Perhaps this exists already, and if not, it should...

[Richard Shaw]

On Fri, Apr 13, 2012 at 3:56 PM, Fernando Cassia <fcassia at gmail.com> wrote:
> But that got me thinking. Shouldn't there be a "meta-command" like
> "open filename.whatever" that just seeks the default file association
> in gnome or whatever, and find the app name, and invoke the right app
> without the end user having to memorize the exact app name associated
> with any given file extension type?.

I haven't tried using this directly but I would think it would do what you need:
$ xdg-open --help
   xdg-open -- opens a file or URL in the user's preferred
   application

Synopsis

   xdg-open { file | URL }

   xdg-open { --help | --manual | --version }

Use 'man xdg-open' or 'xdg-open --manual' for additional info.
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Richard