Using MIME
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If your version of MH is set up for MIME (the multipurpose mail extensions
introduced in an earlier chapter,
you can try MIME features by reading this section.
MIME support was introduced in MH 6.8 and improved in MH 6.8.3.
If you have an earlier version of MH, it probably doesn't handle MIME.
MH has to be configured for MIME when the system is installed; if you
have version 6.8 or later, it still may not support MIME.
To check your version, first run any MH command with its
-help switch.
If the version is 6.8 or higher, and if you see the [MIME] option,
you're halfway there.
The [MIME] option is no guarantee that the other supporting
programs and files are ready.
The Section on Configuring mhn should help.
For now, the best answer is to try reading a message and see what happens.
How well MIME works also depends on the terminal or window system you're
using.
For example, some character-based terminals can display only ASCII
text.
If your computer tries to display a MIME message with non-ASCII
characters like ñ, your terminal may show garbage or some other
unrelated character.
Or, if you're using a workstation or X terminal with a window system, but the
system can't play sounds, a MIME message with audio content will be useless.
If your system's fonts aren't set up correctly, you may not be able to read
messages in other character sets.
If you have trouble with MIME messages, you might go to someone else's
more-sophisticated setup and try displaying the message there.
The section Configuring mhn has much more
information about MIME setup.
MH uses a "Swiss Army Knife" utility called mhn to handle MIME messages.
mhn does message composition, display, storage, listing, and more.
Some programs start mhn for you -- show does, for example.
But you'll also run mhn directly sometimes.
Let's use it to list the contents of the sample MIME message you got in
Section Sending Some Mail: comp, send.
The -list switch lists the contents of the current message or of
the messages you name on its command line:
% mhn -list 6
msg part type/subtype size description
6 multipart/mixed 52K
1 multipart/alternative 1330
1.1 text/enriched 539 Introduction in enriched text
1.2 text/plain 454 Introduction in plain text
2 audio/basic 20K Hello from the author
3 image/gif 17K Book cover
The first line describes the columns of information underneath it.
Next comes a line that tells you about the overall message:
Message 6 has a content type and subtype of multipart/mixed, and it's
approximately 52,000 octets (bytes) long.
(If you're quick at math, you can see that the sizes of the parts don't add up
to 52k.
Curious?
Read ahead about the
-norealsize switch.)
The second line describes part 1 of the message; it is
multipart/alternative.
That means part 1 will have at least two subparts; they're numbered 1.1
and 1.2.
Part 1.1, text/enriched, is "richer" than text/plain, so it'll
be shown if your MH setup can.
Otherwise, show will show you part 1.2.
After the first part are two more:
part 2 has sound and the third has an image.
The Section Listing MIME Message Parts has more about mhn -list.
You don't need to do anything special to read a MIME message.
If a message header has MIME fields, the show command will see them
and do the right thing (if your system is set up correctly).
To find out what your system will do, start by reading the sample MIME
message you requested earlier.
Reading the Header
Different MH systems are configured differently.
When you read the sample message, you may not see the same things I
show here.
You'll probably start by seeing the message header and a prompt:
% show 6
(Message inbox:6)
Date: Mon, 09 Jan 1995
To: Angela Corning <angelac@xyz.edu>
From: mh-mime-sample@online.ora.com (Sample MH/MIME message server)
Subject: Sample MIME message for "MH & xmh" Nutshell Handbook
X-Face: 4'>h,#cS;REmrM.0o;MLO(rQ\6!tC3|K"`%_&L/5r'?`z?YFA'^?O_2;uhD
j}[Ezd'KN;UN]JY>}7NI!3#)pemuo^HLsy?e&d;~eMDvq{tVqg<Dj,:;J_+=`G9:Av
(qc1~%PPox??]:2o`7kWKem,99A>_JaK.QQ>aXK,)ruQhThx8,.X|_@Foa75CW:E[=
@U@5dA'(H`V>Vm{d[)S8AcVpGs1Jw,p6w{LFc?o(}7$@3ani]G[joNpQsJ%^kZhox%
7\gVhT%uu|8"WXlT=U1:opS-:9hL{kZgxhGvUf?bJ4E
MIME-Version: 1.0
(END)
The X-Face: field isn't part of MIME.
