blocks|key|1203606|text|gawk|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1203607|+++awk+'{q=p;p=$0}NR>1{print+q}END{ORS+=+"";+print+p}'+file|code-block|syntax|javascript|1203608|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|$]]

gawk

<pre><code> awk '{q=p;p=$0}NR&gt;1{print q}END{ORS = ""; print p}' file
</code></pre>

blocks|key|1418785|text|还有另一个perl+WTDI：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1418786|perl+-i+-p0777we's/\n\z//'+filename|code-block|syntax|javascript|1418787|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|$]]

Yet another perl WTDI:

<pre><code>perl -i -p0777we's/\n\z//' filename
</code></pre>

blocks|key|1203655|text|我只有一次想要这样做，就是为了编写代码，然后我将代码从文件中复制出来，并将其粘贴到echo+-n+'content'>file语句中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1203656|entityMap^0|15|M|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

The only time I've wanted to do this is for code golf, and then I've just copied my code out of the file and pasted it into an <code>echo -n 'content'&gt;file</code> statement.

blocks|key|1203734|text|如果你想把它做好，你需要这样的东西：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1203735|use+autodie+qw(open+sysseek+sysread+truncate);

my+$file+=+shift;
open+my+$fh,+'%2B>>',+$file;
my+$pos+=+tell+$fh;
sysseek+$fh,+$pos+-+1,+0;
sysread+$fh,+my+$buf,+1+or+die+'No+data+to+read?';

if($buf+eq+"\n"){
++++truncate+$fh,+$pos+-+1;
}|code-block|syntax|javascript|1203736|我们打开文件进行读取和追加；打开进行追加意味着我们已经seek到了文件的末尾。然后，我们使用tell获得文件末尾的数字位置。我们用这个数字找回一个字符，然后我们读取那个字符。如果是换行符，我们将文件截断为换行符之前的字符，否则，我们什么也不做。|offset|length|style|CODE|1203737|对于任何输入，它都以恒定的时间和恒定的空间运行，并且也不需要更多的磁盘空间。|1203738|entityMap^0|0|0|R|4|1A|4|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]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]|$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|P|$]]

If you want to do it right, you need something like this:

<pre><code>use autodie qw(open sysseek sysread truncate);

my $file = shift;
open my $fh, '+&gt;&gt;', $file;
my $pos = tell $fh;
sysseek $fh, $pos - 1, 0;
sysread $fh, my $buf, 1 or die 'No data to read?';

if($buf eq "\n"){
 truncate $fh, $pos - 1;
}
</code></pre>

We open the file for reading and appending; opening for appending means that we are already <code>seek</code>ed to the end of the file. We then get the numerical position of the end of the file with <code>tell</code>. We use that number to seek back one character, and then we read that one character. If it's a newline, we truncate the file to the character before that newline, otherwise, we do nothing.

This runs in constant time and constant space for any input, and doesn't require any more disk space, either.

blocks|key|1203815|text|这是一个很好的、整洁的Python解决方案。我不想在这里简明扼要。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1203816|这会就地修改文件，而不是制作文件的副本并从副本的最后一行中剥离换行符。如果文件很大，这将比被选为最佳答案的Perl解决方案快得多。|1203817|如果最后两个字节是CR/+LF，则将文件截断两个字节；如果最后一个字节是LF，则截断一个字节。如果最后一个字节不是(CR)LF，它不会尝试修改文件。它处理错误。在Python+2.6中测试。|1203818|将其放入一个名为"striplast“的文件中，并使用chmod+%2Bx+striplast。|offset|length|style|CODE|1203819|#!/usr/bin/python

#+strip+newline+from+last+line+of+a+file


import+sys

def+trunc(filename,+new_len):
++++try:
++++++++#+open+with+mode+"append"+so+we+have+permission+to+modify
++++++++#+cannot+open+with+mode+"write"+because+that+clobbers+the+file!
++++++++f+=+open(filename,+"ab")
++++++++f.truncate(new_len)
++++++++f.close()
++++except+IOError:
++++++++print+"cannot+write+to+file:",+filename
++++++++sys.exit(2)

