3 @setfilename emacs-mime
4 @settitle Emacs MIME Manual
10 * Emacs MIME: (emacs-mime). The MIME de/composition library.
15 @setchapternewpage odd
19 This file documents the Emacs MIME interface functionality.
21 Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
23 Permission is granted to copy, distribute and/or modify this document
24 under the terms of the GNU Free Documentation License, Version 1.1 or
25 any later version published by the Free Software Foundation; with no
26 Invariant Sections, with the Front-Cover texts being ``A GNU
27 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
28 license is included in the section entitled ``GNU Free Documentation
29 License'' in the Emacs manual.
31 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
32 this GNU Manual, like GNU software. Copies published by the Free
33 Software Foundation raise funds for GNU development.''
35 This document is part of a collection distributed under the GNU Free
36 Documentation License. If you want to distribute this document
37 separately from the collection, you can do so by adding a copy of the
38 license to the document, as described in section 6 of the license.
44 @title Emacs MIME Manual
46 @author by Lars Magne Ingebrigtsen
49 @vskip 0pt plus 1filll
50 Copyright @copyright{} 1998, 1999, 2000 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.1 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being none, with the Front-Cover texts being ``A GNU
56 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
57 license is included in the section entitled ``GNU Free Documentation
58 License'' in the Emacs manual.
60 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
61 this GNU Manual, like GNU software. Copies published by the Free
62 Software Foundation raise funds for GNU development.''
64 This document is part of a collection distributed under the GNU Free
65 Documentation License. If you want to distribute this document
66 separately from the collection, you can do so by adding a copy of the
67 license to the document, as described in section 6 of the license.
76 This manual documents the libraries used to compose and display
79 This is not a manual meant for users; it's a manual directed at people
80 who want to write functions and commands that manipulate @sc{mime}
83 @sc{mime} is short for @dfn{Multipurpose Internet Mail Extensions}.
84 This standard is documented in a number of RFCs; mainly RFC2045 (Format
85 of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
86 Header Extensions for Non-ASCII Text), RFC2048 (Registration
87 Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
88 recommended that anyone who intends writing @sc{mime}-compliant software
89 read at least RFC2045 and RFC2047.
92 * Interface Functions:: An abstraction over the basic functions.
93 * Basic Functions:: Utility and basic parsing functions.
94 * Decoding and Viewing:: A framework for decoding and viewing.
95 * Composing:: MML; a language for describing MIME parts.
96 * Standards:: A summary of RFCs and working documents used.
97 * Index:: Function and variable index.
101 @node Interface Functions
102 @chapter Interface Functions
103 @cindex interface functions
106 The @code{mail-parse} library is an abstraction over the actual
107 low-level libraries that are described in the next chapter.
109 Standards change, and so programs have to change to fit in the new
110 mold. For instance, RFC2045 describes a syntax for the
111 @code{Content-Type} header that only allows ASCII characters in the
112 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
113 for continuation headers and non-ASCII characters.
115 The traditional way to deal with this is just to update the library
116 functions to parse the new syntax. However, this is sometimes the wrong
117 thing to do. In some instances it may be vital to be able to understand
118 both the old syntax as well as the new syntax, and if there is only one
119 library, one must choose between the old version of the library and the
120 new version of the library.
122 The Emacs MIME library takes a different tack. It defines a series of
123 low-level libraries (@file{rfc2047.el}, @file{rfc2231.el} and so on)
124 that parses strictly according to the corresponding standard. However,
125 normal programs would not use the functions provided by these libraries
126 directly, but instead use the functions provided by the
127 @code{mail-parse} library. The functions in this library are just
128 aliases to the corresponding functions in the latest low-level
129 libraries. Using this scheme, programs get a consistent interface they
130 can use, and library developers are free to create write code that
131 handles new standards.
133 The following functions are defined by this library:
136 @item mail-header-parse-content-type
137 @findex mail-header-parse-content-type
138 Parse a @code{Content-Type} header and return a list on the following
143 (attribute1 . value1)
144 (attribute2 . value2)
151 (mail-header-parse-content-type
152 "image/gif; name=\"b980912.gif\"")
153 @result{} ("image/gif" (name . "b980912.gif"))
156 @item mail-header-parse-content-disposition
157 @findex mail-header-parse-content-disposition
158 Parse a @code{Content-Disposition} header and return a list on the same
159 format as the function above.
