RFC 1343 (rfc1343) - Page 2 of 10


A User Agent Configuration Mechanism for Multimedia Mail Format Information



Alternative Format: Original Text Document





            RFC 1343       Multimedia Mail Configuration       June 1992


            of  a  message  is "foo" it can be displayed to the user via
            the "displayfoo" program.

            This approach means that, with a  one-time  modification,  a
            wide  variety  of  mail  reading  programs  can be given the
            ability to display a  wide  variety  of  types  of  message.
            Moreover,  extending  the  set of media types supported at a
            site becomes a simple matter  of  installing  a  binary  and
            adding  a  single  line to a configuration file.  Crucial to
            this scheme, however, is that all of the user  agents  agree
            on  a common representation and source for the configuration
            file.  This memo proposes such a common representation.

          Location of Configuration Information

            Each  user  agent  must  clearly  obtain  the  configuration
            information  from a common location, if the same information
            is to be  used  to  configure  all  user  agents.   However,
            individual  users  should  be  able to override or augment a
            site's configuration.  The configuration information  should
            therefore  be  obtained  from a designated set of locations.
            The overall  configuration  will  be  obtained  through  the
            virtual  concatenation  of  several individual configuration
            files known as mailcap files.  The configuration information
            will  be obtained from the FIRST matching entry in a mailcap
            file, where "matching" depends on both a  matching  content-
            type   specification,   an   entry   containing   sufficient
            information for the purposes of the  application  doing  the
            searching, and the success of any test in the "test=" field,
            if present.

            The precise location of  the  mailcap  files  is  operating-
            system dependent.  A standard location for UNIX is specified
            in Appendix A.

          Overall Format of a Mailcap File

            Each mailcap file consists of a set of entries that describe
            the  proper  handling  of  one media type at the local site.
            For example, one line might tell how to display a message in
            Group III fax format.  A mailcap file consists of a sequence
            of such individual entries, separated by newlines (according
            to  the operating system's newline conventions). Blank lines
            and lines that start with the "#" character (ASCII  35)  are
            considered  comments,  and are ignored.  Long entries may be
            continued on multiple lines if each non-terminal  line  ends
            with  a  backslash  character ('\', ASCII 92), in which case
            the multiple lines are to be treated  as  a  single  mailcap
            entry.   Note that for such "continued" lines, the backslash
            must be the last character on the line to be continued.

            Thus the overall format of a mailcap file is given,  in  the
            modified BNF of RFC 822, as:




            Borenstein