how to remove new lines in vi editor linux?

I am using Linux (centos flavor) and created a file with the following text:

" hello 



  world 
"

Question:

Now, I opened the file in vi editor mode and am able to remove all non blank characters(backspace or delete keys do nothing). But newline characters persist and I get error saying “no previous regular expression”.

What should I do to remove all the new lines so that my file is just empty?? I have tried backspace key many times but no effect and I do not want to use cat > filename to just overwrite the file to make it empty!

Answer

You can use dd to delete any lines in vi editor.

Example: You have a file having 6 lines and you want to delete all 6 lines:

1. Open the file using ‘vi` editor
2. Go to first line
3. use 6dd