161 @item mail-content-type-get
162 @findex mail-content-type-get
163 Takes two parameters---a list on the format above, and an attribute.
164 Returns the value of the attribute.
167 (mail-content-type-get
168 '("image/gif" (name . "b980912.gif")) 'name)
169 @result{} "b980912.gif"
172 @item mail-header-encode-parameter
173 @findex mail-header-encode-parameter
174 Takes a parameter string and returns an encoded version of the string.
175 This is used for parameters in headers like @code{Content-Type} and
176 @code{Content-Disposition}.
178 @item mail-header-remove-comments
179 @findex mail-header-remove-comments
180 Return a comment-free version of a header.
183 (mail-header-remove-comments
184 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
185 @result{} "Gnus/5.070027 "
188 @item mail-header-remove-whitespace
189 @findex mail-header-remove-whitespace
190 Remove linear white space from a header. Space inside quoted strings
191 and comments is preserved.
194 (mail-header-remove-whitespace
195 "image/gif; name=\"Name with spaces\"")
196 @result{} "image/gif;name=\"Name with spaces\""
199 @item mail-header-get-comment
200 @findex mail-header-get-comment
201 Return the last comment in a header.
204 (mail-header-get-comment
205 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
206 @result{} "Finnish Landrace"
209 @item mail-header-parse-address
210 @findex mail-header-parse-address
211 Parse an address and return a list containing the mailbox and the
215 (mail-header-parse-address
216 "Hrvoje Niksic <hniksic@@srce.hr>")
217 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
220 @item mail-header-parse-addresses
221 @findex mail-header-parse-addresses
222 Parse a string with list of addresses and return a list of elements like
223 the one described above.
226 (mail-header-parse-addresses
227 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
228 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
229 ("sb@@metis.no" . "Steinar Bang"))
232 @item mail-header-parse-date
233 @findex mail-header-parse-date
234 Parse a date string and return an Emacs time structure.
236 @item mail-narrow-to-head
237 @findex mail-narrow-to-head
238 Narrow the buffer to the header section of the buffer. Point is placed
239 at the beginning of the narrowed buffer.
241 @item mail-header-narrow-to-field
242 @findex mail-header-narrow-to-field
243 Narrow the buffer to the header under point. Understands continuation
246 @item mail-header-fold-field
247 @findex mail-header-fold-field
248 Fold the header under point.
250 @item mail-header-unfold-field
251 @findex mail-header-unfold-field
252 Unfold the header under point.
254 @item mail-encode-encoded-word-region
255 @findex mail-encode-encoded-word-region
256 Encode the non-ASCII words in the region. For instance,
257 @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
259 @item mail-encode-encoded-word-buffer
260 @findex mail-encode-encoded-word-buffer
261 Encode the non-ASCII words in the current buffer. This function is
262 meant to be called narrowed to the headers of a message.
264 @item mail-encode-encoded-word-string
265 @findex mail-encode-encoded-word-string
266 Encode the words that need encoding in a string, and return the result.
269 (mail-encode-encoded-word-string
270 "This is naïve, baby")
271 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
274 @item mail-decode-encoded-word-region
275 @findex mail-decode-encoded-word-region
276 Decode the encoded words in the region.
278 @item mail-decode-encoded-word-string
279 @findex mail-decode-encoded-word-string
280 Decode the encoded words in the string and return the result.
283 (mail-decode-encoded-word-string
284 "This is =?iso-8859-1?q?na=EFve,?= baby")
285 @result{} "This is naïve, baby"
290 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
291 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
292 in the subsequent sections.
296 @node Basic Functions
297 @chapter Basic Functions
299 This chapter describes the basic, ground-level functions for parsing and
300 handling. Covered here is parsing @code{From} lines, removing comments
301 from header lines, decoding encoded words, parsing date headers and so
302 on. High-level functionality is dealt with in the next chapter
303 (@pxref{Decoding and Viewing}).
306 * rfc2045:: Encoding @code{Content-Type} headers.
307 * rfc2231:: Parsing @code{Content-Type} headers.
308 * ietf-drums:: Handling mail headers defined by RFC822bis.
309 * rfc2047:: En/decoding encoded words in headers.
310 * time-date:: Functions for parsing dates and manipulating time.
311 * qp:: Quoted-Printable en/decoding.
312 * base64:: Base64 en/decoding.
313 * binhex:: Binhex decoding.
314 * uudecode:: Uuencode decoding.
315 * rfc1843:: Decoding HZ-encoded text.
316 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
323 RFC2045 is the ``main'' @sc{mime} document, and as such, one would
324 imagine that there would be a lot to implement. But there isn't, since
325 most of the implementation details are delegated to the subsequent
328 So @file{rfc2045.el} has only a single function:
331 @item rfc2045-encode-string
332 @findex rfc2045-encode-string
333 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
334 @var{value} will be quoted if there are non-safe characters in it.
