whatis

查询一个命令执行什么功能

## 补充说明

**whatis命令** 是用于查询一个命令执行什么功能，并将查询结果打印到终端上。

whatis命令在用`catman -w`命令创建的数据库中查找command参数指定的命令、系统调用、库函数或特殊文件名。whatis命令显示手册部分的页眉行。然后可以发出man命令以获取附加的信息。whatis命令等同于使用`man -f`命令。

###  语法

```shell
whatis
```

###  实例

```shell
[root@localhost ~]# whatis ls
ls                   (1)  - list directory contents
ls                   (1p)  - list directory contents

[root@localhost ~]# whatis cp
cp                   (1)  - copy files and directories
cp                   (1p)  - copy files

[root@localhost ~]# whatis chown
chown                (1)  - change file owner and group
chown                (1p)  - change the file ownership
chown                (2)  - change ownership of a file
chown                (3p)  - change owner and group of a file

[root@localhost ~]# whatis man
man                  (1)  - format and display the on-line manual pages
man                  (1p)  - display system documentation
man                  (7)  - macros to format man pages
man                 (rpm) - A set of documentation tools: man, apropos and whatis.
man-pages           (rpm) - Man (manual) pages from the Linux Documentation Project.
man.config [man]     (5)  - configuration data for man
```