电脑/linux/bash编程/bash编程高级篇.html

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<header>
<h1 class="title">bash编程高级篇</h1>
</header><nav id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#orgheadline1">1. bash里面的特殊符号</a></li>
<li><a href="#orgheadline7">2. bash里面的array</a>
<ul>
<li><a href="#orgheadline2">2.1. 赋值和引用</a></li>
<li><a href="#orgheadline6">2.2. 其他array操作</a>
<ul>
<li><a href="#orgheadline3">2.2.1. 两个array合并在一起</a></li>
<li><a href="#orgheadline4">2.2.2. 字符串刷成array</a></li>
<li><a href="#orgheadline5">2.2.3. 简单的文件刷成列表</a></li>
</ul>
</li>
</ul>
</li>
<li><a href="#orgheadline8">3. bash批处理</a></li>
</ul>
</div>
</nav>

<div class="outline-2">
<h2 id="orgheadline1">bash里面的特殊符号</h2>
<div class="outline-text-2" id="text-1">
<ul class="org-ul">
<li>$0 本命令名字</li>
<li>$1 $2 &#x2026; 命令接受的参数</li>
<li>$@ 所有参数</li>
<li>$? 命令运行返回的状态</li>
<li>$! 命令运行最后一个进程号</li>
<li>&amp;&amp; <code>cmd1 &amp;&amp; cmd2</code> 前一个命令执行成功才执行第二个命令</li>
<li>; 如果某个命令以 <code>;</code> 结尾，则意思是逐个执行这些命令</li>
<li>&amp; 如果某个命令以 <code>&amp;</code> 结尾，则该命令是异步的和后台执行的</li>
</ul>

<p>
更多信息请参看 <a href="http://stackoverflow.com/questions/5163144/what-are-the-special-dollar-sign-shell-variable">这个网页</a> 。
</p>
</div>
</div>

<div class="outline-2">
<h2 id="orgheadline7">bash里面的array</h2>
<div class="outline-text-2" id="text-2">
<p>
bash编程最好不要过多涉及高级编程的那些内容，那将是很痛苦的，但是在某些情况下你可能需要了解array这个概念。下面来演示这样一个例子，其需求就是在一个自动备份程序之上再加上自动删除逻辑。
</p>

<div class="highlight"><pre><span></span><span class="ch">#! /bin/bash</span>

<span class="nv">DATE</span><span class="o">=</span><span class="k">$(</span>date +%F<span class="k">)</span>
<span class="nv">DAYS</span><span class="o">=</span>30

<span class="c1">## here is the autodump code, and the output filename is whatdump_${DATE}</span>

<span class="c1">### the allowed list</span>
ALLOWED<span class="o">[</span>0<span class="o">]=</span>whatdump_<span class="si">${</span><span class="nv">DATE</span><span class="si">}</span>

<span class="k">for</span> <span class="o">((</span> <span class="nv">i</span><span class="o">=</span>1<span class="p">;</span> i&lt;<span class="o">=</span><span class="si">${</span><span class="nv">DAYS</span><span class="si">}</span><span class="p">;</span> i++ <span class="o">))</span>
<span class="k">do</span>  ALLOWED<span class="o">[</span>i<span class="o">]=</span>whatdump_<span class="k">$(</span>date -d <span class="s2">&quot;now -</span><span class="si">${</span><span class="nv">i</span><span class="si">}</span><span class="s2">days&quot;</span> +<span class="s2">&quot;%F&quot;</span><span class="k">)</span>
<span class="k">done</span>


<span class="c1">### use the python script , it is really hard to write it on bash</span>
python ~/thepython/scripts/whatdump_autoremove.py <span class="si">${</span><span class="nv">ALLOWED</span><span class="p">[@]</span><span class="si">}</span>
</pre></div>

<p>
这个程序整个逻辑就是创建一个名字叫做"whatdump_\({DATE}"的备份文件（你可以通过cron后台服务来控制好每天运行一次），然后我们希望目标文件只保留最近三十天的文件。因为这个逻辑较为复杂，本来我是打算直接将 ~\){DATE}~ 参数传递给python脚本来做接下来的工作的，但是在了解到date命令强大的人类友好的日期时间表达功能（请参考 <a href="http://unix.stackexchange.com/questions/24626/quickly-calculate-date-differences">这个网页</a> ），我决定将整个允许存在的文件名都传递进python脚本中去。
</p>