#+get+input+argument
if+len(sys.argv)+==+2:
++++filename+=+sys.argv[1]
else:
++++filename+=+"--help"++#+wrong+number+of+arguments+so+print+help

if+filename+==+"--help"+or+filename+==+"-h"+or+filename+==+"/?":
++++print+"Usage:+%25s+<filename>"+%25+sys.argv[0]
++++print+"Strips+a+newline+off+the+last+line+of+a+file."
++++sys.exit(1)


try:
++++#+must+have+mode+"b"+(binary)+to+allow+f.seek()+with+negative+offset
++++f+=+open(filename,+"rb")
except+IOError:
++++print+"file+does+not+exist:",+filename
++++sys.exit(2)


SEEK_EOF+=+2
f.seek(-2,+SEEK_EOF)++#+seek+to+two+bytes+before+end+of+file

end_pos+=+f.tell()

line+=+f.read()
f.close()

if+line.endswith("\r\n"):
++++trunc(filename,+end_pos)
elif+line.endswith("\n"):
++++trunc(filename,+end_pos+%2B+1)|code-block|syntax|javascript|1203820|附注:本着"Perl+golf“的精神，下面是我最简短的Python解决方案。它将整个文件从标准输入存储到内存中，去掉末尾的所有换行符，并将结果写入标准输出。没有Perl那么简洁；对于像这样的小的、棘手的、快速的东西，您是无法胜过Perl的。|1203821|从对.rstrip()的调用中删除"\n“，它将剥离文件末尾的所有空白，包括多个空白行。|1203822|将此代码放入"slurp_and_chomp.py“中，然后运行python+slurp_and_chomp.py+<+inputfile+>+outputfile。|1203823|import+sys

sys.stdout.write(sys.stdin.read().rstrip("\n"))|1203824|entityMap^0|0|0|0|R|I|0|0|0|2|9|0|W|1E|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|12|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|13|8|@$H|14|I|15|J|K]]|9|@]|A|$]]|$1|L|3|M|5|N|7|16|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|18|8|@$H|19|I|1A|J|K]]|9|@]|A|$]]|$1|U|3|V|5|6|7|1B|8|@$H|1C|I|1D|J|K]]|9|@]|A|$]]|$1|W|3|X|5|N|7|1E|8|@]|9|@]|A|$O|P]]|$1|Y|3|-4|5|6|7|1F|8|@]|9|@]|A|$]]]|Z|$]]

Here is a nice, tidy Python solution. I made no attempt to be terse here.

This modifies the file in-place, rather than making a copy of the file and stripping the newline from the last line of the copy. If the file is large, this will be much faster than the Perl solution that was chosen as the best answer.

It truncates a file by two bytes if the last two bytes are CR/LF, or by one byte if the last byte is LF. It does not attempt to modify the file if the last byte(s) are not (CR)LF. It handles errors. Tested in Python 2.6.

Put this in a file called "striplast" and <code>chmod +x striplast</code>.

<pre><code>#!/usr/bin/python

# strip newline from last line of a file


import sys

def trunc(filename, new_len):
 try:
 # open with mode "append" so we have permission to modify
 # cannot open with mode "write" because that clobbers the file!
 f = open(filename, "ab")
 f.truncate(new_len)
 f.close()
 except IOError:
 print "cannot write to file:", filename
 sys.exit(2)

# get input argument
if len(sys.argv) == 2:
 filename = sys.argv[1]
else:
 filename = "--help" # wrong number of arguments so print help

if filename == "--help" or filename == "-h" or filename == "/?":
 print "Usage: %s &lt;filename&gt;" % sys.argv[0]
 print "Strips a newline off the last line of a file."
 sys.exit(1)


try:
 # must have mode "b" (binary) to allow f.seek() with negative offset
 f = open(filename, "rb")
except IOError:
 print "file does not exist:", filename
 sys.exit(2)


SEEK_EOF = 2
f.seek(-2, SEEK_EOF) # seek to two bytes before end of file

end_pos = f.tell()

line = f.read()
f.close()

if line.endswith("\r\n"):
 trunc(filename, end_pos)
elif line.endswith("\n"):
 trunc(filename, end_pos + 1)
</code></pre>

P.S. In the spirit of "Perl golf", here's my shortest Python solution. It slurps the whole file from standard input into memory, strips all newlines off the end, and writes the result to standard output. Not as terse as the Perl; you just can't beat Perl for little tricky fast stuff like this.

