Linux / Unix: Shell Remove Empty Lines

I am a new Linux user. I have text files with lots of empty lines. How do I delete all empty lines under Linux or Unix operating systems?

You can use any one of the following utility to delete all empty lines from text file:

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Tutorial details
DifficultyEasy (rss)
Root privilegesNo
RequirementsNone
TimeN/A
[a] sed command

[b] awk command

[c] perl command

Syntax

The syntax is:

command input.txt > output.txt
 
command [option] input.txt > output.txt
 
sed '...' input.txt > output.txt
 
## Gnu/sed
sed -i '...' input.txt 
 
awk '...' input.txt > output.txt

sed command examples

Type the following sed command to delete all empty files:

sed '/^$/d' input.txt > output.txt
cat output.txt

OR

sed -i '/^$/d' input.txt 
cat input.txt

awk command examples

Type the following awk command to delete all empty files:

awk 'NF > 0' input.txt > output.txt
cat output.txt

perl command examples

Type the following perl one liner to delete all empty files and save orignal file as input.txt.backup:

perl -i.backup -n -e "print if /\S/" input.txt

Verify updated files, type:

cat input.txt
cat input.txt.backup
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4 comments… add one
  • Roy Apr 25, 2013 @ 0:24

    You can also use grep :)

    cat output.txt | grep -v “^$” | less

  • Constantine Shulyupin Apr 25, 2013 @ 8:14
    cat --squeeze-blank

    suppress repeated empty output lines

  • MisaT Apr 25, 2013 @ 10:59

    I am using grep also, but like this:

    grep . input.txt > output.txt

    There is a dot between grep and input.txt.

  • Kuldeep Kulkarni Jul 20, 2015 @ 11:06

    you can also do this by:

    grep -v ‘^ ‘ $filename > $newfile

    please note that there is space after ^ in above example.

    -Kuldeep Kulkarni

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