Loading... <p style="text-align: center"> <span style="text-align: center;font-size: 29px;font-family: Calibri">Bash Shell</span><span style="text-align: center;font-family: 宋体;font-size: 29px">编程初学基础篇之一</span></p> <p><span><strong><span style="font-size: 12px;color: red">说明</span></strong><span style="font-size: 12px;color: red">:</span> 本文仅供初学Linux Bash shell学员参考学习,大神们如有兴趣请批评指正!!!</span></p> <p><span> </span><span>相信对于很多Linux初学者或者仅仅是听说Linux还没有接触过的同学会有一种神秘感或者不敢碰触的感觉,今天就帮大家揭开它的神秘面纱,其实并没有那么深不可测,只要你敢,你有决心去下工夫看完以下内容(是时候该逼自己下决心去做一些事情了!!!)。废话少说,浪费大家宝贵时间。</span></p> <p><span> <span style="font-weight: bold;color: red">概述</span></span><span>:</span><span> 以下主要从Bash脚本的格式,变量,基本运算语法和实例来讲解;每个实例都保证运行测试通过,然后截屏与大家分享;大家通过一些简单的实例相信会很快上手,不要灰心,要相信自己;人和人之间的差距就在于用心去做。</span></p> <p style="text-indent: 7px"><strong><span style="color: red;font-family: 宋体">基本内容:</span></strong></p> <ol class=" list-paddingleft-2"> <li> <p><span style="font-size: 12px"><span style="color: red">Shell</span><span style="color: red;font-family: 宋体">脚本的基本格式:</span></span></p> </li> <ol class=" list-paddingleft-2"> <li> <p><span style="font-size: 12px"><span style="font-size: 12px;font-family: 宋体">用</span>vim<span style="font-size: 12px;font-family: 宋体">等编辑器新建一个</span>bash.sh<span style="font-size: 12px;font-family: 宋体">的文本文件,第一行以</span>#!/bin/bash<span style="font-size: 12px;font-family: 宋体">开头即可。</span></span></p> </li> <li> <p><span style="font-size: 12px"><span style="font-size: 12px;font-family: 宋体">一个规范的</span>Shell<span style="font-size: 12px;font-family: 宋体">的基本格式如下:</span></span></p> <p><span style="font-size: 12px;font-family: 宋体"></span></p> </li> </ol> <pre class="brush:bash;toolbar:false">#!/bin/bash # Description :test # Version 0.0.1 # Author:zgq # Date :time</pre> </ol> <p style="text-indent: 14px"><span style="font-size: 12px"><span style="font-family: 宋体">第一行是标准格式,我们在此处仅针对</span><span style="font-family: Calibri">Bash</span><span style="font-family: 宋体">来说,必须这样写,任何一门语言都有其规范;第二行</span><span style="font-family: Calibri">Description</span><span style="font-family: 宋体">简单描述一下</span><span style="font-family: Calibri">Shell</span><span style="font-family: 宋体">的基本功能,第三行</span><span style="font-family: Calibri">Version</span><span style="font-family: 宋体">版本信息,第四行</span><span style="font-family: Calibri">Author</span><span style="font-family: 宋体">:作者信息,第五行</span><span style="font-family: Calibri">Date</span><span style="font-family: 宋体">:日期时间。除了第一行,其他以</span><span style="font-family: Calibri">#</span><span style="font-family: 宋体">开头的行均为注释信息,会被解释器忽略。</span></span></p> <p><span style="font-family: 宋体;font-size: 12px">希望大家在以后实现脚本功能之后将此信息补充完整,存在既有其将来被用到的一天。</span></p> <p style="text-indent: 28px"><span style="font-size: 12px"><strong><span style="font-size: 12px;font-family: 宋体">实例</span></strong><span style="font-size: 12px;font-family: 宋体">:新建一个脚本</span><span style="font-size: 12px;font-family: Calibri">/tmp/test.sh</span><span style="font-size: 12px;font-family: 宋体">实现如下功能:</span></span></p> <p style="text-indent: 28px"><span style="font-size: 12px"><span style="font-size: 12px;font-family: Calibri"> 1) </span><span style="font-size: 12px;font-family: 宋体">新建一个用户</span><span style="font-size: 12px;font-family: Calibri">magedu,</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span style="font-size: 12px"><span style="font-size: 12px;font-family: Calibri">2)</span><span style="font-size: 12px;font-family: 宋体">创建目录</span><span style="font-size: 12px;font-family: Calibri">/tmp/hellobash</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span style="font-size: 12px"><span style="font-size: 12px;font-family: Calibri">3)</span><span style="font-size: 12px;font-family: 宋体">复制</span><span style="font-size: 12px;font-family: Calibri">/etc/rc.d/init.d/functions</span><span style="font-size: 12px;font-family: 宋体">至</span><span style="font-size: 12px;font-family: Calibri">/tmp/hellobash</span><span style="font-size: 12px;font-family: 宋体">中</span></span></p> <p style="margin: 0px 0px 0px 28px;text-align: center;text-indent: 28px"><span style="font-family: 宋体;font-size: 12px"></span></p> <p style="margin: 0px 0px 0px 28px;text-align: left;text-indent: 28px"><span style="font-size: 12px"><span style="font-size: 12px;font-family: 宋体">大家动手新建这个一个简单的脚本,熟悉一下其基本的写法规范。其实</span><span style="font-size: 12px;font-family: Calibri">Shell</span><span style="font-size: 12px;font-family: 宋体">脚本是一个过程式编程语言,把常用的</span><span style="font-size: 12px;font-family: Calibri">Shell</span><span style="font-size: 12px;font-family: 宋体">命令按顺序罗列起来就是一个脚本。</span></span></p> <p style="text-align: center"><img title="1427622042118930.png" alt="bash1.