It's a bitmap image of my face that exmh can display.
If you won't be using exmh, you can tell mhn not to display
X-Face: fields by editing the
mhl.headers file.
Your cursor may be sitting at the end of the last line.
If it is, when you press
RETURN,
MH will probably print a line of information about the first part of
the MIME message.
You're done with the message header, ready to read the body.
Reading the Body
The sample message starts with a multipart/alternative section that has
both plain text and enriched text.
If you're set up to display enriched text, that's what the information
line should show (as this one does):
part 1.1 text/enriched 539 Introduction in enriched text
Press <return> to show content...
Otherwise, you should be prompted with a line that says
"text/plain 454 Introduction in plain text."
Press
RETURN
to read the part:
Welcome to MIME mail!
This is a sample MIME message for the third edition of the book MH & xmh:
Email for Users & Programmers from O'Reilly & Associates.
Right now, you're reading enriched text from the second subpart of a
multipart/alternative content. If your MH setup hadn't been able to show
enriched text, you would have seen plain text instead.
Next, if your MH setup can render them, are an audio greeting card and a
GIF-format picture of the book's cover. Have fun!
--Jerry
Press RETURN to continue (or 'q' to quit):
Depending on your setup, the boldface and italic text may be shown
underlined, highlighted, or displayed in some other way. That depends
on your terminal, the termcap or terminfo setting, the
program that displays the enriched text, and more. (If it works, just
be glad it does! :-))
The next part of the sample message is a short audio message from me
that says "Hi. This is Jerry Peek. Have fun with MIME!" You
don't have to listen to it, though. Any time you see a Press
<return> to show content... prompt, you can skip that part by
pressing your interrupt key -- often, that's
CTRL-C.
You have another choice: You can skip the rest of the message and get
back to a shell prompt by pressing your QUIT key -- typically
CTRL-\ (control-backslash).
But remember that those only work when your cursor
is at the prompt Press <return> to show content...; at other times,
those keys' effects depend on the program you're running to display
the message part. At those times, you should use the "quit" command
that the particular program understands.
A Multipart Body
If the sample MIME message had just one part, you'd get another shell
prompt (like $ or %) on your screen.
But this is a multipart message, so MH will start to process the next part.
The next part of the sample message is audio.
If you try to listen to it, what happens will depend on your setup, of
course.
The simplest case is that the sound plays after you press
RETURN:
part 2 audio/basic 20K Hello from the author
Press <return> to show content...
...my dulcet tones float into your room...
Before MH describes a message part and prompts you to show it, it checks
to see whether it's been configured to display that content-type on your
setup.
In a multipart/alternative message, MH will silently skip parts it
can't display;
if you keep track of the Part numbers it's showing, you'll notice that a
part was skipped.
In a multipart/mixed message, you'll get an error message like this:
mhn: don't know how to display content
(content audio/basic in message 6, part 2)
You also can get an error from a program that MH calls to display content.
For example, the third part of the sample message is a GIFformat
picture of this book's cover.
Most graphical setups that show images are based on the X Window System.
An X program needs your DISPLAY environment variable.
In the example below, mhn has started the xv program to show the
GIF image.
But xv quits because it can't find or open your display:
part 3 image/gif 17K Book cover
Press <return> to show content...
/usr/local/bin/xv: Can't open display
Exit 1
Otherwise, a window will probably pop up on your screen.
If you're using the xv program, you can quit by pointing to the
window and pressing the `q' key.
Or, if you click the third mouse button in that window, you'll get a menu
window with quite a few choices -- including a quit button.
After you quit xv, the image window
should go away; then, the window where you were displaying the sample message
should return to a shell prompt (like %).
You're ready to remove the sample message or go on to other work.
For more information about what MH does to display MIME messages, and
some tips for fixing problems, see the
Section Reading MIME Messages.
By default, show shows all the parts of a message it can (actually,
it calls mhn -show).
You can also use mhn -part n,
where n is the part number,
to see one part of a message; the Section
Showing Part of a MIME Message explains.
Composing a MIME message starts out the same way as a non-MIME message:
type comp (or repl or forw), fill in the header,
and enter the message body.
You don't put any MIME-specific fields in the header; MH does that for you.
