Linux whatis 命令初学者教程（5 个示例）

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1. Linux whatis 命令
2. Q1。如何使用 whatis 命令？
3. Q2。如何获取多个命令的信息？
4. Q3。我们可以在 whatis 中使用通配符吗？
5. Q4。如何让whatis产生调试信息？
6. Q5。 whatis 如何执行搜索？
7. 结论

在了解命令行实用程序时，手册页是最有用的资源之一。但是，手册页包含有关该命令的许多详细信息。有时您可能想快速了解 - 可能在一小行左右 - 命令行工具的作用。好吧，您会很高兴知道存在专门为此目的构建的命令。

在本教程中，我们将使用一些易于理解的示例来讨论 whatis 命令的基础知识。但在我们这样做之前，值得一提的是，这里的所有示例都已经在 Ubuntu 18.04 LTS 和 Debian 10 机器上进行了测试。

Linux whatis 命令

Linux 中的 whatis 命令可让您显示一行手册页描述。以下是它的语法：

whatis  [-dlv?V]  [-r|-w]  [-s  list]  [-m  system[,...]] [-M path] [-L
       locale] [-C file] name ...

以下是工具手册页对其的解释：

       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.

以下是一些 Q&A 风格的示例，可以让您更好地了解 whatis 命令的工作原理。

Q1。如何使用 whatis 命令？

基本用法非常简单。只需传递一个工具名称作为输入，whatis 就会搜索并显示它的单行描述。

这是一个例子：

whatis ls

上述命令产生了以下输出：

ls (1)               - list directory contents

Q2。如何获取多个命令的信息？

这也很简单——只需将工具名称作为输入传递给 whatis。下面是一个例子：

whatis ls cp rm mv

这是此命令产生的输出：

ls (1)               - list directory contents
cp (1)               - copy files and directories
rm (1)               - remove files or directories
mv (1)               - move (rename) files

所以你可以看到 whatis 命令很容易处理多个输入。

Q3.我们可以在 whatis 中使用通配符吗？

是的，可以在 whatis 命令中使用通配符。 -w 命令行选项启用此功能。

这是一个例子；

whatis -w 'who*'

以下是输出：

who (1)              - show who is logged on
whoami (1)           - print effective userid

Q4.如何让whatis产生调试信息？

-d 选项使 whatis 命令在输出中产生调试信息。不用说，这个选项主要是为开发者准备的。

这是一个例子：

whatis -d ls

以下是此命令产生的输出：

From the config file /etc/manpath.config:

Mandatory mandir `/usr/man'.
Mandatory mandir `/usr/share/man'.
Mandatory mandir `/usr/local/share/man'.
Path `/bin' mapped to mandir `/usr/share/man'.
Path `/usr/bin' mapped to mandir `/usr/share/man'.
Path `/sbin' mapped to mandir `/usr/share/man'.
Path `/usr/sbin' mapped to mandir `/usr/share/man'.
Path `/usr/local/bin' mapped to mandir `/usr/local/man'.
Path `/usr/local/bin' mapped to mandir `/usr/local/share/man'.
Path `/usr/local/sbin' mapped to mandir `/usr/local/man'.
Path `/usr/local/sbin' mapped to mandir `/usr/local/share/man'.
Path `/usr/X11R6/bin' mapped to mandir `/usr/X11R6/man'.
Path `/usr/bin/X11' mapped to mandir `/usr/X11R6/man'.
Path `/usr/games' mapped to mandir `/usr/share/man'.
Path `/opt/bin' mapped to mandir `/opt/man'.
Path `/opt/sbin' mapped to mandir `/opt/man'.
Global mandir `/usr/man', catdir `/var/cache/man/fsstnd'.
Global mandir `/usr/share/man', catdir `/var/cache/man'.
Global mandir `/usr/local/man', catdir `/var/cache/man/oldlocal'.
Global mandir `/usr/local/share/man', catdir `/var/cache/man/local'.
Global mandir `/usr/X11R6/man', catdir `/var/cache/man/X11R6'.
Global mandir `/opt/man', catdir `/var/cache/man/opt'.
Added section `1'.
Added section `n'.
Added section `l'.
Added section `8'.
Added section `3'.
Added section `2'.
Added section `3posix'.
Added section `3pm'.
Added section `3perl'.
Added section `3am'.
Added section `5'.
Added section `4'.
Added section `9'.
Added section `6'.
Added section `7'.
`/usr/man'    `'    `1'
`/usr/share/man'    `'    `1'
`/usr/local/share/man'    `'    `1'
`/bin'    `/usr/share/man'    `0'
`/usr/bin'    `/usr/share/man'    `0'
`/sbin'    `/usr/share/man'    `0'
`/usr/sbin'    `/usr/share/man'    `0'
`/usr/local/bin'    `/usr/local/man'    `0'
`/usr/local/bin'    `/usr/local/share/man'    `0'
`/usr/local/sbin'    `/usr/local/man'    `0'
`/usr/local/sbin'    `/usr/local/share/man'    `0'
`/usr/X11R6/bin'    `/usr/X11R6/man'    `0'
`/usr/bin/X11'    `/usr/X11R6/man'    `0'
`/usr/games'    `/usr/share/man'    `0'
`/opt/bin'    `/opt/man'    `0'
`/opt/sbin'    `/opt/man'    `0'
`/usr/man'    `/var/cache/man/fsstnd'    `-1'
`/usr/share/man'    `/var/cache/man'    `-1'
`/usr/local/man'    `/var/cache/man/oldlocal'    `-1'
`/usr/local/share/man'    `/var/cache/man/local'    `-1'
`/usr/X11R6/man'    `/var/cache/man/X11R6'    `-1'
`/opt/man'    `/var/cache/man/opt'    `-1'
`1'    `'    `-5'
`n'    `'    `-5'
`l'    `'    `-5'
`8'    `'    `-5'
`3'    `'    `-5'
`2'    `'    `-5'
`3posix'    `'    `-5'
`3pm'    `'    `-5'
`3perl'    `'    `-5'
`3am'    `'    `-5'
`5'    `'    `-5'
`4'    `'    `-5'
`9'    `'    `-5'
`6'    `'    `-5'
`7'    `'    `-5'

