unable to filter out blank lines ^$ matches nothing

UNIX for Advanced & Expert Users
1

Hi
I've got a file with a lot of blank lines in it or are they?...I tried to remove them by using

grep -v ^$ <filename>

This did not remove anything....I then tried the reverse to see if ^$ indeed matches anything...so I tried

$ grep ^$ grepres.txt
$ grep ^\s*$ grepres.txt

This matched nothing...

..I am a bit of a noob at this so if anyone out there can figure out how to do this using regular expressions...I would really appreciate it...

I've attached the file here

Thanks in advance...

2

To remove blank lines using sed:

sed '/^$/d' infile > outfile
3

If u want to use grep then...

grep . grepres.txt

4

Hi.

My experience has been that I have often received files that contain spaces and TABS in otherwise empty lines. I call these visually empty lines. Usually we want to get rid of these as well as lines which have no characters at all.

Here is what I usually use:

#!/usr/bin/env sh

# @(#) dbl      Delete blank ( visually empty ) lines.
# If POSIX character class does not work, then use
# [ SPACE TAB ].

grep -v '^[[:space:]]*$' $*
# grep -v '^[   ]*$' $*

exit $?

Here is a demonstration script:

#!/bin/bash -

# @(#) s1       Demonstrate visually empty line processing.

echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version =o $(_eat $0 $1) cat grep

FILE=${1-data1}

echo
echo " Input file $FILE:"
cat -A $FILE

echo
echo " Processed with grep '.':"
grep . $FILE

echo
echo " Processing with dbl:"
./dbl $FILE

exit 0

Which produces:

% ./s1
(Versions displayed with local utility "version")
Linux 2.6.11-x1
GNU bash 2.05b.0
cat (coreutils) 5.2.1
grep (GNU grep) 2.5.1

 Input file data1:
First line.$
Next line has no characters.$
$
Next line has 1 space.$
 $
Next line has 1 TAB.$
^I$
Penultimate line.$
Last line.$

 Processed with grep '.':
First line.
Next line has no characters.
Next line has 1 space.

Next line has 1 TAB.

Penultimate line.
Last line.

 Processing with dbl:
First line.
Next line has no characters.
Next line has 1 space.
Next line has 1 TAB.
Penultimate line.
Last line.

Best wishes ... cheers, drl

5

Hi

..sorry didnt mention in my first post that sed '/^$/d' didnt work...

...grep . filename selects everything dosent it..?

....grep -v '^[[:space:]]*$' worked perfectly..

thing is there was a space in the line...dunno why \s*$ didnt work....

thanks a lot drl...

6

This file contain no empty lines. You got some whitespaces in there.