341 RFC2231 defines a syntax for the @code{Content-Type} and
342 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
343 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
346 In short, these headers look something like this:
349 Content-Type: application/x-stuff;
350 title*0*=us-ascii'en'This%20is%20even%20more%20;
351 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
355 They usually aren't this bad, though.
357 The following functions are defined by this library:
360 @item rfc2231-parse-string
361 @findex rfc2231-parse-string
362 Parse a @code{Content-Type} header and return a list describing its
366 (rfc2231-parse-string
367 "application/x-stuff;
368 title*0*=us-ascii'en'This%20is%20even%20more%20;
369 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
370 title*2=\"isn't it!\"")
371 @result{} ("application/x-stuff"
372 (title . "This is even more ***fun*** isn't it!"))
375 @item rfc2231-get-value
376 @findex rfc2231-get-value
377 Takes one of the lists on the format above and returns
378 the value of the specified attribute.
380 @item rfc2231-encode-string
381 @findex rfc2231-encode-string
382 Encode a parameter in headers likes @code{Content-Type} and
383 @code{Content-Disposition}.
391 @dfn{drums} is an IETF working group that is working on the replacement
394 The functions provided by this library include:
397 @item ietf-drums-remove-comments
398 @findex ietf-drums-remove-comments
399 Remove the comments from the argument and return the results.
401 @item ietf-drums-remove-whitespace
402 @findex ietf-drums-remove-whitespace
403 Remove linear white space from the string and return the results.
404 Spaces inside quoted strings and comments are left untouched.
406 @item ietf-drums-get-comment
407 @findex ietf-drums-get-comment
408 Return the last most comment from the string.
410 @item ietf-drums-parse-address
411 @findex ietf-drums-parse-address
412 Parse an address string and return a list that contains the mailbox and
415 @item ietf-drums-parse-addresses
416 @findex ietf-drums-parse-addresses
417 Parse a string that contains any number of comma-separated addresses and
418 return a list that contains mailbox/plain text pairs.
420 @item ietf-drums-parse-date
421 @findex ietf-drums-parse-date
422 Parse a date string and return an Emacs time structure.
424 @item ietf-drums-narrow-to-header
425 @findex ietf-drums-narrow-to-header
426 Narrow the buffer to the header section of the current buffer.
434 RFC2047 (Message Header Extensions for Non-ASCII Text) specifies how
435 non-ASCII text in headers are to be encoded. This is actually rather
436 complicated, so a number of variables are necessary to tweak what this
439 The following variables are tweakable:
442 @item rfc2047-default-charset
443 @vindex rfc2047-default-charset
444 Characters in this charset should not be decoded by this library.
445 This defaults to @code{iso-8859-1}.
447 @item rfc2047-header-encoding-list
448 @vindex rfc2047-header-encoding-list
449 This is an alist of header / encoding-type pairs. Its main purpose is
450 to prevent encoding of certain headers.
452 The keys can either be header regexps, or @code{t}.
454 The values can be either @code{nil}, in which case the header(s) in
455 question won't be encoded, or @code{mime}, which means that they will be
458 @item rfc2047-charset-encoding-alist
459 @vindex rfc2047-charset-encoding-alist
460 RFC2047 specifies two forms of encoding---@code{Q} (a
461 Quoted-Printable-like encoding) and @code{B} (base64). This alist
462 specifies which charset should use which encoding.
464 @item rfc2047-encoding-function-alist
465 @vindex rfc2047-encoding-function-alist
466 This is an alist of encoding / function pairs. The encodings are
467 @code{Q}, @code{B} and @code{nil}.
469 @item rfc2047-q-encoding-alist
470 @vindex rfc2047-q-encoding-alist
471 The @code{Q} encoding isn't quite the same for all headers. Some
472 headers allow a narrower range of characters, and that is what this
473 variable is for. It's an alist of header regexps / allowable character
476 @item rfc2047-encoded-word-regexp
477 @vindex rfc2047-encoded-word-regexp
478 When decoding words, this library looks for matches to this regexp.
482 Those were the variables, and these are this functions:
485 @item rfc2047-narrow-to-field
486 @findex rfc2047-narrow-to-field
487 Narrow the buffer to the header on the current line.
489 @item rfc2047-encode-message-header
490 @findex rfc2047-encode-message-header
491 Should be called narrowed to the header of a message. Encodes according
492 to @code{rfc2047-header-encoding-alist}.
