blocks|key|3368702|text|也许有人可以提供更好的东西，但我认为你最好的选择是|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3368703|LINES=$(cat+/some/big/file+%7C+wc+-l)
MD5=$(cat+/some/big/file+%7C+md5)|code-block|syntax|javascript|3368704|原因是，我认为这是最好的方法，因为您必须以某种方式对文件内容应用两个单独的操作。因此，除非你有一个同时知道如何做的命令，否则你必须读两遍。除了读两遍，这应该是你的问题的解决方案。|3368705|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

May be someone can offer something better, but I think your best shot is

<pre><code>LINES=$(cat /some/big/file | wc -l)
MD5=$(cat /some/big/file | md5)
</code></pre>

The reason, I think it's the best shot, is that one way or another you will have to apply two separate operations to the content of the file. So unless you have a command that knows how to do it at the same time you will have to read it twice.
Beyond reading it twice, that should be a solution to your problem.

blocks|key|1122546|text|这并不能直接回答你的问题...但您只需读取该文件一次，并且不必使用tee。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1122547|SIZE=$(wc+-c+/some/big/file)
MD5=$(md5+/some/big/file)|code-block|syntax|javascript|1122548|那么，这会读取文件多少次呢？一次。这是因为wc+-c实际上并不读取文件，它只是查看文件有多长并返回报告。以下是我的测试：|1122549|$+time+wc+-c+/big/file+>/dev/null
real++++0m0.003s
user++++0m0.000s
sys+++++0m0.000s
$+time+wc+-c+</big/file+>/dev/null
real++++0m0.004s
user++++0m0.000s
sys+++++0m0.000s
$+time+cat+/big/file+%7C+wc+-c+>/dev/null
real++++0m52.945s
user++++0m0.160s
sys+++++0m19.612s|1122550|教训:不要将tee+(或cat)与wc+-c混为一谈，因为这非常浪费时间。只要正常执行md5就行了，不用担心wc+-c。|1122551|注意：wc+-c+<file速度快的原因是它获得了一个普通的文件句柄，就像wc自己调用了open()一样。|1122552|管道性能|1122553|您几乎不应该在管道中使用cat。|1122554|cat+file+%7C+cmd++++#+slow
cmd+<file+++++++++#+fast|1122555|调用cat通常意味着创建一个没有任何用途的额外进程。在某些情况下，就像使用wc+-c一样，它实际上会在管道之后减慢程序的运行速度。我的意思是，你可以把cat放在你喜欢的任何地方，但这太愚蠢了：|1122556|echo+'hello,+world'+%7C+cat
cat+file.txt+%7C+less
cat+file.txt+%7C+cat+%7C+less
cat+file.txt+%7C+cat+%7C+sort+%7C+cat+%7C+cat+%7C+uniq+%7C+cat+>file_unique.txt|1122557|这样更好：|1122558|echo+'hello,+world'
less+file.txt
sort+file.txt+%7C+uniq+>file_unique.txt|1122559|entityMap^0|X|3|0|0|L|5|0|0|6|3|C|3|H|5|17|3|1I|5|0|3|B|11|2|18|6|0|0|C|3|0|0|2|3|11|5|23|3|0|0|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1C|8|@$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1G|8|@$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]|$9|1P|A|1Q|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1R|8|@$9|1S|A|1T|B|C]|$9|1U|A|1V|B|C]|$9|1W|A|1X|B|C]]|D|@]|E|$]]|$1|S|3|T|5|6|7|1Y|8|@]|D|@]|E|$]]|$1|U|3|V|5|6|7|1Z|8|@$9|20|A|21|B|C]]|D|@]|E|$]]|$1|W|3|X|5|H|7|22|8|@]|D|@]|E|$I|J]]|$1|Y|3|Z|5|6|7|23|8|@$9|24|A|25|B|C]|$9|26|A|27|B|C]|$9|28|A|29|B|C]]|D|@]|E|$]]|$1|10|3|11|5|H|7|2A|8|@]|D|@]|E|$I|J]]|$1|12|3|13|5|6|7|2B|8|@]|D|@]|E|$]]|$1|14|3|15|5|H|7|2C|8|@]|D|@]|E|$I|J]]|$1|16|3|-4|5|6|7|2D|8|@]|D|@]|E|$]]]|17|$]]

This doesn't directly answer your question... but you only have to read the file once, and you don't have to use <code>tee</code>.

