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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[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 |
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 '/^$/d' input.txt > output.txt
cat output.txt |
sed '/^$/d' input.txt > output.txt
cat output.txt
OR
sed -i '/^$/d' input.txt
cat input.txt |
sed -i '/^$/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 |
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 |
perl -i.backup -n -e "print if /\S/" input.txt
Verify updated files, type:
cat input.txt
cat input.txt.backup |
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.
You can also use grep :)
cat output.txt | grep -v “^$” | less
suppress repeated empty output lines
I am using grep also, but like this:
grep . input.txt > output.txt
There is a dot between grep and input.txt.
you can also do this by:
grep -v ‘^ ‘ $filename > $newfile
please note that there is space after ^ in above example.
-Kuldeep Kulkarni