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<div class="section" id="bash">
<h1>bash<a class="headerlink" href="#bash" title="Permalink to this headline">¶</a></h1>
<div class="section" id="id1">
<h2>变量的命名与赋值<a class="headerlink" href="#id1" title="Permalink to this headline">¶</a></h2>
<p>变量按作用域分为：局部变量和环境变量（全局变量)。</p>
<ul class="simple">
<li>局部变量设置:<ul>
<li>通过简单赋值: <tt class="docutils literal"><span class="pre">a=1</span></tt>， <strong>等号前后不能有任何空白符</strong> 。</li>
<li>内置函数 <tt class="docutils literal"><span class="pre">declare</span></tt> （不含-x选项）</li>
<li>内置函数 <tt class="docutils literal"><span class="pre">local</span></tt> ，但仅限于函数内使用。函数不使用 <tt class="docutils literal"><span class="pre">local</span></tt> 的变量在整个shell中可见</li>
</ul>
</li>
<li>环境变量设置:<ul>
<li><tt class="docutils literal"><span class="pre">declare</span> <span class="pre">-x</span></tt></li>
<li><tt class="docutils literal"><span class="pre">export</span> <span class="pre">varname=value</span></tt></li>
</ul>
</li>
</ul>
<p>变量的引用： <tt class="docutils literal"><span class="pre">$var</span></tt> 或 <tt class="docutils literal"><span class="pre">${var}</span></tt> ，两者在不引起歧义时等价。</p>
</div>
<div class="section" id="id2">
<h2>位置和特殊参量<a class="headerlink" href="#id2" title="Permalink to this headline">¶</a></h2>
<table border="1" class="docutils">
<colgroup>
<col width="34%" />
<col width="66%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">位置和特殊参量</th>
<th class="head">指代对象</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>$0</td>
<td>脚本名</td>
</tr>
<tr class="row-odd"><td>$#</td>
<td>位置参数个数</td>
</tr>
<tr class="row-even"><td>$*</td>
<td>所有的位置参数</td>
</tr>
<tr class="row-odd"><td>$@</td>
<td>未加引号时与$*的含义相同</td>
</tr>
<tr class="row-even"><td>$1...${N}</td>
<td>单独的位置变量</td>
</tr>
<tr class="row-odd"><td>$$</td>
<td>当前 shell 的 PID</td>
</tr>
<tr class="row-even"><td>$-</td>
<td>当前的 sh 选项设置</td>
</tr>
<tr class="row-odd"><td>$?</td>
<td>已执行的上一条命令的退出值</td>
</tr>
<tr class="row-even"><td>$!</td>
<td>最后一个进入后台的作业 PID</td>
</tr>
<tr class="row-odd"><td>$_</td>
<td>上一条命令的最后一个参数</td>
</tr>
</tbody>
</table>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">说明:</th><td class="field-body"><tt class="docutils literal"><span class="pre">$*</span></tt> 是一个由所有位置参量组成的单一的字符串,由环境变量 IFS 第一个字符分隔;相当于 <tt class="docutils literal"><span class="pre">$1c$2c...</span></tt> , c 是 IFS 的第一个字符;$@是 N 个独立的双引字符串,由空格分隔,即相当于 <tt class="docutils literal"><span class="pre">"$1"</span> <span class="pre">"$2"</span> <span class="pre">...</span> <span class="pre">"$N"</span></tt> 。</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="shell">
<h2>开启、关闭shell特性<a class="headerlink" href="#shell" title="Permalink to this headline">¶</a></h2>
<div class="section" id="set">
<h3>set<a class="headerlink" href="#set" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre>set -o noclobber # 开启noclobber特性
set +o noclobber # 关闭noclobber特性
set -o # 列出所有set控制的每一项特性及其状态
set +o # 以特殊方式列出上述特性
</pre></div>
</div>
</div>
<div class="section" id="shopt">
<h3>shopt<a class="headerlink" href="#shopt" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre>shopt -s dotglob # -s 设置
shopt -u dotglob # -u 取消设置
shopt -o -s noclobber # -o 设置由set控制的特性
shopt # 列出shopt控制的选项
shopt -s # 列出shopt设置开启的特性
shopt -u # 列出shopt设置取消的特性
</pre></div>
</div>
</div>
</div>
<div class="section" id="readline">
<h2>配置Readline库<a class="headerlink" href="#readline" title="Permalink to this headline">¶</a></h2>
<p>使用Readline库的bash和其他程序都会读取由INPUTRC环境变量指定的文件，以获取初始化信息。如果没有设置INPUTRC，这些程序将从文件 <tt class="docutils literal"><span class="pre">~/.inputrc</span></tt> 中读取，忽略其以空白行或以#开头的行。</p>