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-81.png" /></p> <p style="margin: 0px 0px 0px 28px;text-align: left;text-indent: 28px"><span style="font-family: 宋体"></span></p> <p><span> 脚本写完了,我们怎么去执行它呢?</span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-family: 宋体;font-size: 12px">首先用</span><span style="font-family: Calibri;font-size: 12px">ll</span><span style="font-family: 宋体;font-size: 12px">命令看一下此脚本是没有执行权限的,用</span><span style="font-family: Calibri;font-size: 12px">chmod +x /tmp/test.sh </span></span></p> <p style="margin: 0px 0px 0px 28px"><span><span style="font-family: 宋体;font-size: 12px">赋予执行权限;然后用</span><span style="font-family: Calibri;font-size: 12px">bash –n test.sh </span><span style="font-family: 宋体;font-size: 12px">此功能是语法测试,如果没有任何结果则是最好的结果,</span><span style="font-family: Calibri;font-size: 12px">bash –x test.sh </span><span style="font-family: 宋体;font-size: 12px">单步执行显示其运行过程结果;</span></span></p> <p style="text-indent: 28px"><span><span style="font-family: 宋体;font-size: 12px">或者我们直接</span><span style="font-family: Calibri;font-size: 12px">bash test.sh </span><span style="font-family: 宋体;font-size: 12px">执行脚本。</span></span></p> <ol class=" list-paddingleft-2"> <li> <p><span><strong><span style="font-size: 12px;color: red">变量概述:</span></strong></span></p> <p><span><strong><span>Bash</span></strong><strong><span style="font-size: 12px;font-family: 宋体;color: red">变量名称命令规则:</span></strong></span></p> </li> </ol> <p style="text-indent: 56px"><span><span style="font-size: 12px;font-family: Calibri;color: black">a)</span><span style="font-size: 12px;font-family: 宋体;color: black">只能包含字母、数字和下划线,并且不能以数字开头;</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black">b)</span><span style="font-size: 12px;font-family: 宋体;color: black">不能与系统中环境变量重名</span><span style="font-size: 12px;font-family: Calibri;color: black"><br /> c)</span><span style="font-size: 12px;font-family: 宋体;color: black">见名知意</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><strong><span style="font-size: 12px;font-family: Calibri;color: red">Bash</span></strong><strong><span style="font-size: 12px;font-family: 宋体;color: red">变量赋值和撤销:</span></strong></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black">Bash</span><span style="font-size: 12px;font-family: 宋体;color: black">属于弱类型语言,任何变量无需事先声明,可直接使用,值默认都是字符型;</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">格式</span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">变量</span><span style="font-size: 12px;font-family: Calibri;color: black">=</span><span style="font-size: 12px;font-family: 宋体;color: black">值</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">例如:</span><span style="font-size: 12px;font-family: Calibri;color: black"> a=abc</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span> declare -i varname=0</span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><strong><span style="font-size: 12px;font-family: 宋体;color: red">变量撤销:</span></strong><span style="font-size: 12px;font-family: Calibri;color: black"> unset varname</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><strong><span style="font-size: 12px;font-family: 宋体;color: red">变量类别:</span></strong></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">本地变量</span><span style="font-size: 12px;font-family: Calibri;color: black">:</span><span style="font-size: 12px;font-family: 宋体;color: black">作用域为整个</span><span style="font-size: 12px;font-family: Calibri;color: black">bash</span><span style="font-size: 12px;font-family: 宋体;color: black">进程</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">环境变量:作用域为当前</span><span style="font-size: 12px;font-family: Calibri;color: black">shell</span><span style="font-size: 12px;font-family: 宋体;color: black">进程及其子进程</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">局部变量:作用域只对当前代码段有效</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">位置变量</span><span style="font-size: 12px;font-family: Calibri;color: black">:$1,,,$n,${10} ,,,,,</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">特殊变量:</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> $?:</span><span style="font-size: 12px;font-family: 宋体;color: black">状态返回值</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> $#:</span><span style="font-size: 12px;font-family: 宋体;color: black">传递给脚本参数的个数</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> $*:</span><span style="font-size: 12px;font-family: 宋体;color: black">显示所有的参数</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><span style="font-size: 12px;font-family: Calibri;color: black"> $@:</span><span style="font-size: 12px;font-family: 宋体;color: black">引用传递给脚本的所有参数</span></span></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span><strong><span style="font-size: 12px;font-family: Calibri;color: black"> </span></strong><strong><span style="font-size: 12px;font-family: 宋体;color: black">实例:</span><span style="font-size: 12px;font-family: Calibri;color: black"> </span></strong><span style="font-size: 12px;font-family: Calibri;color: black"> </span><span style="font-size: 12px;font-family: 宋体;color: black">写一个脚本如下</span></span></p> <p style="text-align: center"><img title="1427622086278235.png" alt="bash2.