Removing Blank Lines from the File.

In sed 
Type the following sed command to delete all empty files:

Display with out Blank Lines
sed '/^$/d' input.txt

Remove all the Blank Lines from file
sed -i '/^$/d' input.txt
cat input.txt

In awk 

Type the following awk command to delete all empty files:

Display with out Blank Lines
awk NF input.txt

Remove all the Blank Lines from file
awk 'NF  input.txt > output.txt
cat output.txt


In perl
Type the following perl one liner to delete all empty files and save orignal file as input.txt.backup:
Remove all the Blank Lines from file
perl -i.backup -n -e "print if /\S/" input.txt


In vi editor
:g/^$/d
:g will execute a command on lines which match a regex. The regex is 'blank line' and the command is
:d (delete)


In tr
tr -s '\n' < abc.txt

In grep
grep -v "^$" abc.txt