0340bashshell-scripts.htm

来自「鸟哥LINUX 学习课本」· HTM 代码 · 共 1,372 行 · 第 1/5 页

<blockquote>刚刚的『 if then fi 』的形式是以程序来自行判断，那么<b>如果我已经规划好几个项目要来执行，只要选择执行的『种类方式』就可以正确的执行的话</b>，要怎么做呢？最简单的例子就是我们常常使用到的
/etc/rc.d/init.d/ 里头的 scripts 啰！例如：重新启动 xinetd 是使用：
<blockquote><b><font color="#000066" face="SimSun">/etc/rc.d/init.d/xinetd
restart</font></b></blockquote>
注意啰！那个是 restart 的项目，然后 script 就会自动的去搜寻 restart 项目里面的情况去执行！<b><font color="#000099">那个就是
case ... esac</font></b> 的使用模式啰！有没有注意到，开始是『 case 』结束则是使用
case 的倒写『 esac 』喝！很有趣吧！那么这种格式是怎样呢？
<br>&#160;
<table bgcolor="#000000" border="1" cols="1" width="800">
<tbody><tr>
<td><font size="-1" face="SimSun"><font color="#ffffff"><b>case</b>
种类方式(string) <b>in</b>&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</font><font color="#ffff00">
&lt;==开始阶段，那个种类方式可分成两种类型，通常使用 $1 这一种直接下达类型！</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;
种类方式一)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;
程序执行段</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">&#160;&#160;&#160;&#160;&#160;&#160;
;;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;
</font><font color="#ffff00">&lt;==种类方式一的结束符号！</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;
种类方式二)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;
程序执行段</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;
;;</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;
*)</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">&#160;&#160;&#160;&#160;&#160;&#160;
echo "Usage: {种类方式一|种类方式二}"&#160;&#160;&#160;&#160;</font><font color="#ffff00">
&lt;==列出可以利用的参数值！</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;
exit 1</font>
<br><font size="-1" face="SimSun"><font color="#ffffff"><b>esa</b>c&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;
</font><font color="#ffff00">&lt;==这个 case 的设定结束处！</font></font></td>
</tr>
</tbody></table>

<p>在种类方式(string)的格式主要有两种：
</p><ol>
<li>
<font color="#3333ff">直接下达式</font>：就是以『 <font color="#3333ff">执行档案
+ string</font> 』的方式来执行的(/etc/rc.d/init.d 里头的基本设定方式），则
string 可以直接写成『 $1 』（在执行档案后面直接加入参数的第一个参数！）</li>

<li>
<font color="#3333ff">交互式</font>：就是由屏幕输出可能的项目，然后让使用者输入，这个通常必须配合『
read variable 』然后 string 则写成『 $variable 』的格式！</li>
</ol>
同样的，我们建立一个名为 test2.sh 的档案来试做看看。假如我们共可分三段格式来进行实作，分别为
one, two, three ，并假设使用直接下达式，则可以写成：
<br>&#160;
<table bgcolor="#000000" border="1" cols="1" width="700">
<tbody><tr>
<td><font size="-1" face="SimSun"><font color="#ffffff">[test @test
test]# </font><font color="#ffff00">vi test09-case.sh</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">#!/bin/bash</font>
<br><font size="-1" color="#ffffff" face="SimSun"># program:&#160;&#160;&#160;&#160;&#160;
Using case mode</font>
<br><font size="-1" color="#ffffff" face="SimSun"># Made by:&#160;&#160;&#160;&#160;&#160;
VBird</font>
<br><font size="-1" color="#ffffff" face="SimSun"># date:&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;
2002/05/20</font>
<br><font size="-1" color="#ffffff" face="SimSun"># content:&#160;&#160;&#160;&#160;&#160;
I will use this program to study the case mode!</font>
<br><font size="-1" color="#ffffff" face="SimSun"># 1. print
this program</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; echo
"This program will print your selection!"</font>
<p><font size="-1" face="SimSun"><font color="#ffffff">case $1 in&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;</font><font color="#ff9900">
&lt;==使用直接下达指令型态！</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; one)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "your choice is one"</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
;;</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; two)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "your choice is two"</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
;;</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; three)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "your choice is three"</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
;;</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; *)</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "Usage {one|two|three}"&#160;&#160;&#160;&#160;&#160;</font><font color="#ff9900">&#160;
&lt;==列出可以使用的参数（如果使用者下达错误的参数时）</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
exit 1</font>
<br><font size="-1" color="#ffffff" face="SimSun">esac</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">[test @test
test]# </font><font color="#ffff00">sh test09-case.sh&#160;</font><font color="#ffffff">&#160;&#160;&#160;&#160;&#160;</font><font color="#ff9900">
&lt;==执行结果！显示没有相对的参数！所以列出可以参数！</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">This program
will print your selection!</font>
<br><font size="-1" color="#ffffff" face="SimSun">Usage {one|two|three}</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">[test @test
test]# </font><font color="#ffff00">sh test09-case.sh three</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">This program
will print your selection!</font>
<br><font size="-1" color="#ffffff" face="SimSun">your choice
is three</font></p></td>
</tr>
</tbody></table>

