blocks|key|1787967|text|不，一般来说，在Unix中不能这样做。您只能创建/截断(使用>)或附加到文件(使用>>)。一旦被截断，旧的内容就会丢失。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1787968|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

No, in general it can't be done in Unix like this. You can only create/truncate (with >) or append to a file (with >>). Once truncated, the old contents would be lost.

blocks|key|2001711|text|一般来说，这是做不到的。但是Perl有-i开关：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2001712|perl+-i+-ne+'print+if+/SomeRegEx/'+myfile.txt|code-block|syntax|javascript|2001713|写入-i.bak将导致原始文件保存在myfile.txt.bak中。|2001714|(当然，在内部，Perl基本上只是做您已经在做的事情--不涉及任何特殊的魔术。)|2001715|entityMap^0|J|2|0|0|2|6|I|E|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|Z|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|10|8|@]|D|@]|E|$]]]|P|$]]

In general, this can't be done. But Perl has the <code>-i</code> switch:

<pre><code>perl -i -ne 'print if /SomeRegEx/' myfile.txt
</code></pre>

Writing <code>-i.bak</code> will cause the original to be saved in <code>myfile.txt.bak</code>.

(Of course internally, Perl just does basically what you're already doing -- there's no special magic involved.)

blocks|key|2001730|text|Perl有-i开关，sed和Ruby也有|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2001731|sed+-i.bak+-n+'/SomeRegex/p'+file

ruby+-i.bak+-ne+'print+if+/SomeRegex/'+file|code-block|syntax|javascript|2001732|但请注意，它所做的一切都是在后端创建“临时”文件，这是你认为你看不到的，仅此而已。|2001733|除了grep之外的其他方式|2001734|awk|2001735|awk+'/someRegex/'+file+>+t+&&+mv+t+file|2001736|bash|2001737|while+read+-r+line;do+case+"$line"+in+*someregex*)+echo+"$line";;esac;done+<file+>+t+&&+mv+t+file|2001738|entityMap^0|5|2|A|3|E|4|0|0|0|2|4|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|16|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|17|8|@$9|18|A|19|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1A|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|S|3|T|5|6|7|1C|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|1D|8|@]|D|@]|E|$I|J]]|$1|W|3|-4|5|6|7|1E|8|@]|D|@]|E|$]]]|X|$]]

Perl has the <code>-i</code> switch, so does <code>sed</code> and <code>Ruby</code>

<pre><code>sed -i.bak -n '/SomeRegex/p' file

ruby -i.bak -ne 'print if /SomeRegex/' file
</code></pre>

But note that all it ever does is creating "temp" files at the back end which you think you don't see, that's all. 

Other ways, besides <code>grep</code>

awk

<pre><code>awk '/someRegex/' file &gt; t &amp;&amp; mv t file
</code></pre>

bash

<pre><code>while read -r line;do case "$line" in *someregex*) echo "$line";;esac;done &lt;file &gt; t &amp;&amp; mv t file
</code></pre>

blocks|key|1788129|text|请看我在http://petdance.com/perl/command-line-options.pdf上的幻灯片“Perl命令行选项的现场指南”，了解有关使用Perl可以做什么的更多想法。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1788130|entityMap|0|LINK|mutability|MUTABLE|url|http://petdance.com/perl/command-line-options.pdf^0|4|1D|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Take a look at my slides "Field Guide To the Perl Command-Line Options" at <a href="http://petdance.com/perl/command-line-options.pdf" rel="nofollow">http://petdance.com/perl/command-line-options.pdf</a> for more ideas on what you can do in place with Perl.

blocks|key|2001824|text|大多数sed安装都可以进行就地编辑，请查看手册页，您可能需要-i标志。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2001825|entityMap^0|3|3|U|2|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

Most installations of <code>sed</code> can do in-place editing, check the man page, you probably want the <code>-i</code> flag.

blocks|key|1788246|text|要使用vim-way就地编辑文件，请尝试：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1788247|$+ex+-s+%2B'%25!grep+foo'+-cxa+myfile.txt|code-block|syntax|javascript|1788248|或者使用sed或gawk。|offset|length|style|CODE|1788249|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/q/7573368/55075|1|https://stackoverflow.com/q/16529716/55075^0|0|0|4|3|8|4|4|3|0|8|4|1|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@$I|Z|J|10|K|L]|$I|11|J|12|K|L]]|9|@$I|13|J|14|1|15]|$I|16|J|17|1|18]]|A|$]]|$1|M|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]|U|$5|P|Q|R|A|$S|V]]]]

To edit file in-place using vim-way, try:

<pre><code>$ ex -s +'%!grep foo' -cxa myfile.txt
</code></pre>

Alternatively use <a href="https://stackoverflow.com/q/7573368/55075"><code>sed</code></a> or <a href="https://stackoverflow.com/q/16529716/55075"><code>gawk</code></a>.

blocks|key|1788336|text|sponge+(在Debian/Ubuntu的moreutils包中)读取输入直到EOF，并将其写入文件，因此您可以grep文件并将其写回自身。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1788337|如下所示：|1788338|grep+'pattern'+file+%7C+sponge+file|code-block|syntax|javascript|1788339|entityMap|0|LINK|mutability|MUTABLE|url|https://linux.die.net/man/1/sponge^0|0|6|N|9|0|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|F|3|G|5|6|7|12|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|13|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

<a href="https://linux.die.net/man/1/sponge" rel="noreferrer"><code>sponge</code></a> (in <code>moreutils</code> package in Debian/Ubuntu) reads input till EOF and writes it into file, so you can grep file and write it back to itself.

Like this:

<pre><code>grep 'pattern' file | sponge file
</code></pre>

blocks|key|1788370|text|存储在一个变量中，然后将其赋值给原始文件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1788371|A=$(cat+aux.log+%7C+grep+'Something')+&&+echo+"${A}"+>+aux.log|code-block|syntax|javascript|1788372|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Store in a variable and then assign it to the original file:

<pre><code>A=$(cat aux.log | grep 'Something') &amp;&amp; echo "${A}" &gt; aux.log
</code></pre>

I've got a script that calls grep to process a text file. Currently I am doing something like this.

<pre><code>$ grep 'SomeRegEx' myfile.txt &gt; myfile.txt.temp
$ mv myfile.txt.temp myfile.txt
</code></pre>

I'm wondering if there is any way to do in-place processing, as in store the results to the same original file without having to create a temporary file and then replace the original with the temp file when processing is done.

Of course I welcome comments as to why this should or should not be done, but I'm mainly interested in whether it can be done. In this example I'm using <code>grep</code>, but I'm interested about Unix tools in general. Thanks!

In-place processing with grep

Ubuntu

Debian

Unix

Perl

我有一个脚本调用grep来处理一个文本文件。目前我正在做这样的事情。$ grep 'SomeRegEx' myfile.txt > myfile.txt.temp$ mv myfile.txt.temp myfile.txt我想知道是否有任何方法可以进行就地处理，比如将结果存储到相同的原始文件中，而不必创建临时文件，然...

问使用grep进行就地处理
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