Homepage: https://emacswiki.org/emacs/download/extview.el
Updated:
Open files with external viewer
Load the library and try opening a file which has an associated
application in `extview-application-associations' or in mailcap.
`extview-application-associations' can be used to override mailcap
handlers:
(require 'extview)
(push '("\\.pdf$" . "acroread %s") extview-application-associations)
(push '("\\.py$" . nil) extview-application-associations)
(push '("\\.html$" . ask) extview-application-associations)