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, 2002, 2003
22 Free Software Foundation, Inc.
24 Permission is granted to copy, distribute and/or modify this document
25 under the terms of the GNU Free Documentation License, Version 1.1 or
26 any later version published by the Free Software Foundation; with no
27 Invariant Sections, with the Front-Cover texts being ``A GNU
28 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
29 license is included in the section entitled ``GNU Free Documentation
30 License'' in the Emacs manual.
32 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
33 this GNU Manual, like GNU software. Copies published by the Free
34 Software Foundation raise funds for GNU development.''
36 This document is part of a collection distributed under the GNU Free
37 Documentation License. If you want to distribute this document
38 separately from the collection, you can do so by adding a copy of the
39 license to the document, as described in section 6 of the license.
45 @title Emacs MIME Manual
47 @author by Lars Magne Ingebrigtsen
50 @vskip 0pt plus 1filll
51 Copyright @copyright{} 1998, 1999, 2000, 2001, 2002, 2003 Free Software
54 Permission is granted to copy, distribute and/or modify this document
55 under the terms of the GNU Free Documentation License, Version 1.1 or
56 any later version published by the Free Software Foundation; with the
57 Invariant Sections being none, with the Front-Cover texts being ``A GNU
58 Manual'', and with the Back-Cover Texts as in (a) below. A copy of the
59 license is included in the section entitled ``GNU Free Documentation
60 License'' in the Emacs manual.
62 (a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
63 this GNU Manual, like GNU software. Copies published by the Free
64 Software Foundation raise funds for GNU development.''
66 This document is part of a collection distributed under the GNU Free
67 Documentation License. If you want to distribute this document
68 separately from the collection, you can do so by adding a copy of the
69 license to the document, as described in section 6 of the license.
78 This manual documents the libraries used to compose and display
79 @acronym{MIME} messages.
81 This manual is directed at users who want to modify the behaviour of
82 the @acronym{MIME} encoding/decoding process or want a more detailed
83 picture of how the Emacs @acronym{MIME} library works, and people who want
84 to write functions and commands that manipulate @acronym{MIME} elements.
86 @acronym{MIME} is short for @dfn{Multipurpose Internet Mail Extensions}.
87 This standard is documented in a number of RFCs; mainly RFC2045 (Format
88 of Internet Message Bodies), RFC2046 (Media Types), RFC2047 (Message
89 Header Extensions for Non-@acronym{ASCII} Text), RFC2048 (Registration
90 Procedures), RFC2049 (Conformance Criteria and Examples). It is highly
91 recommended that anyone who intends writing @acronym{MIME}-compliant software
92 read at least RFC2045 and RFC2047.
95 * Decoding and Viewing:: A framework for decoding and viewing.
96 * Composing:: @acronym{MML}; a language for describing @acronym{MIME} parts.
97 * Interface Functions:: An abstraction over the basic functions.
98 * Basic Functions:: Utility and basic parsing functions.
99 * Standards:: A summary of RFCs and working documents used.
100 * Index:: Function and variable index.
104 @node Decoding and Viewing
105 @chapter Decoding and Viewing
107 This chapter deals with decoding and viewing @acronym{MIME} messages on a
110 The main idea is to first analyze a @acronym{MIME} article, and then allow
111 other programs to do things based on the list of @dfn{handles} that are
112 returned as a result of this analysis.
115 * Dissection:: Analyzing a @acronym{MIME} message.
116 * Non-MIME:: Analyzing a non-@acronym{MIME} message.
117 * Handles:: Handle manipulations.
118 * Display:: Displaying handles.
119 * Display Customization:: Variables that affect display.
120 * Files and Directories:: Saving and naming attachments.
121 * New Viewers:: How to write your own viewers.
128 The @code{mm-dissect-buffer} is the function responsible for dissecting
129 a @acronym{MIME} article. If given a multipart message, it will recursively
130 descend the message, following the structure, and return a tree of
131 @acronym{MIME} handles that describes the structure of the message.
135 @vindex mm-uu-configure-list
137 Gnus also understands some non-@acronym{MIME} attachments, such as
138 postscript, uuencode, binhex, yenc, shar, forward, gnatsweb, pgp,
139 diff. Each of these features can be disabled by add an item into
140 @code{mm-uu-configure-list}. For example,
144 (add-to-list 'mm-uu-configure-list '(pgp-signed . disabled))
170 Non-@acronym{MIME} forwarded message.
178 @acronym{PGP} signed clear text.
181 @findex pgp-encrypted
182 @acronym{PGP} encrypted clear text.
186 @acronym{PGP} public keys.
189 @findex emacs-sources
190 @vindex mm-uu-emacs-sources-regexp
191 Emacs source code. This item works only in the groups matching
192 @code{mm-uu-emacs-sources-regexp}.
196 @vindex mm-uu-diff-groups-regexp
197 Patches. This is intended for groups where diffs of committed files
198 are automatically sent to. It only works in groups matching
199 @code{mm-uu-diff-groups-regexp}.
206 A @acronym{MIME} handle is a list that fully describes a @acronym{MIME}
209 The following macros can be used to access elements in a handle:
212 @item mm-handle-buffer
213 @findex mm-handle-buffer
214 Return the buffer that holds the contents of the undecoded @acronym{MIME}
218 @findex mm-handle-type
219 Return the parsed @code{Content-Type} of the part.
221 @item mm-handle-encoding
222 @findex mm-handle-encoding
223 Return the @code{Content-Transfer-Encoding} of the part.
225 @item mm-handle-undisplayer
226 @findex mm-handle-undisplayer
227 Return the object that can be used to remove the displayed part (if it
230 @item mm-handle-set-undisplayer
231 @findex mm-handle-set-undisplayer
232 Set the undisplayer object.
234 @item mm-handle-disposition
235 @findex mm-handle-disposition
236 Return the parsed @code{Content-Disposition} of the part.
238 @item mm-handle-disposition
239 @findex mm-handle-disposition
240 Return the description of the part.
242 @item mm-get-content-id
243 Returns the handle(s) referred to by @code{Content-ID}.
251 Functions for displaying, removing and saving.
254 @item mm-display-part
255 @findex mm-display-part
259 @findex mm-remove-part
260 Remove the part (if it has been displayed).
263 @findex mm-inlinable-p
264 Say whether a @acronym{MIME} type can be displayed inline.
266 @item mm-automatic-display-p
267 @findex mm-automatic-display-p
268 Say whether a @acronym{MIME} type should be displayed automatically.
270 @item mm-destroy-part
271 @findex mm-destroy-part
272 Free all resources occupied by a part.
276 Offer to save the part in a file.
280 Offer to pipe the part to some process.
282 @item mm-interactively-view-part
283 @findex mm-interactively-view-part
284 Prompt for a mailcap method to use to view the part.
289 @node Display Customization
290 @section Display Customization
294 @item mm-inline-media-tests
295 @vindex mm-inline-media-tests
296 This is an alist where the key is a @acronym{MIME} type, the second element
297 is a function to display the part @dfn{inline} (i.e., inside Emacs), and
298 the third element is a form to be @code{eval}ed to say whether the part
299 can be displayed inline.
