1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1997, 1999-2014 Free Software Foundation, Inc.
3 @c See file emacs.texi for copying conditions.
5 @chapter International Character Set Support
6 @c This node is referenced in the tutorial. When renaming or deleting
7 @c it, the tutorial needs to be adjusted. (TUTORIAL.de)
8 @cindex international scripts
9 @cindex multibyte characters
10 @cindex encoding of characters
30 Emacs supports a wide variety of international character sets,
31 including European and Vietnamese variants of the Latin alphabet, as
32 well as Arabic scripts, Brahmic scripts (for languages such as
33 Bengali, Hindi, and Thai), Cyrillic, Ethiopic, Georgian, Greek, Han
34 (for Chinese and Japanese), Hangul (for Korean), Hebrew and IPA@.
35 Emacs also supports various encodings of these characters that are used by
36 other internationalized software, such as word processors and mailers.
38 Emacs allows editing text with international characters by supporting
39 all the related activities:
43 You can visit files with non-@acronym{ASCII} characters, save non-@acronym{ASCII} text, and
44 pass non-@acronym{ASCII} text between Emacs and programs it invokes (such as
45 compilers, spell-checkers, and mailers). Setting your language
46 environment (@pxref{Language Environments}) takes care of setting up the
47 coding systems and other options for a specific language or culture.
48 Alternatively, you can specify how Emacs should encode or decode text
49 for each command; see @ref{Text Coding}.
52 You can display non-@acronym{ASCII} characters encoded by the various
53 scripts. This works by using appropriate fonts on graphics displays
54 (@pxref{Defining Fontsets}), and by sending special codes to text
55 displays (@pxref{Terminal Coding}). If some characters are displayed
56 incorrectly, refer to @ref{Undisplayable Characters}, which describes
57 possible problems and explains how to solve them.
60 Characters from scripts whose natural ordering of text is from right
61 to left are reordered for display (@pxref{Bidirectional Editing}).
62 These scripts include Arabic, Hebrew, Syriac, Thaana, and a few
66 You can insert non-@acronym{ASCII} characters or search for them. To do that,
67 you can specify an input method (@pxref{Select Input Method}) suitable
68 for your language, or use the default input method set up when you chose
69 your language environment. If
70 your keyboard can produce non-@acronym{ASCII} characters, you can select an
71 appropriate keyboard coding system (@pxref{Terminal Coding}), and Emacs
72 will accept those characters. Latin-1 characters can also be input by
73 using the @kbd{C-x 8} prefix, see @ref{Unibyte Mode}.
75 With the X Window System, your locale should be set to an appropriate
76 value to make sure Emacs interprets keyboard input correctly; see
77 @ref{Language Environments, locales}.
80 The rest of this chapter describes these issues in detail.
83 * International Chars:: Basic concepts of multibyte characters.
84 * Language Environments:: Setting things up for the language you use.
85 * Input Methods:: Entering text characters not on your keyboard.
86 * Select Input Method:: Specifying your choice of input methods.
87 * Coding Systems:: Character set conversion when you read and
88 write files, and so on.
89 * Recognize Coding:: How Emacs figures out which conversion to use.
90 * Specify Coding:: Specifying a file's coding system explicitly.
91 * Output Coding:: Choosing coding systems for output.
92 * Text Coding:: Choosing conversion to use for file text.
93 * Communication Coding:: Coding systems for interprocess communication.
94 * File Name Coding:: Coding systems for file @emph{names}.
95 * Terminal Coding:: Specifying coding systems for converting
96 terminal input and output.
97 * Fontsets:: Fontsets are collections of fonts
98 that cover the whole spectrum of characters.
99 * Defining Fontsets:: Defining a new fontset.
100 * Modifying Fontsets:: Modifying an existing fontset.
101 * Undisplayable Characters:: When characters don't display.
102 * Unibyte Mode:: You can pick one European character set
103 to use without multibyte characters.
104 * Charsets:: How Emacs groups its internal character codes.
105 * Bidirectional Editing:: Support for right-to-left scripts.
108 @node International Chars
109 @section Introduction to International Character Sets
111 The users of international character sets and scripts have
112 established many more-or-less standard coding systems for storing
113 files. These coding systems are typically @dfn{multibyte}, meaning
114 that sequences of two or more bytes are used to represent individual
115 non-@acronym{ASCII} characters.
118 Internally, Emacs uses its own multibyte character encoding, which
119 is a superset of the @dfn{Unicode} standard. This internal encoding
120 allows characters from almost every known script to be intermixed in a
121 single buffer or string. Emacs translates between the multibyte
122 character encoding and various other coding systems when reading and
123 writing files, and when exchanging data with subprocesses.
126 @findex view-hello-file
127 @cindex undisplayable characters
128 @cindex @samp{?} in display
129 The command @kbd{C-h h} (@code{view-hello-file}) displays the file
130 @file{etc/HELLO}, which illustrates various scripts by showing
131 how to say ``hello'' in many languages. If some characters can't be
132 displayed on your terminal, they appear as @samp{?} or as hollow boxes
133 (@pxref{Undisplayable Characters}).
135 Keyboards, even in the countries where these character sets are
136 used, generally don't have keys for all the characters in them. You
137 can insert characters that your keyboard does not support, using
138 @kbd{C-q} (@code{quoted-insert}) or @kbd{C-x 8 @key{RET}}
139 (@code{insert-char}). @xref{Inserting Text}. Emacs also supports
140 various @dfn{input methods}, typically one for each script or
141 language, which make it easier to type characters in the script.
142 @xref{Input Methods}.
145 The prefix key @kbd{C-x @key{RET}} is used for commands that pertain
146 to multibyte characters, coding systems, and input methods.
