If you find yourself commenting out multiple lines in BASH, there is a simple way of commenting them out using the HERE DOCUMENT feature. Typically you use the hash (#) tag to comment out each line, but that can get tiresome especially if have hundreds of lines. Here’s a better option. Use the HERE DOCUMENT feature in BASH. Anything in between the HERE DOCUMENT will be ignored by BASH and treated as comments.

#<<COMMENT - Remove the # sign to activate the HERE DOCUMENT
echo "1"
echo "3"
echo "4"
#COMMENT - Remove the # sign to activate the HERE DOCUMENT

If you need to reverse them, then just do the following. In this way, you only have to touch 2 lines instead of multiple lines.