set vlc as default media application in Ubuntu, Fedora (and probably other Linux distros) from command line

Given that Totem is the default media player in Ubuntu, one can set VLC as default media player by replacing every instance of "totem.desktop" in the file /usr/share/applications/defaults.list by "vlc.desktop" as follows.
1. sudo cp /usr/share/applications/defaults.list /usr/share/applications/defaults.list.backup
2. sed 's/totem.desktop/vlc.desktop/g' /usr/share/applications/defaults.list > tempfile
3. sudo mv tempfile /usr/share/applications/defaults.list 

References: VLC wiki page

efficient/productive computer user, keyboard shortcuts, tip #7

for any program where editing involved, one can copy, paste, cut, save with Ctrl+S, Ctrl+V, Ctrl+X, and Ctrl+S respectively. Also Ctrl+O should bring open-file menu which is useful to know.

efficient/productive computer user, keyboard shortcuts, tip #6

bring power menu to restart, suspend, hibernate, or power off your computer. Simply do Alt+Ctrl+Delete. Note that one can of course do this from a terminal as well.

efficient/productive computer user, keyboard shortcuts, tip #5

Focus to or unfocus to desktop with OS-key+D or Alt+Ctrl+D

efficient/productive computer user, keyboard shortcuts, tip #4

Focus to or un-focus from desktop with OSkey+D or Ctrl+Alt+D. Note OS-key or operating system key is the key with microsoft logo, or ubuntu logo, or tux on it.

efficient/productive computer user, keyboard shortcuts, tip #3

Do Alt+Ctrl+Arrow to switch between workspaces.

efficient/productive computer user, keyboard shortcuts, tip #2

Do Alt+F10 to resize/maximize a window.