In the body of a MIME message, you'll usually add directives that are
converted into MIME body parts.
Finally, to convert the directives into MIME parts, you run mhn
(is that name starting to sound familiar? :-)) by going to the
What now? prompt and typing edit mhn.
If you almost always send MIME messages, you can automate that last step:
see Section mhn Editing and automhnproc.
For this tour, let's compose a simple message.
To do this on your own, you'll need to know
something about the
structure of a MIME message.
Here's what to type to make the sample message.
Fill in the addresses you'd like to use.
Type the directives in the body (on lines starting with #) as
I've shown them.
You can replace the italic text
with whatever fits your system; if you
have questions about what fits where, read the description below:
% comp
To: yourfriend
cc: you
Subject: Sample MIME message
--------
This test message has three more parts: enriched text,
a copy of my .mh_profile file, and my signature file.
The part ends at the first directive (the first line starting with #).
#<text/enriched [Sample enriched text]
This part has <italic>italic text</italic>, <bold>bold text</bold>,
and, if we're lucky, <bold><italic>bold italic text</italic></bold>.
#application/octet-stream [My MH profile] /home/jerry/.mh_profile
#text/plain [signature] /home/jerry/.signature
^D
--------
What now? e mhn
What now?
When you're done with the message body and the directives in it, typing
edit mhn turns the directives into parts, reads the specified files,
and checks for any other errors in the draft.
When mhn is done, you'll get another What now? prompt;
you can send the draft, list it, or any of the usual choices.
If you list the draft, you may see the raw MIME-encoded message
(if you need a reminder of an encoded multipart draft, look at the
Example Sample multipart message, encoded).
Or if you list it and your lproc: has been
set to show, you'll see the message as the recipient should see it.
What if you type edit mhn and get an error?
Start a text editor from the What now? prompt, edit the directives
and save the draft, then use edit mhn again.
On the other hand, if you want to edit the draft after you've run mhn
with no errors, the draft will have been encoded; you'll need to
recover the original draft with the directives.
Let's take a closer look at the message body and the directives it gave
mhn.
The message body starts with a plain text part.
The part doesn't start with a directive, so mhn automatically
makes its content-type text/plain.
Each part ends at the next directive.
A directive tells mhn to start a new body part.
Each directive starts with the character #.
You can split a long directive onto more than one line by putting a
backslash (\) at the end of the continued line.
The list in the following Table
shows the most common directives.
If you want to send one of the items in the first column, use
a directive like the one shown in the second column.
The second column starts with the syntax of the directive, then
shows an example.
To keep the table simple, I've only listed commonly-used features.
Also, of course, the short explanations in the "What's in the Part"
column may not give you enough information to understand completely.
The Section Composing and Sending MIME Messages
has lots of information and several more examples.
Table: Examples of mhn directives
Data (usually text) you enter on lines after the directive:
#<
#<type/subtype [description]
lines of text
Example:
#<text/plain [Overview of this message]
This message has three parts.
The first part is blah, blah, blah...
Location of external data that recipient will get by FTP, etc.:
#@
#@type/subtype [description] external-parameters
Example:
#@image/gif [Charlie Jones] \
access-type=anon-ftp; name="chuck_jones.gif"; \
directory="pub/staff_pix"; site="ftp.foo.bar"
An existing MH message of yours: #forw
#forw +folder message(s)
Example:
#forw +meetings 38
Data from a file to copy into the message: # ... filename
#type/subtype [description] filename
Example:
#application/postscript [Chapter 5] /doc/nutshell/MHxmh/ch05.ps
A multipart message (not required for multipart/mixed
unless you're creating subparts): #begin ... #end
#begin alternative-or- parallel-or-whatever
put the subparts here
#end
Example:
#begin alternative
#<text/plain [Party invitation]
This is the plain-text version
#<text/enriched [Party invitation]
This is the <bold>enriched-text</bold> version
#application/postscript [Party invitation] \
/u/leah/invite.ps
#end
In all of the directives,
the [description] is optional.
The exmh MH front-end
(intoduced in this Chapter)
handles message composition
in a different way.
It only runs on the X Window System; mhn works anywhere.
This tour is only a brief introduction to the MIME support in MH.
The mhn utility can also:
And more.
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