Huh.  I am not really able to figure this out. I imagine that part of the
problem may be that org tries to use mailcap as a method, and I don't have
any mailcap files. So I attempted this, which does not work:

'((system . "/usr/bin/xdg-open %s")
  (auto-mode . emacs)
  ("\\.odt\\'" . system)
  ("\\.mm\\'" . default)
  ("\\.x?html?\\'" . default)
  ("\\.pdf\\'" . default) )

*Messages* reports that xdg-open has been run, but the file doesn't
actually run.  seting the odt entry to "/usr/bin/libreoffice %s" doesn't
seem to have any effect at all -- the file just opens in emacs. The only
thing that works for now is this bizarre workaround:
'((system . "/usr/bin/libreoffice %s")
   (auto-mode . emacs)
   ("odt" . system)
  ("\\.odt\\'" . "system")
  ("\\.mm\\'" . default)
  ("\\.x?html?\\'" . default)
  ("\\.pdf\\'" . default))
I don't undertand why this would work while the others don't. Of course,
this is a pretty lousy workaround since now everything opens in libreoffice
by default!

On Fri, Sep 16, 2016 at 4:16 AM, Colin Baxter <m43cap@yandex.com> wrote:

> On Thu, Sep 15 2016, Matt Price wrote:
>
> > hi Everyone,
> > I have been through this a million times, but I never seem to remember,
> and have a hard time finding
> > the answer online or in my archives.
> >
> > On a Linux system, how should I set org-file-apps to allow org to open
> odt files in libreoffice, html files
> > in Firefox, and pdf files in evince (especially in export-and-open
> commands)?
> >
> > I have tried a couple of htings; this is what C-h v org-file-apps
> currently says:
> >
> > Its value is ((remote . emacs) (system . mailcap) (t . mailcap))
> > Original value was
> > ((auto-mode . emacs)
> >  ("\\.mm\\'" . default)
> >  ("\\.x?html?\\'" . default)
> >  ("\\.pdf\\'" . default))
> >
> > There's no /etc/mailcap on my mahcine (?), and .mailcap reads:
> >
> > */*; xdg-open "%s"
> >
> > Running `xdg-open file.odt` from a terminal will open the file in
> libreoffice, but exporting to odt and
> > opening with C-c C-e o O opens the file in emacs.  What should I try
> next? Thank you!
> > m
>
> Hi Matt,
>
> I can't stand evince so I've explicitly modified the default for pdf
> files to open xpdf. It could also be used to make open-office files use the
> application you want:
>
> (add-hook 'org-mode-hook
>            '(lambda ()
>             (delete '("\\.pdf\\'" . default) org-file-apps)
>             (add-to-list 'org-file-apps '("\\.pdf\\'" . "xpdf %s"))))
>
>
> Best Wishes.
>