路径
which：查看可执行文件的路径
root@Eternal:~# which locate
/usr/bin/locate
1.5 whereis：查看程序的搜索路径
whereis：查看程序的搜索路径
root@Eternal:~# whereis locate
locate: /usr/bin/locate /usr/share/man/man1/locate.1.gz
