Removing blank lines from a file

Removing blank lines from a file is common requirement. Here are few simple ways we can do it.

1. Using cat and grep

cat "filename" | grep -v ^$ > newfilename

The symbol ^ searches for a string that is followed from the beginning of the line. The symbol $ signifies the end of the line. Thus the combination ^$ means from begingin till the end there is nothing in the line, which would be the case in a blank line.

The same logic applies to all the examples below.

2. Using sed

sed /^$/d filename > newfilename

3. Modifying the fine in place using sed

Please note that this will change the orginal file itself.

sed -i /^$/d filename

4. Using awk

awk "! /^$/{ print $NR } filename > newfilename