301 This variable specifies whether a part @emph{can} be displayed inline,
302 and, if so, how to do it. It does not say whether parts are
303 @emph{actually} displayed inline.
305 @item mm-inlined-types
306 @vindex mm-inlined-types
307 This, on the other hand, says what types are to be displayed inline, if
308 they satisfy the conditions set by the variable above. It's a list of
309 @acronym{MIME} media types.
311 @item mm-automatic-display
312 @vindex mm-automatic-display
313 This is a list of types that are to be displayed ``automatically'', but
314 only if the above variable allows it. That is, only inlinable parts can
315 be displayed automatically.
317 @item mm-automatic-external-display
318 @vindex mm-automatic-external-display
319 This is a list of types that will be displayed automatically in an
322 @item mm-keep-viewer-alive-types
323 @vindex mm-keep-viewer-alive-types
324 This is a list of media types for which the external viewer will not
325 be killed when selecting a different article.
327 @item mm-attachment-override-types
328 @vindex mm-attachment-override-types
329 Some @acronym{MIME} agents create parts that have a content-disposition of
330 @samp{attachment}. This variable allows overriding that disposition and
331 displaying the part inline. (Note that the disposition is only
332 overridden if we are able to, and want to, display the part inline.)
334 @item mm-discouraged-alternatives
335 @vindex mm-discouraged-alternatives
336 List of @acronym{MIME} types that are discouraged when viewing
337 @samp{multipart/alternative}. Viewing agents are supposed to view the
338 last possible part of a message, as that is supposed to be the richest.
339 However, users may prefer other types instead, and this list says what
340 types are most unwanted. If, for instance, @samp{text/html} parts are
341 very unwanted, and @samp{text/richtext} parts are somewhat unwanted,
342 you could say something like:
345 (setq mm-discouraged-alternatives
346 '("text/html" "text/richtext")
348 (remove "text/html" mm-automatic-display))
351 @item mm-inline-large-images
352 @vindex mm-inline-large-images
353 When displaying inline images that are larger than the window, XEmacs
354 does not enable scrolling, which means that you cannot see the whole
355 image. To prevent this, the library tries to determine the image size
356 before displaying it inline, and if it doesn't fit the window, the
357 library will display it externally (e.g. with @samp{ImageMagick} or
358 @samp{xv}). Setting this variable to @code{t} disables this check and
359 makes the library display all inline images as inline, regardless of
362 @item mm-inline-override-types
363 @vindex mm-inline-override-types
364 @code{mm-inlined-types} may include regular expressions, for example to
365 specify that all @samp{text/.*} parts be displayed inline. If a user
366 prefers to have a type that matches such a regular expression be treated
367 as an attachment, that can be accomplished by setting this variable to a
368 list containing that type. For example assuming @code{mm-inlined-types}
369 includes @samp{text/.*}, then including @samp{text/html} in this
370 variable will cause @samp{text/html} parts to be treated as attachments.
372 @item mm-text-html-renderer
373 @vindex mm-text-html-renderer
374 This selects the function used to render @acronym{HTML}. The predefined
375 renderers are selected by the symbols @code{w3},
376 @code{w3m}@footnote{See @uref{http://emacs-w3m.namazu.org/} for more
377 information about emacs-w3m}, @code{links}, @code{lynx},
378 @code{w3m-standalone} or @code{html2text}. If @code{nil} use an
379 external viewer. You can also specify a function, which will be
380 called with a @acronym{MIME} handle as the argument.
382 @item mm-inline-text-html-with-images
383 @vindex mm-inline-text-html-with-images
384 Some @acronym{HTML} mails might have the trick of spammers using
385 @samp{<img>} tags. It is likely to be intended to verify whether you
386 have read the mail. You can prevent your personal informations from
387 leaking by setting this option to @code{nil} (which is the default).
388 It is currently ignored by Emacs/w3. For emacs-w3m, you may use the
389 command @kbd{t} on the image anchor to show an image even if it is
390 @code{nil}.@footnote{The command @kbd{T} will load all images. If you
391 have set the option @code{w3m-key-binding} to @code{info}, use @kbd{i}
394 @item mm-w3m-safe-url-regexp
395 @vindex mm-w3m-safe-url-regexp
396 A regular expression that matches safe URL names, i.e. URLs that are
397 unlikely to leak personal information when rendering @acronym{HTML}
398 email (the default value is @samp{\\`cid:}). If @code{nil} consider
401 @item mm-inline-text-html-with-w3m-keymap
402 @vindex mm-inline-text-html-with-w3m-keymap
403 You can use emacs-w3m command keys in the inlined text/html part by
404 setting this option to non-@code{nil}. The default value is @code{t}.
406 @item mm-external-terminal-program
407 @vindex mm-external-terminal-program
408 The program used to start an external terminal.
412 @node Files and Directories
413 @section Files and Directories
417 @item mm-default-directory
418 @vindex mm-default-directory
419 The default directory for saving attachments. If @code{nil} use
420 @code{default-directory}.
422 @item mm-tmp-directory
423 @vindex mm-tmp-directory
424 Directory for storing temporary files.
426 @item mm-file-name-rewrite-functions
427 @vindex mm-file-name-rewrite-functions
428 A list of functions used for rewriting file names of @acronym{MIME}
429 parts. Each function is applied successively to the file name.
430 Ready-made functions include
433 @item mm-file-name-delete-control
434 @findex mm-file-name-delete-control
435 Delete all control characters.
437 @item mm-file-name-delete-gotchas
438 @findex mm-file-name-delete-gotchas
439 Delete characters that could have unintended consequences when used
440 with flawed shell scripts, i.e. @samp{|}, @samp{>} and @samp{<}; and
441 @samp{-}, @samp{.} as the first character.