Remove the "\n" from the call to <code>.rstrip()</code> and it will strip all white space from the end of the file, including multiple blank lines.

Put this into "slurp_and_chomp.py" and then run <code>python slurp_and_chomp.py &lt; inputfile &gt; outputfile</code>.

<pre><code>import sys

sys.stdout.write(sys.stdin.read().rstrip("\n"))
</code></pre>

blocks|key|1419012|text|sed+':a;/%5E\n*$/{$d;N;};/\n$/ba'+file|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1419013|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|1419038|text|使用dd：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1419039|file='/path/to/file'
[[+"$(tail+-c+1+"${file}"+%7C+tr+-dc+'\n'+%7C+wc+-c)"+-eq+1+]]+&&+\
++++printf+""+%7C+dd++of="${file}"+seek=$(($(stat+-f+"%25z"+"${file}")+-+1))+bs=1+count=1
++++#printf+""+%7C+dd++of="${file}"+seek=$(($(wc+-c+<+"${file}")+-+1))+bs=1+count=1|code-block|syntax|javascript|1419040|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|$]]

Using dd:

<pre><code>file='/path/to/file'
[[ "$(tail -c 1 "${file}" | tr -dc '\n' | wc -c)" -eq 1 ]] &amp;&amp; \
 printf "" | dd of="${file}" seek=$(($(stat -f "%z" "${file}") - 1)) bs=1 count=1
 #printf "" | dd of="${file}" seek=$(($(wc -c &lt; "${file}") - 1)) bs=1 count=1
</code></pre>

blocks|key|1203922|text|还有另一个答案FTR+(也是我最喜欢的！)：echo/cat，你想要剥离的东西，并通过反引号捕获输出。最后的换行符将被去掉。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1203923|#+Sadly,+outputs+newline,+and+we+have+to+feed+the+newline+to+sed+to+be+portable
echo+thingy+%7C+sed+-e+'s/thing/sill/'

#+No+newline!+Happy.
out=`echo+thingy+%7C+sed+-e+'s/thing/sill/'`
printf+%25s+"$out"

#+Similarly+for+files:
file=`cat+file_ending_in_newline`
printf+%25s+"$file"+>+file_no_newline|code-block|syntax|javascript|1203924|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|$]]

Yet another answer FTR (and my favourite!): echo/cat the thing you want to strip and capture the output through backticks. The final newline will be stripped. For example:

<pre><code># Sadly, outputs newline, and we have to feed the newline to sed to be portable
echo thingy | sed -e 's/thing/sill/'

# No newline! Happy.
out=`echo thingy | sed -e 's/thing/sill/'`
printf %s "$out"

# Similarly for files:
file=`cat file_ending_in_newline`
printf %s "$file" &gt; file_no_newline
</code></pre>

blocks|key|1419123|text|我也有类似的问题，但是我正在处理一个windows文件，并且需要保留这些CRLF+--我在linux上的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1419124|sed+'s/\r//g'+orig+%7C+awk+'{if+(NR>1)+printf("\r\n");+printf("%25s",$0)}'+>+tweaked|code-block|syntax|javascript|1419125|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|$]]

I had a similar problem, but was working with a windows file and need to keep those CRLF -- my solution on linux:

<pre><code>sed 's/\r//g' orig | awk '{if (NR&gt;1) printf("\r\n"); printf("%s",$0)}' &gt; tweaked
</code></pre>

blocks|key|1419169|text|perl+-pi+-e+'s/\n$//+if(eof)'+your_file|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1419170|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|1204073|text|sed+-n+"1+x;1+!H
$+{x;s/\n*$//p;}
"+YourFile|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1204074|应删除文件中最后一次出现的\n。无法处理大型文件(由于sed缓冲区限制)|unstyled|1204075|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 "1 x;1 !H
$ {x;s/\n*$//p;}
" YourFile
</code></pre>

