164

How do I remove empty/blank (including spaces only) lines in a file in Unix/Linux using the command line?

contents of file.txt

Line:Text
1:<blank>
2:AAA
3:<blank>
4:BBB
5:<blank>
6:<space><space><space>CCC
7:<space><space>
8:DDD

output desired

1:AAA
2:BBB
3:<space><space><space>CCC
4:DDD
3

9 Answers 9

198

This sed line should do the trick:

sed -i '/^$/d' file.txt

The -i means it will edit the file in-place.

6
118

grep

Simple solution is by using grep (GNU or BSD) command as below.

  • Remove blank lines (not including lines with spaces).

    grep . file.txt
    
  • Remove completely blank lines (including lines with spaces).

    grep "\S" file.txt
    

Note: If you get unwanted colors, that means your grep is aliases to grep --color=auto (check by type grep). In that case, you can add --color=none parameter, or just run the command as \grep (which ignores the alias).


ripgrep

Similar with ripgrep (suitable for much larger files).

Remove blank lines not including lines with spaces:

rg -N . file.txt

or including lines with spaces:

rg -N "\S" file.txt

See also:

9
  • 8
    grep . seems to be the simplest solution.
    – Leo
    Mar 21, 2018 at 21:36
  • The downside of grep . compared to the other solutions is that it will highlight all the text in red. The other solutions can preserve the original colors. Compare unbuffer apt search foo | grep . to unbuffer apt search foo | grep -v ^$
    – wisbucky
    Apr 25, 2019 at 23:09
  • 3
    @wisbucky You see colors, because grep is aliased to grep --color=auto on your system (check by: type grep). You can run it as \grep or use --color=none parameter.
    – kenorb
    Apr 25, 2019 at 23:26
  • @kenorb If you use grep --color=none ., you will get all white text, which overrides the color formatting of the original command (example: apt search foo)
    – wisbucky
    Apr 26, 2019 at 2:01
  • grep . will match lines containing only spaces, which the OP says is not desired.
    – Jim L.
    Jul 19, 2019 at 21:53
37
sed '/^$/d' file.txt

d is the sed command to delete a line. ^$ is a regular expression matching only a blank line, a line start followed by a line end.

2
  • This command does not produce the same output as OP requested (it produces 5 lines, not 4).
    – kenorb
    Jul 22, 2019 at 9:31
  • 1
    You likely need sed '/^[[:space:]]*$/d' file.txt. Credits to stackoverflow.com/a/16414489/123897
    – jpbochi
    Sep 7, 2023 at 16:19
23

You can use the -v option with grep to remove the matching empty lines.

Like this

grep -Ev "^$" file.txt
3
  • 5
    I don't believe you need the -E, at least not with GNU grep, but apart from that I'm so pleased to see this done with grep! It's what I reach for in preference to sed, every time; in-line filters seem to me to be better than in-line editors.
    – MadHatter
    Mar 28, 2011 at 22:45
  • If you want to skip the commented and blank lines, especially while dealing with conf files use grep -Ev '^#|^$' file.txt Mar 7, 2019 at 4:11
  • 1
    grep (GNU grep) 3.4 requires -E if you are using @GovindKailas' command Aug 15, 2020 at 4:07
20

Here is an awk solution:

awk NF file.txt

With Awk, NF only set on non-blank lines. When this condition match, Awk default action is to print the whole line.

9

To remove empty lines, you could squeeze new line repeats with tr:

cat file.txt | tr -s '\n' '\n'
2
  • This produces 6 lines, not 4 as OP requested.
    – kenorb
    Jul 22, 2019 at 9:34
  • the second '\n' seems to be unnecessary
    – logicor
    Mar 16, 2023 at 22:17
2

xargs if you dont mind stripping leading whitespace

$ docker run -it --rm alpine sh
/ # cat <<eof > /tmp/file
> one
>
>   two
> three
>
>
>   four
> eof
/ # cat /tmp/file
one

  two
three


  four
/ # cat /tmp/file | xargs -n1
one
two
three
four
1

Ex/Vim

Here is the method using ex editor (part of Vim):

ex -s +'v/\S/d' -cwq test.txt

For multiple files (edit in-place):

ex -s +'bufdo!v/\S/d' -cxa *.txt

Note: The :bufdo command is not POSIX.

Without modifying the file (just print on the standard output):

cat test.txt | ex -s +'v/\S/d' +%p +q! /dev/stdin
1

For me @martigin-heemels command was throwing error this fixed it (ie a dummy param to i),

sed -i '' '/^$/d' file.txt

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