494 @item rfc2047-encode-region
495 @findex rfc2047-encode-region
496 Encodes all encodable words in the region specified.
498 @item rfc2047-encode-string
499 @findex rfc2047-encode-string
500 Encode a string and return the results.
502 @item rfc2047-decode-region
503 @findex rfc2047-decode-region
504 Decode the encoded words in the region.
506 @item rfc2047-decode-string
507 @findex rfc2047-decode-string
508 Decode a string and return the results.
516 While not really a part of the @sc{mime} library, it is convenient to
517 document this library here. It deals with parsing @code{Date} headers
518 and manipulating time. (Not by using tesseracts, though, I'm sorry to
521 These functions convert between five formats: A date string, an Emacs
522 time structure, a decoded time list, a second number, and a day number.
524 Here's a bunch of time/date/second/day examples:
527 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
528 @result{} (54 21 12 12 9 1998 6 nil 7200)
530 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
531 @result{} (13818 19266)
533 (time-to-seconds '(13818 19266))
534 @result{} 905595714.0
536 (seconds-to-time 905595714.0)
537 @result{} (13818 19266 0)
539 (time-to-days '(13818 19266))
542 (days-to-time 729644)
543 @result{} (961933 65536)
545 (time-since '(13818 19266))
548 (time-less-p '(13818 19266) '(13818 19145))
551 (subtract-time '(13818 19266) '(13818 19145))
554 (days-between "Sat Sep 12 12:21:54 1998 +0200"
555 "Sat Sep 07 12:21:54 1998 +0200")
558 (date-leap-year-p 2000)
561 (time-to-day-in-year '(13818 19266))
564 (time-to-number-of-days
566 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
567 @result{} 4.146122685185185
570 And finally, we have @code{safe-date-to-time}, which does the same as
571 @code{date-to-time}, but returns a zero time if the date is
572 syntactically malformed.
574 The five data representations used are the following:
578 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
579 12:21:54 1998 +0200"}.
582 An internal Emacs time. For instance: @code{(13818 26466)}.
585 A floating point representation of the internal Emacs time. For
586 instance: @code{905595714.0}.
589 An integer number representing the number of days since 00000101. For
590 instance: @code{729644}.
593 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
597 All the examples above represent the same moment.
599 These are the functions available:
603 Take a date and return a time.
605 @item time-to-seconds
606 Take a time and return seconds.
608 @item seconds-to-time
609 Take seconds and return a time.
612 Take a time and return days.
615 Take days and return a time.
618 Take a date and return days.
620 @item time-to-number-of-days
621 Take a time and return the number of days that represents.
623 @item safe-date-to-time
624 Take a date and return a time. If the date is not syntactically valid,
625 return a "zero" date.
628 Take two times and say whether the first time is less (i. e., earlier)
629 than the second time.
632 Take a time and return a time saying how long it was since that time.
635 Take two times and subtract the second from the first. I. e., return
636 the time between the two times.
639 Take two days and return the number of days between those two days.
641 @item date-leap-year-p
642 Take a year number and say whether it's a leap year.
644 @item time-to-day-in-year
645 Take a time and return the day number within the year that the time is
654 This library deals with decoding and encoding Quoted-Printable text.
656 Very briefly explained, qp encoding means translating all 8-bit
657 characters (and lots of control characters) into things that look like
658 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
661 The following functions are defined by the library:
664 @item quoted-printable-decode-region
665 @findex quoted-printable-decode-region
666 QP-decode all the encoded text in the specified region.
668 @item quoted-printable-decode-string
669 @findex quoted-printable-decode-string
670 Decode the QP-encoded text in a string and return the results.
672 @item quoted-printable-encode-region
673 @findex quoted-printable-encode-region
674 QP-encode all the encodable characters in the specified region. The third
675 optional parameter @var{fold} specifies whether to fold long lines.
676 (Long here means 72.)
678 @item quoted-printable-encode-string
679 @findex quoted-printable-encode-string
680 QP-encode all the encodable characters in a string and return the
690 Base64 is an encoding that encodes three bytes into four characters,
691 thereby increasing the size by about 33%. The alphabet used for
692 encoding is very resistant to mangling during transit.
694 The following functions are defined by this library:
697 @item base64-encode-region
698 @findex base64-encode-region
699 base64 encode the selected region. Return the length of the encoded
700 text. Optional third argument @var{no-line-break} means do not break
701 long lines into shorter lines.
703 @item base64-encode-string
704 @findex base64-encode-string
705 base64 encode a string and return the result.