<p>
有兴趣的可以了解下date命令-d选项的灵活表达支持，比如 date -d "now -3days" 就是现在之前三天的日期时间，而 date -d "+3weeks" 就是现在三周之后的日期时间。用兴趣的可以继续了解下，这个date命令的-d选项真的好强大。比如下面这几行代码（来自 <a href="http://www.thegeekstuff.com/2013/05/date-command-examples/">这个网页</a> ）:
</p>

<div class="highlight"><pre><span></span>$ date --date<span class="o">=</span><span class="s1">&#39;3 seconds ago&#39;</span>
Mon May <span class="m">20</span> 21:59:20 PDT 2013

$ date --date<span class="o">=</span><span class="s2">&quot;1 day ago&quot;</span>
Sun May <span class="m">19</span> 21:59:36 PDT 2013

$ date --date<span class="o">=</span><span class="s2">&quot;yesterday&quot;</span>
Sun May <span class="m">19</span> 22:00:26 PDT 2013

$ date --date<span class="o">=</span><span class="s2">&quot;1 month ago&quot;</span>
Sat Apr <span class="m">20</span> 21:59:58 PDT 2013

$ date --date<span class="o">=</span><span class="s2">&quot;1 year ago&quot;</span>
Sun May <span class="m">20</span> 22:00:09 PDT 2012
</pre></div>

<p>
好了下面详细讲一下这里array涉及到的语法。
</p>
</div>

<div class="outline-3">
<h3 id="orgheadline2">赋值和引用</h3>
<div class="outline-text-3" id="text-2-1">
<pre>
=&gt;array[0]="hello"
=&gt;array[1]="world!"
=&gt;echo ${array[0]} ${array[1]}
hello world!
</pre>

<p>
这种表达和我们常见的那种数组概念相近，记得索引从0开始这个惯例即可。然后或者如下一起赋值:
</p>

<pre>
=&gt;array2=("hello" "python")
=&gt;echo ${array2[@]}
hello python
</pre>

<p>
上面的 \({arrayname[@]} 这种表达方式就是引用所有的array，这个 ~@~ 符号是特殊符号。然后还有 ~\){#arrayname[@]}~ 这种表达是返回这个array的长度。
</p>

<pre>
=&gt;echo ${#array2[@]}
2
</pre>

<p>
然后最后这句:
</p>
<pre>
python ~/thepython/scripts/whatdump_autoremove.py ${ALLOWED[@]}
</pre>
<p>
就是将收集到的所有允许的文件名array传递进python脚本中去了。在python脚本中一个粗糙的做法就是如下这样引用
</p>

<pre>
def main(args,path=""):
    print args

main(sys.argv[1:])
</pre>

<p>
这样所有的这些array就传递进args里面去了，读者有兴趣可以试一下，这个args在python中就是一个列表对象了。到python里面了更复杂的逻辑我们都可以很快写出来了，我就不说了。
</p>

<p>
大概类似下面所示，注意这里的pathlib在python3.4之后才会有，之前需要用pip安装之。
</p>
<div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/env python</span>
<span class="c1"># -*- coding: utf-8 -*-</span>
<span class="kn">from</span> <span class="nn">__future__</span> <span class="kn">import</span> <span class="n">print_function</span>
<span class="kn">import</span> <span class="nn">sys</span>
<span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">datetime</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">from</span> <span class="nn">pathlib</span> <span class="kn">import</span> <span class="n">Path</span>
<span class="kn">import</span> <span class="nn">shutil</span>


<span class="k">def</span> <span class="nf">main</span><span class="p">(</span><span class="n">args</span><span class="p">,</span><span class="n">path</span><span class="o">=</span><span class="s2">&quot;&quot;</span><span class="p">):</span>
    <span class="n">allowed</span> <span class="o">=</span> <span class="n">args</span>
    <span class="n">p</span> <span class="o">=</span> <span class="n">Path</span><span class="p">(</span><span class="n">path</span><span class="p">)</span>
    <span class="n">pfolds</span> <span class="o">=</span> <span class="p">[</span><span class="n">p</span> <span class="k">for</span> <span class="n">p</span> <span class="ow">in</span> <span class="n">p</span><span class="o">.</span><span class="n">iterdir</span><span class="p">()</span> <span class="k">if</span> <span class="n">p</span><span class="o">.</span><span class="n">is_dir</span><span class="p">()]</span>
    <span class="k">print</span><span class="p">(</span><span class="n">pfolds</span><span class="p">)</span>
    <span class="k">for</span> <span class="n">p</span> <span class="ow">in</span> <span class="n">pfolds</span><span class="p">:</span>
        <span class="k">if</span> <span class="n">p</span><span class="o">.</span><span class="n">name</span> <span class="ow">in</span> <span class="n">allowed</span><span class="p">:</span>
            <span class="k">print</span><span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">name</span><span class="p">,</span><span class="s2">&quot;passed&quot;</span><span class="p">)</span>
        <span class="k">else</span><span class="p">:</span>
            <span class="k">print</span><span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">name</span><span class="p">,</span><span class="s2">&quot;removed&quot;</span><span class="p">)</span>
            <span class="c1">### really do the remove thing</span>
            <span class="n">shutil</span><span class="o">.</span><span class="n">rmtree</span><span class="p">(</span><span class="n">p</span><span class="o">.</span><span class="n">name</span><span class="p">)</span>