443 @item mm-file-name-delete-whitespace
444 @findex mm-file-name-delete-whitespace
445 Remove all whitespace.
447 @item mm-file-name-trim-whitespace
448 @findex mm-file-name-trim-whitespace
449 Remove leading and trailing whitespace.
451 @item mm-file-name-collapse-whitespace
452 @findex mm-file-name-collapse-whitespace
453 Collapse multiple whitespace characters.
455 @item mm-file-name-replace-whitespace
456 @findex mm-file-name-replace-whitespace
457 @vindex mm-file-name-replace-whitespace
458 Replace whitespace with underscores. Set the variable
459 @code{mm-file-name-replace-whitespace} to any other string if you do
460 not like underscores.
463 The standard Emacs functions @code{capitalize}, @code{downcase},
464 @code{upcase} and @code{upcase-initials} might also prove useful.
466 @item mm-path-name-rewrite-functions
467 @vindex mm-path-name-rewrite-functions
468 List of functions used for rewriting the full file names of @acronym{MIME}
469 parts. This is used when viewing parts externally, and is meant for
470 transforming the absolute name so that non-compliant programs can find
471 the file where it's saved.
478 Here's an example viewer for displaying @code{text/enriched} inline:
481 (defun mm-display-enriched-inline (handle)
484 (mm-insert-part handle)
485 (save-window-excursion
486 (enriched-decode (point-min) (point-max))
487 (setq text (buffer-string))))
488 (mm-insert-inline handle text)))
491 We see that the function takes a @acronym{MIME} handle as its parameter. It
492 then goes to a temporary buffer, inserts the text of the part, does some
493 work on the text, stores the result, goes back to the buffer it was
494 called from and inserts the result.
496 The two important helper functions here are @code{mm-insert-part} and
497 @code{mm-insert-inline}. The first function inserts the text of the
498 handle in the current buffer. It handles charset and/or content
499 transfer decoding. The second function just inserts whatever text you
500 tell it to insert, but it also sets things up so that the text can be
501 ``undisplayed'' in a convenient manner.
507 @cindex MIME Composing
509 @cindex MIME Meta Language
511 Creating a @acronym{MIME} message is boring and non-trivial. Therefore,
512 a library called @code{mml} has been defined that parses a language
513 called @acronym{MML} (@acronym{MIME} Meta Language) and generates
514 @acronym{MIME} messages.
516 @findex mml-generate-mime
517 The main interface function is @code{mml-generate-mime}. It will
518 examine the contents of the current (narrowed-to) buffer and return a
519 string containing the @acronym{MIME} message.
522 * Simple MML Example:: An example @acronym{MML} document.
523 * MML Definition:: All valid @acronym{MML} elements.
524 * Advanced MML Example:: Another example @acronym{MML} document.
525 * Encoding Customization:: Variables that affect encoding.
526 * Charset Translation:: How charsets are mapped from @sc{mule} to @acronym{MIME}.
527 * Conversion:: Going from @acronym{MIME} to @acronym{MML} and vice versa.
528 * Flowed text:: Soft and hard newlines.
532 @node Simple MML Example
533 @section Simple MML Example
535 Here's a simple @samp{multipart/alternative}:
538 <#multipart type=alternative>
539 This is a plain text part.
540 <#part type=text/enriched>
541 <center>This is a centered enriched part</center>
545 After running this through @code{mml-generate-mime}, we get this:
548 Content-Type: multipart/alternative; boundary="=-=-="
554 This is a plain text part.
557 Content-Type: text/enriched
560 <center>This is a centered enriched part</center>
567 @section MML Definition
569 The @acronym{MML} language is very simple. It looks a bit like an SGML
570 application, but it's not.
572 The main concept of @acronym{MML} is the @dfn{part}. Each part can be of a
573 different type or use a different charset. The way to delineate a part
574 is with a @samp{<#part ...>} tag. Multipart parts can be introduced
575 with the @samp{<#multipart ...>} tag. Parts are ended by the
576 @samp{<#/part>} or @samp{<#/multipart>} tags. Parts started with the
577 @samp{<#part ...>} tags are also closed by the next open tag.
579 There's also the @samp{<#external ...>} tag. These introduce
580 @samp{external/message-body} parts.
582 Each tag can contain zero or more parameters on the form
583 @samp{parameter=value}. The values may be enclosed in quotation marks,
584 but that's not necessary unless the value contains white space. So
585 @samp{filename=/home/user/#hello$^yes} is perfectly valid.
587 The following parameters have meaning in @acronym{MML}; parameters that have no
588 meaning are ignored. The @acronym{MML} parameter names are the same as the
589 @acronym{MIME} parameter names; the things in the parentheses say which
590 header it will be used in.
594 The @acronym{MIME} type of the part (@code{Content-Type}).
597 Use the contents of the file in the body of the part
598 (@code{Content-Disposition}).
601 The contents of the body of the part are to be encoded in the character
602 set specified (@code{Content-Type}). @xref{Charset Translation}.
605 Might be used to suggest a file name if the part is to be saved
606 to a file (@code{Content-Type}).
609 Valid values are @samp{inline} and @samp{attachment}
610 (@code{Content-Disposition}).
613 Valid values are @samp{7bit}, @samp{8bit}, @samp{quoted-printable} and
614 @samp{base64} (@code{Content-Transfer-Encoding}). @xref{Charset
618 A description of the part (@code{Content-Description}).
621 RFC822 date when the part was created (@code{Content-Disposition}).
623 @item modification-date
624 RFC822 date when the part was modified (@code{Content-Disposition}).
627 RFC822 date when the part was read (@code{Content-Disposition}).
630 Who to encrypt/sign the part to. This field is used to override any
631 auto-detection based on the To/CC headers.
634 Identity used to sign the part. This field is used to override the
638 The size (in octets) of the part (@code{Content-Disposition}).
641 What technology to sign this @acronym{MML} part with (@code{smime}, @code{pgp}
645 What technology to encrypt this @acronym{MML} part with (@code{smime},
646 @code{pgp} or @code{pgpmime})
650 Parameters for @samp{text/plain}:
654 Formatting parameter for the text, valid values include @samp{fixed}
655 (the default) and @samp{flowed}. Normally you do not specify this
656 manually, since it requires the textual body to be formatted in a
657 special way described in RFC 2646. @xref{Flowed text}.
660 Parameters for @samp{application/octet-stream}:
664 Type of the part; informal---meant for human readers
665 (@code{Content-Type}).
668 Parameters for @samp{message/external-body}:
672 A word indicating the supported access mechanism by which the file may
673 be obtained. Values include @samp{ftp}, @samp{anon-ftp}, @samp{tftp},
674 @samp{localfile}, and @samp{mailserver}. (@code{Content-Type}.)
