In Mac, the QuickLook feature allows you to preview your files without opening them. For Linux users, particularly for those with Gnome desktop, you can also get a similar QuickLook functionality in your desktop with Gloobus-Preview. Gloobus-Preview is an extension for the Gnome desktop designed to enable a full screen preview of any kind of file. You can use it to preview your presentation slides, pdf files or even to listen to a mp3 track, all without having to open their default applications.