#!/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 $?

#!/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

% ./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.