The shortcuts usually depend on the window manager you're using. If you're using Ubuntu you should have Gnome as default windomanager so you could use the Gnome Control Center
to set the shortcuts you want.
Another way, is use a tool like Xbindkeys
which is indipendent from the window manager and reads the key configuration from a simple text file usually ~/.xbindkeysrc
.
So you could install Xbindkeys
in your system with:
sudo apt-get install xbindkeys
Then in the bash
script you could add a new entry in the ~/xbindkeysrc
config file to add your shortcut.