Unseen Sequence¶

If the profile entry `Unseen-Sequence' is present and non-empty, then show will remove each of the messages shown from each sequence named by the profile entry.

Showing the Contents¶

Mhshow prints messages in a convenient representation. If show is outputting to a terminal, then a pager will be placed between the terminal and show.

The headers of each message are displayed with mhl using the standard format file mhl.headers. You may specify an alternate format file with the -form formfile switch. If the format file mhl.null is specified, then the display of the message headers is suppressed.

Next, the contents are extracted from the message and are stored in a temporary file. Usually, the name of the temporary file is the word `show' followed by a string of characters. Occasionally, the method used to display a content (described next), requires that the file end in a specific suffix. For example, the soffice command (part of the StarOffice package) can be used to display Microsoft Word content, but it uses the suffix to determine how to display the file. If no suffix is present, the file is not correctly loaded. Similarly, older versions of the gs command append a `.ps' suffix to the filename if one was missing. As a result, these cannot be used to read the default temporary file.

To get around this, your profile can contain lines of the forms:

mhshow-suffix-<type>/<subtype>: <suffix>
mhshow-suffix-<type>: <suffix>

to specify a suffix which can be automatically added to the temporary file created for a specific content type. For example, the following lines might appear in your profile:

mhshow-suffix-text: .txt
mhshow-suffix-application/msword: .doc
mhshow-suffix-application/PostScript: .ps

to automatically append a suffix to the temporary files.

The method used to display the different contents in the messages bodies will be determined by a `display string'. To find the display string, show will first search your profile for an entry of the form:

to determine the display string. If this isn't found, show will search for an entry of the form:

to determine the display string.

If a display string is found, any escapes (given below) will be expanded. The result will be executed under `/bin/sh', with the standard input set to the content.

The display string may contain the following escapes:

%l	Display listing prior to displaying content
%f	Insert filename containing content
%F	%f, but stdin is terminal not content
%a	Insert parameters from Content-Type field
%s	Insert content subtype
%c	Insert foreign charset
%d	Insert content description
%%	The character %

Mhshow processes the MIME parts serially, i.e. the next display process is executed after the previous one has terminated.

Further, when show is display a content, typing QUIT (usually control-\) will tell show to wrap things up immediately.

Note that if the content being displayed is multipart, but not one of the subtypes listed above, then the f- and F-escapes expand to multiple filenames, one for each subordinate content. Further, stdin is not redirected from the terminal to the content.

If a display string is not found, show has the following default values:

mhshow-show-text/plain: %liconv -f <source-charset>
mhshow-show-message/rfc822: %lshow -file %F

If a subtype of type text doesn't have a profile entry, it will be treated as text/plain.

show has default methods for handling multipart messages of subtype mixed, alternative, parallel, and digest. Any unknown subtype of type multipart (without a profile entry), will be treated as multipart/mixed.

If none of these apply, then show will complain.

Example entries might be:

mhshow-show-audio/basic: raw2audio 2>/dev/null | play
mhshow-show-image: xv %f
mhshow-show-application/PostScript: lpr -Pps

When expanding %f and %F escapes, the file names get wrapped in single-quotes automatically.

Finally, show will process each message serially - it won't start showing the next message until all the commands executed to display the current message have terminated. Although a multipart content may contain advice to display the parts in parallel, show will never do so.

Showing Alternate Character Sets¶

Because a content of type text might be in a non-ASCII character set, when show encounters a `charset' parameter for this content, it checks if your terminal can display this character set natively. show checks this by first examining the the environment variable $MM_CHARSET and if not set, taking the character encoding of the current locale.

If the character set of text/plain cannot be displayed natively, then the default display method converts the content automatically by piping it through:

Note that if you have a custom `mhshow-show-*' display string, you need to care yourself for converting the encodings. (The foreign charset is available through the %c escape.)

The tool iconv needs to be available.

`mhshow-charset-*' profile entries are not supported anymore.

Messages of Type message/partial¶

show cannot directly display messages of type partial. You must reassemble them first into a normal message using mhstore. Check the man page for mhstore(1) for details.

External Access¶

Mhshow does not automatically retrieve message/external-body parts (anymore), but prints the relevant information to enable the user to retrieve the files manually.

User Environment¶

Because the display environment in which show operates may vary for different machines, show will look for the environment variable $MHSHOW. If present, this specifies the name of an additional user profile which should be read. Hence, when a user logs in on a particular display device, this environment variable should be set to refer to a file containing definitions useful for the given display device. Normally, only entries that deal with the methods to display different content type and subtypes

mhshow-show-<type>/<subtype>
mhshow-show-<type>

need be present in this additional profile. Finally, show will attempt to consult one other additional user profile, e.g.,

which is created automatically during mmh installation.