CU Amiga Super CD-ROM 27/CU Amiga Magazine's Super CD-ROM 27 (1998)(EMAP Images)(GB)[!][issue 1998-10].iso/GoodBye/JohnKennedy/February96.lha/FEATURES/MIME.LHA/mime.doc

Text File | 1996-02-06 | 7.5 KB | 216 lines

Wired World


A picture's worth a thousand words...

Why limit your email to text? With MIME you can include
graphics, sounds -- even animations.


If you been using electronic mail or lurking around in the
Usenet newsgroups, you will probably have come across files
which have been UUENCODED. UUENCODING is a method of
converting a standard binary file, for example a program or
IFF image, into a mass of text. The text can then be sent
via email or included in a news posting.

UUENCODING is required because text systems only use 7 bits
out of 8 to store the various letters and punctucation
symbols. If you sent a program and missed out one bit in
eight, whatever arrived at the other end would be totally
useless.

Image:mime1.iff
Caption: When you UUENCODE a file it is converted into text.
You can't read it, but you can UUDECODE it to bring back the
original file.

MIME is an attempt at making this UUENCODING process as
simple and invisible as possible. It stands for
"Multipurpose Internet Mail Extensions". It too encodes
binary files into text format, but this time uses a slightly
different standard called Base64. However, the important
thing is the way in which the MIME mailing program works.

Unlike the traditional UUENCODE way, the user does not need
to play around with messy CLI only utilities. Instead, they
only need drag a file or two into a special window and it is
converted automatically. Each file is convered into a MIME
"partial" and included in the mail message. It is even more
impressive is what happens when the message reaches its
destination, for when set up properly, an image will
automatically be displayed, and a MED tune automatically
played. MIME is the ultimate way to exchange data by
electronic mail.


Subhead: Using METATOOL

To use MIME on the Amiga, you'll need a program called
MetaTool. MetaTool was written by Ellis Pritchard and is
available from the Aminet. I'm assuming that you already
have a email system operating on the Amiga, and therefore
have experience with either a Mailkick or AmiPOP program for
sending and receiving mail. For example, if you are a Demon
customer you'll be using the SendMail program for handling
the mail transfer.

Before you can start using MetaTool, you will need to make
sure that you have set up some environmental variables.
These sound horrendous, but it only means you need to
include the settings for your user name, domain name and
host name. The user name will be the name of your internet
postbox, and this will be the first name you picked when you
signed up with your service provider. The domain name is the
section you didn't pick yourself after @ sign in your email
address, and the host name the part you chose. For example,
my email address is "[e-mail]" and so I set
the variables like this:

setenv USER Johnk
setenv DOMAINNAME thegap.com
setenv HOST infosys-2

If your address was "[e-mail]" then you
would set the variables like this:

setenv USER brian
setenv DOMAINNAME demon.co.uk
setenv HOST toastrack

You can either type these directly into the Shell every time
you re-boot your Amiga, or save yourself a lot of time and
include them in your s:user-startup file. You may find that
they have been created for you when you installed AmiTCP:
you can check by typing setenv by itself and see watch to
see if USER, DOMAINNAME and HOST whizz past.

You'll also need to be using everyone's favourite Graphical
User Interface, Magic User Interface. If you are a heavy
Internet user you will probably alreay have MUI installed to
let you run AMosic or IBrowse.

Starting MetaTool should be painless if you remembered the
right setenv commands. and you'll see your "mail box"
included in the list. Open it up, and you are ready to send
a MIME message.

image: mime2.iff)
caption: MetaTool organises the mail into different
mailboxes. The name comes from the USERNAME environmental
variable.


Press Right Amiga-N to create a new message. You see the
compose window appear, and there will already be one element
in the list on the left. This is the "header", and you
should select it and press the EDIT button. Now you can
enter the email address of the recepient and any subject the
message may have.


Image: mime3.iff
caption: You can send copies of your mail message to others
by including names in other fields.



The easiest way to create a message is to drag and drop
icons into the window. Create a text file, and save it. Then
find the icon and drag it into the window. You can drag and
drop IFF images, LHA files or just about anything you can
imaging. Metatool will package them all up and when you
click on SEND or DISPATCH it will use the mailer program you
have running to send the message over the Internet.

You can also create parts of the message manually, without
dragging and dropping. Click on the NEW button, and you can
select the type of the object you want to send. You will
then be given a file requestor so you can select the file.

Image: mime4.iff
Caption: You can drag-and-drop files, or create them from
scratch and use a file requestor.


When you receive a MIME message, you can view it in MetaTool
simply by clicking on the constituent parts in the mesage
list. But how does the Amiga know what to do with each type
of file? This is the tricky section, but it's the only way
to really harness the power of the MIME system.


Subhead: MailCaps and MimeTypes


To alter what happens to existing files, or to add support
for your own specific application programs, you will need to
enter the murky world of the files called "mailcap" and
"mime.types". Both are in the MetaTool drawer, and you
should edit both with a standard text editor. Before you
start message about with them, it might be a good idea to
make a copy.

image: mime5.iff
Caption: Mailcap and meta.types are the two magic files for
determining what happens when you send and receive MIME mail.


The first file, mime.types, is to help MetaTool work out
what sort of file you have just dropped on top of it. By
default it will recognise many graphics formats, as well the
Amiga-specific AmigaGuide format. Here is how the AmigaGuide
format is included:


text/x-aguide        guide GUIDE

It's nothing too amazing: the file is obviously text based,
so the definition begins with "text/". It's not a standard
extension so there is an "x-" added to make this clear. Then
we have the possible file extension names in upper and lower
case.

The mailcap file tells MetaTool what to do when a MIME file
is received. Let's see how it mentions AmigaGuide files:


text/x-aguide; MultiView %s; label="An AmigaGuide file"; edit="emacs %s"

The matching line in the mailcap file tells MetaTool that
when a x-aguide file is shown, the Amiga must use Multiview.
That's what the section "MultiView %s" means, as the "%s"
will be replaced with the filename.

The last part of the line tells MetaTool what to do when the
file is edited. In this case, the emacs program is spawned.
You may not have emacs on your Amiga (I certainly don't,
because I'm sane) and you may want to edit this line to
reflect your own choice, such as CygnusEd or GoldEd.

You can easily extend this system yourself to both control
exactly what application is triggered to take card of an
incoming partial, and to add support for many other file
types. As long as both your system and the system of whoever
you are sending the message to have suitable entries in
mime.types and mailcap you should be able to send almost
anything by email.



image: mime6.iff
Caption: Cruel but funny -- MIME can be used to send
pictures as easily as text.




John Kennedy