Spark修煉之道（基礎篇）——Linux大資料開發基礎：第十三節：Shell程式設計入門（五)

本節主要內容

1. while迴圈控制結構
2. if條件判斷

3. until迴圈控制結構

   1. while迴圈控制結構

   本節例子來源：http://blog.chinaunix.net/uid-25880122-id-2901409.html 
   語法格式：

<code class="hljs livecodeserver has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> expression
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">do</span>
<span class="hljs-command" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">command</span></span>
<span class="hljs-command" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">command</span></span>
done</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

（1）計數器格式

適用於迴圈次數已知或固定時

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim whileLoop.sh</span>
.<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#!/bin/bash</span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>((<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span><<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>))
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">do</span>
echo <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span>
let i++
done

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># chmod a+x whileLoop.sh </span>
root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./whileLoop.sh </span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>

（2）標誌符結束while迴圈

<code class="hljs bash has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root@sparkslave02:~/ShellLearning/Chapter13<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim flagWhileLoop.sh</span>
<span class="hljs-shebang" style="color: rgb(0, 102, 102); box-sizing: border-box;">#!/bin/bash</span>
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Please input the num (1~~10): "</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#接受使用者輸入</span>
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">read</span> num
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> [[ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$num</span> != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span> ]]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">do</span>
 <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#if語句，後面詳細介紹，這裡判斷是否小於4</span>
 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$num</span> <span class="hljs-operator" style="box-sizing: border-box;">-lt</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span> ]
 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
    <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Too small ,Try again.."</span>
    <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">read</span> num
 <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷是否大於4</span>
 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">elif</span> [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$num</span> <span class="hljs-operator" style="box-sizing: border-box;">-gt</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span> ]
 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
    <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Too big ,Try again.. "</span>
    <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">read</span> num
 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">exit</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>
 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">fi</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">done</span>
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">echo</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Yes ,you are right !!"</span>

root@sparkslave02:~/ShellLearning/Chapter13<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># chmod a+x flagWhileLoop.sh root@sparkslave02:~/ShellLearning/Chapter13# ./flagWhileLoop.sh </span>
Please input the num (<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>~~<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>): 
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>
Yes ,you are right !!
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul>

## 2. if條件判斷## 
參考：http://blog.chinaunix.net/uid-20735106-id-3434959.html 
shell 指令碼中的if條件判斷功能十分強大，但使用也異常複雜，其語法格式：

<code class="hljs bash has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>  條件
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
 Command
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>
 Command
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#if條件判斷的結束，用反拼表示</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">fi</span>                           </code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

最常用的判斷為：判斷字串、判斷數字、判斷檔案及邏輯判斷等

（1）判斷字串

<code class="hljs lua has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ str1=str2 ];<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span> fi  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">----當兩個字串相同時返回真</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ str1!=str2 ];<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span> fi <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">----當兩個字串不相等時返回真</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -n str1 ];<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span> fi    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">----當字串的長度大於0時返回真 (判斷變數是否有值)</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -z str1 ];<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span> fi    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">----當字串的長度為0時返回真</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim if01.sh</span>
str1=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hello"</span>
str2=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"hell"</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷兩字串是否相等</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ str1=str2 ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"equal"</span>
fi

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷兩字串是否不等</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ str1!=str2 ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"not equal"</span>
fi

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷字串長度是否大於0</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -n str1 ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"the length of str1 is not zero"</span>
fi

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷字串長度是否等於0</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -z str1 ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"the length of str1 is not zero, it can't be executed"</span>
fi

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./if01.sh </span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">not</span> equal
the length of str1 is <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">not</span> zero
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li></ul>

（2）判斷數字

<code class="hljs livecodeserver has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int1</span> -eq <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int2</span>    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--相等</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int1</span> -ne <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int2</span>    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--不相等</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int1</span> -gt <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int2</span>    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--大於</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int1</span> -ge <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int2</span>    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--大於等於</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int1</span> -lt <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int2</span>    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--小於</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int1</span> -le <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int2</span>    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--小於等於</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>

使用示例：

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim if02.sh</span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>
j=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span> -lt <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$j</span> ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
   echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i is less than j"</span>
fi

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$j</span> -gt <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span> ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
   echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"j is great than i"</span>
fi

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># chmod a+x if02.sh </span>

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./if02.sh </span>
i is less than j
j is great than i
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>

（3）判斷檔案

檔案判斷常用命令如下：

<code class="hljs livecodeserver has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.</span> -r <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--使用者可讀為真</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2.</span> -w <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--使用者可寫為真</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3.</span> -x <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--使用者可執行為真</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4.</span> -f <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--檔案存在且為正規檔案為真</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5.</span> -d <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--如果是存在目錄為真</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6.</span> -c <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--檔案存在且為字元裝置檔案</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7.</span> -b <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--檔案存在且為塊裝置檔案</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">8.</span> -s <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--檔案大小為非0為真，可以判斷檔案是否為空</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">9.</span> -e <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">file</span>        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--如果檔案存在為真</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

使用示例：

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim if03.sh</span>
root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># chmod a+x if03.sh </span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷檔案是否存在</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -f if03.sh ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
   echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"if03.sh exists!!"</span>
fi
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷目錄是否存在</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -d ../<span class="hljs-constant" style="box-sizing: border-box;">Chapter13</span> ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
   echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"directory Chapter13 exists!!"</span>
fi

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./if03.sh </span>
if03.sh exists!!
directory <span class="hljs-constant" style="box-sizing: border-box;">Chapter13</span> exists!!
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li></ul>

（4）邏輯判斷

邏輯判斷主要有下面三個命令

<code class="hljs livecodeserver has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.</span> -<span class="hljs-operator" style="box-sizing: border-box;">a</span>     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--與</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2.</span> -o     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--或</span>
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3.</span> !      <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">--非</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

使用示例：

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim if04.sh</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">#判斷if04.sh檔案與目錄Chapter13是否同時存在，同時存在則為真</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -f if04.sh -a -d ../<span class="hljs-constant" style="box-sizing: border-box;">Chapter13</span> ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
   echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"file if04.sh and directory Chapter13  both exists!!!"</span>
fi

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># chmod a+x if04.sh </span>
root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./if04.sh </span>
file if04.sh <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">and</span> directory <span class="hljs-constant" style="box-sizing: border-box;">Chapter13</span>  both exists!!!
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

（5）if [] then else fi的用法

前面給出的例子都是if [] then fi的形式，這裡再給出if [] then else fi的用法

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim if05.sh</span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span> -lt <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span> ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i is less than 6"</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i is great than or equal  6"</span>
fi

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># chmod a+x if05.sh </span>
root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./if05.sh </span>
i is great than <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">or</span> equal  <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span>

</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul>

（6）if [] then elif then else fi的用法

多種判斷，看示例程式碼就能明白：

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># cp if05.sh if06.sh</span>
root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim if06.sh</span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span> -le <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span> ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i is less than 6"</span>
elif [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span> -eq <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span> ]
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i equal 7"</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>
  echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i is great than 7"</span>
fi

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./if06.sh </span>
i equal <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span>
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>

## 3. until迴圈控制結構##

語法格式：

<code class="hljs livecodeserver has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">until</span> condition
  <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">do</span>
     <span class="hljs-command" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">command</span></span>
 done</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

使用示例：

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># vim until01.sh</span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">until</span> [ <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$i</span> -gt <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span> ]  
 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">do</span>
 let i+=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>
 echo <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i=$i"</span>  
done

root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># chmod a+x until01.sh </span>
root<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@sparkslave02</span><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:~/ShellLearning/Chapter13</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"># ./until01.sh </span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>
i=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">3</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>