Replace newlines with literal \n

Question

This stackoverflow question has an answer to replace newlines with sed, using the format sed ':a;N;$!ba;s/\n/ /g'.

This works, but not for special characters like \r, \n, etc.

What I'm trying to do is to replace the newline character by a literal \n. Tried

sed ':a;N;$!ba;s/\n/\\n/g' 

and

sed ':a;N;$!ba;s/\n/\\\n/g' 

also

sed ":a;N;$!ba;s/\n/'\'n/g" 

but all to no avail. Sed keeps replacing the newline character.... with a newline character.

Thoughts?

Edited after first answer:

For the sake of completeness the commands run are :

PostContent=cat $TextTable | sed -E ':a;N;$!ba;s/\r{0,1}\n/\\n/g'

Where TextTable is a variable linking to a text file containing a JSON output in the following format :

{"posts":[{"title":"mysupertest","slug":"bi-test","markdown":"##TEST First things first ! To TEST this TEST TEST, click the download button below. If you need more information about the TEST TEST, you can  read the Table of Contents below.  <a href='/assets/TEST.pdf' style='border-radius:5px; padding: 4px 15px; background-color:#008CBA; color:white; text-decoration:none; float:right;' download> Download </a>   ##TEST OF TEST   ###TEST TEST PLATFORM TEST GUIDE WaTESTve TEST SetupTEST TESTTEST TESTTESTETESTTETSTTEST TESTTESTTTETST TESTTES TESTTESTESSTSTESTESTTES TEST","image":"http://localhost:3000/myimage.jpg","featured":false,"page":false,"status":"draft","language":"en_US","meta_title":null,"meta_description":null,"author":"4","publishedBy":null,"tags":[{"uuid":"ember2034","name":"implementation guides","slug":null,"description":null,"meta_title":null,"meta_description":null,"image":null,"visibility":"public"}]}]} 

Answer 1

Is this all you're trying to do?

$ cat file a b c  $ awk '{printf "%s\\n", $0}' file a\nb\nc\n$ 

or even:

$ awk -v ORS='\\n' '1' file a\nb\nc\n$ 

Run dos2unix on the input file first to strip the \rs if you like, or use -v RS='\r?\n' with GNU awk or do sub(/\r$/,""); before the printf or any other of a dozen or so clear, simple ways to handle it.

sed is for simple substitutions on individual lines, that is all. For anything else you should be using awk.