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 
This sed line should do the trick:
sed -i '/^$/d' file.txt The -i means it will edit the file in-place.
\s* is the same solution given by stackoverflow question bad flag in substitute command: 'e' grepSimple solution is by using grep (GNU or BSD) command as below.
Remove blank lines (not including lines with spaces).
grep . file.txt Remove completely blank lines (including lines with spaces).
grep "\S" file.txt Note: If you get unwanted colors, that means your grep is aliases to grep --color=auto (check by type grep). In that case, you can add --color=none parameter, or just run the command as \grep (which ignores the alias).
ripgrepSimilar with ripgrep (suitable for much larger files).
Remove blank lines not including lines with spaces:
rg -N . file.txt or including lines with spaces:
rg -N "\S" file.txt See also:
grep . seems to be the simplest solution. grep . compared to the other solutions is that it will highlight all the text in red. The other solutions can preserve the original colors. Compare unbuffer apt search foo | grep . to unbuffer apt search foo | grep -v ^$ 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. grep --color=none ., you will get all white text, which overrides the color formatting of the original command (example: apt search foo) grep . will match lines containing only spaces, which the OP says is not desired. 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.
sed '/^[[:space:]]*$/d' file.txt. Credits to stackoverflow.com/a/16414489/123897 You can use the -v option with grep to remove the matching empty lines.
Like this
grep -Ev "^$" file.txt 
-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. grep -Ev '^#|^$' file.txt grep (GNU grep) 3.4 requires -E if you are using @GovindKailas' command 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.
To remove empty lines, you could squeeze new line repeats with tr:
cat file.txt | tr -s '\n' '\n' 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 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 For me @martigin-heemels command was throwing error this fixed it (ie a dummy param to i),
sed -i '' '/^$/d' file.txt
The simplest solution I have ever found:
cat file.txt | strings strings command is designed to extract printable text from binary files, not for text processing. While it does remove non-printable characters, it doesn't specifically target blank lines. Does it remove blank lines? Yes, but not reliably. It removes lines containing only spaces or non-printable characters, but not in a predictable way. If your file contains special characters or non-ASCII text, strings may unintentionally filter them out. Cheers! Remove lines that are blank or contain only spaces using sed:
sed '/^\ *$/d' file.txt 