WARNING
MIME-tools requires MIME::Base64 and MIME::QuotedPrint. It will work
with versions as old as 2.20, but some tests (when you do "make test")
will fail for MIME::QuotedPrint older than 3.03.
NAME
MIME-tools - modules for parsing (and creating!) MIME entities
SYNOPSIS
Here's some pretty basic code for parsing a MIME message, and outputting
its decoded components to a given directory:
use MIME::Parser;
### Create parser, and set some parsing options:
my $parser = new MIME::Parser;
$parser->output_under("$ENV{HOME}/mimemail");
### Parse input:
$entity = $parser->parse(\*STDIN) or die "parse failed\n";
### Take a look at the top-level entity (and any parts it has):
$entity->dump_skeleton;
Here's some code which composes and sends a MIME message containing
three parts: a text file, an attached GIF, and some more text:
use MIME::Entity;
### Create the top-level, and set up the mail headers:
$top = MIME::Entity->build(Type =>"multipart/mixed",
From => "me\@myhost.com",
To => "you\@yourhost.com",
Subject => "Hello, nurse!");
### Part #1: a simple text document:
$top->attach(Path=>"./testin/short.txt");
### Part #2: a GIF file:
$top->attach(Path => "./docs/mime-sm.gif",
Type => "image/gif",
Encoding => "base64");
### Part #3: some literal text:
$top->attach(Data=>$message);
### Send it:
open MAIL, "| /usr/lib/sendmail -t -oi -oem" or die "open: $!";
$top->print(\*MAIL);
close MAIL;
For more examples, look at the scripts in the examples directory of the
MIME-tools distribution.
DESCRIPTION
MIME-tools is a collection of Perl5 MIME:: modules for parsing,
decoding, *and generating* single- or multipart (even nested multipart)
MIME messages. (Yes, kids, that means you can send messages with
attached GIF files).
REQUIREMENTS
You will need the following installed on your system:
File::Path
File::Spec
IPC::Open2 (optional)
IO::Scalar, ... from the IO-stringy distribution
MIME::Base64
MIME::QuotedPrint
Net::SMTP
Mail::Internet, ... from the MailTools distribution.
See the Makefile.PL in your distribution for the most-comprehensive list
of prerequisite modules and their version numbers.
A QUICK TOUR
Overview of the classes
Here are the classes you'll generally be dealing with directly:
(START HERE) results() .-----------------.
\ .-------->| MIME:: |
.-----------. / | Parser::Results |
| MIME:: |--' `-----------------'
| Parser |--. .-----------------.
`-----------' \ filer() | MIME:: |
| parse() `-------->| Parser::Filer |
| gives you `-----------------'
| a... | output_path()
| | determines
| | path() of...
| head() .--------. |
| returns... | MIME:: | get() |
V .-------->| Head | etc... |
.--------./ `--------' |
.---> | MIME:: | |
`-----| Entity | .--------. |
parts() `--------'\ | MIME:: | /
returns `-------->| Body |<---------'
sub-entities bodyhandle() `--------'
(if any) returns... | open()
| returns...
|
V
.--------. read()
| IO:: | getline()
| Handle | print()
`--------' etc...
To illustrate, parsing works this way:
* The "parser" parses the MIME stream. A parser is an instance of
`MIME::Parser'. You hand it an input stream (like a filehandle) to
parse a message from: if the parse is successful, the result is an
"entity".
* A parsed message is represented by an "entity". An entity is an instance
of `MIME::Entity' (a subclass of `Mail::Internet'). If the message
had "parts" (e.g., attachments), then those parts are "entities" as
well, contained inside the top-level entity. Each entity has a
"head" and a "body".
* The entity's "head" contains information about the message. A "head" is
an instance of `MIME::Head' (a subclass of `Mail::Header'). It
contains information from the message header: content type, sender,
subject line, etc.
* The entity's "body" knows where the message data is. You can ask to
"open" this data source for *reading* or *writing*, and you will get
back an "I/O handle".