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-5.png" /></p> <p style="margin: 0px 0px 0px 28px;text-indent: 28px"><span style="color: black;font-family: 宋体"></span></p> <p style="margin: 0px 0px 0px 28px;text-align: center;text-indent: 28px"><span style="font-family: 宋体"></span></p> <p style="margin: 0px 0px 0px 28px;text-align: center;text-indent: 28px"><span style="font-family: 宋体"></span></p> <p style="margin: 0px 0px 0px 28px;text-align: left;text-indent: 28px"><span>执行结果解析:在脚本后面输入了4个参数,那么$1的值为1,$2的值为2,$*的值为所有参数值,$#的值为参数的个数4个,$@的值是所有参数的值,$0的值为返回脚本的名称,$?的值为此脚本执行状态的返回值0,脚本执行成功的状态返回值为0,如果脚本执行错误会返回1-255的值; </span></p> <p style="margin: 0px 0px 0px 28px;text-align: left;text-indent: 28px"><span><span style="font-family: Calibri;font-size: 12px;color: black"> </span><span style="font-family: 宋体;font-size: 12px;color: black">实例扩展:写一个如下脚本运行</span></span></p> <p style="text-align: center"><img title="1427622392516093.png" alt="bash4.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-91.png" /></p> <p style="text-align: center"><img title="1427622447829321.png" alt="bash15.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-80.png" /></p> <p style="margin: 0px 0px 0px 28px;text-align: left;text-indent: 28px"><span><span style="font-size: 12px;color: black"> </span><span style="font-size: 12px;color: black">结果分析:输入四个参数,</span><span style="font-size: 12px;color: black">$1</span><span style="font-size: 12px;color: black">的返回值为</span><span style="font-size: 12px;color: black">1</span><span style="font-size: 12px;color: black">,</span><span style="font-size: 12px;color: black">$2</span><span style="font-size: 12px;color: black">的返回值为</span><span style="font-size: 12px;color: black">3</span><span style="font-size: 12px;color: black">,</span><span style="font-size: 12px;color: black">$*</span><span style="font-size: 12px;color: black">的返回值为</span><span style="font-size: 12px;color: black">3</span><span style="font-size: 12px;color: black">和</span><span style="font-size: 12px;color: black">4</span><span style="font-size: 12px;color: black">,所有参数的值(可以理解为一共四个参数,两个</span><span style="font-size: 12px;color: black">shift,</span><span style="font-size: 12px;color: black">所以把左边两个参数值释放),</span><span style="font-size: 12px;color: black">$#</span><span style="font-size: 12px;color: black">返回参数的个数</span><span style="font-size: 12px;color: black">2</span><span style="font-size: 12px;color: black">个。由以上结果可以得出</span><span style="font-size: 12px;color: black">shift [n]</span><span style="font-size: 12px;color: black">的作用是把左边</span><span style="font-size: 12px;color: black">n</span><span style="font-size: 12px;color: black">个参数的值释放掉;</span><span style="font-size: 12px"> </span></span></p> <p style="text-align: left"><span><span style="font-size: 12px;font-family: Calibri"><span> </span><strong><span>Bash</span></strong></span><strong><span style="font-size: 12px;font-family: 宋体;color: red">基本运算:</span></strong></span></p> <p style="text-align: left"><span>Bash 支持很多运算符,包括算数运算符、关系运算符、布尔运算符、字符串运算符和文件测试运算符。expr 是一款表达式计算工具,使用它能完成表达式的求值操作</span></p> <p style="text-align: left"><strong><span style="color: red;font-family: Calibri"> </span></strong><span style="font-size: 12px"><strong><span style="color: red;font-family: Calibri"> 1</span></strong><strong><span style="color: red;font-family: 宋体">、算术运算:</span><span style="color: red;font-family: Calibri"> </span></strong></span></p> <table width="576" cellpadding="0"> <tbody> <tr class="firstRow" style="height: 23px"> <td width="122" height="23" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">+</span></p> </td> <td width="233" height="23" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="margin: 0px 0px 0px 28px;text-align: left"><span style="color: black;font-family: 宋体;font-size: 12px">加法</span></p> </td> <td height="23" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">`expr $a + $b` </span><span style="font-size: 12px;color: black;font-family: 宋体">结果为</span><span style="font-size: 12px;color: black;font-family: Calibri"> 30</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> <tr style="height: 29px"> <td width="122" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">–</span></p> </td> <td width="233" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: 宋体;font-size: 12px">减法</span></p> </td> <td height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">`expr $a – $b` </span><span style="font-size: 12px;color: black;font-family: 宋体">结果为</span><span style="font-size: 12px;color: black;font-family: Calibri"> 10</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> <tr style="height: 28px"> <td width="122" height="28" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">*</span></p> </td> <td width="233" height="28" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: 宋体;font-size: 12px">乘法</span></p> </td> <td height="28" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">`expr $a \* $b` </span><span style="font-size: 12px;color: black;font-family: 宋体">结果为</span><span style="font-size: 12px;color: black;font-family: Calibri"> 200</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> <tr style="height: 29px"> <td width="122" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">/</span></p> </td> <td width="233" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: 宋体;font-size: 12px">除法</span></p> </td> <td height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">`expr $b / $a` </span><span style="font-size: 12px;color: black;font-family: 宋体">结果为</span><span style="font-size: 12px;color: black;font-family: Calibri"> 2</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> <tr style="height: 29px"> <td width="122" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">%</span></p> </td> <td width="233" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: 宋体;font-size: 12px">取余</span></p> </td> <td height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">`expr $b % $a` </span><span style="font-size: 12px;color: black;font-family: 宋体">结果为</span><span style="font-size: 12px;color: black;font-family: Calibri"> 0</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> <tr style="height: 29px"> <td width="122" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">=</span></p> </td> <td width="233" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: 宋体;font-size: 12px">赋值</span></p> </td> <td height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">a=$b </span><span style="font-size: 12px;color: black;font-family: 宋体">将把变量</span><span style="font-size: 12px;color: black;font-family: Calibri"> b </span><span style="font-size: 12px;color: black;font-family: 宋体">的值赋给</span><span style="font-size: 12px;color: black;font-family: Calibri"> a</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> <tr style="height: 43px"> <td width="122" height="43" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">==</span></p> </td> <td width="233" height="43" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: 宋体">相等。用于比较两个数字,相同则返回</span><span style="font-size: 12px;color: black;font-family: Calibri"> true</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> <td height="43" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">[ $a == $b ] </span><span style="font-size: 12px;color: black;font-family: 宋体">返回</span><span style="font-size: 12px;color: black;font-family: Calibri"> false</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> <tr style="height: 21px"> <td width="122" height="21" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="color: black;font-family: Calibri;font-size: 12px">!=</span></p> </td> <td width="233" height="21" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: 宋体">不相等。用于比较两个数字,不相同则返回</span><span style="font-size: 12px;color: black;font-family: Calibri"> true</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> <td height="21" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;color: black;font-family: Calibri">[ $a != $b ] </span><span style="font-size: 12px;color: black;font-family: 宋体">返回</span><span style="font-size: 12px;color: black;font-family: Calibri"> true</span><span style="font-size: 12px;color: black;font-family: 宋体">。</span></span></p> </td> </tr> </tbody> </table> <p style="text-align: left"><span style="font-size: 12px"><span style="font-size: 12px;font-family: 宋体">乘号(*)前边必须加反斜杠(\)才能实现乘法运算;</span><span style="font-size: 12px;color: black;font-family: Calibri"> </span></span></p> <p style="text-align: left"><span style="color: black;font-family: 宋体;font-size: 12px">实例:</span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622480942578.png" alt="bash5.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-5-1.png" /></span></p> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体">执行结果如下:</span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622497116818.png" alt="bash6.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-1.png" /></span></p> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: left"><span style="color: black;font-family: Calibri"> </span><span><span> </span><strong><span>2</span></strong><strong><span>、关系运算</span></strong></span></p> <p style="margin: 0px 0px 0px 28px;text-align: left"><span><strong><span style="font-family: 宋体;font-size: 12px;color: red">关系运算</span></strong><span style="font-family: 宋体;font-size: 12px">符只支持数字,不支持字符串,除非字符串的值是数字。