707 @item base64-decode-region
708 @findex base64-decode-region
709 base64 decode the selected region. Return the length of the decoded
710 text. If the region can't be decoded, return @code{nil} and don't
713 @item base64-decode-string
714 @findex base64-decode-string
715 base64 decode a string and return the result. If the string can't be
716 decoded, @code{nil} is returned.
727 @code{binhex} is an encoding that originated in Macintosh environments.
728 The following function is supplied to deal with these:
731 @item binhex-decode-region
732 @findex binhex-decode-region
733 Decode the encoded text in the region. If given a third parameter, only
734 decode the @code{binhex} header and return the filename.
744 @code{uuencode} is probably still the most popular encoding of binaries
745 used on Usenet, although @code{base64} rules the mail world.
747 The following function is supplied by this package:
750 @item uudecode-decode-region
751 @findex uudecode-decode-region
752 Decode the text in the region.
762 RFC1843 deals with mixing Chinese and ASCII characters in messages. In
763 essence, RFC1843 switches between ASCII and Chinese by doing this:
766 This sentence is in ASCII.
767 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
770 Simple enough, and widely used in China.
772 The following functions are available to handle this encoding:
775 @item rfc1843-decode-region
776 Decode HZ-encoded text in the region.
778 @item rfc1843-decode-string
779 Decode a HZ-encoded string and return the result.
787 The @file{~/.mailcap} file is parsed by most @sc{mime}-aware message
788 handlers and describes how elements are supposed to be displayed.
789 Here's an example file:
793 audio/wav; wavplayer %s
796 This says that all image files should be displayed with @code{gimp}, and
797 that WAVE audio files should be played by @code{wavplayer}.
799 The @code{mailcap} library parses this file, and provides functions for
803 @item mailcap-mime-data
804 @vindex mailcap-mime-data
805 This variable is an alist of alists containing backup viewing rules.
812 @item mailcap-parse-mailcaps
813 @findex mailcap-parse-mailcaps
814 Parse the @code{~/.mailcap} file.
816 @item mailcap-mime-info
817 Takes a @sc{mime} type as its argument and returns the matching viewer.
824 @node Decoding and Viewing
825 @chapter Decoding and Viewing
827 This chapter deals with decoding and viewing @sc{mime} messages on a
830 The main idea is to first analyze a @sc{mime} article, and then allow
831 other programs to do things based on the list of @dfn{handles} that are
832 returned as a result of this analysis.
835 * Dissection:: Analyzing a @sc{mime} message.
836 * Non-MIME:: Analyzing a non-@sc{mime} message.
837 * Handles:: Handle manipulations.
838 * Display:: Displaying handles.
839 * Customization:: Variables that affect display.
840 * New Viewers:: How to write your own viewers.
847 The @code{mm-dissect-buffer} is the function responsible for dissecting
848 a @sc{mime} article. If given a multipart message, it will recursively
849 descend the message, following the structure, and return a tree of
850 @sc{mime} handles that describes the structure of the message.
855 Gnus also understands some non-MIME attachments, such as postscript,
856 uuencode, binhex, shar, forward, gnatsweb, pgp. Each of these features
857 can be disabled by add an item into @code{mm-uu-configure-list}.
862 (add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
884 Non-@sc{mime} forwarded message.
892 PGP signed clear text.
895 @findex pgp-encrypted
896 PGP encrypted clear text.
903 @findex emacs-sources
904 Emacs source code. This item works only in the groups matching
905 @code{mm-uu-emacs-sources-regexp}.
