blocks|key|1712076|text|我不知道sed如何，但可以用head完成|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1712077|head+-n+-2+myfile.txt|code-block|syntax|javascript|1712078|entityMap^0|4|3|E|4|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

I don't know about <code>sed</code>, but it can be done with <code>head</code>:

<pre><code>head -n -2 myfile.txt
</code></pre>

blocks|key|1926138|text|如果可以选择硬编码n，则可以使用对sed的顺序调用。例如，要删除最后三行，请删除最后一行三次：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1926139|sed+'$d'+file+%7C+sed+'$d'+%7C+sed+'$d'|code-block|syntax|javascript|1926140|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|$]]

If hardcoding n is an option, you can use sequential calls to sed. For instance, to delete the last three lines, delete the last one line thrice:

<pre><code>sed '$d' file | sed '$d' | sed '$d'
</code></pre>

blocks|key|1712484|text|从sed+one-liners|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1712485|#+delete+the+last+10+lines+of+a+file
sed+-e+:a+-e+'$d;N;2,10ba'+-e+'P;D'+++#+method+1
sed+-n+-e+:a+-e+'1,10!{P;N;D;};N;ba'++#+method+2|code-block|syntax|javascript|1712486|看起来就是你要找的。|1712487|entityMap|0|LINK|mutability|MUTABLE|url|http://www.unixguide.net/unix/sedoneliner.shtml^0|1|E|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

From the <a href="http://www.unixguide.net/unix/sedoneliner.shtml">sed one-liners</a>:

<pre><code># delete the last 10 lines of a file
sed -e :a -e '$d;N;2,10ba' -e 'P;D' # method 1
sed -n -e :a -e '1,10!{P;N;D;};N;ba' # method 2
</code></pre>

Seems to be what you are looing for.

blocks|key|1926343|text|为了完整起见，我想添加我的解决方案。我最终用标准的ed完成了这项工作|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1926344|ed+-s+sometextfile+<<<+$'-2,$d\nwq'|code-block|syntax|javascript|1926345|这将使用就地编辑删除最后两行(尽管它使用了/tmp中的临时文件!!)|1926346|entityMap^0|P|2|0|0|L|4|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|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

Just for completeness I would like to add my solution.
I ended up doing this with the standard <code>ed</code>:

<pre><code>ed -s sometextfile &lt;&lt;&lt; $'-2,$d\nwq'
</code></pre>

This deletes the last 2 lines using in-place editing (although it does use a temporary file in <code>/tmp</code> !!)

blocks|key|1713241|text|要真正就地截断非常大的文件，我们可以使用truncate命令。它不知道行，但tail+%2B+wc可以将行转换为字节：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1713242|file=bigone.log
lines=3
truncate+-s+-$(tail+-$lines+$file+%7C+wc+-c)+$file|code-block|syntax|javascript|1713243|如果同时写入文件，则存在明显的竞争条件。在这种情况下，使用head可能更好-它从文件的开头开始计算字节(注意磁盘IO)，所以我们将始终在行边界上截断(如果文件被主动写入，可能会比预期的更多)：|1713244|truncate+-s+$(head+-n+-$lines+$file+%7C+wc+-c)+$file|1713245|如果登录尝试失败，请将密码替换为用户名，这很方便：|1713246|truncate+-s+$(head+-n+-5+/var/log/secure+%7C+wc+-c)+/var/log/secure|1713247|entityMap^0|K|8|12|4|19|2|0|0|T|4|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]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|16|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|T|$]]

To truncate very large files truly in-place we have <code>truncate</code> command.
It doesn't know about lines, but <code>tail</code> + <code>wc</code> can convert lines to bytes:

<pre><code>file=bigone.log
lines=3
truncate -s -$(tail -$lines $file | wc -c) $file
</code></pre>

There is an obvious race condition if the file is written at the same time.
In this case it may be better to use <code>head</code> - it counts bytes from the beginning of file (mind disk IO), so we will always truncate on line boundary (possibly more lines than expected if file is actively written): 

<pre><code>truncate -s $(head -n -$lines $file | wc -c) $file
</code></pre>

Handy one-liner if you fail login attempt putting password in place of username:

<pre><code>truncate -s $(head -n -5 /var/log/secure | wc -c) /var/log/secure
</code></pre>

blocks|key|1926037|text|这可能适用于您(GNU+sed)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1926038|sed+':a;$!N;1,4ba;P;$d;D'+file|code-block|syntax|javascript|1926039|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|$]]

This might work for you (GNU sed):