* You can open() a "body" and get an "I/O handle" to read/write message
data. This handle is an object that is basically like an IO::Handle
or a FileHandle... it can be any class, so long as it supports a
small, standard set of methods for reading from or writing to the
underlying data source.
A typical multipart message containing two parts -- a textual greeting
and an "attached" GIF file -- would be a tree of MIME::Entity objects,
each of which would have its own MIME::Head. Like this:
.--------.
| MIME:: | Content-type: multipart/mixed
| Entity | Subject: Happy Samhaine!
`--------'
|
`----.
parts |
| .--------.
|---| MIME:: | Content-type: text/plain; charset=us-ascii
| | Entity | Content-transfer-encoding: 7bit
| `--------'
| .--------.
|---| MIME:: | Content-type: image/gif
| Entity | Content-transfer-encoding: base64
`--------' Content-disposition: inline;
filename="hs.gif"
Parsing messages
You usually start by creating an instance of MIME::Parser and setting up
certain parsing parameters: what directory to save extracted files to,
how to name the files, etc.
You then give that instance a readable filehandle on which waits a MIME
message. If all goes well, you will get back a MIME::Entity object (a
subclass of Mail::Internet), which consists of...
* A MIME::Head (a subclass of Mail::Header) which holds the MIME header
data.
* A MIME::Body, which is a object that knows where the body data is. You
ask this object to "open" itself for reading, and it will hand you
back an "I/O handle" for reading the data: this is a FileHandle-like
object, and could be of any class, so long as it conforms to a
subset of the IO::Handle interface.
If the original message was a multipart document, the MIME::Entity
object will have a non-empty list of "parts", each of which is in turn a
MIME::Entity (which might also be a multipart entity, etc, etc...).
Internally, the parser (in MIME::Parser) asks for instances of
MIME::Decoder whenever it needs to decode an encoded file. MIME::Decoder
has a mapping from supported encodings (e.g., 'base64') to classes whose
instances can decode them. You can add to this mapping to try out
new/experiment encodings. You can also use MIME::Decoder by itself.
Composing messages
All message composition is done via the MIME::Entity class. For single-
part messages, you can use the MIME::Entity/build constructor to create
MIME entities very easily.
For multipart messages, you can start by creating a top-level
`multipart' entity with MIME::Entity::build(), and then use the similar
MIME::Entity::attach() method to attach parts to that message. *Please
note:* what most people think of as "a text message with an attached GIF
file" is *really* a multipart message with 2 parts: the first being the
text message, and the second being the GIF file.
When building MIME a entity, you'll have to provide two very important
pieces of information: the *content type* and the *content transfer
encoding*. The type is usually easy, as it is directly determined by the
file format; e.g., an HTML file is `text/html'. The encoding, however,
is trickier... for example, some HTML files are `7bit'-compliant, but
others might have very long lines and would need to be sent `quoted-
printable' for reliability.
See the section on encoding/decoding for more details, as well as the
section on "A MIME PRIMER".
Sending email
Since MIME::Entity inherits directly from Mail::Internet, you can use
the normal Mail::Internet mechanisms to send email. For example,
$entity->smtpsend;
Encoding/decoding support
The MIME::Decoder class can be used to *encode* as well; this is done
when printing MIME entities. All the standard encodings are supported
(see the section on "A MIME PRIMER" for details):
Encoding: | Normally used when message contents are:
-------------------------------------------------------------------
7bit | 7-bit data with under 1000 chars/line, or multipart.
8bit | 8-bit data with under 1000 chars/line.
binary | 8-bit data with some long lines (or no line breaks).
quoted-printable | Text files with some 8-bit chars (e.g., Latin-1 text).
base64 | Binary files.
Which encoding you choose for a given document depends largely on (1)
what you know about the document's contents (text vs binary), and (2)
whether you need the resulting message to have a reliable encoding for
7-bit Internet email transport.
