This may sound elementary question. But how do I add new line in my shell script?
This works:
echo '###'

This prints \n ### and not ### on a new line...
echo "\n ###"

Have you tried

echo ""
echo "###"

hi,
just try

echo "\n"

There are different versions of echo, some of which will print a newline when they see \n (and some will only do it when invoked with the -e option).

The portable way is to echo nothing, since echo (without options) will always supply a newline.

echo

echo "foo
bar
baz"

cat <<HERE
foo
bar
baz
HERE