How sed inserting one blank line only if precede non blank line

[almarhoom abadan]

How sed inserting one blank line as this keep failing:

sed -Ee '/^---/{n;/^\s*$/b;i \n' -e 'b}; b; q' -- one.txt

---
n
WORKING_DIR

In order to insert one blank line right after

---

line not followed by blank line, then keep the rest as is
E.g. below is qualified to be worked on:

---
WORKING_DIR

Fail too by using

\\n

i.e.

sed -Ee '/^---/{n;/^\s*$/b;i \\n' -e 'b}; b; q' -- one.txt

As it inserts two blank line:

---


WORKING_DIR

Please help guide correct path, thanks much

[Tim Holloway]

welcome to the Ranch, almahoom!

Putting control characters into regexes on Linux/Unix command lines can be maddening. More so since the rules change between raw command-line input and scripts, much less between different unix-like systems and shells.

But I found this discussion helpful: https://stackoverflow.com/questions/45620124/insert-blank-line-before-line-matching-pattern-in-sed

On my Linux system, this particular expression worked like a charm:

sed '/happy/s/^/\n/' test where the a blank line gets inserted before the line that contains "happy" in the file named test.