Should remove any last occurence of \n in file. Not working on huge file (due to sed buffer limitation)

blocks|key|1204105|text|ruby：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1204106|ruby+-ne+'print+$stdin.eof+?+$_.strip+:+$_'|code-block|syntax|javascript|1204107|或者：|1204108|ruby+-ane+'q=p;p=$_;puts+q+if+$.>1;END{print+p.strip!}'|1204109|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|$]]

ruby:

<pre><code>ruby -ne 'print $stdin.eof ? $_.strip : $_'
</code></pre>

or:

<pre><code>ruby -ane 'q=p;p=$_;puts q if $.&gt;1;END{print p.strip!}'
</code></pre>

blocks|key|1204208|text|单行文件的一种非常简单的方法，需要来自coreutils的GNU+echo：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1204209|/bin/echo+-n+$(cat+$file)|code-block|syntax|javascript|1204210|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|$]]

A very simple method for single-line files, requiring GNU echo from coreutils:

<pre><code>/bin/echo -n $(cat $file)
</code></pre>

blocks|key|1204245|text|POSIX+SED：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1204246|'${/%5E$/d}'|offset|length|1204247|$+-+match+last+line


{+COMMANDS+}+-+A+group+of+commands+may+be+enclosed+between+{+and+}+characters.+This+is+particularly+useful+when+you+want+a+group+of+commands+to+be+triggered+by+a+single+address+(or+address-range)+match.|code-block|syntax|javascript|1204248|entityMap|0|LINK|mutability|MUTABLE|url|http://sed.js.org/?gist=82a50915abacbaf9d36801d5ad3d9665^0|0|0|A|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@$D|U|E|V|1|W]]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

POSIX SED:

<a href="http://sed.js.org/?gist=82a50915abacbaf9d36801d5ad3d9665" rel="nofollow">'${/^$/d}'</a>

<pre><code>$ - match last line


{ COMMANDS } - A group of commands may be enclosed between { and } characters. This is particularly useful when you want a group of commands to be triggered by a single address (or address-range) match.
</code></pre>

blocks|key|1204343|text|一个快速的解决方案是使用gnu实用程序truncate。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1204344|[+-z+$(tail+-c1+file)+]+&&+truncate+-s-1+file|code-block|syntax|javascript|1204345|如果文件有尾随的新行，则测试将为真。|1204346|删除非常快，真正到位，不需要新的文件，搜索也是从最后读取一个字节(tail+-c1)。|1204347|entityMap^0|J|8|0|0|0|X|8|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]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

A fast solution is using the gnu utility <code>truncate</code>:

<pre><code>[ -z $(tail -c1 file) ] &amp;&amp; truncate -s-1 file
</code></pre>

The test will be true if the file does have a trailing new line.

The removal is very fast, truly in place, no new file is needed and the search is also reading from the end just one byte (<code>tail -c1</code>).

I have some files that I'd like to delete the last newline if it is the last character in a file. <code>od -c</code> shows me that the command I run does write the file with a trailing new line:

<pre><code>0013600 n t &gt; \n
</code></pre>

I've tried a few tricks with sed but the best I could think of isn't doing the trick:

<pre><code>sed -e '$s/$.*$\n$/\1/' abc
</code></pre>

Any ideas how to do this?

How can I delete a newline if it is the last character in a file?

Python

Perl

我有一些文件，如果最后一个换行符是文件中的最后一个字符，我想删除它。od -c向我展示了我运行的命令确实会在文件的末尾添加一个新行：0013600   n   t  >  \n我已经用sed尝试了一些技巧，但我能想到的最好的办法就是不这样做：sed -e '$s/$.*$\n$/\1/' abc你知道该怎么做吗？

问如果换行符是文件中的最后一个字符，我如何删除它？
EN

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问如果换行符是文件中的最后一个字符，我如何删除它？
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