Howto delete empty lines using sed command under Linux / UNIX

Posted on in Categories , , last updated December 17, 2007

Q. I need to delete all empty lines but could not figure out sed command for the same? How do I delete all empty lines with sed?

A. sed is a stream editor and perfect for these kind of work.

You need to use d command under sed which is act as the delete function.

Sed Delete Empty Line Syntax

sed ‘/^$/d’ <input-file>
echo LINE | sed ‘/^$/d’
echo $VAR | sed ‘/^$/d’

So to delete all empty lines from a file called /tmp/data.txt, enter:
$ sed '/^$/d' /tmp/data.txt
To store output to another file use redirection operator:
$ sed '/^$/d' /tmp/data.txt > /tmp/output.txt

Deleting a line that matches a pattern

You can also match a word or a pattern to delete. For example
$ cat data.txt
Output:

This is a test
Linux rulez
Windows sucks
Redhat is good server disro

To delete all lines that contain a ‘Windows’ word, enter:
$ sed '/Windows/d' /tmp/data.txt > /tmp/output.data.txt
GNU Sed support -i option to edit files in place:
$ sed -i '/Windows/d' /tmp/data.txt

See more sed examples:

=> Delete text or paragraph between two sections using sed

Updated for accuracy.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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29 comment

  2. replace:

    $ sed ‘/Windows/d’ /tmp/data.txt

    with

    $ sed -i ‘/Windows/d’ /tmp/data.txt

    Otherwise the command will take no effect on the file /tmp/data.txt, just will dump on stdout.

    $ man sed

    Reply Report comment

  5. This command
    $ sed ‘/^$/d’ /tmp/data.txt > /tmp/output.txt
    is deleting the last line entry from data file.
    for e.g.
    data.txt
    1

    2
    3

    4

    5
    the output is
    1
    2
    3
    4

    last line entry is not there.

    Reply Report comment

  6. Actually here you might have stopped writting the file after entering 5. You need to press enter button then stop using ^z. Then you will have the result without any data loss.

    Reply Report comment

  9. The following command works only for null rows, but not in case of spaces:
    sed ‘/^$/d’ filename.
    For eg:
    My record looks like this
    1234

    5678

    91011
    Here after 1234 it is space and so it remains. But after 5678 it is null row and so it is removed. so the result will be
    1234

    5678
    91011.

    Plz tell me what shall I do to eliminate spaces.

    Reply Report comment

  17. I have the same problem what Maddy reported above. My last line is getting deleted when i am trying to delete blank lines using sed command. I cannot amend the file since it is process generated but have to remove the blank lines once the process finishes writing into the file. Please help.

    Reply Report comment

  23. Dear friend,

    I have a problem of comparing two files: e.g.
    file1 starts here:
    computer libraray
    books
    fiction
    case study
    group study
    financial crisis

    file 2 starts here:
    case
    crisis
    computer

    I want to compare two files and want to delete lines from file1 which comntains entries in file2. i am using the script as followed but getting error. any help appreciated

    result should be like,

    books
    fiction
    group study

    #!/bin/sh

    while read line1
    do
    while read line2

    do
    sed ‘/$line1/d’ $file2.txt
    done <file2.txt
    file2= $cdr02-05.txt

    done result.txt

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  24. I did not write the code which i used:

    #!/bin/sh

    while read line1
    do
    while read line2

    do
    sed ‘/$line1/d’ $file2.txt
    done <file2.txt
    file2.txt= $file2.txt

    done result.txt

    Reply Report comment

  26. Gaurav,
    you can do it two ways cat | grep -v “#” >> newfile.txt;

    Or you can cat | sed -e s!#!!g >> newfile.txt

    Or you can cat | sed -e s/#//g >> newfile.txt.

    Hope that helps.

    Reply Report comment

  27. Hi,

    Can any1 help in getting the desired output.

    My data is like

    1 A
    2 B
    3 C

    4 D
    5 E
    6 F

    7 G
    8 H
    9 I

    i WANT THE OUT PUT LIKE

    1 A 4 D 7 G
    2 B 5 E 8 H
    3 C 6 F 9 I

    THANKS IN ADVANCE!!

    Reply Report comment

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