Linux基础之xargs命令的入门实例
<p><span><strong>简介</strong></span></p>
<p>
xargs命令有两个要点。第一，你必须列出目标文件。第二，你必须指定对每个文件需要执行的命令或脚本。</p>
<p>
xargs命令被用来处理分布在不同目录下的文件：</p>
<ul>
<li>
计算所有文件的行数</li>
<li>
打印指定文件的第一行</li>
<li>
对每个文件执行一个自定义脚本</li>
</ul>
<p>
xargs可以将输入内容（通常通过命令行管道传递），转成后续命令的参数，通常用途有：</p>
<ul>
<li>
命令组合：尤其是一些命令不支持管道输入，比如ls。</li>
<li>
避免参数过长：xargs可以通过-nx来将参数分组，避免参数过长。</li>
</ul>
<p>
<strong>使用语法如下</strong></p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_541903">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash plain">Usage: </code><code class="bash functions">xargs</code> <code class="bash plain">... COMMAND INITIAL-ARGS...</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash plain">Run COMMAND with arguments INITIAL-ARGS and </code><code class="bash functions">more</code> <code class="bash plain">arguments </code><code class="bash functions">read</code> <code class="bash plain">from input.</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<span><strong>入门例子</strong></span></p>
<p>
首先，创建测试文件</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_631191">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">touch</code> <code class="bash plain">a.js b.js c.js</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
接着，运行如下命令：</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_686519">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">ls</code> <code class="bash plain">*.js | </code><code class="bash functions">xargs</code> <code class="bash functions">ls</code> <code class="bash plain">-al</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
输出如下：</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_655445">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash plain">-rw-r--r-- 1 a wheel 0 12 18 16:18 a.js</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash plain">-rw-r--r-- 1 a wheel 0 12 18 16:18 b.js</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">-rw-r--r-- 1 a wheel 0 12 18 16:18 c.js</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
命令解释：</p>
<ul>
<li>
首先，ls *.js的输出为a.js b.js c.js。</li>
<li>
通过管道，将a.js b.js c.js作为xargs的输入参数。</li>
<li>
xargs命令收到输入参数后，对参数进行解析，以空格/换行作为分隔符，拆分成多个参数，这里变成a.js、b.js、c.js。</li>
<li>
xargs将拆分后的参数，传递给后续的命令，作为后续命令的参数，也就是说，组成这样的命令ls -al a.js b.js c.js。</li>
</ul>
<p>
可以加上-t参数，在执行后面的命令前，先将命令打印出来。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_240718">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">ls</code> <code class="bash plain">*.js | </code><code class="bash functions">xargs</code> <code class="bash plain">-t </code><code class="bash functions">ls</code> <code class="bash plain">-al</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
输出如下，可以看到多了一行内容ls -al a.js b.js c.js，这就是实际运行的命令。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_645868">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">ls</code> <code class="bash plain">-al a.js b.js c.js</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash plain">-rw-r--r-- 1 a wheel 0 12 18 16:18 a.js</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">-rw-r--r-- 1 a wheel 0 12 18 16:18 b.js</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">-rw-r--r-- 1 a wheel 0 12 18 16:18 c.js</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<span><strong>例子：参数替换</strong></span></p>
<p>
有的时候，我们需要用到原始的参数，可以通过参数-i或-I实现。参数说明如下</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_76824">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash plain">-I R same as --replace=R (R must be specified)</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash plain">-i,--replace= Replace R </code><code class="bash keyword">in</code> <code class="bash plain">initial arguments with names</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash spaces"> </code><code class="bash functions">read</code> <code class="bash plain">from standard input. If R is</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash spaces"> </code><code class="bash plain">unspecified, assume {}</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
例子如下，将所有的.js结尾的文件，都加上.backup后缀。-I '{}'表示将后面命令行的{}替换成前面解析出来的参数。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_980492">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">ls</code> <code class="bash plain">*.js | </code><code class="bash functions">xargs</code> <code class="bash plain">-t -I </code><code class="bash string">'{}'</code> <code class="bash functions">mv</code> <code class="bash plain">{} {}.backup</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
展开后的命令如下：</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_239039">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">mv</code> <code class="bash plain">a.js a.js.backup</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">mv</code> <code class="bash plain">b.js b.js.backup</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash functions">mv</code> <code class="bash plain">c.js c.js.backup</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<span><strong>例子：参数分组</strong></span></p>
<p>
命令行对参数最大长度有限制，xargs通过-nx对参数进行分组来解决这个问题。</p>
<p>
首先，创建4个文件用来做实验。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_141957">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">touch</code> <code class="bash plain">a.js b.js c.js d.js</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