677 The RFC822 date after which the file may no longer be fetched.
678 (@code{Content-Type}.)
681 The size (in octets) of the file. (@code{Content-Type}.)
684 Valid values are @samp{read} and @samp{read-write}
685 (@code{Content-Type}).
689 Parameters for @samp{sign=smime}:
694 File containing key and certificate for signer.
698 Parameters for @samp{encrypt=smime}:
703 File containing certificate for recipient.
708 @node Advanced MML Example
709 @section Advanced MML Example
711 Here's a complex multipart message. It's a @samp{multipart/mixed} that
712 contains many parts, one of which is a @samp{multipart/alternative}.
715 <#multipart type=mixed>
716 <#part type=image/jpeg filename=~/rms.jpg disposition=inline>
717 <#multipart type=alternative>
718 This is a plain text part.
719 <#part type=text/enriched name=enriched.txt>
720 <center>This is a centered enriched part</center>
722 This is a new plain text part.
723 <#part disposition=attachment>
724 This plain text part is an attachment.
728 And this is the resulting @acronym{MIME} message:
731 Content-Type: multipart/mixed; boundary="=-=-="
739 Content-Type: image/jpeg;
741 Content-Disposition: inline;
743 Content-Transfer-Encoding: base64
745 /9j/4AAQSkZJRgABAQAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRof
746 Hh0aHBwgJC4nICIsIxwcKDcpLDAxNDQ0Hyc5PTgyPC4zNDL/wAALCAAwADABAREA/8QAHwAA
747 AQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQR
748 BRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RF
749 RkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ip
750 qrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/9oACAEB
751 AAA/AO/rifFHjldNuGsrDa0qcSSHkA+gHrXKw+LtWLrMb+RgTyhbr+HSug07xNqV9fQtZrNI
752 AyiaE/NuBPOOOP0rvRNE880KOC8TbXXGCv1FPqjrF4LDR7u5L7SkTFT/ALWOP1xXgTuXfc7E
753 sx6nua6rwp4IvvEM8chCxWxOdzn7wz6V9AaB4S07w9p5itow0rDLSY5Pt9K43xO66P4xs71m
754 2QXiGCbA4yOVJ9+1aYORkdK434lyNH4ahCnG66VT9Nj15JFbPdX0MS43M4VQf5/yr2vSpLnw
755 5ZW8dlCZ8KFXjOPX0/mK6rSPEGt3Angu44fNEReHYNvIH3TzXDeKNO8RX+kSX2ouZkicTIOc
756 L+g7E810ulFjpVtv3bwgB3HJyK5L4quY/C9sVxk3ij/xx6850u7t1mtp/wDlpEw3An3Jr3Dw
757 34gsbWza4nBlhC5LDsaW6+IFgupQyCF3iHH7gA7c9R9ay7zx6t7aX9jHC4smhfBkGCvHGfrm
758 tLQ7hbnRrV1GPkAP1x1/Hr+Ncr8Vzjwrbf8AX6v/AKA9eQRyYlQk8Yx9K6XTNbkgia2ciSIn
759 7p5Ga9Atte0LTLKO6it4i7dVRFJDcZ4PvXN+JvEMF9bILVGXJLSZ4zkjivRPDaeX4b08HOTC
760 pOffmua+KkbS+GLVUGT9tT/0B68eeIpIFYjB70+OOVXyoOM9+M1eaWeCLzHPyHGO/NVWvJJm
761 jQ8KGH1NfQWhXSXmh2c8eArRLwO3HSv/2Q==
764 Content-Type: multipart/alternative; boundary="==-=-="
770 This is a plain text part.
773 Content-Type: text/enriched;
777 <center>This is a centered enriched part</center>
783 This is a new plain text part.
786 Content-Disposition: attachment
789 This plain text part is an attachment.
794 @node Encoding Customization
795 @section Encoding Customization
799 @item mm-body-charset-encoding-alist
800 @vindex mm-body-charset-encoding-alist
801 Mapping from @acronym{MIME} charset to encoding to use. This variable is
802 usually used except, e.g., when other requirements force a specific
803 encoding (digitally signed messages require 7bit encodings). The
807 ((iso-2022-jp . 7bit)
808 (iso-2022-jp-2 . 7bit)
814 As an example, if you do not want to have ISO-8859-1 characters
815 quoted-printable encoded, you may add @code{(iso-8859-1 . 8bit)} to
816 this variable. You can override this setting on a per-message basis
817 by using the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
819 @item mm-coding-system-priorities
820 @vindex mm-coding-system-priorities
821 Prioritize coding systems to use for outgoing messages. The default
822 is @code{nil}, which means to use the defaults in Emacs. It is a list of
823 coding system symbols (aliases of coding systems does not work, use
824 @kbd{M-x describe-coding-system} to make sure you are not specifying
825 an alias in this variable). For example, if you have configured Emacs
826 to prefer UTF-8, but wish that outgoing messages should be sent in
827 ISO-8859-1 if possible, you can set this variable to
828 @code{(iso-latin-1)}. You can override this setting on a per-message
829 basis by using the @code{charset} @acronym{MML} tag (@pxref{MML Definition}).
831 @item mm-content-transfer-encoding-defaults
832 @vindex mm-content-transfer-encoding-defaults
833 Mapping from @acronym{MIME} types to encoding to use. This variable is usually
834 used except, e.g., when other requirements force a safer encoding
835 (digitally signed messages require 7bit encoding). Besides the normal
836 @acronym{MIME} encodings, @code{qp-or-base64} may be used to indicate that for
837 each case the most efficient of quoted-printable and base64 should be
838 used. You can override this setting on a per-message basis by using
839 the @code{encoding} @acronym{MML} tag (@pxref{MML Definition}).
841 @item mm-use-ultra-safe-encoding
842 @vindex mm-use-ultra-safe-encoding
843 When this is non-@code{nil}, it means that textual parts are encoded as
844 quoted-printable if they contain lines longer than 76 characters or
845 starting with "From " in the body. Non-7bit encodings (8bit, binary)
846 are generally disallowed. This reduce the probability that a non-8bit
847 clean MTA or MDA changes the message. This should never be set
848 directly, but bound by other functions when necessary (e.g., when
849 encoding messages that are to be digitally signed).
853 @node Charset Translation
854 @section Charset Translation
857 During translation from @acronym{MML} to @acronym{MIME}, for each
858 @acronym{MIME} part which has been composed inside Emacs, an appropriate
859 charset has to be chosen.