path directory /usr/local/sbin is in the config file
adding /usr/local/man to manpath
adding /usr/local/share/man to manpath

path directory /usr/local/bin is in the config file
/usr/local/man is already in the manpath
/usr/local/share/man is already in the manpath

path directory /usr/sbin is in the config file
adding /usr/share/man to manpath

path directory /usr/bin is in the config file
/usr/share/man is already in the manpath

path directory /sbin is in the config file
/usr/share/man is already in the manpath

path directory /bin is in the config file
/usr/share/man is already in the manpath

path directory /usr/games is in the config file
/usr/share/man is already in the manpath

path directory /usr/local/games is not in the config file
but does have a ../man, man, ../share/man, or share/man subdirectory
/usr/local/man is already in the manpath

path directory /snap/bin is not in the config file
and doesn't have ../man, man, ../share/man, or share/man subdirectories

adding mandatory man directories

warning: /usr/man: No such file or directory
/usr/share/man is already in the manpath
/usr/local/share/man is already in the manpath
add_nls_manpaths(): processing /usr/local/man:/usr/local/share/man:/usr/share/man
checking for locale en_IN
adding /usr/local/man to manpathlist
adding /usr/local/share/man to manpathlist
adding /usr/share/man to manpathlist
adding /usr/local/man to manpathlist
adding /usr/local/share/man to manpathlist
adding /usr/share/man to manpathlist
Removing duplicate manpath entry /usr/local/share/man (1) -> /usr/local/man (0)
Removing duplicate manpath entry /usr/local/man (2) -> /usr/local/man (0)
Removing duplicate manpath entry /usr/local/share/man (2) -> /usr/local/man (0)
Removing duplicate manpath entry /usr/share/man (2) -> /usr/share/man (1)
final search path = /usr/local/man:/usr/share/man
path=/usr/local/man
warning: can't read the fallback whatis text database /usr/local/man/whatis
path=/usr/share/man
name:      ls
sec. ext:  1
section:   1
comp. ext: gz
id:        A
mtime:     1516268629.000000000
pointer:   -
filter:    -
whatis:    list directory contents

ls (1)               - list directory contents
hashtable_free: 1 entries, 1 (100%) unique

Q5. whatis 如何执行搜索？

这是手册页的相关摘录：

       index databases are used during the search,  and  are  updated  by  the
       mandb  program.   Depending  on your installation, this may be run by a
       periodic cron job, or may need to be  run  manually  after  new  manual
       pages  have  been installed.  To produce an old style text whatis data?
       base from the relative index database, issue the command:

       whatis -M manpath -w '*' | sort > manpath/whatis

       where manpath is a manual page hierarchy such as /usr/man.

结论

如果您对 Linux 命令行工具非常感兴趣，或者您的日常工作涉及处理手册页，那么 whatis 命令可能是一个对您有帮助的工具。我们已经在这里讨论了一些 whatis 命令行选项。有关更多信息，请访问工具手册页。