Block Comments in a Shell Script

There is no block comment on shell script.

Using vi (yes, vi) you can easily comment from line n to m

<ESC>
:10,100s/^/#/

(that reads, from line 10 to 100 substitute line start (^) with a # sign.)

and un comment with

<ESC>
:10,100s/^#//

(that reads, from line 10 to 100 substitute line start (^) followed by # with noting //.)

vi is almost universal anywhere where there is /bin/sh.

You can use:

if [ 1 -eq 0 ]; then
  echo "The code that you want commented out goes here."
  echo "This echo statement will not be called."
fi

The following should work for sh,bash, ksh and zsh.

The blocks of code to be commented can be put inside BEGINCOMMENT and ENDCOMMENT:

[ -z $BASH ] || shopt -s expand_aliases
alias BEGINCOMMENT="if [ ]; then"
alias ENDCOMMENT="fi"

BEGINCOMMENT
  echo "This line appears in a commented block"
  echo "And this one too!"
ENDCOMMENT

echo "This is outside the commented block"

Executing the above code would result in:

This is outside the commented block

In order to uncomment the code blocks thus commented, say

alias BEGINCOMMENT="if : ; then"

instead of

alias BEGINCOMMENT="if [ ]; then"

in the example above.

if you can dodge the single quotes:

__='
blah blah comment.
'

Use : ' to open and ' to close.

For example:

: '
This is a
very neat comment
in bash
'

This is from Vegas's example found here