912 A @sc{mime} handle is a list that fully describes a @sc{mime}
915 The following macros can be used to access elements in a handle:
918 @item mm-handle-buffer
919 @findex mm-handle-buffer
920 Return the buffer that holds the contents of the undecoded @sc{mime}
924 @findex mm-handle-type
925 Return the parsed @code{Content-Type} of the part.
927 @item mm-handle-encoding
928 @findex mm-handle-encoding
929 Return the @code{Content-Transfer-Encoding} of the part.
931 @item mm-handle-undisplayer
932 @findex mm-handle-undisplayer
933 Return the object that can be used to remove the displayed part (if it
936 @item mm-handle-set-undisplayer
937 @findex mm-handle-set-undisplayer
938 Set the undisplayer object.
940 @item mm-handle-disposition
941 @findex mm-handle-disposition
942 Return the parsed @code{Content-Disposition} of the part.
944 @item mm-handle-disposition
945 @findex mm-handle-disposition
946 Return the description of the part.
948 @item mm-get-content-id
949 Returns the handle(s) referred to by @code{Content-ID}.
957 Functions for displaying, removing and saving.
960 @item mm-display-part
961 @findex mm-display-part
965 @findex mm-remove-part
966 Remove the part (if it has been displayed).
969 @findex mm-inlinable-p
970 Say whether a @sc{mime} type can be displayed inline.
972 @item mm-automatic-display-p
973 @findex mm-automatic-display-p
974 Say whether a @sc{mime} type should be displayed automatically.
976 @item mm-destroy-part
977 @findex mm-destroy-part
978 Free all resources occupied by a part.
982 Offer to save the part in a file.
986 Offer to pipe the part to some process.
988 @item mm-interactively-view-part
989 @findex mm-interactively-view-part
990 Prompt for a mailcap method to use to view the part.
996 @section Customization
1000 @item mm-inline-media-tests
1001 This is an alist where the key is a @sc{mime} type, the second element
1002 is a function to display the part @dfn{inline} (i.e., inside Emacs), and
1003 the third element is a form to be @code{eval}ed to say whether the part
1004 can be displayed inline.
1006 This variable specifies whether a part @emph{can} be displayed inline,
1007 and, if so, how to do it. It does not say whether parts are
1008 @emph{actually} displayed inline.
1010 @item mm-inlined-types
1011 This, on the other hand, says what types are to be displayed inline, if
1012 they satisfy the conditions set by the variable above. It's a list of
1013 @sc{mime} media types.
1015 @item mm-automatic-display
1016 This is a list of types that are to be displayed ``automatically'', but
1017 only if the above variable allows it. That is, only inlinable parts can
1018 be displayed automatically.
1020 @item mm-attachment-override-types
1021 Some @sc{mime} agents create parts that have a content-disposition of
1022 @samp{attachment}. This variable allows overriding that disposition and
1023 displaying the part inline. (Note that the disposition is only
1024 overridden if we are able to, and want to, display the part inline.)
1026 @item mm-discouraged-alternatives
1027 List of @sc{mime} types that are discouraged when viewing
1028 @samp{multipart/alternative}. Viewing agents are supposed to view the
1029 last possible part of a message, as that is supposed to be the richest.
1030 However, users may prefer other types instead, and this list says what
1031 types are most unwanted. If, for instance, @samp{text/html} parts are
1032 very unwanted, and @samp{text/richtech} parts are somewhat unwanted,
1033 you could say something like:
1036 (setq mm-discouraged-alternatives
1037 '("text/html" "text/richtext")
1038 mm-automatic-display
1039 (remove "text/html" mm-automatic-display))
1042 @item mm-inline-large-images-p
1043 When displaying inline images that are larger than the window, XEmacs
1044 does not enable scrolling, which means that you cannot see the whole
1045 image. To prevent this, the library tries to determine the image size
1046 before displaying it inline, and if it doesn't fit the window, the
1047 library will display it externally (e.g. with @samp{ImageMagick} or
1048 @samp{xv}). Setting this variable to @code{t} disables this check and
1049 makes the library display all inline images as inline, regardless of
1052 @item mm-inline-override-p
1053 @code{mm-inlined-types} may include regular expressions, for example to
1054 specify that all @samp{text/.*} parts be displayed inline. If a user
1055 prefers to have a type that matches such a regular expression be treated
1056 as an attachment, that can be accomplished by setting this variable to a
1057 list containing that type. For example assuming @code{mm-inlined-types}
1058 includes @samp{text/.*}, then including @samp{text/html} in this
1059 variable will cause @samp{text/html} parts to be treated as attachments.
1065 @section New Viewers
1067 Here's an example viewer for displaying @code{text/enriched} inline:
1070 (defun mm-display-enriched-inline (handle)
1073 (mm-insert-part handle)
1074 (save-window-excursion
1075 (enriched-decode (point-min) (point-max))
1076 (setq text (buffer-string))))
1077 (mm-insert-inline handle text)))
1080 We see that the function takes a @sc{mime} handle as its parameter. It
1081 then goes to a temporary buffer, inserts the text of the part, does some
1082 work on the text, stores the result, goes back to the buffer it was
1083 called from and inserts the result.
1085 The two important helper functions here are @code{mm-insert-part} and
1086 @code{mm-insert-inline}. The first function inserts the text of the
1087 handle in the current buffer. It handles charset and/or content
1088 transfer decoding. The second function just inserts whatever text you
1089 tell it to insert, but it also sets things up so that the text can be
1090 ``undisplayed' in a convenient manner.