In general, only `quoted-printable' and `base64' guarantee reliable
transport of all data; the other three "no-encoding" encodings simply
pass the data through, and are only reliable if that data is 7bit ASCII
with under 1000 characters per line, and has no conflicts with the
multipart boundaries.
I've considered making it so that the content-type and encoding can be
automatically inferred from the file's path, but that seems to be asking
for trouble... or at least, for Mail::Cap...
Message-logging
MIME-tools is a large and complex toolkit which tries to deal with a
wide variety of external input. It's sometimes helpful to see what's
really going on behind the scenes. There are several kinds of messages
logged by the toolkit itself:
Debug messages
These are printed directly to the STDERR, with a prefix of `"MIME-
tools: debug"'.
Debug message are only logged if you have turned the debugging entry
elsewhere in this document on in the MIME::Tools configuration.
Warning messages
These are logged by the standard Perl warn() mechanism to indicate
an unusual situation. They all have a prefix of `"MIME-tools:
warning"'.
Warning messages are only logged if `$^W' is set true and
MIME::Tools is not configured to be the quiet entry elsewhere in
this document .
Error messages
These are logged by the standard Perl warn() mechanism to indicate
that something actually failed. They all have a prefix of `"MIME-
tools: error"'.
Error messages are only logged if `$^W' is set true and MIME::Tools
is not configured to be the quiet entry elsewhere in this document .
Usage messages
Unlike "typical" warnings above, which warn about problems
processing data, usage-warnings are for alerting developers of
deprecated methods and suspicious invocations.
Usage messages are currently only logged if `$^W' is set true and
MIME::Tools is not configured to be the quiet entry elsewhere in
this document .
When a MIME::Parser (or one of its internal helper classes) wants to
report a message, it generally does so by recording the message to the
MIME::Parser::Results object immediately before invoking the appropriate
function above. That means each parsing run has its own trace-log which
can be examined for problems.
Configuring the toolkit
If you want to tweak the way this toolkit works (for example, to turn on
debugging), use the routines in the MIME::Tools module.
debugging
Turn debugging on or off. Default is false (off).
MIME::Tools->debugging(1);
quiet
Turn the reporting of warning/error messages on or off. Default is
true, meaning that these message are silenced.
MIME::Tools->quiet(1);
version
Return the toolkit version.
print MIME::Tools->version, "\n";
THINGS YOU SHOULD DO
Take a look at the examples
The MIME-Tools distribution comes with an "examples" directory. The
scripts in there are basically just tossed-together, but they'll give
you some ideas of how to use the parser.
Run with warnings enabled
*Always* run your Perl script with `-w'. If you see a warning about a
deprecated method, change your code ASAP. This will ease upgrades
tremendously.
Avoid non-standard encodings
Don't try to MIME-encode using the non-standard MIME encodings. It's
just not a good practice if you want people to be able to read your
messages.
Plan for thrown exceptions
For example, if your mail-handling code absolutely must not die, then
perform mail parsing like this:
$entity = eval { $parser->parse(\*INPUT) };
Parsing is a complex process, and some components may throw exceptions
if seriously-bad things happen. Since "seriously-bad" is in the eye of
the beholder, you're better off *catching* possible exceptions instead
of asking me to propagate `undef' up the stack. Use of exceptions in
reusable modules is one of those religious issues we're never all going
to agree upon; thankfully, that's what `eval{}' is good for.
Check the parser results for warnings/errors
As of 5.3xx, the parser tries extremely hard to give you a MIME::Entity.
If there were any problems, it logs warnings/errors to the underlying
"results" object (see the MIME::Parser::Results manpage). Look at that
object after each parse. Print out the warnings and errors, *especially*
if messages don't parse the way you thought they would.
Don't plan on printing exactly what you parsed!
*Parsing is a (slightly) lossy operation.* Because of things like
ambiguities in base64-encoding, the following is *not* going to spit out
its input unchanged in all cases:
$entity = $parser->parse(\*STDIN);
$entity->print(\*STDOUT);
If you're using MIME::Tools to process email, remember to save the data
you parse if you want to send it on unchanged. This is vital for things
like PGP-signed email.