<p>那么对谈式的 case 又如何呢？嗯！我们利用上面的方式来修改一下内容啰！
<br>&#160;
<table bgcolor="#000000" border="1" cols="1" width="500">
<tbody><tr>
<td><font size="-1" face="SimSun"><font color="#ffffff">[root @test
test]# </font><font color="#ffff00">vi test10-case.sh</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">#!/bin/bash</font>
<br><font size="-1" color="#ffffff" face="SimSun"># program:&#160;&#160;&#160;&#160;&#160;
Using case mode</font>
<br><font size="-1" color="#ffffff" face="SimSun"># Made by:&#160;&#160;&#160;&#160;&#160;
VBird</font>
<br><font size="-1" color="#ffffff" face="SimSun"># date:&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;
2002/06/27</font>
<br><font size="-1" color="#ffffff" face="SimSun"># content:&#160;&#160;&#160;&#160;&#160;
I will use this program to study the case mode!</font>
<br><font size="-1" color="#ffffff" face="SimSun"># 1. print
this program</font>
<br><font size="-1" color="#ffffff" face="SimSun">echo "Press
your select one, two, three"</font>
<br><font size="-1" color="#ffffff" face="SimSun">read number</font>
<p><font size="-1" color="#ffffff" face="SimSun">case $number
in</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; one)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "your choice is one"</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
;;</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; two)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "your choice is two"</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
;;</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; three)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "your choice is three"</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
;;</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160; *)</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
echo "Usage {one|two|three}"</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
exit 1</font>
<br><font size="-1" color="#ffffff" face="SimSun">esac</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">[root @test
test]#</font><font color="#ffff00"> sh test10-case.sh</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">Press your
select one, two, three</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">two&#160;&#160;</font><font color="#ff9900">
&lt;=这一行是您输入的呦！</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">your choice
is two</font></p></td>
</tr>
</tbody></table>

</p><p>如何！很简单吧！以后对于 /etc/rc.d/init.d/ 里头的 script 就应该看的懂了吧！此外，由于还有所谓的『<font color="#3333ff">函数(function)</font>』也就是『先将需要执行的程序段写成一个小区块，而这个小区块则以一个名称来取代之』，简单的方式可以请您参考一下您系统中的
/etc/rc.d/init.d/sendmail ！注意看一下 start() 底下的那些个咚咚！你就可以知道什么意思了！由于我们这里并不教你如何写程序（基本上，
scripts 就是小程序啦！还好！ VBird 以前就有程序的底子！不然还真怕 script
呢！），所以就只好点到为止啰！</p></blockquote>

<hr width="100%"><a name="cycle"></a><font color="#000099"><font size="+1">循环：</font>for....do....done,
while...do...done, until...do...done,</font>
<blockquote>在程序段当中，最常使用到的就是循环了！循环是很重要的一项工具，尤其是具有判断形式的循环，很常被使用来判断一些事项的可行性与否！但是程序怎么知道什么时候应该要停止这个程序呢？呵呵！就需要加入判断啰！好了，最简单的判断式可以是底下几种：
<ul>
<li>
<font face="SimSun"><b>for</b> <b>((</b> 条件一; 条件二; 条件三 <b>))</b></font></li>

<li>
<font face="SimSun"><b>for</b> variable <b>in</b> variable1 variable2 .....</font></li>

<li>
<font face="SimSun"><b>while</b> <b>[</b> condition1 <b>]</b> &amp;&amp;
{ || } [ condition2 ] ...</font></li>

