How can I insert a new line after each character in shell script?

Question

Assuming I have the following string:

abcdefghi

Which command can I use so that the outcome is:

a
b
c
d
e
f
g
h
i

I just started coding so I hope someone can help me.

Answer 1

There is a tool called fold which inserts linebreaks, and you can tell it do add one after every character:

$ fold -w 1 <<< 'abcdefghi'
a
b
c
d
e
f
g
h
i

<<< is used to indicate a here string. If your shell doesn't support that, you can pipe to fold instead:

echo 'abcdefghi' | fold -w 1