Use one of the following commands to remove blank lines from a file.
1. Using the grep command:
$ grep -v "^$" file.txt
2. Using the sed command:
$ sed '/^$/d' file.txt
3. Using the awk command:
$ awk '/./' file.txt
4. Using the tr command:
$ tr -s '\n' < file.txt
You also can pipe the output of each command to a new file, like follows:
$ grep -v "^$" input.txt > output.txt