一、whatis
用法:whatis 命令A
查看命令A的用途
eg:
查看命令touch的用途:
[root@localhost Desktop]# whatis touch
touch (1) - change file timestamps
touch (1p) - change file access and modification times
注意:如果显示没有解释,则可通过mandb更新一下。
[root@localhost Desktop]# whatis command
command: nothing appropriate.
[root@localhost Desktop]# mandb
二、help
用法:命令A --help
查看命令A的基本用法
eg:
查看命令touch的基本用法:
[root@localhost Desktop]# touch --help
Usage: touch [OPTION]... FILE...
Update the access and modification times of each FILE to the current time.
A FILE argument that does not exist is created empty, unless -c or -h
is supplied.
A FILE argument string of - is handled specially and causes touch to
change the times of the file associated with standard output.
Mandatory arguments to long options are mandatory for short options too.
-a change only the access time
-c, --no-create do not create any files
-d, --date=STRING parse STRING and use it instead of current time
-f (ignored)
-h, --no-dereference affect each symbolic link instead of any referenced
file (useful only on systems that can change the
timestamps of a symlink)
-m change only the modification time
-r, --reference=FILE use this file's times instead of current time
-t STAMP use [[CC]YY]MMDDhhmm[.ss] instead of current time
--time=WORD change the specified time:
WORD is access, atime, or use: equivalent to -a
WORD is modify or mtime: equivalent to -m
--help display this help and exit
--version output version information and exit
Note that the -d and -t options accept different time-date formats.
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Full documentation at: <https://www.gnu.org/software/coreutils/touch>
or available locally via: info '(coreutils) touch invocation'
其中:
显示 | 含义 |
---|---|
[内容] | 表示在执行时可加可不加的内容 |
… | 表示加入的内容个数任意 |
<内容> | 表示在执行操作时必须加入的 |
三、man
用法:man 级别 对象
1、man级别
1 :查看命令的帮助
2 : 查看可被系统调用的函数的帮助
3 : 查看函数调用的帮助
4 : 查看系统特殊文件的帮助
5 : 查看系统配置文件的帮助
6 : 查看游戏的帮助
7 : 查看特殊包的帮助
8 : 查看系统管理命令的帮助
9 : 查看和内核相关规则的帮助
2、man 命令
查看命令用法
eg:查看passwd命令用法
[root@localhost Desktop]# man passwd
3、man -k 命令
查看命令在系统中有多少个级别的man
eg:查看passwd在系统中有多少个级别的man
[root@localhost Desktop]# man -k passwd
passwd (1) - update user's authentication tokens
passwd (5) - password file
从结果可知,passwd总共有两个级别的man(1和5)。
eg:
man 5 passwd(5表示查看系统配置文件的帮助) ,即查看/etc/passwd文件
[root@localhost Desktop]# man 5 passwd