1096 @cindex MIME Composing
1098 @cindex MIME Meta Language
1100 Creating a @sc{mime} message is boring and non-trivial. Therefore, a
1101 library called @code{mml} has been defined that parses a language called
1102 MML (@sc{mime} Meta Language) and generates @sc{mime} messages.
1104 @findex mml-generate-mime
1105 The main interface function is @code{mml-generate-mime}. It will
1106 examine the contents of the current (narrowed-to) buffer and return a
1107 string containing the @sc{mime} message.
1110 * Simple MML Example:: An example MML document.
1111 * MML Definition:: All valid MML elements.
1112 * Advanced MML Example:: Another example MML document.
1113 * Charset Translation:: How charsets are mapped from @sc{mule} to MIME.
1114 * Conversion:: Going from @sc{mime} to MML and vice versa.
1118 @node Simple MML Example
1119 @section Simple MML Example
1121 Here's a simple @samp{multipart/alternative}:
1124 <#multipart type=alternative>
1125 This is a plain text part.
1126 <#part type=text/enriched>
1127 <center>This is a centered enriched part</center>
1131 After running this through @code{mml-generate-mime}, we get this:
1134 Content-Type: multipart/alternative; boundary="=-=-="
1140 This is a plain text part.
1143 Content-Type: text/enriched
1146 <center>This is a centered enriched part</center>
1152 @node MML Definition
1153 @section MML Definition
1155 The MML language is very simple. It looks a bit like an SGML
1156 application, but it's not.
1158 The main concept of MML is the @dfn{part}. Each part can be of a
1159 different type or use a different charset. The way to delineate a part
1160 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
1161 with the @samp{<#multipart ...>} tag. Parts are ended by the
1162 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
1163 @samp{<#part ...>} tags are also closed by the next open tag.
1165 There's also the @samp{<#external ...>} tag. These introduce
1166 @samp{external/message-body} parts.
1168 Each tag can contain zero or more parameters on the form
1169 @samp{parameter=value}. The values may be enclosed in quotation marks,
1170 but that's not necessary unless the value contains white space. So
1171 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
1173 The following parameters have meaning in MML; parameters that have no
1174 meaning are ignored. The MML parameter names are the same as the
1175 @sc{mime} parameter names; the things in the parentheses say which
1176 header it will be used in.
1180 The @sc{mime} type of the part (@code{Content-Type}).
1183 Use the contents of the file in the body of the part
1184 (@code{Content-Disposition}).
1187 The contents of the body of the part are to be encoded in the character
1188 set speficied (@code{Content-Type}).
1191 Might be used to suggest a file name if the part is to be saved
1192 to a file (@code{Content-Type}).
1195 Valid values are @samp{inline} and @samp{attachment}
1196 (@code{Content-Disposition}).
1199 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
1200 @samp{base64} (@code{Content-Transfer-Encoding}).
1203 A description of the part (@code{Content-Description}).
1206 RFC822 date when the part was created (@code{Content-Disposition}).
1208 @item modification-date
1209 RFC822 date when the part was modified (@code{Content-Disposition}).
1212 RFC822 date when the part was read (@code{Content-Disposition}).
1215 The size (in octets) of the part (@code{Content-Disposition}).
1218 What technology to sign this MML part with (@code{smime}, @code{pgp}
1222 What technology to encrypt this MML part with (@code{smime},
1223 @code{pgp} or @code{pgpmime})
1227 Parameters for @samp{application/octet-stream}:
1231 Type of the part; informal---meant for human readers
1232 (@code{Content-Type}).
1235 Parameters for @samp{message/external-body}:
1239 A word indicating the supported access mechanism by which the file may
1240 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
1241 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
1244 The RFC822 date after which the file may no longer be fetched.
1245 (@code{Content-Type}.)
1248 The size (in octets) of the file. (@code{Content-Type}.)
1251 Valid values are @samp{read} and @samp{read-write}
1252 (@code{Content-Type}).
1256 Parameters for @samp{sign=smime}:
1261 File containing key and certificate for signer.
1265 Parameters for @samp{encrypt=smime}:
1270 File containing certificate for recipient.
1275 @node Advanced MML Example
1276 @section Advanced MML Example
1278 Here's a complex multipart message. It's a @samp{multipart/mixed} that
1279 contains many parts, one of which is a @samp{multipart/alternative}.