Understand how international characters are represented
The MIME standard allows for text strings in headers to contain
characters from any character set, by using special sequences which look
like this:
=?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?=
To be consistent with the existing Mail::Field classes, MIME::Tools does
*not* automatically unencode these strings, since doing so would lose
the character-set information and interfere with the parsing of fields
(see the "decode_headers" entry in the MIME::Parser manpage for a full
explanation). That means you should be prepared to deal with these
encoded strings.
The most common question then is, how do I decode these encoded strings?
The answer depends on what you want to decode them *to*: ASCII, Latin1,
UTF-8, etc. Be aware that your "target" representation may not support
all possible character sets you might encounter; for example, Latin1
(ISO-8859-1) has no way of representing Big5 (Chinese) characters. A
common practice is to represent "untranslateable" characters as "?"s, or
to ignore them completely.
To unencode the strings into some of the more-popular Western byte
representations (e.g., Latin1, Latin2, etc.), you can use the decoders
in MIME::WordDecoder (see the MIME::WordDecoder manpage). The simplest
way is by using `unmime()', a function wrapped around your "default"
decoder, as follows:
use MIME::WordDecoder;
...
$subject = unmime $entity->head->get('subject');
One place this *is* done automatically is in extracting the recommended
filename for a part while parsing. That's why you should start by
setting up the best "default" decoder if the default target of Latin1
isn't to your liking.
THINGS I DO THAT YOU SHOULD KNOW ABOUT
Fuzzing of CRLF and newline on input
RFC-1521 dictates that MIME streams have lines terminated by CRLF
(`"\r\n"'). However, it is extremely likely that folks will want to
parse MIME streams where each line ends in the local newline character
`"\n"' instead.
An attempt has been made to allow the parser to handle both CRLF and
newline-terminated input.
Fuzzing of CRLF and newline when decoding
The `"7bit"' and `"8bit"' decoders will decode both a `"\n"' and a
`"\r\n"' end-of-line sequence into a `"\n"'.
The `"binary"' decoder (default if no encoding specified) still outputs
stuff verbatim... so a MIME message with CRLFs and no explicit encoding
will be output as a text file that, on many systems, will have an
annoying ^M at the end of each line... *but this is as it should be*.
Fuzzing of CRLF and newline when encoding/composing
All encoders currently output the end-of-line sequence as a `"\n"', with
the assumption that the local mail agent will perform the conversion
from newline to CRLF when sending the mail. However, there probably
should be an option to output CRLF as per RFC-1521.
Inability to handle multipart boundaries with embedded newlines
Let's get something straight: this is an evil, EVIL practice. If your
mailer creates multipart boundary strings that contain newlines, give it
two weeks notice and find another one. If your mail robot receives MIME
mail like this, regard it as syntactically incorrect, which it is.
Ignoring non-header headers
People like to hand the parser raw messages straight from POP3 or from a
mailbox. There is often predictable non-header information in front of
the real headers; e.g., the initial "From" line in the following
message:
From - Wed Mar 22 02:13:18 2000
Return-Path: <eryq@zeegee.com>
Subject: Hello
The parser simply ignores such stuff quietly. Perhaps it shouldn't, but
most people seem to want that behavior.
Fuzzing of empty multipart preambles
Please note that there is currently an ambiguity in the way preambles
are parsed in. The following message fragments *both* are regarded as
having an empty preamble (where `\n' indicates a newline character):
Content-type: multipart/mixed; boundary="xyz"\n
Subject: This message (#1) has an empty preamble\n
\n
--xyz\n
...
Content-type: multipart/mixed; boundary="xyz"\n
Subject: This message (#2) also has an empty preamble\n
\n
\n
--xyz\n
...
In both cases, the *first* completely-empty line (after the "Subject")
marks the end of the header.