<pre><code>SIZE=$(wc -c /some/big/file)
MD5=$(md5 /some/big/file)
</code></pre>

So, how many times does this read the file? Once. This is because <code>wc -c</code> doesn't actually read the file, it just looks at how long it is and reports back. Here are my tests:

<pre><code>$ time wc -c /big/file &gt;/dev/null
real 0m0.003s
user 0m0.000s
sys 0m0.000s
$ time wc -c &lt;/big/file &gt;/dev/null
real 0m0.004s
user 0m0.000s
sys 0m0.000s
$ time cat /big/file | wc -c &gt;/dev/null
real 0m52.945s
user 0m0.160s
sys 0m19.612s
</code></pre>

The lesson: don't mix <code>tee</code> (or <code>cat</code>) with <code>wc -c</code>, because it's a big waste of time. Just do the <code>md5</code> normally and don't worry about <code>wc -c</code>.

Note: The reason why <code>wc -c &lt;file</code> is fast is because it gets an ordinary file handle, just as if <code>wc</code> had called <code>open()</code> itself.

<h2>Pipe performance</h2>

You should almost never use <code>cat</code> in a pipe.

<pre><code>cat file | cmd # slow
cmd &lt;file # fast
</code></pre>

Calling <code>cat</code> usually means creating an extra process which serves no purpose. In some cases, as with <code>wc -c</code>, it actually slows down the program after the pipe. I mean, you could stick <code>cat</code> anywhere you like, but it's just silly:

<pre><code>echo 'hello, world' | cat
cat file.txt | less
cat file.txt | cat | less
cat file.txt | cat | sort | cat | cat | uniq | cat &gt;file_unique.txt
</code></pre>

This is better:

<pre><code>echo 'hello, world'
less file.txt
sort file.txt | uniq &gt;file_unique.txt
</code></pre>

blocks|key|1128073|text|您可以使用FIFO和临时文件来执行此操作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1128074|input=/some/big/file
mkfifo+tmp
wc+-l+<tmp+>wc.out+&
md5=$(tee+<"$input"+tmp+%7C+md5sum)
fg
lines=$(cat+wc.out)
rm+tmp
rm+wc.out|code-block|syntax|javascript|1128075|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|$]]

You can do this with a FIFO and temporary files.

<pre><code>input=/some/big/file
mkfifo tmp
wc -l &lt;tmp &gt;wc.out &amp;
md5=$(tee &lt;"$input" tmp | md5sum)
fg
lines=$(cat wc.out)
rm tmp
rm wc.out
</code></pre>

blocks|key|1122561|text|我不认为您可以从>()+(Process+substitution)中导出变量。如果您不介意将输出重定向到临时文件，那么只需将文件读入变量即可。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1122562|示例|1122563|tee+<+/some/big/file+>(cmd1+>+tmp1)+>(cmd2+>+tmp2)+%7C+...
CMD1_OUT=$(cat+tmp1)
CMD2_OUT=$(cat+tmp2)|code-block|syntax|javascript|1122564|entityMap|0|LINK|mutability|MUTABLE|url|http://tldp.org/LDP/abs/html/process-sub.html^0|8|3|D|K|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|6|7|10|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|11|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

I don't think you can export a variable from the <code>&gt;()</code> (<a href="http://tldp.org/LDP/abs/html/process-sub.html" rel="nofollow">Process substitution</a>). If you don't mind redirecting the output to temporary files you can then just read the file into a variable.

Example

<pre><code>tee &lt; /some/big/file &gt;(cmd1 &gt; tmp1) &gt;(cmd2 &gt; tmp2) | ...
CMD1_OUT=$(cat tmp1)
CMD2_OUT=$(cat tmp2)
</code></pre>

I have this:

<pre><code>tee &lt; /some/big/file &gt;(wc -c) &gt;(md5sum) | ...
</code></pre>

Instead of writing the results of <code>wc -c</code> and <code>md5sum</code> to stdout, I want to store the results into two variables for later processing. I don't want to read the file more than once. How can I accomplish that?

How to store the output of a Bash command inside >() in a variable?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有这个：tee < /some/big/file >(wc -c) >(md5sum) | ...我不想将wc -c和md5sum的结果写到标准输出中，而是希望将结果存储到两个变量中，以便以后处理。我不想多次读取该文件。我如何才能做到这一点？

问如何将Bash命令的输出存储在>()中的变量中？
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问如何将Bash命令的输出存储在>()中的变量中？EN