然后运行如下命令：</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_39656">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">ls</code> <code class="bash plain">*.js | </code><code class="bash functions">xargs</code> <code class="bash plain">-t -n2 </code><code class="bash functions">ls</code> <code class="bash plain">-al</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
输出如下，-n2表示，将参数以2个为一组，传给后面的命令。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_498532">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">ls</code> <code class="bash plain">-al a.js b.js </code>
</div>
<div class="line number2 index1 alt1">
<code class="bash plain">-rw-r--r-- 1 root root 0 Dec 18 16:52 a.js</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">-rw-r--r-- 1 root root 0 Dec 18 16:52 b.js</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash functions">ls</code> <code class="bash plain">-al c.js d.js </code>
</div>
<div class="line number5 index4 alt2">
<code class="bash plain">-rw-r--r-- 1 root root 0 Dec 18 16:52 c.js</code>
</div>
<div class="line number6 index5 alt1">
<code class="bash plain">-rw-r--r-- 1 root root 0 Dec 18 16:52 d.js</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<span><strong>例子：特殊文件名</strong></span></p>
<p>
有的时候，文件名可能存在特殊字符，比如下面的文件名中存在空格。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_7093">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">touch</code> <code class="bash string">'hello 01.css'</code> <code class="bash string">'hello 02.css'</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
运行之前的命令会报错，因为xargs是以空格/换行作为分隔符，于是就会出现预期之外的行为。</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_732620">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
<div class="line number2 index1 alt1">
2</div>
<div class="line number3 index2 alt2">
3</div>
<div class="line number4 index3 alt1">
4</div>
<div class="line number5 index4 alt2">
5</div>
<div class="line number6 index5 alt1">
6</div>
<div class="line number7 index6 alt2">
7</div>
<div class="line number8 index7 alt1">
8</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash comments"># 命令</code>
</div>
<div class="line number2 index1 alt1">
<code class="bash functions">find</code> <code class="bash plain">. -name </code><code class="bash string">'*.css'</code> <code class="bash plain">| </code><code class="bash functions">xargs</code> <code class="bash plain">-t </code><code class="bash functions">ls</code> <code class="bash plain">-al</code>
</div>
<div class="line number3 index2 alt2">
<code class="bash comments">#输出</code>
</div>
<div class="line number4 index3 alt1">
<code class="bash functions">ls</code> <code class="bash plain">-al .</code><code class="bash plain">/hello</code> <code class="bash plain">01.css .</code><code class="bash plain">/hello</code> <code class="bash plain">02.css </code><code class="bash comments"># 展开后的命令</code>
</div>
<div class="line number5 index4 alt2">
<code class="bash functions">ls</code><code class="bash plain">: cannot access .</code><code class="bash plain">/hello</code><code class="bash plain">: No such </code><code class="bash functions">file</code> <code class="bash plain">or directory</code>
</div>
<div class="line number6 index5 alt1">
<code class="bash functions">ls</code><code class="bash plain">: cannot access 01.css: No such </code><code class="bash functions">file</code> <code class="bash plain">or directory</code>
</div>
<div class="line number7 index6 alt2">
<code class="bash functions">ls</code><code class="bash plain">: cannot access .</code><code class="bash plain">/hello</code><code class="bash plain">: No such </code><code class="bash functions">file</code> <code class="bash plain">or directory</code>
</div>
<div class="line number8 index7 alt1">
<code class="bash functions">ls</code><code class="bash plain">: cannot access 02.css: No such </code><code class="bash functions">file</code> <code class="bash plain">or directory</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
xargs是这样解决这个问题的。</p>
<ul>
<li>
-print0：告诉find命令，在输出文件名之后，跟上NULL字符，而不是换行符；</li>
<li>
-0：告诉xargs，以NULL作为参数分隔符；</li>
</ul>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_443611">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">find</code> <code class="bash plain">. -name </code><code class="bash string">'*.css'</code> <code class="bash plain">-print0 | </code><code class="bash functions">xargs</code> <code class="bash plain">-0 -t </code><code class="bash functions">ls</code> <code class="bash plain">-al</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<span><strong>例子：日志备份</strong></span></p>
<p>
将7天前的日志备份到特定目录</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_807583">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
1</div>
</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash functions">find</code> <code class="bash plain">. -mtime +7 | </code><code class="bash functions">xargs</code> <code class="bash plain">-I </code><code class="bash string">'{}'</code> <code class="bash functions">mv</code> <code class="bash plain">{} </code><code class="bash plain">/tmp/otc-svr-logs/</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
<span><strong>总结</strong></span></p>
<p>
以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。</p>
<p>
<strong>相关链接</strong></p>
<p>
https://craftsmanbai.gitbooks...</p>
<p>
http://wiki.jikexueyuan.com/p...</p>
<p>
原文链接：https://segmentfault.com/a/1190000012566053</p>
頁:
[1]