Shell中如何删除文本比较长的行的实现方法
<p><strong> Shell中如何删除文本比较长的行的实现方法</strong></p>
<p>
有的时候需要对文件执行删除删除操作，这个时候比较常用的会使用vi命令中的dd命令，比如先执行10G(跳转到第10行)，然后再执行20dd(删除20行)，但实际情况未必是这么常规，比如说，要删除文件中，某行长度超过200个字符的行，如果文本比较小，还好，如果是几万行，几十万行的呢？ 这个想用vi就不现实了。 我然想到的办法就是:比如说，通过sed,awk,egrep命令来达到目的。 举个简单例子。</p>
<p>
假如说如下文本文件，要将其中长度为5字符以上的给删除掉。</p>
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<div class="syntaxhighlighterbash" id="highlighter_623440">
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<span>?</span>
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<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>
<div class="line number9 index8 alt2">
9</div>
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<code class="bash plain">root@linux</code><code class="bash comments"># cat data </code>
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<div class="line number2 index1 alt1">
<code class="bash plain">1 </code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">22 </code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">333 </code>
</div>
<div class="line number5 index4 alt2">
<code class="bash plain">4444 </code>
</div>
<div class="line number6 index5 alt1">
<code class="bash plain">55555 </code>
</div>
<div class="line number7 index6 alt2">
<code class="bash plain">666666 </code>
</div>
<div class="line number8 index7 alt1">
<code class="bash plain">7777777 </code>
</div>
<div class="line number9 index8 alt2">
<code class="bash plain">88888888 </code>
</div>
</div>
</td>
</tr></tbody></table>
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<p>
<strong>方法一： 使用awk命令的length()函数</strong></p>
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<div class="syntaxhighlighterbash" id="highlighter_905515">
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<span>?</span>
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<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>
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<code class="bash plain">root@linux</code><code class="bash comments"># cat data | awk '{if (length($0) <=4 ) print $0}' </code>
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<div class="line number2 index1 alt1">
<code class="bash plain">1 </code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">22 </code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">333 </code>
</div>
<div class="line number5 index4 alt2">
<code class="bash plain">4444 </code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
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<p>
<strong>方法二： 使用grep命令 </strong></p>
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<span>?</span>
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<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>
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<code class="bash plain">root@linux</code><code class="bash comments"># cat data | egrep -w '^.{1,4}' </code>
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<div class="line number2 index1 alt1">
<code class="bash plain">1 </code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">22 </code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">333 </code>
</div>
<div class="line number5 index4 alt2">
<code class="bash plain">4444 </code>
</div>
</div>
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</tr></tbody></table>
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<p>
<strong>方法三： 使用sed命令</strong></p>
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<div class="syntaxhighlighterbash" id="highlighter_254108">
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<span>?</span>
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<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>
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<code class="bash plain">root@linux</code><code class="bash comments"># cat data | sed -n '/^.\{5,\}/!w NewFile' </code>
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<code class="bash plain">root@linux</code><code class="bash comments"># cat NewFile </code>
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<div class="line number3 index2 alt2">
<code class="bash plain">1 </code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">22 </code>
</div>
<div class="line number5 index4 alt2">
<code class="bash plain">333 </code>
</div>
<div class="line number6 index5 alt1">
<code class="bash plain">4444 </code>
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</td>
</tr></tbody></table>
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<p>
<strong>备注:</strong></p>
<p>
1. 使用awk,grep命令的时候，可以将处理好的文件重定向到另外一个新文件中<br>
2. egrep -w参数，表示仅跟模式匹配的单词<br>
3. ^. 表示以任意字符开头的行，这个和-w命令匹配使用，这个很关键，否则找不到<br>
4. !w !表示所有模式不匹配的，w是输出，写入到新文件NewFile文件中</p>
<p>
如有疑问请留言或者到本站社区交流讨论，感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！</p>
<p>
原文链接：http://blog.csdn.net/jerry_1126/article/details/77871972</p>
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