UNIX:用冒号替换换行符，在EOF之前保留换行符 [英] UNIX: Replace Newline w/ Colon, Preserving Newline Before EOF

问题描述

我有一个文本文件("INPUT.txt")，格式为:

I have a text file ("INPUT.txt") of the format:

A<LF>
B<LF>
C<LF>
D<LF>
X<LF>
Y<LF>
Z<LF>
<EOF>

我需要重新格式化为:

A:B:C:D:X:Y:Z<LF>
<EOF>

我知道您可以使用"sed"来做到这一点.通过"sed"实现此目标的Google点击量高达10亿.但是我试图强调可读性，简单性，并使用正确的工具来完成正确的工作. "sed"是一个使用和隐藏换行符的行编辑器.可能不是这项工作的正确工具！

I know you can do this with 'sed'. There's a billion google hits for doing this with 'sed'. But I'm trying to emphasis readability, simplicity, and using the correct tool for the correct job. 'sed' is a line editor that consumes and hides newlines. Probably not the right tool for this job!

我认为这项工作的正确工具是"tr".我可以使用以下命令用冒号替换所有换行符:

I think the correct tool for this job would be 'tr'. I can replace all the newlines with colons with the command:

cat INPUT.txt | tr '\n' ':'

我完成了99％的工作.不过，我现在有一个问题.通过用冒号替换所有换行符，我不仅在序列的末尾得到了一个多余的冒号，而且在输入的末尾也丢失了回车符.看起来像这样:

There's 99% of my work done. I have a problem, now, though. By replacing all the newlines with colons, I not only get an extraneous colon at the end of the sequence, but I also lose the carriage return at the end of the input. It looks like this:

A:B:C:D:X:Y:Z:<EOF>

现在，我需要从输入末尾删除冒号.但是，如果我尝试通过"sed"传递此处理后的输入以删除最后一个冒号(我认为现在应该正确使用"sed")，我会发现自己遇到了第二个问题.输入完全不再由换行符终止！对于所有命令，"sed"都将彻底失败，因为它永远找不到输入的第一行的结尾！

Now, I need to remove the colon from the end of the input. However, if I attempt to pass this processed input through 'sed' to remove the final colon (which would now, I think, be a proper use of 'sed'), I find myself with a second problem. The input is no longer terminated by a newline at all! 'sed' fails outright, for all commands, because it never finds the end of the first line of input!

似乎在某些输入的末尾添加换行符是非常非常常见的任务，并且考虑到我自己非常想写一个程序用C语言来完成(这需要大约八行代码) ，我无法想象还没有一种非常简单的方法可以使用Linux内核中已经可用的工具来做到这一点.

It seems like appending a newline to the end of some input is a very, very common task, and considering I myself was just sorely tempted to write a program to do it in C (which would take about eight lines of code), I can't imagine there's not already a very simple way to do this with the tools already available to you in the Linux kernel.

推荐答案

这应该可以完成(不需要cat和echo):

This should do the job (cat and echo are unnecessary):

tr '\n' ':' < INPUT.TXT | sed 's/:$/\n/'

仅使用sed:

sed -n ':a; $ ! {N;ba}; s/\n/:/g;p' INPUT.TXT

没有任何外部条件的重击:

Bash without any externals:

string=($(<INPUT.TXT))
string=${string[@]/%/:}
string=${string//: /:}
string=${string%*:}

在sh中使用循环:

colon=''
while read -r line
do
    string=$string$colon$line
    colon=':'
done < INPUT.TXT

使用AWK:

awk '{a=a colon $0; colon=":"} END {print a}' INPUT.TXT

或者:

awk '{printf colon $0; colon=":"} END {printf "\n" }' INPUT.TXT

这是纯Bash的另一种方式:

Here's another way in pure Bash:

string=($(<INPUT.TXT))
saveIFS=$IFS
IFS=':'
newstring="${string[*]}"
IFS=$saveIFS

这是 使用echo的另一种方式:

Here's yet another way which does use echo:

echo "$(tr '\n' ':' < INPUT.TXT | head -c -1)"

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