861 @vindex mail-parse-charset
862 If you are running a non-@sc{mule} Emacs, this process is simple: If the
863 part contains any non-@acronym{ASCII} (8-bit) characters, the @acronym{MIME} charset
864 given by @code{mail-parse-charset} (a symbol) is used. (Never set this
865 variable directly, though. If you want to change the default charset,
866 please consult the documentation of the package which you use to process
867 @acronym{MIME} messages.
868 @xref{Various Message Variables, , Various Message Variables, message,
869 Message Manual}, for example.)
870 If there are only @acronym{ASCII} characters, the @acronym{MIME} charset US-ASCII is
876 @vindex mm-mime-mule-charset-alist
877 Things are slightly more complicated when running Emacs with @sc{mule}
878 support. In this case, a list of the @sc{mule} charsets used in the
879 part is obtained, and the @sc{mule} charsets are translated to @acronym{MIME}
880 charsets by consulting the variable @code{mm-mime-mule-charset-alist}.
881 If this results in a single @acronym{MIME} charset, this is used to encode
882 the part. But if the resulting list of @acronym{MIME} charsets contains more
883 than one element, two things can happen: If it is possible to encode the
884 part via UTF-8, this charset is used. (For this, Emacs must support
885 the @code{utf-8} coding system, and the part must consist entirely of
886 characters which have Unicode counterparts.) If UTF-8 is not available
887 for some reason, the part is split into several ones, so that each one
888 can be encoded with a single @acronym{MIME} charset. The part can only be
889 split at line boundaries, though---if more than one @acronym{MIME} charset is
890 required to encode a single line, it is not possible to encode the part.
892 When running Emacs with @sc{mule} support, the preferences for which
893 coding system to use is inherited from Emacs itself. This means that
894 if Emacs is set up to prefer UTF-8, it will be used when encoding
895 messages. You can modify this by altering the
896 @code{mm-coding-system-priorities} variable though (@pxref{Encoding
899 The charset to be used can be overridden by setting the @code{charset}
900 @acronym{MML} tag (@pxref{MML Definition}) when composing the message.
902 The encoding of characters (quoted-printable, 8bit etc) is orthogonal
903 to the discussion here, and is controlled by the variables
904 @code{mm-body-charset-encoding-alist} and
905 @code{mm-content-transfer-encoding-defaults} (@pxref{Encoding
912 A (multipart) @acronym{MIME} message can be converted to @acronym{MML}
913 with the @code{mime-to-mml} function. It works on the message in the
914 current buffer, and substitutes @acronym{MML} markup for @acronym{MIME}
915 boundaries. Non-textual parts do not have their contents in the buffer,
916 but instead have the contents in separate buffers that are referred to
917 from the @acronym{MML} tags.
920 An @acronym{MML} message can be converted back to @acronym{MIME} by the
921 @code{mml-to-mime} function.
923 These functions are in certain senses ``lossy''---you will not get back
924 an identical message if you run @code{mime-to-mml} and then
925 @code{mml-to-mime}. Not only will trivial things like the order of the
926 headers differ, but the contents of the headers may also be different.
927 For instance, the original message may use base64 encoding on text,
928 while @code{mml-to-mime} may decide to use quoted-printable encoding, and
931 In essence, however, these two functions should be the inverse of each
932 other. The resulting contents of the message should remain equivalent,
938 @cindex format=flowed
940 The Emacs @acronym{MIME} library will respect the @code{use-hard-newlines}
941 variable (@pxref{Hard and Soft Newlines, ,Hard and Soft Newlines,
942 emacs, Emacs Manual}) when encoding a message, and the
943 ``format=flowed'' Content-Type parameter when decoding a message.
945 On encoding text, lines terminated by soft newline characters are
946 filled together and wrapped after the column decided by
947 @code{fill-flowed-encode-column}. This variable controls how the text
948 will look in a client that does not support flowed text, the default
949 is to wrap after 66 characters. If hard newline characters are not
950 present in the buffer, no flow encoding occurs.
952 On decoding flowed text, lines with soft newline characters are filled
953 together and wrapped after the column decided by
954 @code{fill-flowed-display-column}. The default is to wrap after
960 @node Interface Functions
961 @chapter Interface Functions
962 @cindex interface functions
965 The @code{mail-parse} library is an abstraction over the actual
966 low-level libraries that are described in the next chapter.
968 Standards change, and so programs have to change to fit in the new
969 mold. For instance, RFC2045 describes a syntax for the
970 @code{Content-Type} header that only allows @acronym{ASCII} characters in the
971 parameter list. RFC2231 expands on RFC2045 syntax to provide a scheme
972 for continuation headers and non-@acronym{ASCII} characters.
974 The traditional way to deal with this is just to update the library
975 functions to parse the new syntax. However, this is sometimes the wrong
976 thing to do. In some instances it may be vital to be able to understand
977 both the old syntax as well as the new syntax, and if there is only one
978 library, one must choose between the old version of the library and the
979 new version of the library.
981 The Emacs @acronym{MIME} library takes a different tack. It defines a
982 series of low-level libraries (@file{rfc2047.el}, @file{rfc2231.el}
983 and so on) that parses strictly according to the corresponding
984 standard. However, normal programs would not use the functions
985 provided by these libraries directly, but instead use the functions
986 provided by the @code{mail-parse} library. The functions in this
987 library are just aliases to the corresponding functions in the latest
988 low-level libraries. Using this scheme, programs get a consistent
989 interface they can use, and library developers are free to create
990 write code that handles new standards.
992 The following functions are defined by this library:
995 @item mail-header-parse-content-type
996 @findex mail-header-parse-content-type
997 Parse a @code{Content-Type} header and return a list on the following
1002 (attribute1 . value1)
1003 (attribute2 . value2)
1010 (mail-header-parse-content-type
1011 "image/gif; name=\"b980912.gif\"")
1012 @result{} ("image/gif" (name . "b980912.gif"))
1015 @item mail-header-parse-content-disposition
1016 @findex mail-header-parse-content-disposition
1017 Parse a @code{Content-Disposition} header and return a list on the same
1018 format as the function above.
1020 @item mail-content-type-get
1021 @findex mail-content-type-get
1022 Takes two parameters---a list on the format above, and an attribute.
1023 Returns the value of the attribute.
1026 (mail-content-type-get
1027 '("image/gif" (name . "b980912.gif")) 'name)
1028 @result{} "b980912.gif"
1031 @item mail-header-encode-parameter
1032 @findex mail-header-encode-parameter
1033 Takes a parameter string and returns an encoded version of the string.
1034 This is used for parameters in headers like @code{Content-Type} and
1035 @code{Content-Disposition}.
