Perl +如何在文件中的单词之前添加行

Question

I write the following code in my bash script ( runs on redhat 7.2 version )

in order to add the content of $info variable before the word – 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

after we run the code the output of file that we can see is too long and its better to separate the line to 3 lines

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:

So I add “\\n” in the info line as the following: and we run the code again

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

but the file still not include the new lines ( actually the "\\n" are in line )

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:

while Expected results should be:

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:

Where I am wrong here?

Answer 1

The problem here is that in Bash double quotes don't cause \\n to be interpreted as a newline character.

For this, I think I'd just include literal newlines in the string:

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

Otherwise, you could use printf , but that seems overkill:

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