如何删除文件中除第一个匹配行之外的重复行 [英] how to delete the duplicate lines in file except the first matched line

问题描述

在下面的配置文件中

/etc/fine-tune.conf

我们有重复的行

clean_history_in_os=true

我们要删除包含 clean_history_in_os=true 的所有行除了文件中第一个匹配的行

we want to delete all the lines that include clean_history_in_os=true except the first matched line in the file

到目前为止我所做的是

  sed  -i '/clean_history_in_os=true/d' /etc/fine-tune.conf

但问题是 sed 删除了所有clean_history_in_os=true"行

but the problem is that sed delete all "clean_history_in_os=true" lines

我很乐意得到解决这个问题的想法，

I will happy to get ideas to solve this issue ,

推荐答案

使用 Perl

perl -i -ne'next if /clean_history_in_os=true/ && ++$ok > 1; print' file

这会在该行上增加计数器并且如果 >1 跳过该行，否则打印

This increments the counter when on that line and if > 1 it skips the line, otherwise prints

问题是，如果我们将模式作为 shell 变量，如何将模式传递给 Perl.下面我假设 shell 变量 $VAR 包含字符串 clean_history...

The question came up of how to pass the pattern to Perl if we have it as a shell variable. Below I assume that the shell variable $VAR contains the string clean_history...

在所有这些中，shell 变量的值直接用作正则表达式中的模式.如果它是问题中的文字字符串，则下面的代码如给定.但是，如果可能存在特殊字符，则应将其转义；因此，在正则表达式中使用时，您可能希望在模式之前使用 Q.作为一般注意事项，应该注意不要使用来自 shell 的输入来运行代码(比如在 /e 下).

In all this a shell variable's value is directly used as a pattern in a regex. If it's the literal string from the question then the code below goes as given. However, if there may be special characters they should be escaped; so you may want to precede the pattern with Q when used in regex. As a general note, one should take care to not use input from the shell to run code (say under /e).

• 将其作为参数传递，然后在 @ARGV

  perl -i -ne'
      BEGIN { $qr=shift; }; 
      next if /$qr/ && ++$ok > 1; print
  ' "$VAR" file

BEGIN 块 在运行之前的 BEGIN 阶段运行(因此不适用于以下迭代).其中 shift 从 @ARGV 中删除第一个元素，在上面的调用中，它是 $VAR 中的值，首先由 shell 插入.然后文件名 file 保留在 @ARGV 中，以便在 -n 下处理(打开文件并迭代其行)

where the BEGIN block runs in the BEGIN phase, before runtime (so not for the following iterations). In it shift removes the first element from @ARGV, which in the above invocation is the value in $VAR, first interpolated by shell. Then the filename file remains in @ARGV, so available for processing under -n (file is opened and its lines iterated over)

使用 -s 开关，为程序启用命令行开关

Use the -s switch, which enables command-line switches for the program

  perl -i -s -ne'next if /$qr/ && ++$ok > 1; print' -- -qr="$VAR" file

--(在''下的一行程序之后)标记程序参数的开始；然后 -qr 将一个变量 $qr 引入到程序中，并为它分配了一个如上的值(只有 -qr 变量 >$qr 得到值 1，所以是一个标志).

The -- (after the one-line program under '') marks the start of arguments for the program; then -qr introduces a variable $qr into the program, with a value assigned to it as above (with just -qr the variable $qr gets value 1, so is a flag).

任何此类选项都必须出现在可能的文件名之前，并将它们从 @ARGV 中删除，以便程序可以正常处理提交的文件.

Any such options must come before possible filenames, and they are removed from @ARGV so the program can then normally process the submitted files.

导出 bash 变量，使其成为可以在 Perl 程序中通过 %ENV hash

Export the bash variable, making it an environment variable which can then be accessed in the Perl program via %ENV hash

  export VAR="clean_history..."
  perl -i -ne'next if /$ENV{VAR}/ && ++$ok > 1; print' file

或者，如果$VAR仅用于这一行，则可以使用较短的(必须在一行上)

or, if $VAR is used only in this one-liner, can use the shorter (what must be on one line)

    VAR="clean_history..."  perl -i -ne'...' file
    

我宁愿推荐前两个选项中的任何一个，而不是这个.

I would rather recommend either of the first two options, over this one.

这些是将输入传递给完全在命令行(单行)上输入的 Perl 程序的方法，无需 STDIN 或文件.使用脚本最好使用库，首先Getopt::Long.

These are ways to pass input to a Perl program entered entirely on the command-line (one-liner), without STDIN or files. With a script better use a library, in the first place Getopt::Long.

对评论中给出的问题进行了改进，指定如果短语 clean_... 以 # 开头，则应完全跳过该行.单独测试最简单

A refinement of the question given in a comment specifies that if the phrase clean_... starts with a # then that line should be skipped altogether. It's simplest to separately test for that

next if /#$qr/; next if /$qr/ && ++$ok > 1; print

或者，依靠短路

next if /#$qr/ || (/$qr/ && ++$ok > 1); print

第一个版本不太容易出错，而且可能更清晰.

The first version is less error prone and probably clearer.

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