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wb9688
Asked: 2015-06-13 07:25:40 +0800 CST

How do I remove blank lines from files?

  • 772

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

text-processing

5 Answers

  1. Best Answer

    Using sed

    Type the following command:

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

    Using grep

    Type the following command:

    grep -v '^$' input.txt > output.txt
    • 13

  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.

    • 8

  3. 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

    • 0

  4. 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.

    • 0

  5. 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
    • 0