<div class="section" id="id3">
<h3>变量<a class="headerlink" href="#id3" title="Permalink to this headline">¶</a></h3>
<div class="highlight-python"><div class="highlight"><pre>set veriable value
</pre></div>
</div>
</div>
<div class="section" id="id4">
<h3>键绑定<a class="headerlink" href="#id4" title="Permalink to this headline">¶</a></h3>
<p>用户可以用以下两种方式，指定按键序列到Readline命令的映射绑定。</p>
<div class="highlight-python"><div class="highlight"><pre>keyname: command_name
" Keystroke_sequence ": command_name
</pre></div>
</div>
<p>比如:</p>
<div class="highlight-python"><div class="highlight"><pre>control-u: kill-whole-line
</pre></div>
</div>
<p>第二种形式中可以使用反斜杠转义序列来描述特殊的键如：CONTROL(\C)、META(\M)、ESCAPE(\e)</p>
<p>使用 <tt class="docutils literal"><span class="pre">bind</span> <span class="pre">-P</span></tt> 命令显示所有Readline命令列表，vi模式下使用的命令均以vi开头，其余的则在emacs模式下可用，使用 <tt class="docutils literal"><span class="pre">bind</span> <span class="pre">-P</span> <span class="pre">command_name</span></tt> 查看某命令绑定的按键序列。</p>
<p>可以用双引号将文本括起来（只在emacs模式下可用），以绑定该文本:</p>
<div class="highlight-python"><div class="highlight"><pre>"LOS": "The Linux Operating System"
</pre></div>
</div>
<p>使用该命令后，当用户输入LOS时，bash就会插入相应字符串。</p>
</div>
<div class="section" id="id5">
<h3>条件结构<a class="headerlink" href="#id5" title="Permalink to this headline">¶</a></h3>
<p>语法如下：</p>
<div class="highlight-bash"><div class="highlight"><pre><span class="nv">$if</span> <span class="o">[</span><span class="nb">test</span><span class="o">[=</span>value<span class="o">]]</span>
commands
<span class="o">[</span><span class="nv">$else</span>
commands
<span class="nv">$endif</span>
</pre></div>
</div>
<p>其中，<strong>test</strong> 为mode、term或bash。如：</p>
<div class="highlight-bash"><div class="highlight"><pre><span class="nv">$if</span> <span class="nv">mode</span><span class="o">=</span>vi
<span class="nv">$if</span> <span class="nv">term</span><span class="o">=</span>xterm
<span class="nv">$if</span> bash
</pre></div>
</div>
</div>
</div>
<div class="section" id="id6">
<h2>别名<a class="headerlink" href="#id6" title="Permalink to this headline">¶</a></h2>
<p>bash下使用语法：</p>
<div class="highlight-bash"><div class="highlight"><pre><span class="nb">alias</span> <span class="o">[</span>name<span class="o">[=</span>value<span class="o">]]</span> <span class="c">#等号左右没有空格或制表符，value两边必须有括号</span>
<span class="nb">alias </span><span class="nv">ls</span><span class="o">=</span><span class="s1">'ls -F'</span> <span class="c">#别名不替换自己，避免可能存在的无限递归。</span>
<span class="c">#别名中若使用双引号，则引号内容中的变量将进行扩展，单引号则不会。</span>
<span class="c">#使用./command或执行该命令的绝对路径名将阻止shell调用别名。</span>
<span class="nb">alias</span> <span class="c">#查看已定义的别名</span>
</pre></div>
</div>
</div>
<div class="section" id="id7">
<h2>数组<a class="headerlink" href="#id7" title="Permalink to this headline">¶</a></h2>
<p>bash支持一维数组，默认下标从0开始：</p>
<div class="highlight-bash"><div class="highlight"><pre><span class="nv">names</span><span class="o">=([</span>2<span class="o">]=</span>alice <span class="o">[</span>0<span class="o">]=</span>hatter <span class="o">[</span>1<span class="o">]=</span>duchess<span class="o">)</span>
<span class="nv">names</span><span class="o">=(</span>hatter duchess alice<span class="o">)</span>
<span class="nv">names</span><span class="o">=(</span>hatter <span class="o">[</span>5<span class="o">]=</span>duchess alice<span class="o">)</span> <span class="c">#names[0]=hatter names[5]=duchess names[6]=alice</span>
<span class="c">#下标为1,2,3,4的元素不存在</span>
<span class="c"># 引用格式:</span>
<span class="k">${</span><span class="nv">array</span><span class="p">[i]</span><span class="k">}</span>
