How to comment out code in a file VIA Terminal

Question

I am following This Tutorial to make my Android an external monitor for my Ubuntu 12.04 computer.

How do I do the following:

Edit your vnc session file

$ vi ~/.vnc/xstartup

Comment out everything and put this at the end

gnome-session &

Answer 1

With sed and echo are 2 commands in terminal . I am not using vi (editor) I prefer the simplest nano (editor) but now we will use sed (stream editor) and echo (line displayer) combined with tee (reader) trough a pipe | .

sed 's/^/#/g' -i ~/.vnc/xstartup

echo 'gnome-session &' | tee -a ~/.vnc/xstartup

If the file is admin protected (needs privileges) then

sudo sed 's/^/#/g' -i ~/.vnc/xstartup

echo 'gnome-session &' |sudo tee -a ~/.vnc/xstartup

Thanks