vim, duplicate whole line to the end of each line?

How to copy the current line content to the end of each line for the whole file ?
For example:

From

hello 
world 
!

To

hello     hello 
world     world 
!         !

>Solution :

:%s/^\(.*\)$/\1 \1

• % – whole file
• s/^\(.*\)$ – match line from the beginning to end
• /\1 \1 – replace it with matched text two times.

This won’t put them in a single column though if there aren’t trailing whitespaces, I’ve put here . as trailing whitespace:

# no trailing whitspaces
hello           hello
hello           hello
world           world
!           !

# with trailing whitespaces
hello           hello
hello           hello
world           world
!....           !....