Block Comments in a Shell Script

Question

Is there a simple way to comment out a block of code in a shell script?

Answer 1

You could use Vi/Vim's Visual Block mode which is designed for stuff like this:

Ctrl-V  
Highlight first element in rows you want commented  
Shift-i  
#  
esc  

Uncomment would be:

Ctrl-V  
Highlight #'s  
d  
l  

This is vi's interactive way of doing this sort of thing rather than counting or reading line numbers.

Lastly, in Gvim you use ctrl-q to get into Visual Block mode rather than ctrl-v (because that's the shortcut for paste).

Answer 2

In bash:

#!/bin/bash
echo before comment
: <<'END'
bla bla
blurfl
END
echo after comment

The ' and ' around the END delimiter are important, otherwise things inside the block like for example $(command) will be parsed and executed.

For an explanation, see this and this question.

Answer 3

In Vim:

1. go to first line of block you want to comment
2. shift-V (enter visual mode), up down highlight lines in block
3. execute the following on selection :s/^/#/

4. the command will look like this:

     :'<,'>s/^/#
   

5. hit enter

e.g.

shift-V
jjj
:s/^/#
<enter>

Answer 4

Another mode is: If your editor HAS NO BLOCK comment option,

1. Open a second instance of the editor (for example File=>New File...)
2. From THE PREVIOUS file you are working on, select ONLY THE PART YOU WANT COMMENT
3. Copy and paste it in the window of the new temporary file...
4. Open the Edit menu, select REPLACE and input as string to be replaced '\n'
5. input as replace string: '\n#'
6. press the button 'replace ALL'

DONE

it WORKS with ANY editor

Answer 5

Use : ' to open and ' to close.

For example:

: '
This is a
very neat comment
in bash
'

This is from Vegas's example found here

Answer 6

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.