Ubuntu – What does `!!` mean in `sudo !!`

command linesudo

I am a user of Ubuntu with not much experience and I have been using sudo.

What does sudo !! do and how?

!! in bash is an alias for the previous command (see Event Designators). So it re-runs the previous command with sudo permissions.

~/ is shorthand for the current user's home folder. So if your user name is "foobar" it expands to /home/foobar/

In Unix/linux . means the current directory in your case /etc/mds-1.2-beta4/sana/config/etc/Gapache2. There are also many shortcuts like:

So to move all folders and files from /etc/mds-1.2-beta4/sana/config/etc/Gapache2 to /etc/apache2/sites-available, the command will be like this

mv ./* /etc/apache2/sites-available/

UPDATE: This link is a good resource for basic UNIX commands