linux常用命令-帮助命令-授之以渔

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http://blog.csdn.net/hello_hwc

我的虚拟机系统是CentOS，版本较老，谅解
一、为什么要学习帮助命令？

授人以鱼不如授人以渔，学会了怎么看帮助文档，是寻找到一个解决一类问题，而不是一个问题的方法。

二、常用的几个命名

1、man

-w 打印相关帮助文档的位置

-k
在man页中查找指定字符串和apropos命令相同

-f
和whatis相同

然后我们通过man ls命令来详细分析下man page中的内容

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[root@localhost ~]# man ls

LS(1) User Commands LS(1)





NAME

ls - list directory contents





SYNOPSIS

ls [OPTION]... [FILE]...





DESCRIPTION

List information about the FILEs (the current directory by

default). Sort entries alphabetically if none of -cftuvSUX

nor --sort.





Mandatory arguments to long options are mandatory for short

options too.





-a, --all

do not ignore entries starting with .





-A, --almost-all

do not list implied . and ..

...中间省略

AUTHOR

Written by Richard Stallman and David MacKenzie.





REPORTING BUGS

Report bugs to <bug-coreutils@gnu.org>.





COPYRIGHT

Copyright © 2006 Free Software Foundation, Inc.

This is free software. You may redistribute copies of it

under the terms of the GNU General Public License

<http://www.gnu.org/licenses/gpl.html>. There is NO WAR-

RANTY, to the extent permitted by law.





SEE ALSO

The full documentation for ls is maintained as a Texinfo man-

ual. If the info and ls programs are properly installed at

your site, the command





info ls





should give you access to the complete manual.





ls 5.97 February 2010 LS(1)

这里可以看到，info ls可以给出详细描述

首先会看到NAME，COPYRIGHT等每一部分的title，具体代表含义参照以下

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NAME 名字，简单的命令是用来做什么的

SYNOPSIS 简短的指令使用语法

DESCRIPTION 详细的描述命令的使用方法

OPTIONS 针对SYNOPSIS，进行详细的阐述

COMMANDS 执行的时候可下达的命令

FILES 指令相关的文件

SEE ALSO 和这个指令相关的命令

EXAMPLE 范例

BUGS 尚存在的漏洞

COPYRIGHT 版权信息

REPORTING BUGS 发现Bug可以上传的邮箱

AUTHOR 作者

然后，又会看到LS（1）后面跟了一个1，这个数字也是有特定含义的

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1 指令或者可执行文档

2 内核可调用的函数

3 常用函数库

4 档案说明

5 档案格式

6 游戏

7 linux系统的说明性内容

8 root可用的管理命名

9 和内核相关的文件

在man页中如何翻页，查找

箭头上下
上下行切换

Home/End
到第一页、最后一页

/String
查找一个字符串，n下一个查找到的结果，N上一个

q
结束这次

何时用man命令

我的心得是：这个命令基本不熟悉，需要详细的去看看自己想要的功能如何使用的时候，一般顺序是NAME-SYNOPSIS-DESCRIPTION-EXAMPLE

2、--help

列出常用命名的常用选项

使用场合：知道这个命令的使用领域，和简单使用方法，只是不熟悉某些选项

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[root@localhost ~]# file --help

Usage: file [OPTION]... [FILE]...

Determine file type of FILEs.



-m, --magic-file LIST use LIST as a colon-separated list of magic

number files

-z, --uncompress try to look inside compressed files

-b, --brief do not prepend filenames to output lines

-c, --checking-printout print the parsed form of the magic file, use in

conjunction with -m to debug a new magic file

before installing it

-f, --files-from FILE read the filenames to be examined from FILE

-F, --separator string use string as separator instead of `:'

-i, --mime output mime type strings

-k, --keep-going don't stop at the first match

-L, --dereference causes symlinks to be followed

-n, --no-buffer do not buffer output

-N, --no-pad do not pad output

-p, --preserve-date preserve access times on files

-r, --raw don't translate unprintable chars to \ooo

-s, --special-files treat special (block/char devices) files as

ordinary ones

--help display this help and exit

--version output version information and exit

3、whatis

查找whatis的数据库，寻找关键字的描述信息。在我们学会了man之后，可以直接man whatis来看信息

使用场合：我们想知道这个命令使用来干嘛的，或者我们想知道这个命令的种类

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[root@localhost ~]# whatis ls

ls (1) - list directory contents

ls (1p) - list directory contents

[root@localhost ~]# whatis CD

cd (1p) - change the working directory

cd [builtins] (1) - bash built-in commands, see bash(1)

4、help

查看shell内建指令的帮助信息，例如我们cd就是一个bash内建指令

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[root@localhost ~]# cd --help

bash: cd: --: invalid option

cd: usage: cd [-L|-P] [dir]

[root@localhost ~]# help cd

cd: cd [-L|-P] [dir]

Change the current directory to DIR. The variable $HOME is the

default DIR. The variable CDPATH defines the search path for

the directory containing DIR. Alternative directory names in CDPATH

are separated by a colon (:). A null directory name is the same as

the current directory, i.e. `.'. If DIR begins with a slash (/),

then CDPATH is not used. If the directory is not found, and the

shell option `cdable_vars' is set, then try the word as a variable

name. If that variable has a value, then cd to the value of that

variable. The -P option says to use the physical directory structure

instead of following symbolic links; the -L option forces symbolic links

to be followed.

其他的内建指令

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alias, bg, bind, break, builtin, cd, command,

compgen, complete, continue, declare, dirs, disown, echo,

enable, eval, exec, exit, export, fc, fg, getopts, hash, help,

history, jobs, kill, let, local, logout, popd, printf, pushd,

pwd, read, readonly, return, set, shift, shopt, source, sus-

pend, test, times, trap, type, typeset, ulimit, umask, una-

lias, unset, wait