blocks|key|331283|text|使用sed，只是为了多样化：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|331284|ls+-l+%7C+sed+-n+2p|code-block|syntax|javascript|331285|使用此替代方案看起来更有效，因为它在打印所需行时停止读取输入，可能会在进给过程中生成SIGPIPE，这可能会生成不需要的错误消息：|331286|ls+-l+%7C+sed+-n+-e+'2{p;q}'|331287|我经常看到这种情况，所以我通常使用第一个(无论如何，它更容易输入)，尽管ls不是一个当它获得SIGPIPE时会抱怨的命令。|331288|对于一系列行：|331289|ls+-l+%7C+sed+-n+2,4p|331290|对于多个行范围：|331291|ls+-l+%7C+sed+-n+-e+2,4p+-e+20,30p
ls+-l+%7C+sed+-n+-e+'2,4p;20,30p'|331292|entityMap^0|2|3|0|0|0|0|10|2|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|19|8|@]|D|@]|E|$]]|$1|S|3|T|5|H|7|1A|8|@]|D|@]|E|$I|J]]|$1|U|3|V|5|6|7|1B|8|@]|D|@]|E|$]]|$1|W|3|X|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|Y|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|Z|$]]

Using <code>sed</code>, just for variety:

<pre><code>ls -l | sed -n 2p
</code></pre>

Using this alternative, which looks more efficient since it stops reading the input when the required line is printed, may generate a SIGPIPE in the feeding process, which may in turn generate an unwanted error message:

<pre><code>ls -l | sed -n -e '2{p;q}'
</code></pre>

I've seen that often enough that I usually use the first (which is easier to type, anyway), though <code>ls</code> is not a command that complains when it gets SIGPIPE.

For a range of lines:

<pre><code>ls -l | sed -n 2,4p
</code></pre>

For several ranges of lines:

<pre><code>ls -l | sed -n -e 2,4p -e 20,30p
ls -l | sed -n -e '2,4p;20,30p'
</code></pre>

blocks|key|328579|text|ls+-l+%7C+head+-2+%7C+tail+-1|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|328580|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

blocks|key|328588|text|除了漂亮的头部/尾部方式之外：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|328589|ls+-al+%7C+awk+'NR==2'|code-block|syntax|javascript|328590|或|328591|ls+-al+%7C+sed+-n+'2p'|328592|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Alternative to the nice head / tail way:

<pre><code>ls -al | awk 'NR==2'
</code></pre>

or

<pre><code>ls -al | sed -n '2p'
</code></pre>

blocks|key|330144|text|来自sed1line|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|330145|#+print+line+number+52
sed+-n+'52p'+++++++++++++++++#+method+1
sed+'52!d'+++++++++++++++++++#+method+2
sed+'52q;d'++++++++++++++++++#+method+3,+efficient+on+large+files|code-block|syntax|javascript|330146|来自awk1line|330147|#+print+line+number+52
awk+'NR==52'
awk+'NR==52+{print;exit}'++++++++++#+more+efficient+on+large+files|330148|entityMap|0|LINK|mutability|MUTABLE|url|http://sed.sf.net/sed1line.txt|1|http://www.pement.org/awk/awk1line.txt^0|2|8|0|0|0|2|8|1|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]]|C|$]]|$1|K|3|L|5|F|7|15|8|@]|9|@]|C|$G|H]]|$1|M|3|-4|5|6|7|16|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

From <a href="http://sed.sf.net/sed1line.txt" rel="noreferrer">sed1line</a>:

<pre><code># print line number 52
sed -n '52p' # method 1
sed '52!d' # method 2
sed '52q;d' # method 3, efficient on large files
</code></pre>

From <a href="http://www.pement.org/awk/awk1line.txt" rel="noreferrer">awk1line</a>:

<pre><code># print line number 52
awk 'NR==52'
awk 'NR==52 {print;exit}' # more efficient on large files
</code></pre>

blocks|key|3089630|text|为了完整起见;-)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3089631|更短的代码|3089632|find+/+%7C+awk+NR==3|code-block|syntax|javascript|3089633|寿命较短|3089634|find+/+%7C+awk+'NR==3+{print+$0;+exit}'|3089635|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

For the sake of completeness ;-)

shorter code

<pre><code>find / | awk NR==3
</code></pre>

shorter life

<pre><code>find / | awk 'NR==3 {print $0; exit}'
</code></pre>

blocks|key|331258|text|试试这个sed版本：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|331259|ls+-l+%7C+sed+'2+!+d'|code-block|syntax|javascript|331260|上面写着“删除不是第二行的所有行”。|331261|entityMap^0|4|3|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Try this <code>sed</code> version:

<pre><code>ls -l | sed '2 ! d'
</code></pre>

It says "delete all the lines that aren't the second one".

blocks|key|3089762|text|您可以使用awk：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3089763|ls+-l+%7C+awk+'NR==2'|code-block|syntax|javascript|3089764|更新|3089765|由于off-by-one错误，上面的代码不会得到我们想要的结果：ls+-l命令的第一行是合计行。为此，以下修改后的代码将起作用：|offset|length|style|BOLD|3089766|ls+-l+%7C+awk+'NR==3'|3089767|entityMap^0|0|0|0|W|5|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@$K|W|L|X|M|N]]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

You can use awk:

<pre><code>ls -l | awk 'NR==2'
</code></pre>

<h3>Update</h3>

The above code will not get what we want because of off-by-one error: the ls -l command's first line is the total line. For that, the following revised code will work:

<pre><code>ls -l | awk 'NR==3'
</code></pre>

blocks|key|3302515|text|Perl对您来说容易吗？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3302516|$+perl+-n+-e+'if+($.+==+7)+{+print;+exit(0);+}'|code-block|syntax|javascript|3302517|显然，用你想要的任何数字代替7。|3302518|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|$]]

Is Perl easily available to you?

