Perl +如何在文件中的单词之前添加行答案

【问题标题】：Perl + how to add lines before word in filePerl +如何在文件中的单词之前添加行
【发布时间】：2018-12-18 12:39:11
【问题描述】：

我在我的 bash 脚本中编写了以下代码（在 redhat 7.2 版本上运行）

为了在单词前添加$info变量的内容——ERROR: in file

export info="The Postfix error(8) delivery agent processes delivery requests from the queue manager. Each request specifies a queue file, a sender address, the reason for non-delivery (specified as the next-hop destination), and recipient"
perl -i -plne 'print "$ENV{info}" if(/ERROR:/);' file

运行代码后，我们可以看到文件的输出太长，最好将行分隔为 3 行

more file

The Postfix error(8) delivery agent processes delivery requests from the queue manager. Each request specifies a queue file, a sender address, the reason for non-delivery (specified as the next-hop destination), and recipient
ERROR:

所以我在信息行中添加了“\n”，如下所示：然后我们再次运行代码

export info="The Postfix error(8) delivery agent processes delivery requests from the queue manager. \nEach request specifies a queue file, a sender address, \nthe reason for non-delivery (specified as the next-hop destination), and recipient"
perl -i -plne 'print "$ENV{info}" if(/ERROR:/);' file

但文件仍然不包含新行（实际上“\n”在行中）

The Postfix error(8) delivery agent processes delivery requests from the queue manager. \nEach request specifies a queue file, a sender address, \nthe reason for non-delivery (specified as the next-hop destination), and recipient
ERROR:

而预期结果应该是：

The Postfix error(8) delivery agent processes delivery requests from the queue manager. 
Each request specifies a queue file, a sender address, 
the reason for non-delivery (specified as the next-hop destination), and recipient
ERROR:

我哪里错了？

【问题讨论】：

标签： linux bash shell perl

【解决方案1】：

这里的问题是，在 Bash 中，双引号不会导致 \n 被解释为换行符。

为此，我想我只是在字符串中包含文字换行符：

export info="The Postfix error(8) delivery agent processes delivery requests from the 
queue manager.
Each request specifies a queue file, a sender address,
the reason for non-delivery (specified as the next-hop destination), and recipient"
perl -i -plne 'print "$ENV{info}" if(/ERROR:/);' file

否则，您可以使用printf，但这似乎有点过头了：

export info=$(printf "The Postfix error(8) delivery agent processes delivery requests from the queue manager. \nEach request specifies a queue file, a sender address, \nthe reason for non-delivery (specified as the next-hop destination), and recipient")
perl -i -plne 'print "$ENV{info}" if(/ERROR:/);' file

【讨论】：