<span class="k">for </span>i in <span class="s2">"${array[@]}"</span>;<span class="k">do</span> <span class="c"># ${array[@]}或${array[*]} 获取所有元素</span>
<span class="nb">echo</span> <span class="nv">$i</span>
<span class="k">done</span>
<span class="k">${</span><span class="p">!array[@]</span><span class="k">}</span> <span class="c"># 获取有元素的下标，如开头第三个数组有值的下标：0,5,6</span>
<span class="k">${#</span><span class="nv">array</span><span class="p">[@]</span><span class="k">}</span> 或 <span class="k">${#</span><span class="nv">array</span><span class="p">[*]</span><span class="k">}</span> <span class="c"># 获取非NULL元素个数</span>
</pre></div>
</div>
</div>
<div class="section" id="id8">
<h2>函数<a class="headerlink" href="#id8" title="Permalink to this headline">¶</a></h2>
<p>shell函数存放在物理内存(RAM)中而不是磁盘文件中，因此，shell访问函数的数度快于访问脚本的速度，而且shell还对函数预处理，启动速度也比脚本快的多。shell函数的执行和调用实在同一个shell中进行，而脚本中若定义太多函数，启动一个子shell的开销将变得很大。</p>
<p>shell函数声明可以放在 <tt class="docutils literal"><span class="pre">~/.bash_profile</span></tt> 或使用该函数的脚本中，也可直接放在命令行中。使用unset命令删除变量和函数。</p>
<p>函数声明：</p>
<div class="highlight-bash"><div class="highlight"><pre><span class="o">[</span><span class="k">function</span><span class="o">]</span> <span class="k">function</span>-name <span class="o">()</span>
<span class="o">{</span>
commands
<span class="o">}</span>
</pre></div>
</div>
</div>
<div class="section" id="id9">
<h2>命令行扩展<a class="headerlink" href="#id9" title="Permalink to this headline">¶</a></h2>
<div class="section" id="id10">
<h3>花括号扩展<a class="headerlink" href="#id10" title="Permalink to this headline">¶</a></h3>
<div class="highlight-bash"><div class="highlight"><pre><span class="nb">echo </span>chap_<span class="o">{</span>one,two,three<span class="o">}</span>.txt
mkdir var<span class="o">{</span>A,B,C<span class="o">}</span> <span class="c"># mkdir var[A-C]不可行</span>
<span class="c">#花括号里至少要有一个逗号并且没有未引用的空白字符，可以嵌套使用</span>
</pre></div>
</div>
</div>
<div class="section" id="id11">
<h3>算术扩展<a class="headerlink" href="#id11" title="Permalink to this headline">¶</a></h3>
<div class="highlight-bash"><div class="highlight"><pre><span class="k">$(())</span>
<span class="k">$((</span>expression<span class="k">))</span> <span class="c"># 计算expression，可作为参数传递给命令或命令行任何数字位置上</span>
<span class="nb">read </span>age
<span class="k">$((</span><span class="m">60</span><span class="o">-</span>age<span class="k">))</span>
<span class="k">$((</span><span class="m">2</span><span class="o">*</span><span class="nv">$x</span><span class="o">+</span><span class="m">2</span><span class="o">*</span><span class="nv">$y</span><span class="k">))</span>
<span class="k">$((</span><span class="m">2</span><span class="o">*</span>x+2*y<span class="k">))</span> <span class="c">#等价于上式</span>
<span class="nb">let</span> 内置命令
<span class="nb">let</span> <span class="s2">"number=$(wc -l < letter.txt)/66 +1"</span>
<span class="nb">let </span><span class="nv">a</span><span class="o">=</span>5+3 <span class="nv">b</span><span class="o">=</span>7+2
<span class="nb">let</span> <span class="s2">"i= i+2"</span> <span class="c"># 带空格需要加引号</span>
<span class="c"># 使用let或$(())进行算术扩展时，引用变量可以不在变量名前加$符号，但推荐加。</span>
<span class="nb">declare</span> –i num
<span class="nv">num</span><span class="o">=</span>hello <span class="c">#error!</span>
<span class="nv">num</span><span class="o">=</span>5 + 5 <span class="c">#error!不能有空格</span>
<span class="nv">num</span><span class="o">=</span><span class="s2">"4 * 6"</span> <span class="c">#带引号,可以有空格</span>
<span class="nv">num</span><span class="o">=</span>6.789 <span class="c">#num=6 去尾</span>
</pre></div>