1037 @item mail-header-remove-comments
1038 @findex mail-header-remove-comments
1039 Return a comment-free version of a header.
1042 (mail-header-remove-comments
1043 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1044 @result{} "Gnus/5.070027 "
1047 @item mail-header-remove-whitespace
1048 @findex mail-header-remove-whitespace
1049 Remove linear white space from a header. Space inside quoted strings
1050 and comments is preserved.
1053 (mail-header-remove-whitespace
1054 "image/gif; name=\"Name with spaces\"")
1055 @result{} "image/gif;name=\"Name with spaces\""
1058 @item mail-header-get-comment
1059 @findex mail-header-get-comment
1060 Return the last comment in a header.
1063 (mail-header-get-comment
1064 "Gnus/5.070027 (Pterodactyl Gnus v0.27) (Finnish Landrace)")
1065 @result{} "Finnish Landrace"
1068 @item mail-header-parse-address
1069 @findex mail-header-parse-address
1070 Parse an address and return a list containing the mailbox and the
1074 (mail-header-parse-address
1075 "Hrvoje Niksic <hniksic@@srce.hr>")
1076 @result{} ("hniksic@@srce.hr" . "Hrvoje Niksic")
1079 @item mail-header-parse-addresses
1080 @findex mail-header-parse-addresses
1081 Parse a string with list of addresses and return a list of elements like
1082 the one described above.
1085 (mail-header-parse-addresses
1086 "Hrvoje Niksic <hniksic@@srce.hr>, Steinar Bang <sb@@metis.no>")
1087 @result{} (("hniksic@@srce.hr" . "Hrvoje Niksic")
1088 ("sb@@metis.no" . "Steinar Bang"))
1091 @item mail-header-parse-date
1092 @findex mail-header-parse-date
1093 Parse a date string and return an Emacs time structure.
1095 @item mail-narrow-to-head
1096 @findex mail-narrow-to-head
1097 Narrow the buffer to the header section of the buffer. Point is placed
1098 at the beginning of the narrowed buffer.
1100 @item mail-header-narrow-to-field
1101 @findex mail-header-narrow-to-field
1102 Narrow the buffer to the header under point. Understands continuation
1105 @item mail-header-fold-field
1106 @findex mail-header-fold-field
1107 Fold the header under point.
1109 @item mail-header-unfold-field
1110 @findex mail-header-unfold-field
1111 Unfold the header under point.
1113 @item mail-header-field-value
1114 @findex mail-header-field-value
1115 Return the value of the field under point.
1117 @item mail-encode-encoded-word-region
1118 @findex mail-encode-encoded-word-region
1119 Encode the non-@acronym{ASCII} words in the region. For instance,
1120 @samp{Naïve} is encoded as @samp{=?iso-8859-1?q?Na=EFve?=}.
1122 @item mail-encode-encoded-word-buffer
1123 @findex mail-encode-encoded-word-buffer
1124 Encode the non-@acronym{ASCII} words in the current buffer. This function is
1125 meant to be called narrowed to the headers of a message.
1127 @item mail-encode-encoded-word-string
1128 @findex mail-encode-encoded-word-string
1129 Encode the words that need encoding in a string, and return the result.
1132 (mail-encode-encoded-word-string
1133 "This is naïve, baby")
1134 @result{} "This is =?iso-8859-1?q?na=EFve,?= baby"
1137 @item mail-decode-encoded-word-region
1138 @findex mail-decode-encoded-word-region
1139 Decode the encoded words in the region.
1141 @item mail-decode-encoded-word-string
1142 @findex mail-decode-encoded-word-string
1143 Decode the encoded words in the string and return the result.
1146 (mail-decode-encoded-word-string
1147 "This is =?iso-8859-1?q?na=EFve,?= baby")
1148 @result{} "This is naïve, baby"
1153 Currently, @code{mail-parse} is an abstraction over @code{ietf-drums},
1154 @code{rfc2047}, @code{rfc2045} and @code{rfc2231}. These are documented
1155 in the subsequent sections.
1159 @node Basic Functions
1160 @chapter Basic Functions
1162 This chapter describes the basic, ground-level functions for parsing and
1163 handling. Covered here is parsing @code{From} lines, removing comments
1164 from header lines, decoding encoded words, parsing date headers and so
1165 on. High-level functionality is dealt with in the next chapter
1166 (@pxref{Decoding and Viewing}).
1169 * rfc2045:: Encoding @code{Content-Type} headers.
1170 * rfc2231:: Parsing @code{Content-Type} headers.
1171 * ietf-drums:: Handling mail headers defined by RFC822bis.
1172 * rfc2047:: En/decoding encoded words in headers.
1173 * time-date:: Functions for parsing dates and manipulating time.
1174 * qp:: Quoted-Printable en/decoding.
1175 * base64:: Base64 en/decoding.
1176 * binhex:: Binhex decoding.
1177 * uudecode:: Uuencode decoding.
1178 * yenc:: Yenc decoding.
1179 * rfc1843:: Decoding HZ-encoded text.
1180 * mailcap:: How parts are displayed is specified by the @file{.mailcap} file
1187 RFC2045 is the ``main'' @acronym{MIME} document, and as such, one would
1188 imagine that there would be a lot to implement. But there isn't, since
1189 most of the implementation details are delegated to the subsequent
1192 So @file{rfc2045.el} has only a single function:
1195 @item rfc2045-encode-string
1196 @findex rfc2045-encode-string
1197 Takes a parameter and a value and returns a @samp{PARAM=VALUE} string.
1198 @var{value} will be quoted if there are non-safe characters in it.
1205 RFC2231 defines a syntax for the @code{Content-Type} and
1206 @code{Content-Disposition} headers. Its snappy name is @dfn{MIME
1207 Parameter Value and Encoded Word Extensions: Character Sets, Languages,
1210 In short, these headers look something like this:
1213 Content-Type: application/x-stuff;
1214 title*0*=us-ascii'en'This%20is%20even%20more%20;
1215 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1219 They usually aren't this bad, though.
1221 The following functions are defined by this library:
1224 @item rfc2231-parse-string
1225 @findex rfc2231-parse-string
1226 Parse a @code{Content-Type} header and return a list describing its
1230 (rfc2231-parse-string
1231 "application/x-stuff;
1232 title*0*=us-ascii'en'This%20is%20even%20more%20;
1233 title*1*=%2A%2A%2Afun%2A%2A%2A%20;
1234 title*2=\"isn't it!\"")
1235 @result{} ("application/x-stuff"
1236 (title . "This is even more ***fun*** isn't it!"))