</span></span></p> <table cellpadding="0"> <tbody> <tr class="firstRow"> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><strong><span style="font-family: 宋体;font-size: 12px">运算符</span></strong></span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><strong><span style="font-family: 宋体;font-size: 12px">说明</span></strong></span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><strong><span style="font-family: 宋体;font-size: 12px">举例</span></strong></span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-eq</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">检测两个数是否相等,相等返回 true。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">[ $a -eq $b ] 返回 true。</span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-ne</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">检测两个数是否相等,不相等返回 true。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">[ $a -ne $b ] 返回 true。</span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-gt</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">检测左边的数是否大于右边的,如果是,则返回 true。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">[ $a -gt $b ] 返回 false。</span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-lt</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">检测左边的数是否小于右边的,如果是,则返回 true。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">[ $a -lt $b ] 返回 true。</span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-ge</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">检测左边的数是否大等于右边的,如果是,则返回 true。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">[ $a -ge $b ] 返回 false。</span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-le</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">检测左边的数是否小于等于右边的,如果是,则返回 true。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span style="font-family: 宋体;font-size: 12px">[ $a -le $b ] 返回 true。</span></p> </td> </tr> </tbody> </table> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622534114626.png" alt="bash7.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-90.png" /></span></p> <p><span>执行结果如下:</span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622576397363.png" alt="bash8.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-84.png" /></span></p> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: left"><span><strong><span>字符串运算:</span><span> </span></strong></span></p> <table cellpadding="0"> <tbody> <tr class="firstRow"> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>运算符</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>说明</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>举例</span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>=</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测两个字符串是否相等,相等返回 true。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ $a = $b ] 返回 false。</span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>!=</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测两个字符串是否相等,不相等返回 true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span><span style="font-size: 12px;font-family: Calibri;color: black">[ $a != $b ] </span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-z</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span><span style="font-size: 12px;font-family: 宋体;color: black">检测字符串长度是否为</span><span style="font-size: 12px;font-family: Calibri;color: black">0</span><span style="font-size: 12px;font-family: 宋体;color: black">,为</span><span style="font-size: 12px;font-family: Calibri;color: black">0</span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span><span style="font-size: 12px;font-family: Calibri;color: black">[ -z $a ] </span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> false</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-n</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span><span style="font-size: 12px;font-family: 宋体;color: black">检测字符串长度是否为</span><span style="font-size: 12px;font-family: Calibri;color: black">0</span><span style="font-size: 12px;font-family: 宋体;color: black">,不为</span><span style="font-size: 12px;font-family: Calibri;color: black">0</span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span><span style="font-size: 12px;font-family: Calibri;color: black">[ -n $a ] </span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> </tr> <tr> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>str</span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span><span style="font-size: 12px;font-family: 宋体;color: black">检测字符串是否为空,不为空返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> <td style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span><span style="font-size: 12px;font-family: Calibri;color: black">[ $a ] </span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> </tr> </tbody> </table> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622618626916.png" alt="bash9.