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

Answer 1

With the -zoption you can do

sed -z 's/\n/\\n/g' file

or

sed -z "s/\n/\\\n/g" file