Tcllib MIME

MIME, a Tcllib module, provides commands to create and manipulate MIME parts.

Synopsis edit

package require mime

Documentation edit

official reference for development release
official reference for latest release

Description edit

Based upon the MIME package from Marshall T. Rose, which has a hard dependency upon Trf. Tcllib's variation converts that into a soft dependency. It tries to use Trf to gain performance but falls back to pure tcl if that package is not present.

Example: Basic edit

The distribution documentation deserves many more examples. Until CL makes the time to update it, we'll keep several of them here. In this example, individual mail items might well have originated as return values from the pop3 package.

package require mime

set item {From [email protected] Tue May 29 11:49:26 EDT 2001
Date: Tue, 29 May 2001 11:03:02 -0500
From: Cameron Laird <[email protected]>
To: [email protected],[email protected]
Subject: some subject
Message-ID: <[email protected]>

This is only a test.}

# A production version deserves exception-handling.
set token [mime::initialize -string $item]

puts "The subject is '[mime::getheader $token Subject]'."

Address parsing is an area where many, MANY square wheels have been reinvented, in part because RFC 822 (and updates ... g) are so poorly understood. Here's an example of a correct usage:

# Take $item from above.
set token [mime::initialize -string $item]

set to [mime::getheader $token To]
puts "The (unparsed) recipients are '$to'."
set parsed [mime::parseaddress $to]
foreach element $parsed {
    array set array $element
    puts "One deliverable address is $array(address)."
}

This prints

The (unparsed) recipients are '[email protected],[email protected]'.
One deliverable address is [email protected].
One deliverable address is [email protected].

In the above example, $to is set as the result of

mime::getheader $token To

. This value is a list. However, in mime 1.5.4, mime::parseaddress wants a string so the that line should be:

set parsed [mime::parsedaddress [lindex $to 0]]

The curly braces were being treated as part of the string. That gave almost correct results. :)

Mail with special characters edit

It took me quite some time to come up with a version that can send an email with special characters (german Umlaute) and is correctly displayed in windows and unix.

package require smtp
set text {some text with 8 special characters äöü ÄÖÜ ß €}
set tok [mime::initialize -canonical text/plain -param {charset "utf-8"} \
    -encoding 8bit -string [encoding convertto utf-8 $text]
set erg [smtp::sendmessage $tok \
    -servers localhost \
    -recipients myself@localhost \
    -usetls 1 \
    -username myself \
    -password password \
    -header [
        list Subject [mime::word_encode utf-8 quoted-printable $text]] \
    -header [list From myself@localhost] \
    -header [list To myself@localhost] \
]

another version was

set tok [mime::initialize -canonical text/plain -param {charset "iso8859-1"} \
    -encoding 8bit -string $text]

but this doesn't show the Euro-Symbol. Using iso8859-16 doesn't work with windows mail program outlook.

There are lots of versions and combinations to try. An additional joy are ancient versions of tcllib used by colleagues.

Misc edit

Things to explain: performance issues (large messages: headers, split, buffering); package (including fix-up); examples; exception-(mis)handling; magic arrays; ...

CL has found two principal difficulties in trying to use mime with 8.0 or early 8.1: the "format %c ..." change (explain) and the incompatibility in interpretation of "\n" vs. {\n} to regsub (explain).

One of the difficulties in explaining mime is its flexibility. It can do many, many things, and it's hard to know where to begin explaining it. In a case like this, I like a few examples--feel free to think of them as a cookbook of recipes for starting points. How, for instance, can you use Tcl to automate emission of a message which includes an attachment?

One definite fault of 0.8 is that it only reports some of the filenames of attachments it detects (explain Content-Disposition alternative). CL has code that repairs this, but has yet to check it in.

As this is noted nowhere, use mime::word_encode to encode your headers according to your needs. As an example we are using

set subject_encoded [mime::word_encode "iso8859-1" base64 $subject]

to make sure the subject is encoded as well .

OpenACS has a complex_send procedure that makes use of a lot of the mime functionality. It is contained in [1].

Historical: mime::initialize edit

In earlier versions of MIME,

mime::initialize ... -string ...

could be slow. See ime::initialize has to perform better

, Cameron Laird, comp.lang.tcl, 2001-11-08.

That is probably not the best way to process a message of unknown size anyway. There is an example of a different approach in Sorting mail into Maildirs.

Andreas Kupries: One issue with performance (splitting a large string at each character created thousands of Tcl_Obj's containing all the same character, gobbling up memory like mad) was solved for Tcl 8.4a3, by Donal Fellows.

This performance improvement was also one of the Changes in Tcl/Tk 8.3.3.

MIME	Category Tcllib