Linux / Unix: Shell Remove Empty Lines

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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:

[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

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

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4 comment

  1. I am using grep also, but like this:

    grep . input.txt > output.txt

    There is a dot between grep and input.txt.

  2. 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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