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Tech Tip: View Config Files Without Comments

Aug 04, 2009  By David Berner
 in

I've been using this grep invocation for years to trim comments out of config files. Comments are great but can get in your way if you just want to see the currently running configuration. I've found files hundreds of lines long which had fewer than ten active configuration lines, it's really hard to get an overview of what's going on when you have to wade through hundreds of lines of comments. 

$ grep ^[^#] /etc/ntp.conf

The regex ^[^#] matches the first character of any line, as long as that character that is not a #. Because blank lines don't have a first character they're not matched either, resulting in a nice compact output of just the active configuration lines.

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invert it!

evran's picture
Submitted by evran (not verified) on Sat, 09/26/2009 - 23:07.

$ grep ^[#] /etc/ntp.conf

Egrep to remove comments and empty lines

Paula R's picture
Submitted by Paula R (not verified) on Sat, 08/15/2009 - 01:47.

egrep -v '^#|^$' /etc/ntp.conf

sed trick

Anonymous's picture
Submitted by Anonymous (not verified) on Thu, 08/13/2009 - 08:10.

alias cleanconfig='sed -e '\''s/#.*//'\'' -e '\''s/[ ^I]*$//'\'' -e '\''/^$/ d'\'''

I like vim syntax

m.roshany's picture
Submitted by m.roshany (not verified) on Wed, 08/12/2009 - 07:32.

I like vim syntax highlighting in these cases :)

My version of filtering is

rc3's picture
Submitted by rc3 (not verified) on Sun, 08/09/2009 - 22:29.

My version of filtering is very similar to the last comment before mine:
egrep -v "^[[:cntrl:] ]*[#;] file
This also filters out comment lines starting with tab(s), followed by # or ; (openvpn's configuration file is a good example that uses both # and ; as the comment characters.)

To make filtering easier, I add the following function into my ~/.bashrc

cf() { [ $# -lt 1 ] && echo "Usage: $0 file" && return; egrep -v "^[[:cntrl:] ]*[#;] $1; }

If I want to view a config file without comment and empty lines, I simply do a

cf config_file

Cheers.

My version of filtering is

rc3's picture
Submitted by rc3 (not verified) on Mon, 08/10/2009 - 11:42.

Sorry, dropped the part that filters empty lines, here's the corrected one:
egrep -v "^[[:cntrl:] ]*[#;]|^$"

And I found it to be more convenient to define the above command in alias, i.e., I add this line to ~/.bashrc

alias cf='egrep -v "^[[:cntrl:] ]*[#;]|^$"'

Now I can use it in either way of the followings:

cat config_file|cf
cf config_file

I simply do this: $:

Anonymous's picture
Submitted by Anonymous (not verified) on Thu, 08/06/2009 - 15:30.

I simply do this:

$: "editor" /etc/file_to_view

where "editor" is your favorite editor...then I dynamically filter out the comments using my brain.

come on, this tip is sooo basic - are we going to permute all the possible little CLI tricks one can do and then
compete with one another over who's script is better? - geez.

Testy are we

Anonymous's picture
Submitted by Anonymous (not verified) on Mon, 08/10/2009 - 16:00.

A bit on the testy side. Get back in the lab, get to work and shut up.

Use 'cut' instead

Anonymous's picture
Submitted by Anonymous (not verified) on Thu, 08/06/2009 - 08:54.

Better use cut to clear comments from your files. This way you can clear away comments after regular text too. If you want to get rid of extra newlines, you can add a tr.

cut -f1 -d"#" FILENAME | tr -s '\n'

Here's mine

Howard Owen's picture
Submitted by Howard Owen (not verified) on Thu, 08/06/2009 - 05:36.

alias jdp='perl -ne "print unless (/^\s*([#!;]|\/\/|$)/);"'

"jdp" == "just data please"

I use this command to strip

Edo's picture
Submitted by Edo (not verified) on Thu, 08/06/2009 - 03:59.

I use this command to strip comments from any files I find

grep -vE '(^[[:space:]]*($|(#|!|;|//)))'

P.S. I made an alias ;)

grep -vE

Anonymous's picture
Submitted by Anonymous (not verified) on Sat, 08/14/2010 - 13:08.

grep -vE '(^[[:space:]]*($|(#|!|;|//)))'

That's not so good if you have some line something like that :

include /bla/bla.conf # include bla

you lost that line if you use that command.

This get very similar

svl's picture
Submitted by svl (not verified) on Wed, 08/05/2009 - 16:40.

This get very similar effect, with less type ;)
$ grep -v '#' /etc/ntp.conf

grep -v '#' file might filter out valid lines

rc3's picture
Submitted by rc3 (not verified) on Sun, 08/09/2009 - 22:35.

Be careful when you use
grep -v '#' file
as it'll filter lines containing #'s, regardless # is the beginning character of a line or not. In other words, lines like this will be filtered as well:
var1=some_value # define var1
Obviously you don't want that line to be filtered.

I've used that one, too, but it's not as good

Seth Rightmer's picture
Submitted by Seth Rightmer (not verified) on Wed, 08/05/2009 - 21:32.

It won't strip out blank lines like the regex in the article.

Hi, I also use a lot: $

Anonymous's picture
Submitted by Anonymous (not verified) on Tue, 08/04/2009 - 11:45.

Hi,

I also use a lot:
$ egrep -v "^[[:space:]]*#|^$" /etc/ntp.conf

In case there are spaces in front of the comments.

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