</div>
<p>let支持的操作符：</p>
<table border="1" class="docutils">
<colgroup>
<col width="50%" />
<col width="50%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">操作符</th>
<th class="head">含 义</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td>-</td>
<td>负号</td>
</tr>
<tr class="row-odd"><td>!</td>
<td>逻辑非</td>
</tr>
<tr class="row-even"><td>~</td>
<td>按位取反</td>
</tr>
<tr class="row-odd"><td>*</td>
<td>乘法</td>
</tr>
<tr class="row-even"><td>/</td>
<td>除法</td>
</tr>
<tr class="row-odd"><td>%</td>
<td>求模</td>
</tr>
<tr class="row-even"><td>+</td>
<td>加法</td>
</tr>
<tr class="row-odd"><td>-</td>
<td>减法</td>
</tr>
<tr class="row-even"><td><<</td>
<td>左移位</td>
</tr>
<tr class="row-odd"><td>>></td>
<td>右移位</td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre"><=</span> <span class="pre">>=</span> <span class="pre"><</span> <span class="pre">></span> <span class="pre">==</span> <span class="pre">!=</span></tt></td>
<td>关系运算符</td>
</tr>
<tr class="row-odd"><td>&</td>
<td>按位与</td>
</tr>
<tr class="row-even"><td>^|</td>
<td>异或</td>
</tr>
<tr class="row-odd"><td>&&</td>
<td>逻辑与</td>
</tr>
<tr class="row-even"><td>||</td>
<td>逻辑或</td>
</tr>
<tr class="row-odd"><td>!</td>
<td>逻辑非</td>
</tr>
<tr class="row-even"><td>=</td>
<td>赋值</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">*=</span> <span class="pre">/=</span> <span class="pre">%=</span> <span class="pre">+=</span> <span class="pre">-=</span></tt></td>
<td> </td>
</tr>
<tr class="row-even"><td><tt class="docutils literal"><span class="pre"><<=</span> <span class="pre">>>=</span> <span class="pre">&=</span> <span class="pre">^=</span> <span class="pre">|=</span></tt></td>
<td>赋值简写符</td>
</tr>
<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">++</span> <span class="pre">--</span></tt></td>
<td>自增 自减</td>
</tr>
<tr class="row-even"><td>**</td>
<td>乘方</td>
</tr>
<tr class="row-odd"><td>expr?expr:expr</td>
<td>条件表达式</td>
</tr>
<tr class="row-even"><td>expr1,expr2</td>
<td>逗号表达式</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="id12">
<h3>命令扩展<a class="headerlink" href="#id12" title="Permalink to this headline">¶</a></h3>
<div class="highlight-bash"><div class="highlight"><pre><span class="c">#两种方式</span>
<span class="k">$(</span><span class="nb">command</span><span class="k">)</span>
<span class="sb">`</span> <span class="nb">command</span><span class="sb">`</span> <span class="c"># 这里是反引号，非单引号</span>
<span class="nv">a</span><span class="o">=</span><span class="k">$(</span><span class="nb">pwd</span><span class="k">)</span>
</pre></div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">bash</a><ul>
<li><a class="reference internal" href="#id1">变量的命名与赋值</a></li>
<li><a class="reference internal" href="#id2">位置和特殊参量</a></li>
<li><a class="reference internal" href="#shell">开启、关闭shell特性</a><ul>
<li><a class="reference internal" href="#set">set</a></li>
<li><a class="reference internal" href="#shopt">shopt</a></li>
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<li><a class="reference internal" href="#id3">变量</a></li>
<li><a class="reference internal" href="#id4">键绑定</a></li>
<li><a class="reference internal" href="#id5">条件结构</a></li>
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<li><a class="reference internal" href="#id7">数组</a></li>
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<li><a class="reference internal" href="#id9">命令行扩展</a><ul>
<li><a class="reference internal" href="#id10">花括号扩展</a></li>
<li><a class="reference internal" href="#id11">算术扩展</a></li>
<li><a class="reference internal" href="#id12">命令扩展</a></li>
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