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-65.png" /></span></p> <p><span>执行结果如下:</span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622631106690.png" alt="bash10.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-9.png" /></span></p> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: left"><span><strong><span style="font-size: 12px;color: red">布尔运算符</span></strong></span></p> <table width="634" cellpadding="0"> <tbody> <tr class="firstRow" style="height: 14px"> <td width="61" height="14" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><strong><span style="font-family: 宋体;font-size: 12px;color: black">运算符</span></strong></span></p> </td> <td width="348" height="14" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><strong><span style="font-family: 宋体;font-size: 12px;color: black">说明</span></strong></span></p> </td> <td width="217" height="14" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><strong><span style="font-family: 宋体;font-size: 12px;color: black">举例</span></strong></span></p> </td> </tr> <tr style="height: 14px"> <td width="61" height="14" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span>!</span></p> </td> <td width="348" height="14" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><span style="font-size: 12px;font-family: 宋体;color: black">非运算,表达式为</span><span style="font-size: 12px;font-family: Calibri;color: black"> true </span><span style="font-size: 12px;font-family: 宋体;color: black">则返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> false</span><span style="font-size: 12px;font-family: 宋体;color: black">,否则返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> <td width="217" height="14" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><span style="font-size: 12px;font-family: Calibri;color: black">[ ! false ] </span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> </tr> <tr style="height: 29px"> <td width="61" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span>-o</span></p> </td> <td width="348" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><span style="font-size: 12px;font-family: 宋体;color: black">或运算,有一个表达式为</span><span style="font-size: 12px;font-family: Calibri;color: black"> true </span><span style="font-size: 12px;font-family: 宋体;color: black">则返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> <td width="217" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><span style="font-size: 12px;font-family: Calibri;color: black">[ $a -lt 20 -o $b -gt 100 ] </span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> </tr> <tr style="height: 29px"> <td width="61" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span>-a</span></p> </td> <td width="348" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><span style="font-size: 12px;font-family: 宋体;color: black">与运算,两个表达式都为</span><span style="font-size: 12px;font-family: Calibri;color: black"> true </span><span style="font-size: 12px;font-family: 宋体;color: black">才返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> true</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> <td width="217" height="29" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span><span style="font-size: 12px;font-family: Calibri;color: black">[ $a -lt 20 -a $b -gt 100 ] </span><span style="font-size: 12px;font-family: 宋体;color: black">返回</span><span style="font-size: 12px;font-family: Calibri;color: black"> false</span><span style="font-size: 12px;font-family: 宋体;color: black">。</span></span></p> </td> </tr> </tbody> </table> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622650122386.png" alt="bash11.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-49.png" /></span></p> <p><span style="color: black;font-family: 宋体;font-size: 12px">执行结果如下:</span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622661968236.png" alt="bash12.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-62.png" /></span></p> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p><span style="color: black;font-family: Calibri"> </span><span style="font-size: 12px"><strong><span style="color: red;font-family: 宋体">文件测试运算符列表:</span></strong></span></p> <table width="591" cellpadding="0"> <tbody> <tr class="firstRow" style="height: 24px"> <td width="48" height="24" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span style="font-size: 12px"><strong><span style="font-size: 12px;font-family: 宋体">操作符</span></strong></span></p> </td> <td width="416" height="24" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span style="font-size: 12px"><strong><span style="font-size: 12px;font-family: 宋体">说明</span></strong></span></p> </td> <td height="24" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: center"><span style="font-size: 12px"><strong><span style="font-size: 12px;font-family: 宋体">举例</span></strong></span></p> </td> </tr> <tr style="height: 36px"> <td width="48" height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-b file</span></p> </td> <td width="416" height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否是块设备文件,如果是,则返回 true。