Is substitution linking possible in the vi editor?

Question

I am trying to edit with two conditions in the vi.

example text)

hello world!
-apple watermelon
test text

two condition must be met.

1. start with -
2. I want to replace only the first letter of a word with a html tag (The first letter may not be the alphabet)

I tried substitution via pipe in vi, but i cant

Expected

hello world!
-<b>a</b>pple <b>w<b>atermelon
test text

Answer 1

You can use

:g/^-/s#\<\(.\)#<b>\1</b>#g

Meaning:

• for every line that starts with - (:g/^-/)
• substitute
  • the first character after a break (\<\(.\)) (while capturing it)
  • replace it with <b>\1</b> (\1 referencing the captured value)
  • multiple times per line (the g flag, remove this unless :set gdefault? returns nogdefault)