Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

Command to Hide Comments

Posted on 2002-07-09
13
Medium Priority
?
208 Views
Last Modified: 2013-12-15
I am often presented with config files modified by someone else and would like to make sure they are correct.
The problem with most config files is that there are only a few lines of active code and often hundreds of lines of comments.

Is there a simple bash command that will cat a file and skip all blank lines and all lines that start with #?

One of my techs wrote a perl script but that seems overkill.

0
Comment
Question by:davidpm
  • 6
  • 2
  • 2
  • +2
13 Comments
 
LVL 38

Expert Comment

by:yuzh
ID: 7142195
use can use the following command line to do the job:

assume your file name is: yourfile.txt

cat yourfile.txt | grep -v "^#" | grep -v "^$" | more

you can redirect to "less" or another file.
0
 
LVL 14

Expert Comment

by:chris_calabrese
ID: 7143371
I'll second that.
0
 
LVL 51

Expert Comment

by:ahoffmann
ID: 7143970
# only one process needed:
  awk '($1 ~ /^#/){next}(NF==0){next}{print}' file
0
Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

 

Author Comment

by:davidpm
ID: 7147748
Thanks ahoffman but I'm ready for another language just yet.

The following works:
cat test.conf | grep -v "^#" | grep -v "^[[:space:]]*$"

The last grep means match if the line only has zero or more whitespace characters in it. This should match space and tab etc.

That last part is a little hard to remember. Is there a trimmer way of doing the same thing?


0
 
LVL 38

Accepted Solution

by:
yuzh earned 200 total points
ID: 7148539
You can define a function in your .profile

eg:

readconf ()
{
cat $1 | | grep -v "^#" | grep -v "^[[:space:]]*$"

}


to use it:

readconf test.conf
0
 
LVL 51

Expert Comment

by:ahoffmann
ID: 7148647
FYI,
my suggestion works with any flaviour of awk on any UNIX,
"[[:space]]" is GNU-grep (and derivates) only (well, the default on Linux anyway).
And if performance or resources are in question: only one process ;-)
0
 
LVL 3

Expert Comment

by:DVB
ID: 7185552
egrep -v "(^#|^$)" /path/to/file
0
 
LVL 51

Expert Comment

by:ahoffmann
ID: 7186300
DVB: s/"/'/g
 and it still does not remove all comment lines
0
 
LVL 51

Expert Comment

by:ahoffmann
ID: 7186305
egrep -v '([ \t]*#|^[ \t]*$)' file
0
 
LVL 14

Expert Comment

by:chris_calabrese
ID: 7189200
What the heck...

egrep -v '^[ \t]*(#|$)' file
0
 
LVL 51

Expert Comment

by:ahoffmann
ID: 7190003
contest closed?
LOL
0
 
LVL 51

Expert Comment

by:ahoffmann
ID: 7313884
wow, the longest (characters and cpu time) suggestion got the grade ;-)

davidpm, could you please explain your decision?

(yuzh, no offence)
0
 
LVL 3

Expert Comment

by:DVB
ID: 7314188
I think it was the easiest to read. Regular expressions can get complicated.
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

I am a long time windows user and for me it is normal to have spaces in directory and file names. Changing to Linux I found myself frustrated when I moved my windows data over to my new Linux computer. The problem occurs when at the command line.…
If you have a server on collocation with the super-fast CPU, that doesn't mean that you get it running at full power. Here is a preamble. When doing inventory of Linux servers, that I'm administering, I've found that some of them are running on l…
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
How to Install VMware Tools in Red Hat Enterprise Linux 6.4 (RHEL 6.4) Step-by-Step Tutorial
Suggested Courses
Course of the Month12 days, 21 hours left to enroll

971 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question