<pre><code>sed ':a;$!N;1,4ba;P;$d;D' file
</code></pre>

blocks|key|1712676|text|上面的大多数答案似乎都需要GNU命令/扩展：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1712677|++++$+head+-n+-2+myfile.txt
++++-2:+Badly+formed+number|code-block|syntax|javascript|1712678|要获得更具可移植性的解决方案：|1712679|+++++perl+-ne+'push(@fifo,$_);print+shift(@fifo)+if+@fifo+>+10;'|1712680|或|1712681|+++++perl+-ne+'push(@buf,$_);END{print+@buf[0+...+$#buf-10]}'|1712682|1712683|+++++awk+'{buf[NR-1]=$0;}END{+for+(+i=0;+i+<+(NR-10);+i%2B%2B){+print+buf[i];}+}'|1712684|其中"10“是"n”。|1712685|entityMap^0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|X|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Z|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|O|3|L|5|6|7|11|8|@]|9|@]|A|$]]|$1|P|3|Q|5|D|7|12|8|@]|9|@]|A|$E|F]]|$1|R|3|S|5|6|7|13|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|U|$]]

Most of the above answers seem to require GNU commands/extensions:

<pre><code> $ head -n -2 myfile.txt
 -2: Badly formed number
</code></pre>

For a slightly more portible solution:

<pre><code> perl -ne 'push(@fifo,$_);print shift(@fifo) if @fifo &gt; 10;'
</code></pre>

OR

<pre><code> perl -ne 'push(@buf,$_);END{print @buf[0 ... $#buf-10]}'
</code></pre>

OR

<pre><code> awk '{buf[NR-1]=$0;}END{ for ( i=0; i &lt; (NR-10); i++){ print buf[i];} }'
</code></pre>

Where "10" is "n".

blocks|key|1926023|text|有了这里的答案，您已经了解到sed不是适用于此应用程序的最佳工具。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1926024|然而，我确实认为在使用sed时有一种方法可以做到这一点；其思想是附加N行来容纳空间，直到您能够在不使用EOF的情况下进行读取。当命中EOF时，打印hold空格的内容并退出。|1926025|sed+-e+'$!{N;N;N;N;N;N;H;}'+-e+x|code-block|syntax|javascript|1926026|上面的sed命令将省略最后5行。|1926027|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

With the answers here you'd have already learnt that sed is not the best tool for this application. 

However I do think there is a way to do this in using sed; the idea is to append N lines to hold space untill you are able read without hitting EOF. When EOF is hit, print the contents of hold space and quit.

<pre><code>sed -e '$!{N;N;N;N;N;N;H;}' -e x
</code></pre>

The sed command above will omit last 5 lines.

blocks|key|1713493|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1713494|a)统计您要编辑的文件的行数：|1713495|+n=`cat+myfile+%7Cwc+-l`|code-block|syntax|javascript|1713496|b)从该数字中减去要删除的行数：|1713497|+x=$((n-3))|1713498|c)告诉sed从行号($x)删除到末尾：|offset|length|style|CODE|1713499|+sed+"$x,\$d"+myfile|1713500|entityMap^0|0|0|0|0|0|B|2|0|0^^$0|@$1|2|3|-4|4|5|6|V|7|@]|8|@]|9|$]]|$1|A|3|B|4|5|6|W|7|@]|8|@]|9|$]]|$1|C|3|D|4|E|6|X|7|@]|8|@]|9|$F|G]]|$1|H|3|I|4|5|6|Y|7|@]|8|@]|9|$]]|$1|J|3|K|4|E|6|Z|7|@]|8|@]|9|$F|G]]|$1|L|3|M|4|5|6|10|7|@$N|11|O|12|P|Q]]|8|@]|9|$]]|$1|R|3|S|4|E|6|13|7|@]|8|@]|9|$F|G]]|$1|T|3|-4|4|5|6|14|7|@]|8|@]|9|$]]]|U|$]]

It can be done in 3 steps:

a) Count the number of lines in the file you want to edit:

<pre><code> n=`cat myfile |wc -l`
</code></pre>

b) Subtract from that number the number of lines to delete:

<pre><code> x=$((n-3))
</code></pre>

c) Tell sed to delete from that line number (<code>$x</code>) to the end:

<pre><code> sed "$x,\$d" myfile
</code></pre>

blocks|key|1926103|text|您可以使用wc+-l+<file>获得行的总数，并使用|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1926104|head+-n+<total+lines+-+lines+to+remove>+<file>|1926105|entityMap^0|5|C|0|0|1A|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

You can get the total count of lines with <code>wc -l &lt;file&gt;</code> and use

<code>head -n &lt;total lines - lines to remove&gt; &lt;file&gt;</code>

blocks|key|1926306|text|尝试执行以下命令：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1926307|n+=+line+number
tail+-r+file_name+%7C+sed+'1,nd'+%7C+tail+-r|code-block|syntax|javascript|1926308|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|$]]

Try the following command:

<pre><code>n = line number
tail -r file_name | sed '1,nd' | tail -r
</code></pre>

blocks|key|1712829|text|这将从file中删除最后3行|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1712830|for+i+in+$(seq+1+3);+do+sed+-i+'$d'+file;+done;|1712831|entityMap^0|3|4|0|0|1B|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

This will remove the last 3 lines from <code>file</code>:

<code>for i in $(seq 1 3); do sed -i '$d' file; done;</code>

blocks|key|1926205|text|我更喜欢这个解决方案；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1926206|head+-$(gcalctool+-s+$(cat+file+%7C+wc+-l)-N)+file|code-block|syntax|javascript|1926207|其中N是要删除的行数。|1926208|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|$]]

I prefer this solution;

<pre><code>head -$(gcalctool -s $(cat file | wc -l)-N) file
</code></pre>

where N is the number of lines to remove.

blocks|key|1712705|text|要删除最后4行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1712706|$+nl+-b+a+file+%7C+sort+-k1,1nr+%7C+sed+'1,+4+d'+%7C+sort+-k1,1n+%7C+sed+'s/%5E+*[0-9]*\t//'+++|code-block|syntax|javascript|1712707|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|$]]

To delete last 4 lines:

<pre><code>$ nl -b a file | sort -k1,1nr | sed '1, 4 d' | sort -k1,1n | sed 's/^ *[0-9]*\t//' 
</code></pre>

blocks|key|1712723|text|sed+-n+':pre
1,4+{N;b+pre
++++}
:cycle
$!{P;N;D;b+cycle
++}'+YourFile|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1712724|posix版本|unstyled|1712725|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>sed -n ':pre
1,4 {N;b pre
 }
:cycle
$!{P;N;D;b cycle
 }' YourFile
</code></pre>

posix version

blocks|key|1927156|text|为了删除文件的最后N行，您可以使用相同的概念|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1927157|$+sed+'2,4d'+file|code-block|syntax|javascript|1927158|您可以使用combo+with+tail命令来反转文件:如果N是5|1927159|$+tail+-r+file+%7C+sed+'1,5d'+file+%7C+tail+-r+>+file|1927160|而且这种方式也可以在head+-n+-5+file命令不能运行的地方运行(就像在mac上一样！)。|offset|length|style|CODE|1927161|entityMap^0|0|0|0|0|A|F|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]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@$M|X|N|Y|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

For deleting the last N lines of a file, you can use the same concept of

<pre><code>$ sed '2,4d' file
</code></pre>

You can use a combo with tail command to reverse the file: if N is 5

<pre><code>$ tail -r file | sed '1,5d' file | tail -r &gt; file
</code></pre>

And this way runs also where <code>head -n -5 file</code> command doesn't run (like on a mac!).

blocks|key|1713646|text|在docker中，这对我很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1713647|head+--lines=-N+file_path+>>+file_path|code-block|syntax|javascript|1713648|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|$]]

In docker, this worked for me:
<pre><code>head --lines=-N file_path &gt;&gt; file_path
</code></pre>

blocks|key|1713664|text|#!/bin/sh

echo+'Enter+the+file+name+:+'
read+filename

echo+'Enter+the+number+of+lines+from+the+end+that+needs+to+be+deleted+:'
read+n

#Subtracting+from+the+line+number+to+get+the+nth+line
m=`expr+$n+-+1`

#+Calculate+length+of+the+file
len=`cat+$filename%7Cwc+-l`

#Calculate+the+lines+that+must+remain
lennew=`expr+$len+-+$m`

sed+"$lennew,$+d"+$filename|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1713665|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|$]]

<pre class="lang-sh prettyprint-override"><code>#!/bin/sh

echo 'Enter the file name : '
read filename

echo 'Enter the number of lines from the end that needs to be deleted :'
read n

#Subtracting from the line number to get the nth line
m=`expr $n - 1`

# Calculate length of the file
len=`cat $filename|wc -l`

#Calculate the lines that must remain
lennew=`expr $len - $m`

sed &quot;$lennew,$ d&quot; $filename
</code></pre>

blocks|key|1713518|text|这将删除最后12行|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1713519|sed+-n+-e+:a+-e+'1,10!{P;N;D;};N;ba'|code-block|syntax|javascript|1713520|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|$]]

This will remove the last 12 lines

<pre><code>sed -n -e :a -e '1,10!{P;N;D;};N;ba'
</code></pre>

I want to remove some n lines from the end of a file. Can this be done using sed?

For example, to remove lines from 2 to 4, I can use

<pre><code>$ sed '2,4d' file
</code></pre>

But I don't know the line numbers. I can delete the last line using 

<pre><code>$sed $d file
</code></pre>

but I want to know the way to remove n lines from the end. Please let me know how to do that using sed or some other method.

How to use sed to remove the last n lines of a file

Docker

我想从文件的末尾删除一些n行。使用sed可以做到这一点吗？例如，要删除从2到4的行，我可以使用$ sed '2,4d' file但我不知道行号。我可以使用以下命令删除最后一行$sed $d file但我想知道从末尾删除n行的方法。请告诉我如何使用sed或其他方法来做这件事。

问如何使用sed删除文件的最后n行
EN

回答 19

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问如何使用sed删除文件的最后n行
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