1239 @item rfc2231-get-value
1240 @findex rfc2231-get-value
1241 Takes one of the lists on the format above and returns
1242 the value of the specified attribute.
1244 @item rfc2231-encode-string
1245 @findex rfc2231-encode-string
1246 Encode a parameter in headers likes @code{Content-Type} and
1247 @code{Content-Disposition}.
1255 @dfn{drums} is an IETF working group that is working on the replacement
1258 The functions provided by this library include:
1261 @item ietf-drums-remove-comments
1262 @findex ietf-drums-remove-comments
1263 Remove the comments from the argument and return the results.
1265 @item ietf-drums-remove-whitespace
1266 @findex ietf-drums-remove-whitespace
1267 Remove linear white space from the string and return the results.
1268 Spaces inside quoted strings and comments are left untouched.
1270 @item ietf-drums-get-comment
1271 @findex ietf-drums-get-comment
1272 Return the last most comment from the string.
1274 @item ietf-drums-parse-address
1275 @findex ietf-drums-parse-address
1276 Parse an address string and return a list that contains the mailbox and
1277 the plain text name.
1279 @item ietf-drums-parse-addresses
1280 @findex ietf-drums-parse-addresses
1281 Parse a string that contains any number of comma-separated addresses and
1282 return a list that contains mailbox/plain text pairs.
1284 @item ietf-drums-parse-date
1285 @findex ietf-drums-parse-date
1286 Parse a date string and return an Emacs time structure.
1288 @item ietf-drums-narrow-to-header
1289 @findex ietf-drums-narrow-to-header
1290 Narrow the buffer to the header section of the current buffer.
1298 RFC2047 (Message Header Extensions for Non-@acronym{ASCII} Text) specifies how
1299 non-@acronym{ASCII} text in headers are to be encoded. This is actually rather
1300 complicated, so a number of variables are necessary to tweak what this
1303 The following variables are tweakable:
1306 @item rfc2047-default-charset
1307 @vindex rfc2047-default-charset
1308 Characters in this charset should not be decoded by this library.
1309 This defaults to @code{iso-8859-1}.
1311 @item rfc2047-header-encoding-alist
1312 @vindex rfc2047-header-encoding-alist
1313 This is an alist of header / encoding-type pairs. Its main purpose is
1314 to prevent encoding of certain headers.
1316 The keys can either be header regexps, or @code{t}.
1318 The values can be either @code{nil}, in which case the header(s) in
1319 question won't be encoded, or @code{mime}, which means that they will be
1322 @item rfc2047-charset-encoding-alist
1323 @vindex rfc2047-charset-encoding-alist
1324 RFC2047 specifies two forms of encoding---@code{Q} (a
1325 Quoted-Printable-like encoding) and @code{B} (base64). This alist
1326 specifies which charset should use which encoding.
1328 @item rfc2047-encoding-function-alist
1329 @vindex rfc2047-encoding-function-alist
1330 This is an alist of encoding / function pairs. The encodings are
1331 @code{Q}, @code{B} and @code{nil}.
1333 @item rfc2047-q-encoding-alist
1334 @vindex rfc2047-q-encoding-alist
1335 The @code{Q} encoding isn't quite the same for all headers. Some
1336 headers allow a narrower range of characters, and that is what this
1337 variable is for. It's an alist of header regexps / allowable character
1340 @item rfc2047-encoded-word-regexp
1341 @vindex rfc2047-encoded-word-regexp
1342 When decoding words, this library looks for matches to this regexp.
1346 Those were the variables, and these are this functions:
1349 @item rfc2047-narrow-to-field
1350 @findex rfc2047-narrow-to-field
1351 Narrow the buffer to the header on the current line.
1353 @item rfc2047-encode-message-header
1354 @findex rfc2047-encode-message-header
1355 Should be called narrowed to the header of a message. Encodes according
1356 to @code{rfc2047-header-encoding-alist}.
1358 @item rfc2047-encode-region
1359 @findex rfc2047-encode-region
1360 Encodes all encodable words in the region specified.
1362 @item rfc2047-encode-string
1363 @findex rfc2047-encode-string
1364 Encode a string and return the results.
1366 @item rfc2047-decode-region
1367 @findex rfc2047-decode-region
1368 Decode the encoded words in the region.
1370 @item rfc2047-decode-string
1371 @findex rfc2047-decode-string
1372 Decode a string and return the results.
1380 While not really a part of the @acronym{MIME} library, it is convenient to
1381 document this library here. It deals with parsing @code{Date} headers
1382 and manipulating time. (Not by using tesseracts, though, I'm sorry to
1385 These functions convert between five formats: A date string, an Emacs
1386 time structure, a decoded time list, a second number, and a day number.
1388 Here's a bunch of time/date/second/day examples:
1391 (parse-time-string "Sat Sep 12 12:21:54 1998 +0200")
1392 @result{} (54 21 12 12 9 1998 6 nil 7200)
1394 (date-to-time "Sat Sep 12 12:21:54 1998 +0200")
1395 @result{} (13818 19266)
1397 (time-to-seconds '(13818 19266))
1398 @result{} 905595714.0
1400 (seconds-to-time 905595714.0)
1401 @result{} (13818 19266 0)
1403 (time-to-days '(13818 19266))
1406 (days-to-time 729644)
1407 @result{} (961933 65536)
1409 (time-since '(13818 19266))
1412 (time-less-p '(13818 19266) '(13818 19145))
1415 (subtract-time '(13818 19266) '(13818 19145))
1418 (days-between "Sat Sep 12 12:21:54 1998 +0200"
1419 "Sat Sep 07 12:21:54 1998 +0200")
1422 (date-leap-year-p 2000)
1425 (time-to-day-in-year '(13818 19266))
1428 (time-to-number-of-days
1430 (date-to-time "Mon, 01 Jan 2001 02:22:26 GMT")))
1431 @result{} 4.146122685185185
1434 And finally, we have @code{safe-date-to-time}, which does the same as
1435 @code{date-to-time}, but returns a zero time if the date is
1436 syntactically malformed.
1438 The five data representations used are the following:
1442 An RFC822 (or similar) date string. For instance: @code{"Sat Sep 12
1443 12:21:54 1998 +0200"}.
1446 An internal Emacs time. For instance: @code{(13818 26466)}.
1449 A floating point representation of the internal Emacs time. For
1450 instance: @code{905595714.0}.
1453 An integer number representing the number of days since 00000101. For
1454 instance: @code{729644}.
