Howto delete empty lines using sed command under Linux / UNIX

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, 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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30 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

  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.

  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.

  7. awesome, your the first to hit it. I don’t know why this was taking me so long. You’ve been bookmark’d

  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.

  12. A better way (taking into account, if there are any white-spaces (spaces/tabs)) to delete blank lines would be sed -i ‘/^[ \t]*$/d’ input.txt

  14. great stuff here . I like the web site . For all my FAQ’s i will come here .

    Thanks
    Rajesh Matcha

  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.

  22. I managed.. I’ll post the script later for anyone whois interested :)

    thanks!

    btw, I just LOVE your site!

  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

  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

  25. Hi
    Please can u provide a command to delete a character from the whole file.
    for ex – If I want to remove # from a file abc.txt.
    Thanks

  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.

  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!!

  29. Hi, I have an issue, please help:
    input.txt file
    ~1
    001
    81648736247637
    common
    7483748*********
    –3space
    836546475764
    0034
    +87485
    –2Spaces
    985467
    ~1
    ~2
    001
    93845439867534
    comon
    623847632846*******
    347584737
    –2spaces
    8675467
    00234
    +19381234
    —3spaces
    ~2

    I want to print each record including spaces between ~1 to ~1, ~2 to ~2 …so on into rows for each record start with ~ and ends with next ~.
    ex :
    output.txt
    00181648736247637common7483748********* —3space836546475764
    0034+87485–2Spaces985467 …as my first row
    00193845439867534comon623847632846*******347584737–2spaces867546700234+19381234—3spaces ….as my second row and so on.
    Could you pls help..
    Thanks in advance

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