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(emacs-mime)mailcap

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mailcap
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   As specified by RFC 1524, MIME-aware message handlers parse
"mailcap" files from a default list, which can be overridden by the
`MAILCAP' environment variable.  These describe how elements are
supposed to be displayed.  Here's an example file:

     image/*; gimp -8 %s
     audio/wav; wavplayer %s

   This says that all image files should be displayed with `gimp', and
that WAVE audio files should be played by `wavplayer'.

   The `mailcap' library parses such files, and provides functions for
matching types.

 - Variable: mailcap-mime-data
     This variable is an alist of alists containing backup viewing
     rules for MIME types.  These are overridden by rules for a type
     found in mailcap files.  The outer alist is keyed on the major
     content-type and the inner alists are keyed on the minor
     content-type (which can be a regular expression).

     For example:
          (("application"
            ("octet-stream"
             (viewer . mailcap-save-binary-file)
             (non-viewer . t)
             (type . "application/octet-stream"))
            ("plain"
             (viewer . view-mode)
             (test fboundp 'view-mode)
             (type . "text/plain")))

 - User Option: mailcap-default-mime-data
     This variable is the default value of `mailcap-mime-data'.  It
     exists to allow setting the value using Custom.  It is merged with
     values from mailcap files by `mailcap-parse-mailcaps'.

   Although it is not specified by the RFC, MIME tools normally use a
common means of associating file extensions with defualt MIME types in
the absence of other information about the type of a file.  The
information is found in per-user files `~/.mime.types' and system
`mime.types' files found in quasi-standard places.  Here is an example:

     application/x-dvi	dvi
     audio/mpeg		mpga mpega mp2 mp3
     image/jpeg		jpeg jpg jpe

 - Variable: mailcap-mime-extensions
     This variable is an alist MIME types keyed by file extensions.
     This is overridden by entries found in `mime.types' files.

 - User Option: mailcap-default-mime-extensions
     This variable is the default value of `mailcap-mime-extensions'.
     It exists to allow setting the value using Custom.  It is merged
     with values from mailcap files by `mailcap-parse-mimetypes'.

   Interface functions:

 - Function: mailcap-parse-mailcaps &optional path force
     Parse all the mailcap files specified in a path string PATH and
     merge them with the values from `mailcap-mime-data'.  Components of
     PATH are separated by the `path-separator' character appropriate
     for the system.  If FORCE is non-`nil', the files are re-parsed
     even if they have been parsed already.  If PATH is omitted, use
     the value of environment variable `MAILCAPS' if it is set;
     otherwise (on GNU and Unix) use the path defined in RFC 1524, plus
     `/usr/local/etc/mailcap'.

 - Function: mailcap-parse-mimetypes &optional path force
     Parse all the mimetypes specified in a path string PATH and merge
     them with the values from `mailcap-mime-extensions'.  Components
     of PATH are separated by the `path-separator' character
     appropriate for the system.  If PATH is omitted, use the value of
     environment variable `MIMETYPES' if set; otherwise use a default
     path consistent with that used by `mailcap-parse-mailcaps'.  If
     FORCE is non-`nil', the files are re-parsed even if they have been
     parsed already.

 - Function: mailcap-mime-info string &optional request
     Gets the viewer command for content-type STRING.  `nil' is
     returned if none is found.  Expects STRING to be a complete
     content-type header line.

     If REQUEST is non-`nil' it specifies what information to return.
     If it is nil or the empty string, the viewer (second field of the
     mailcap entry) will be returned.  If it is a string, then the
     mailcap field corresponding to that string will be returned
     (`print', `description', whatever).  If it is a number, all the
     information for this viewer is returned.  If it is `all', then all
     possible viewers for this type is returned.

 - Function: mailcap-mime-types
     This function returns a list of all the defined media types.

 - Function: mailcap-extension-to-mime extension
     This function returns the content type defined for a file with the
     given EXTENSION.