</span></p> </td> <td height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -b $file ] 返回 false。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-c file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否是字符设备文件,如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -b $file ] 返回 false。</span></p> </td> </tr> <tr style="height: 36px"> <td width="48" height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-d file</span></p> </td> <td width="416" height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否是目录,如果是,则返回 true。</span></p> </td> <td height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -d $file ] 返回 false。</span></p> </td> </tr> <tr style="height: 36px"> <td width="48" height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-f file</span></p> </td> <td width="416" height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否是普通文件(既不是目录,也不是设备文件),如果是,则返回 true。</span></p> </td> <td height="36" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -f $file ] 返回 true。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-g file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否设置了 SGID 位,如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -g $file ] 返回 false。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-k file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否设置了粘着位(Sticky Bit),如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -k $file ] 返回 false。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-p file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否是具名管道,如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -p $file ] 返回 false。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-u file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否设置了 SUID 位,如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -u $file ] 返回 false。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-r file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否可读,如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -r $file ] 返回 true。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-w file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否可写,如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -w $file ] 返回 true。</span></p> </td> </tr> <tr style="height: 18px"> <td width="48" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-x file</span></p> </td> <td width="416" height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否可执行,如果是,则返回 true。</span></p> </td> <td height="18" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -x $file ] 返回 true。</span></p> </td> </tr> <tr style="height: 19px"> <td width="48" height="19" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-s file</span></p> </td> <td width="416" height="19" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件是否为空(文件大小是否大于0),不为空返回 true。</span></p> </td> <td height="19" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -s $file ] 返回 true。</span></p> </td> </tr> <tr style="height: 17px"> <td width="48" height="17" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>-e file</span></p> </td> <td width="416" height="17" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>检测文件(包括目录)是否存在,如果是,则返回 true。</span></p> </td> <td height="17" style="padding: 1px;border: 1px solid windowtext;background-color: transparent"> <p style="text-align: left"><span>[ -e $file ] 返回 true。</span></p> </td> </tr> </tbody> </table> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622681912308.png" alt="bash13.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-33.png" /></span></p> <p><span style="color: black;font-family: 宋体;font-size: 12px">执行结果如下:</span></p> <p style="text-align: center"><span style="color: black;font-family: 宋体"><img title="1427622691138992.png" alt="bash14.png" src="//cto.wang/usr/uploads/2016/07/20160703155847-26.png" /></span></p> <p style="text-align: center"><span style="font-family: 宋体"></span></p> <p style="text-align: left"><span>好了,时间紧,就先说到这里,有不完整和补充的地方希望大家指正。接下来有时间在说Shell的基本语法格式条件语句:if,case,循环语句:for while,until.希望大家有好的意见和建议并批评指正!!!我们一点一滴的去慢慢稳扎稳打,相信有一天你会成为你想成为的人!!!</span></p> <p style="text-align: left"><span> </span></p> 最后修改:2021 年 12 月 10 日 10 : 53 AM © 允许规范转载 赞赏 如果觉得我的文章对你有用,请随意赞赏 赞赏作者 支付宝微信