<span class="k">if</span> <span class="n">__name__</span> <span class="o">==</span> <span class="s1">&#39;__main__&#39;</span><span class="p">:</span>
    <span class="c1">### 切换到autodump目录</span>
    <span class="n">os</span><span class="o">.</span><span class="n">chdir</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">expanduser</span><span class="p">(</span><span class="s2">&quot;~/autodump&quot;</span><span class="p">))</span>

    <span class="n">main</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">:])</span>
</pre></div>
</div>
</div>


<div class="outline-3">
<h3 id="orgheadline6">其他array操作</h3>
<div class="outline-text-3" id="text-2-2">
<p>
你可能还会需要在bash中进行其他array操作，只是一般能够传递python就传进python中去，然后后面的再深加工吧。更多内容读者请参看 <a href="http://www.thegeekstuff.com/2010/06/bash-array-tutorial/">这个网页</a> 。下面我简介一下我觉得应该还是有点用的内容。
</p>
</div>


<div class="outline-4">
<h4 id="orgheadline3">两个array合并在一起</h4>
<div class="outline-text-4" id="text-2-2-1">
<p>
这在合并某些array结果然后传递进python脚本中有用。
</p>
<pre>
=&gt;Unix1=('Debian' 'Red hat' 'Ubuntu' 'Suse')
=&gt;Unix2=('Fedora' 'UTS' 'OpenLinux')
=&gt;Unix3=("${Unix1[@]}" "AIX" "HP-UX")
=&gt;Unix4=("${Unix2[@]}" "${Unix3[@]}")
=&gt;echo ${Unix3[@]}
Debian Red hat Ubuntu Suse AIX HP-UX
=&gt;echo ${Unix4[@]}
Fedora UTS OpenLinux Debian Red hat Ubuntu Suse AIX HP-UX
</pre>
</div>
</div>


<div class="outline-4">
<h4 id="orgheadline4">字符串刷成array</h4>
<div class="outline-text-4" id="text-2-2-2">
<p>
看到这里，我想读者应该猜到了，圆括号里面放着一列字符串然后就自动成为array了:
</p>
<pre>
=&gt;string="hello bash"
=&gt;test=(${string})
=&gt;echo ${test[@]}
hello bash
=&gt;echo ${test[1]}
bash
=&gt;echo ${test[0]}
hello
</pre>
</div>
</div>

<div class="outline-4">
<h4 id="orgheadline5">简单的文件刷成列表</h4>
<div class="outline-text-4" id="text-2-2-3">
<p>
这里就简单复制前面提及的那个网页的代码了，其实说白了还是和字符串转array一个道理，就是读取了一下文件即可。
</p>
<pre>
#Example file
$ cat logfile
Welcome
to
thegeekstuff
Linux
Unix

$ cat loadcontent.sh
#!/bin/bash
filecontent=( `cat "logfile" `)
</pre>
</div>
</div>
</div>
</div>


<div class="outline-2">
<h2 id="orgheadline8">bash批处理</h2>
<div class="outline-text-2" id="text-3">
<p>
这个在bash编程123那里也说一点，这里再强调一下，python脚本的命令行参数，如果是输入文件，我喜欢简单起见就单个文件，然后具体bash的时候，如下简单写一下批量处理命令即可，很简单的，就不用麻烦python脚本那边又要处理单个文件的情况又要处理多个文件的情况，还要缩进一次，多麻烦啊。
</p>

<div class="highlight"><pre><span></span><span class="k">for</span> f in <span class="k">$(</span>ls *.pdf<span class="k">)</span><span class="p">;</span> <span class="k">do</span> infome_image_convert_format --outputformat<span class="o">=</span>png <span class="si">${</span><span class="nv">f</span><span class="si">}</span> --dpi<span class="o">=</span><span class="m">300</span> <span class="p">;</span> <span class="k">done</span>
</pre></div>
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