How do I remove blank lines from files?

Question

I have a file (hosts) with some lines without content, how do I remove that lines without content?

Answer 1

Using sed

Type the following command:

sed '/^$/d' input.txt > output.txt

Using grep

Type the following command:

grep -v '^$' input.txt > output.txt

Answer 2

Many ways:

1. Use sed and edit the file in place.

   sudo sed -i -rn '/\S/p' /etc/hosts
   

2. Same, but with Perl:

   sudo perl -i -ne 'print if /\S/' /etc/hosts
   

3. Newer versions of GNU awk, in place again:

   sudo awk -i inplace '/\S/' file
   

All of the above solutions will also remove lines that contain nothing but whitespace. If you only want to remove empty lines, and leave lines that contain spaces or tabs etc, change the /\S/ to /^$/ in all of the above examples.

Answer 3

Sometimes the other commands will fail to remove blank lines if the lines contain a blank space. The following will remove all blank lines including lines that contain only blank spaces.

grep -v '^[[:space:]]*$' input.txt > output.txt

Answer 4

You can use Vim in Ex mode:

ex -sc v/./d -cx hosts

1. /./ find non blank lines

2. v invert selection

3. d delete

4. x save and close

Answer 5

You can do this in the default Ubuntu Text Editor (gedit) by:

• Press Ctrl+H to open Find and Replace
• In the 'Find' box, enter \n\n which signifies two new lines without text in-between them.
• In the 'Replace' box, enter \n
• Click 'Replace All'

If the text file was produced in windows, you may want to try \r\n.