But we should clearly ignore the *second* empty line in message #2,
since it fills the role of *"the newline which is only there to make
sure that the boundary is at the beginning of a line"*. Such newlines
are *never* part of the content preceding the boundary; thus, there is
no preamble "content" in message #2.
However, it seems clear that message #1 *also* has no preamble
"content", and is in fact merely a compact representation of an empty
preamble.
Use of a temp file during parsing
*Why not do everything in core?* Although the amount of core available
on even a modest home system continues to grow, the size of attachments
continues to grow with it. I wanted to make sure that even users with
small systems could deal with decoding multi-megabyte sounds and movie
files. That means not being core-bound.
As of the released 5.3xx, MIME::Parser gets by with only one temp file
open per parser. This temp file provides a sort of infinite scratch
space for dealing with the current message part. It's fast and
lightweight, but you should know about it anyway.
Why do I assume that MIME objects are email objects?
Achim Bohnet once pointed out that MIME headers do nothing more than
store a collection of attributes, and thus could be represented as
objects which don't inherit from Mail::Header.
I agree in principle, but RFC-1521 says otherwise. RFC-1521 [MIME]
headers are a syntactic subset of RFC-822 [email] headers. Perhaps a
better name for these modules would have been RFC1521:: instead of
MIME::, but we're a little beyond that stage now.
When I originally wrote these modules for the CPAN, I agonized for a
long time about whether or not they really should subclass from
Mail::Internet (then at version 1.17). Thanks to Graham Barr, who
graciously evolved MailTools 1.06 to be more MIME-friendly, unification
was achieved at MIME-tools release 2.0. The benefits in reuse alone have
been substantial.
A MIME PRIMER
So you need to parse (or create) MIME, but you're not quite up on the
specifics? No problem...
Glossary
Here are some definitions adapted from RFC-1521 explaining the
terminology we use; each is accompanied by the equivalent in MIME::
module terms...
attachment
An "attachment" is common slang for any part of a multipart message
-- except, perhaps, for the first part, which normally carries a
user message describing the attachments that follow (e.g.: "Hey
dude, here's that GIF file I promised you.").
In our system, an attachment is just a MIME::Entity under the top-
level entity, probably one of its parts.
body
The "body" of an entity is that portion of the entity which follows
the header and which contains the real message content. For example,
if your MIME message has a GIF file attachment, then the body of
that attachment is the base64-encoded GIF file itself.
A body is represented by an instance of MIME::Body. You get the body
of an entity by sending it a bodyhandle() message.
body part
One of the parts of the body of a multipart /entity. A body part has
a /header and a /body, so it makes sense to speak about the body of
a body part.
Since a body part is just a kind of entity, it's represented by an
instance of MIME::Entity.
entity
An "entity" means either a /message or a /body part. All entities
have a /header and a /body.
An entity is represented by an instance of MIME::Entity. There are
instance methods for recovering the header (a MIME::Head) and the
body (a MIME::Body).
header
This is the top portion of the MIME message, which contains the
"Content-type", "Content-transfer-encoding", etc. Every MIME entity
has a header, represented by an instance of MIME::Head. You get the
header of an entity by sending it a head() message.
message
A "message" generally means the complete (or "top-level") message
being transferred on a network.
There currently is no explicit package for "messages"; under MIME::,
messages are streams of data which may be read in from files or
filehandles. You can think of the MIME::Entity returned by the
MIME::Parser as representing the full message.
Content types
This indicates what kind of data is in the MIME message, usually as
*majortype/minortype*. The standard major types are shown below. A more-
comprehensive listing may be found in RFC-2046.
application
Data which does not fit in any of the other categories, particularly
data to be processed by some type of application program.
`application/octet-stream', `application/gzip',
`application/postscript'...
audio
Audio data. `audio/basic'...
image
Graphics data. `image/gif', `image/jpeg'...
message
A message, usually another mail or MIME message. `message/rfc822'...
multipart
A message containing other messages. `multipart/mixed',
`multipart/alternative'...
text
Textual data, meant for humans to read. `text/plain', `text/html'...
video
Video or video+audio data. `video/mpeg'...
