MIME$HELP.HLB  —  SHOW  CONTENT_TYPE
    Displays a table of message Content-Types/subtypes that MIME
    recognizes for viewing with the READ command, and their
    associated application viewer to invoke. Other MIME content
    types and subtypes can be configured in the optional
    MIME$MAILCAP.DAT file.

1  –  Examples 

 MIME> SHOW CONTENT_TYPE

 Known Content-types:
 Content-Type: text/html
 Content-Type: text/plain
    Edit Command: EDIT/TPU
 Content-Type: message/rfc822
 Content-Type: image/*
    View Command:  $SYS$SYSTEM:XV.EXE %s

 This example shows there are four "Known Content-types" or types of
 MIME messages the MIME utility can read. Three are of the type
 "text" and one is of the type "image". Their respective subtypes
 are "HTML," "PLAIN" and "RFC822". The fourth type is "image" and
 the wildcard (*) indicates that any subtype of image, (for example,
 .JPEG or .GIF), can be displayed on this system using the X-Viewer
 application ($SYS$SYSTEM:XV.EXE).

 The editor is set to EDIT/EDT for the text/plain MIME messages. This
 is the default MIME editor unless specified within MAIL, defined by
 MAIL$EDIT logical, or set in the MIME$MAILCAP.DAT file. Refer to the
 NEW or EDIT command /EDIT qualifier for further information about
 setting the editor.

 See MIME$MAILCAP.DAT and the examples for more information.

2  –  MIME$MAILCAP.DAT 

 The Content-Type table defines how an attachment is read, and
 optionally,  how its output is converted when extracted with the
 X-FDL=file option. It is constructed from program built-in types
 and is read from the optional MIME$MAILCAP.DAT configuration files
 (if they exist).

   SYS$MANAGER:MIME$MAILCAP.DAT

   SYS$LOGIN:MIME$MAILCAP.DAT

 System-wide Content-Types are specified by the file
 SYS$MANAGER:MIME$MAILCAP.DAT and can be supplemented with
 additional entries found in the SYS$LOGIN:MIME$MAILCAP.DAT file.
 These files are not created by default for customization on a per
 system/site basis. The MIME$MAILCAP.DAT file follows the general
 format of (Request for Comments) RFC 1524.

   TYPE/SUBTYPE VIEW_COMMAND

 The Content-Type table is constructed beginning with the built-in
 types, then adding the system definitions from the system manager's
 MIME$MAILCAP.DAT file, and ending with data from the user's
 default login directory MIME$MAILCAP.DAT file.

 The entries are displayed in order of the most recently defined
 (LIFO) entries. In the case of duplicate entries, the first entry
 is used. This allows a user to customize their own environment while
 the system manager defines a default system or site environment
 for all users.

 Note that by default, only the minimal ASCII types and subtypes are
 defined. This allows customizing MIME to the system, and for security
 reasons, allows a regulated site environment.

 Consider the effect of a malicious user mailing a harmful image
 (.EXE) file that is executed upon being read with the OpenVMS MIME
 utility. RFC 2046 lists certain security considerations that should
 be noted, such as PostScript files that include PostScript operators
 such as "deletefile" and others that can be used in a malicious
 manner.

 For more information, see Example_MIME$MAILCAP.DAT help section.

3  –  Example MIME$MAILCAP.DAT 

 #
 #       SYS$MANAGER:MIME$MAILCAP.DAT  - system wide definitions
 #
 #       SYS$LOGIN:MIME$MAILCAP.DAT    - user specific definitions
 #
 #  FORMAT:
 #
 #	 TYPE/SUBTYPE;  VIEW_COMMAND;	options
 #
 #
 # Netscape handles .HTML, .HTM (and others if you want)
 # ----------------------------
 # - for URL -
 #     text/html; netscape -remote "openURL(%s,new-window)"
 # - for file -
 #     text/html; netscape -remote openfile(%s)
 #
 text/html; netscape -remote "openURL(%s,new-window)"
 #
 # A continuation line character '\'
 #
 text/htm; \
     netscape -remote \
     "openURL(%s,new-window)"
 #
 # X-View handles images ('*' = wildcard subtype)
 # ---------------------
 # image/bmp; xv %s
 image/*; xv %s
 #
 # CDA Viewer handles DDIF, PS,
 # ----------------------------
 # application/ddif; view/select=x_display/FORMAT=ddif %s
 #
 #   ! Note: There are security considerations with
 #           .PS (and .EXE) files - (file access, write...)
 #           Refer to RFC 2046
 #
 # application/ps; view/select=x_display/FORMAT=PS %s
 #
 # X-PDF handles portable document format
 # --------------------------------------
 #
 #  Note: The following definition specifies extracting a PDF
 #        subtype file attachment and to CONVERT the output file
 #        characteristics and record attributes using the FDL
 #        PDF_FILE.FDL file. This definition can be overridden
 #        with the qualifier /FDL=filename for the EXTRACT command.
 #
 #        This can be used with any subtype.
 #
 #          application/pdf; XPDF %s; x-fdl=SYS$MANAGER:PDF_FILE.FDL
 #
 application/pdf; XPDF %s
 #
 #
 # DECsound
 # --------
 audio/x-aud; sound -volume 100 -speaker -play %s
 #
 # Applications we do not have
 # ---------------------------
 #application/doc;
 #application/msword;
 #application/xls;
 #application/msexcel;
 #application/vnd.ms-excel;
 #application/ppt;
 #application/vnd.ms-powerpoint;
 #
 # In-Line Text - No scroll support, allows query by page and quit
 # ------------
 message/rfc822; TYPE/PAGE=SAVE %s
 #
 #
 # Text - Change the default as above, override the default mail editor
 # ----
 text/plain; TYPE/PAGE=SAVE %s; edit=lsedit %s
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