<li>
<font face="SimSun"><b>until</b> <b>[</b> condition1 <b>]</b> &amp;&amp;
{ || } [ condition2 ] ...</font></li>
</ul>
for 是已经知道有多少个 run 了，即是已经知道要跑几次了，至于 until 与 while
则分别是：
<ul>
<li>
『<b><font color="#3333ff">until：直到条件相同的时候才离开程序</font></b>』；</li>

<li>
『<b><font color="#3333ff">while：当条件相同的时候，就继续做！</font></b>』</li>
</ul>
这两者不太相同的啦！</blockquote>

<blockquote>好了！我们先来谈一下最简单的循环，就是利用 for 这个东西来进行！好了，假设我们计算
1 + 2 + 3 .... + 100 ，以 script 要如何写呢？有很多的方式，我们来谈一谈
do...done 好了！
<br>&#160;
<table bgcolor="#000000" border="1" cols="1" width="500">
<tbody><tr>
<td><font size="-1" face="SimSun"><font color="#ffffff">[test @test
test]# </font><font color="#ffff00">vi test11-loop.sh</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">#!/bin/bash</font>
<br><font size="-1" color="#ffffff" face="SimSun"># Using for
and loop</font>
<br><font size="-1" color="#ffffff" face="SimSun"># VBird 2002/06/27</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">declare -i
s&#160; </font><font color="#ff9900"># &lt;==变量宣告</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">for (( i=1;
i&lt;=100; i=i+1 ))</font>
<br><font size="-1" color="#ffffff" face="SimSun">do</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
s=s+i</font>
<br><font size="-1" color="#ffffff" face="SimSun">done</font>
<br><font size="-1" color="#ffffff" face="SimSun">echo "The count
is ==&gt; $s"</font>
<p><font size="-1" face="SimSun"><font color="#ffffff">[test @test
test]#</font><font color="#ffff00"> sh test11-loop.sh</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">The count is
==&gt; 5050</font></p></td>
</tr>
</tbody></table>

<p>请注意！<b><font color="#000099" face="SimSun"> for (( 条件一;
条件二; 条件三))</font></b> 这是必须要的！
</p><ul>
<li>
条件一：这可以看成是『初始值』，如上面的例子中，初始值是 i=1 啦！</li>

<li>
条件二：这可以看成是『符合值』，如上面的例子中，当 i&lt;=100 的时候都是符合条件的！</li>

<li>
条件三：这可以看成是『步阶』！也就是说， i 每次都加一！</li>
</ul>
<font face="SimSun">所以啦！上面的例子是说：由 i=1 开始到 i&lt;= 100 ，每次
i 都加一来执行底下的程序段（就是 s=s+i ），当 i &gt;100 （也就是 i=101 ）就跳出这一段程序段</font>！怎样！不难吧！</blockquote>

<blockquote>好了！那么使用 while 或者是 until 要怎样执行呢？其实都是差不多的情况！我们使用底下的两个
script 来进行 1 ~ 100 的累加动作！
<br>&#160;
<table bgcolor="#000000" border="1" cols="1" width="500">
<tbody><tr>
<td><font size="-1" color="#ffffcc" face="SimSun">1. 使用 while
：</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">[test @test
test]# </font><font color="#ffff00">vi test12-loop.sh</font></font>
<br><font size="-1" color="#ffffff" face="SimSun">#!/bin/bash</font>
<br><font size="-1" color="#ffffff" face="SimSun"># Using while
and loop</font>
<br><font size="-1" color="#ffffff" face="SimSun"># VBird 2002/06/27</font>
<br><font size="-1" color="#ffffff" face="SimSun">declare -i
i</font>
<br><font size="-1" color="#ffffff" face="SimSun">declare -i
s</font>
<br><font size="-1" color="#ffffff" face="SimSun">while [ "$i"
!= "101" ]</font>
<br><font size="-1" color="#ffffff" face="SimSun">do</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
s=s+i</font>
<br><font size="-1" color="#ffffff" face="SimSun">&#160;&#160;&#160;&#160;&#160;&#160;&#160;
i=i+1</font>
<br><font size="-1" color="#ffffff" face="SimSun">done</font>
<br><font size="-1" color="#ffffff" face="SimSun">echo "The count
is ==&gt; $s"</font>
<p><font size="-1" color="#ffffcc" face="SimSun">2. 使用 until
：</font>
<br><font size="-1" face="SimSun"><font color="#ffffff">[test @test
test]# </font><font color="#ffff00">vi test13-loop.sh<