1282 <#multipart type=mixed>
1283 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
1284 <#multipart type=alternative>
1285 This is a plain text part.
1286 <#part type=text/enriched name=enriched.txt>
1287 <center>This is a centered enriched part</center>
1289 This is a new plain text part.
1290 <#part disposition=attachment>
1291 This plain text part is an attachment.
1295 And this is the resulting @sc{mime} message:
1298 Content-Type: multipart/mixed; boundary="=-=-="
1306 Content-Type: image/jpeg;
1307 filename="~/rms.jpg"
1308 Content-Disposition: inline;
1309 filename="~/rms.jpg"
1310 Content-Transfer-Encoding: base64
1312 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
1313 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
1314 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
1315 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
1316 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
1317 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
1318 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
1319 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
1320 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
1321 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
1322 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
1323 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
1324 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
1325 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
1326 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
1327 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
1328 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
1331 Content-Type: multipart/alternative; boundary="==-=-="
1337 This is a plain text part.
1340 Content-Type: text/enriched;
1344 <center>This is a centered enriched part</center>
1350 This is a new plain text part.
1353 Content-Disposition: attachment
1356 This plain text part is an attachment.
1361 @node Charset Translation
1362 @section Charset Translation
1365 During translation from MML to @sc{mime}, for each @sc{mime} part which
1366 has been composed inside Emacs, an appropriate charset has to be chosen.
1368 @vindex mail-parse-charset
1369 If you are running a non-@sc{mule} Emacs, this process is simple: If the
1370 part contains any non-ASCII (8-bit) characters, the @sc{mime} charset
1371 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
1372 variable directly, though. If you want to change the default charset,
1373 please consult the documentation of the package which you use to process
1375 @xref{Various Message Variables, , Various Message Variables, message,
1376 Message Manual}, for example.)
1377 If there are only ASCII characters, the @sc{mime} charset US-ASCII is
1383 @vindex mm-mime-mule-charset-alist
1384 Things are slightly more complicated when running Emacs with @sc{mule}
1385 support. In this case, a list of the @sc{mule} charsets used in the
1386 part is obtained, and the @sc{mule} charsets are translated to @sc{mime}
1387 charsets by consulting the variable @code{mm-mime-mule-charset-alist}.
1388 If this results in a single @sc{mime} charset, this is used to encode
1389 the part. But if the resulting list of @sc{mime} charsets contains more
1390 than one element, two things can happen: If it is possible to encode the
1391 part via UTF-8, this charset is used. (For this, Emacs must support
1392 the @code{utf-8} coding system, and the part must consist entirely of
1393 characters which have Unicode counterparts.) If UTF-8 is not available
1394 for some reason, the part is split into several ones, so that each one
1395 can be encoded with a single @sc{mime} charset. The part can only be
1396 split at line boundaries, though---if more than one @sc{mime} charset is
1397 required to encode a single line, it is not possible to encode the part.
1403 A (multipart) @sc{mime} message can be converted to MML with the
1404 @code{mime-to-mml} function. It works on the message in the current
1405 buffer, and substitutes MML markup for @sc{mime} boundaries.
1406 Non-textual parts do not have their contents in the buffer, but instead
1407 have the contents in separate buffers that are referred to from the MML
1411 An MML message can be converted back to @sc{mime} by the
1412 @code{mml-to-mime} function.
1414 These functions are in certain senses ``lossy''---you will not get back
1415 an identical message if you run @sc{mime-to-mml} and then
1416 @sc{mml-to-mime}. Not only will trivial things like the order of the
1417 headers differ, but the contents of the headers may also be different.
1418 For instance, the original message may use base64 encoding on text,
1419 while @sc{mml-to-mime} may decide to use quoted-printable encoding, and
1422 In essence, however, these two functions should be the inverse of each
1423 other. The resulting contents of the message should remain equivalent,
1430 The Emacs @sc{mime} library implements handling of various elements
1431 according to a (somewhat) large number of RFCs, drafts and standards
1432 documents. This chapter lists the relevant ones. They can all be
1433 fetched from @uref{http://quimby.gnus.org/notes/}.
1438 Standard for the Format of ARPA Internet Text Messages.
1441 Standard for Interchange of USENET Messages
1444 Format of Internet Message Bodies
1450 Message Header Extensions for Non-ASCII Text
1453 Registration Procedures
1456 Conformance Criteria and Examples
1459 MIME Parameter Value and Encoded Word Extensions: Character Sets,
1460 Languages, and Continuations
1463 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1466 @item draft-ietf-drums-msg-fmt-05.txt
1467 Draft for the successor of RFC822
1470 The MIME Multipart/Related Content-type
1473 The Multipart/Report Content Type for the Reporting of Mail System
1474 Administrative Messages
1477 Communicating Presentation Information in Internet Messages: The
1478 Content-Disposition Header Field
1494 @c coding: iso-8859-1