Content transfer encodings
This is how the message body is packaged up for safe transit. There are
the 5 major MIME encodings. A more-comprehensive listing may be found in
RFC-2045.
7bit
No encoding is done at all. This label simply asserts that no 8-bit
characters are present, and that lines do not exceed 1000 characters
in length (including the CRLF).
8bit
No encoding is done at all. This label simply asserts that the
message might contain 8-bit characters, and that lines do not exceed
1000 characters in length (including the CRLF).
binary
No encoding is done at all. This label simply asserts that the
message might contain 8-bit characters, and that lines may exceed
1000 characters in length. Such messages are the *least* likely to
get through mail gateways.
base64
A standard encoding, which maps arbitrary binary data to the 7bit
domain. Like "uuencode", but very well-defined. This is how you
should send essentially binary information (tar files, GIFs, JPEGs,
etc.).
quoted-printable
A standard encoding, which maps arbitrary line-oriented data to the
7bit domain. Useful for encoding messages which are textual in
nature, yet which contain non-ASCII characters (e.g., Latin-1,
Latin-2, or any other 8-bit alphabet).
TERMS AND CONDITIONS
Eryq (eryq@zeegee.com), ZeeGee Software Inc (http://www.zeegee.com).
Dianne Skoll (dianne@skoll.ca)
Copyright (c) 1998, 1999 by ZeeGee Software Inc (www.zeegee.com).
Copyright (c) 2004 by Roaring Penguin Software Inc (www.roaringpenguin.com)
Copyright (c) 2022 by Dianne Skoll
All rights reserved. This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself. See the COPYING
file in the distribution for details.
SUPPORT
Please file bug reports via rt.cpan.org.
AUTHOR
MIME-tools was created by:
___ _ _ _ _ ___ _
/ _ \| '_| | | |/ _ ' / Eryq, (eryq@zeegee.com)
| __/| | | |_| | |_| | President, ZeeGee Software Inc.
\___||_| \__, |\__, |__ http://www.zeegee.com/
|___/ |___/
Released as MIME-parser (1.0): 28 April 1996. Released as MIME-tools
(2.0): Halloween 1996. Released as MIME-tools (4.0): Christmas 1997.
Released as MIME-tools (5.0): Mother's Day 2000.
MIME-tools is currently maintained by Dianne Skoll <dfs@roaringoenguin.com>
ACKNOWLEDGMENTS
This kit would not have been possible but for the direct contributions
of the following:
Gisle Aas The MIME encoding/decoding modules.
Laurent Amon Bug reports and suggestions.
Graham Barr The new MailTools.
Achim Bohnet Numerous good suggestions, including the I/O model.
Kent Boortz Initial code for RFC-1522-decoding of MIME headers.
Andreas Koenig Numerous good ideas, tons of beta testing,
and help with CPAN-friendly packaging.
Igor Starovoitov Bug reports and suggestions.
Jason L Tibbitts III Bug reports, suggestions, patches.
Not to mention the Accidental Beta Test Team, whose bug reports (and
comments) have been invaluable in improving the whole:
Phil Abercrombie
Mike Blazer
Brandon Browning
Kurt Freytag
Steve Kilbane
Jake Morrison
Rolf Nelson
Joel Noble
Michael W. Normandin
Tim Pierce
Andrew Pimlott
Dragomir R. Radev
Nickolay Saukh
Russell Sutherland
Larry Virden
Zyx
Please forgive me if I've accidentally left you out. Better yet, email
me, and I'll put you in.
SEE ALSO
Search CPAN for MIME::tools.
Users of this toolkit may wish to read the documentation of Mail::Header
and Mail::Internet.
The MIME format is documented in RFCs 1521-1522, and more recently in
RFCs 2045-2049.
The MIME header format is an outgrowth of the mail header format
documented in RFC 822.