How to remove empty/blank lines from a file in Unix (including spaces)?

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

Solution 1:

This sed line should do the trick:

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

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

Solution 2:

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:

• How to remove blank lines from a file (including tab and spaces)?
• With sed: Delete empty lines using sed
• With awk: Remove blank lines using awk

Solution 3:

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.