<pre><code>$ perl -n -e 'if ($. == 7) { print; exit(0); }'
</code></pre>

Obviously substitute whatever number you want for 7.

blocks|key|3089836|text|另一张海报建议|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3089837|ls+-l+%7C+head+-2+%7C+tail+-1|code-block|syntax|javascript|3089838|但是如果你把头插入尾巴，看起来直到第N行的所有东西都被处理了两次。|3089839|将尾部连接到头部|3089840|ls+-l+%7C+tail+-n+%2B2+%7C+head+-n1|3089841|会更有效率吗？|3089842|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

Another poster suggested

<pre><code>ls -l | head -2 | tail -1
</code></pre>

but if you pipe head into tail, it looks like everything up to line N is processed twice.

Piping tail into head

<pre><code>ls -l | tail -n +2 | head -n1
</code></pre>

would be more efficient?

blocks|key|330140|text|是的，最有效的方法(如Jonathan+Leffler已经指出的)是将sed与print+&quit一起使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|330141|set+-o+pipefail++++++++++++++++++++++++#+cf.+help+set
time+-p+ls+-l+%7C+sed+-n+-e+'2{p;q;}'++++#+only+print+the+second+line+&+quit+(on+Mac+OS+X)
echo+"$?:+${PIPESTATUS[*]}"++++++++++++#+cf.+man+bash+%7C+less+-p+'PIPESTATUS'|code-block|syntax|javascript|330142|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|$]]

Yes, the most efficient way (as already pointed out by Jonathan Leffler) is to use sed with print &amp; quit:

<pre><code>set -o pipefail # cf. help set
time -p ls -l | sed -n -e '2{p;q;}' # only print the second line &amp; quit (on Mac OS X)
echo "$?: ${PIPESTATUS[*]}" # cf. man bash | less -p 'PIPESTATUS'
</code></pre>

blocks|key|3302699|text|嗯|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3302700|在我的情况下，sed不起作用。我建议：|3302701|“奇数”行1，3，5，7的|3302702|+...ls+%7Cawk+'0+==+(NR%2B1)+%25+2‘|blockquote|3302703|3302704|对于"even“行2,4,6,8+ls+%7Cawk+'0+==+(NR)+%25+2'|3302705|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|P|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|Q|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|R|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|S|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|M|$]]

Hmm

sed did not work in my case.
I propose:

<blockquote>
 for "odd" lines 1,3,5,7... ls |awk '0 == (NR+1) % 2'
 
 for "even" lines 2,4,6,8 ls |awk '0 == (NR) % 2'
</blockquote>

blocks|key|3089730|text|为了更完整..|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3089731|ls+-l+%7C+(for+((x=0;x<2;x%2B%2B))+;+do+read+;+done+;+head+-n1)|code-block|syntax|javascript|3089732|去掉第二行，然后打印出第一行。所以，它打印第三行。|3089733|如果这只是第二行..|3089734|ls+-l+%7C+(read;+head+-n1)|3089735|根据需要放入尽可能多的‘read’。|3089736|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

For more completeness..

<pre><code>ls -l | (for ((x=0;x&lt;2;x++)) ; do read ; done ; head -n1)
</code></pre>

Throw away lines until you get to the second, then print out the first line after that. So, it prints the 3rd line.

If it's just the second line..

<pre><code>ls -l | (read; head -n1)
</code></pre>

Put as many 'read's as necessary.

Is there any bash command that will let you get the nth line of STDOUT?

That is to say, something that would take this

<pre><code>$ ls -l
-rw-r--r--@ 1 root wheel my.txt
-rw-r--r--@ 1 root wheel files.txt
-rw-r--r--@ 1 root wheel here.txt
</code></pre>

and do something like

<pre><code>$ ls -l | magic-command 2
-rw-r--r--@ 1 root wheel files.txt
</code></pre>

I realize this would be bad practice when writing scripts meant to be reused, BUT when working with the shell day to day it'd be useful to me to be able to filter my STDOUT in such a way. 

I also realize this would be semi-trivial command to write (buffer STDOUT, return a specific line), but I want to know if there's some standard shell command to do this that would be available without me dropping a script into place.

Command to get nth line of STDOUT

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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有没有什么bash命令可以让你得到STDOUT的第n行？这就是说，一些需要这个的东西$ ls -l-rw-r--r--@ 1 root  wheel my.txt-rw-r--r--@ 1 root  wheel files.txt-rw-r--r--@ 1 root  wheel here.txt然后做一些像这样的事情$ ls -l | magic-command 2-rw-r--r--@ 1 

问获取STDOUT第n行的命令
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