1457 A list of decoded time. For instance: @code{(54 21 12 12 9 1998 6 t
1461 All the examples above represent the same moment.
1463 These are the functions available:
1467 Take a date and return a time.
1469 @item time-to-seconds
1470 Take a time and return seconds.
1472 @item seconds-to-time
1473 Take seconds and return a time.
1476 Take a time and return days.
1479 Take days and return a time.
1482 Take a date and return days.
1484 @item time-to-number-of-days
1485 Take a time and return the number of days that represents.
1487 @item safe-date-to-time
1488 Take a date and return a time. If the date is not syntactically valid,
1489 return a ``zero'' date.
1492 Take two times and say whether the first time is less (i. e., earlier)
1493 than the second time.
1496 Take a time and return a time saying how long it was since that time.
1499 Take two times and subtract the second from the first. I. e., return
1500 the time between the two times.
1503 Take two days and return the number of days between those two days.
1505 @item date-leap-year-p
1506 Take a year number and say whether it's a leap year.
1508 @item time-to-day-in-year
1509 Take a time and return the day number within the year that the time is
1518 This library deals with decoding and encoding Quoted-Printable text.
1520 Very briefly explained, qp encoding means translating all 8-bit
1521 characters (and lots of control characters) into things that look like
1522 @samp{=EF}; that is, an equal sign followed by the byte encoded as a hex
1525 The following functions are defined by the library:
1528 @item quoted-printable-decode-region
1529 @findex quoted-printable-decode-region
1530 QP-decode all the encoded text in the specified region.
1532 @item quoted-printable-decode-string
1533 @findex quoted-printable-decode-string
1534 Decode the QP-encoded text in a string and return the results.
1536 @item quoted-printable-encode-region
1537 @findex quoted-printable-encode-region
1538 QP-encode all the encodable characters in the specified region. The third
1539 optional parameter @var{fold} specifies whether to fold long lines.
1540 (Long here means 72.)
1542 @item quoted-printable-encode-string
1543 @findex quoted-printable-encode-string
1544 QP-encode all the encodable characters in a string and return the
1554 Base64 is an encoding that encodes three bytes into four characters,
1555 thereby increasing the size by about 33%. The alphabet used for
1556 encoding is very resistant to mangling during transit.
1558 The following functions are defined by this library:
1561 @item base64-encode-region
1562 @findex base64-encode-region
1563 base64 encode the selected region. Return the length of the encoded
1564 text. Optional third argument @var{no-line-break} means do not break
1565 long lines into shorter lines.
1567 @item base64-encode-string
1568 @findex base64-encode-string
1569 base64 encode a string and return the result.
1571 @item base64-decode-region
1572 @findex base64-decode-region
1573 base64 decode the selected region. Return the length of the decoded
1574 text. If the region can't be decoded, return @code{nil} and don't
1577 @item base64-decode-string
1578 @findex base64-decode-string
1579 base64 decode a string and return the result. If the string can't be
1580 decoded, @code{nil} is returned.
1591 @code{binhex} is an encoding that originated in Macintosh environments.
1592 The following function is supplied to deal with these:
1595 @item binhex-decode-region
1596 @findex binhex-decode-region
1597 Decode the encoded text in the region. If given a third parameter, only
1598 decode the @code{binhex} header and return the filename.
1607 @code{uuencode} is probably still the most popular encoding of binaries
1608 used on Usenet, although @code{base64} rules the mail world.
1610 The following function is supplied by this package:
1613 @item uudecode-decode-region
1614 @findex uudecode-decode-region
1615 Decode the text in the region.
1623 @code{yenc} is used for encoding binaries on Usenet. The following
1624 function is supplied by this package:
1627 @item yenc-decode-region
1628 @findex yenc-decode-region
1629 Decode the encoded text in the region.
1640 RFC1843 deals with mixing Chinese and @acronym{ASCII} characters in messages. In
1641 essence, RFC1843 switches between @acronym{ASCII} and Chinese by doing this:
1644 This sentence is in @acronym{ASCII}.
1645 The next sentence is in GB.~@{<:Ky2;S@{#,NpJ)l6HK!#~@}Bye.
1648 Simple enough, and widely used in China.
1650 The following functions are available to handle this encoding:
1653 @item rfc1843-decode-region
1654 Decode HZ-encoded text in the region.
1656 @item rfc1843-decode-string
1657 Decode a HZ-encoded string and return the result.
1665 The @file{~/.mailcap} file is parsed by most @acronym{MIME}-aware message
1666 handlers and describes how elements are supposed to be displayed.
1667 Here's an example file:
1671 audio/wav; wavplayer %s
1672 application/msword; catdoc %s ; copiousoutput ; nametemplate=%s.doc
1675 This says that all image files should be displayed with @code{gimp},
1676 that WAVE audio files should be played by @code{wavplayer}, and that
1677 MS-WORD files should be inlined by @code{catdoc}.
1679 The @code{mailcap} library parses this file, and provides functions for
1683 @item mailcap-mime-data
1684 @vindex mailcap-mime-data
1685 This variable is an alist of alists containing backup viewing rules.
1689 Interface functions:
1692 @item mailcap-parse-mailcaps
1693 @findex mailcap-parse-mailcaps
1694 Parse the @file{~/.mailcap} file.
1696 @item mailcap-mime-info
1697 Takes a @acronym{MIME} type as its argument and returns the matching viewer.
1707 The Emacs @acronym{MIME} library implements handling of various elements
1708 according to a (somewhat) large number of RFCs, drafts and standards
1709 documents. This chapter lists the relevant ones. They can all be
1710 fetched from @uref{http://quimby.gnus.org/notes/}.
1715 Standard for the Format of ARPA Internet Text Messages.
1718 Standard for Interchange of USENET Messages
1721 Format of Internet Message Bodies
1727 Message Header Extensions for Non-@acronym{ASCII} Text
1730 Registration Procedures
1733 Conformance Criteria and Examples
1736 @acronym{MIME} Parameter Value and Encoded Word Extensions: Character Sets,
1737 Languages, and Continuations
1740 HZ - A Data Format for Exchanging Files of Arbitrarily Mixed Chinese and
1741 @acronym{ASCII} characters
1743 @item draft-ietf-drums-msg-fmt-05.txt
1744 Draft for the successor of RFC822
1747 The @acronym{MIME} Multipart/Related Content-type
1750 The Multipart/Report Content Type for the Reporting of Mail System
1751 Administrative Messages
1754 Communicating Presentation Information in Internet Messages: The
1755 Content-Disposition Header Field
1758 Documentation of the text/plain format parameter for flowed text.
1774 @c coding: iso-8859-1