Multi-Line Comments in Shell Script

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Multi-Line Comments in Shell Script

The UNIX shell script is a powerful beast. You can pretty much write anything in shell scripts that you can also write in other languages. The thing is that UNIX shell script only support single line comments, with a hash (#) mark. So to comment out the following example, you'd have to put a hash mark in front of every line:

# if [ -f "${distroFile}" ]
# then
#   cp "${distroFile}" "${tmpDir}"
# else
#   echo "*** ${distroFile} does not exist!"
#   exit
# fi

Well, that's a lot of work. As you can see in the example above, that's seven hash marks. And you'd have to change the cursor position for every hash mark. Don't you wish there is a C or Java-like multi-line comment (/* */) sequence?

Well, today, I got the bright idea of comment out multi-line shell script source codes by surrounding them in function calls. The same example above would be changed to the following:

comment1 ()
{
if [ -f "${distroFile}" ]
then
  cp "${distroFile}" "${tmpDir}"
else
  echo "*** ${distroFile} does not exist!"
  exit
fi
}

Now, isn't that must easier and neater?

Chieh Cheng
Tue, 29 Apr 2008 17:36:57 +0000

This is another way:

:<<supercalifragilisticexpialidocious
echo "This will not get printed"
echo "Yet another escape"
supercalifragilisticexpialidocious

Reference: http://www.unix.com/shell-programming-scripting/39478-block . . .

Jatin Sharma
Mon, 16 Jun 2008 16:46:56 +0000

Really useful considering the behavior of the vi editor in Unix/Linux.

Good Stuff. Thank you

Venkatagiri Vatlam
Thu, 25 Sep 2008 14:14:28 +0000

csh doesn't have functions. But Jatin's supercalifragilisticexpialidocious example works great in csh.

The function method works even if you put the multi-line comments inside another function.

Chieh Cheng
Fri, 03 Jul 2009 17:55:39 +0000

Thanks, i served too!!

Bye

Hans Ancieta
Thu, 14 Apr 2011 14:55:58 +0000

Nice style of commenting....looks neat and classy...;)

xtatic
Thu, 20 Oct 2011 09:47:25 +0000

#!/bin/bash
:<<'comment'
echo -n "Enter some text > "
read text
echo "You entered: $text"
comment
echo "Line after multiline comments" >>>>>>this is echo in not getting print after multiline comments.

but comment(){} its working ...really nice and neat trick.

Suprabhat
Wed, 16 Nov 2011 11:21:36 +0000

I was laughing when I saw this. Real Neat. Good Job !

Avinash
Wed, 30 Jan 2013 11:45:19 +0300

well, apparently if I have developer's musing that I want to record this method wouldn't work, right? - cause stuff like a TODO list that I want to maintain as part of a future release wouldn't be allowed under a comment unless i qualify every statement that I write there by an echo command.

Sam
Wed, 06 Feb 2013 21:27:02 +0300

Or create a specific function for comments (this functions does nothing, by the way):

comment() { :; }

now you can enter comments anywhere with any amount of lines:

echo "hello worlds"
comment "this is a comment"
echo "bye cruel worlds"
comments "
this is a
multi line
comment"

Donat Callens
Thu, 21 Feb 2013 12:25:02 +0300

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