Recently I had a need to count the number of empty lines in a text file. After some digging into the man pages of grep I was able to come up with a one liner which was able to do it.
Following my tradition of documenting one liners, I am going to document this one as well š
Assumption
By empty line, I mean any line which either has no characters or has only whitespace (space, tab) characters.
Command
For the impatient in you, here is the actual command.
Explanation
-P '\S'– This selects all lines that have a non whitespace character-c– Print the count of matching lines-v– Select only the non-matching lines
So, we are first matching all lines that have a non whitespace character and then use -v option to ignore them and then -c option to print the count instead of the actual line.
If we wanted the count of all non-empty lines, then we just have to remove the -v option from the above command.
Hope this is helpful. Happy Grep’ing š
Hey Sudar,
The notification mail of this post had the command completely stripped off.
Thanks for reporting this. Can you kindly forward the mail to me. I am using feedburner and I think it is getting into some issues.
May be time to replace it with a custom solution.
Like anand said above, the subscription mail stripped off the one-liner command.
BTW, why not `grep -c -e ‘^\s*$’ filename` ?
-c for counting the number of matches
-e to let grep know that a regular expression follows
The literal meaning of regular expression used in the above solution is “to match if a start of line, following by a whitespace or tab for any number of times, including zero times, followed by the end of line”.
Also, which version of grep you use? On a mac with BSD grep (2.5.1-FreeBSD), the ‘-P’ is not implemented. In Ubuntu with GNU grep (2.10), your solution works, though.
Kindly forward the email. I will have a look at it. Not sure why it is getting stripped.
There is absolutely no reason to not use it. It is just that I found the other one first š
I am using 2.5.1 (GNU grep) in Mac Lion. `-P` works for me, but I guess I would have upgraded to GnU grep sometime back.
Done.
Also forwarded another issue with the comment subscription via another email (the email that I use for comment subscription is different from the email used for blog subscription).