149 @findex what-cursor-position
150 The command @kbd{C-x =} (@code{what-cursor-position}) shows
151 information about the character at point. In addition to the
152 character position, which was described in @ref{Position Info}, this
153 command displays how the character is encoded. For instance, it
154 displays the following line in the echo area for the character
158 Char: c (99, #o143, #x63) point=28062 of 36168 (78%) column=53
161 The four values after @samp{Char:} describe the character that
162 follows point, first by showing it and then by giving its character
163 code in decimal, octal and hex. For a non-@acronym{ASCII} multibyte
164 character, these are followed by @samp{file} and the character's
165 representation, in hex, in the buffer's coding system, if that coding
166 system encodes the character safely and with a single byte
167 (@pxref{Coding Systems}). If the character's encoding is longer than
168 one byte, Emacs shows @samp{file ...}.
170 As a special case, if the character lies in the range 128 (0200
171 octal) through 159 (0237 octal), it stands for a ``raw'' byte that
172 does not correspond to any specific displayable character. Such a
173 ``character'' lies within the @code{eight-bit-control} character set,
174 and is displayed as an escaped octal character code. In this case,
175 @kbd{C-x =} shows @samp{part of display ...} instead of @samp{file}.
177 @cindex character set of character at point
178 @cindex font of character at point
179 @cindex text properties at point
180 @cindex face at point
181 With a prefix argument (@kbd{C-u C-x =}), this command displays a
182 detailed description of the character in a window:
186 The character set name, and the codes that identify the character
187 within that character set; @acronym{ASCII} characters are identified
188 as belonging to the @code{ascii} character set.
191 The character's script, syntax and categories.
194 What keys to type to input the character in the current input method
195 (if it supports the character).
198 The character's encodings, both internally in the buffer, and externally
199 if you were to save the file.
202 If you are running Emacs on a graphical display, the font name and
203 glyph code for the character. If you are running Emacs on a text
204 terminal, the code(s) sent to the terminal.
207 The character's text properties (@pxref{Text Properties,,,
208 elisp, the Emacs Lisp Reference Manual}), including any non-default
209 faces used to display the character, and any overlays containing it
210 (@pxref{Overlays,,, elisp, the same manual}).
213 Here's an example, with some lines folded to fit into this manual:
216 position: 1 of 1 (0%), column: 0
217 character: @^e (displayed as @^e) (codepoint 234, #o352, #xea)
218 preferred charset: unicode (Unicode (ISO10646))
219 code point in charset: 0xEA
221 syntax: w which means: word
222 category: .:Base, L:Left-to-right (strong), c:Chinese,
223 j:Japanese, l:Latin, v:Viet
224 to input: type "C-x 8 RET HEX-CODEPOINT" or "C-x 8 RET NAME"
225 buffer code: #xC3 #xAA
226 file code: #xC3 #xAA (encoded by coding system utf-8-unix)
227 display: by this font (glyph code)
228 xft:-unknown-DejaVu Sans Mono-normal-normal-
229 normal-*-15-*-*-*-m-0-iso10646-1 (#xAC)
231 Character code properties: customize what to show
232 name: LATIN SMALL LETTER E WITH CIRCUMFLEX
233 old-name: LATIN SMALL LETTER E CIRCUMFLEX
234 general-category: Ll (Letter, Lowercase)
235 decomposition: (101 770) ('e' '^')
238 @node Language Environments
239 @section Language Environments
240 @cindex language environments
242 All supported character sets are supported in Emacs buffers whenever
243 multibyte characters are enabled; there is no need to select a
244 particular language in order to display its characters.
245 However, it is important to select a @dfn{language
246 environment} in order to set various defaults. Roughly speaking, the
247 language environment represents a choice of preferred script rather
248 than a choice of language.
250 The language environment controls which coding systems to recognize
251 when reading text (@pxref{Recognize Coding}). This applies to files,
252 incoming mail, and any other text you read into Emacs. It may also
253 specify the default coding system to use when you create a file. Each
254 language environment also specifies a default input method.
256 @findex set-language-environment
257 @vindex current-language-environment
258 To select a language environment, customize
259 @code{current-language-environment} or use the command @kbd{M-x
260 set-language-environment}. It makes no difference which buffer is
261 current when you use this command, because the effects apply globally
262 to the Emacs session. See the variable @code{language-info-alist} for
263 the list of supported language environments, and use the command
264 @kbd{C-h L @var{lang-env} @key{RET}} (@code{describe-language-environment})
265 for more information about the language environment @var{lang-env}.
266 Supported language environments include:
277 @cindex Brazilian Portuguese
278 Brazilian Portuguese,
286 Chinese-BIG5, Chinese-CNS, Chinese-EUC-TW, Chinese-GB,
287 Chinese-GB18030, Chinese-GBK,
291 Cyrillic-ALT, Cyrillic-ISO, Cyrillic-KOI8,
331 Latin-1, Latin-2, Latin-3, Latin-4, Latin-5, Latin-6, Latin-7,
387 To display the script(s) used by your language environment on a
388 graphical display, you need to have suitable fonts.
389 @xref{Fontsets}, for more details about setting up your fonts.
391 @findex set-locale-environment
392 @vindex locale-language-names
393 @vindex locale-charset-language-names
395 Some operating systems let you specify the character-set locale you
396 are using by setting the locale environment variables @env{LC_ALL},
397 @env{LC_CTYPE}, or @env{LANG}. (If more than one of these is
398 set, the first one that is nonempty specifies your locale for this
399 purpose.) During startup, Emacs looks up your character-set locale's
400 name in the system locale alias table, matches its canonical name
401 against entries in the value of the variables
402 @code{locale-charset-language-names} and @code{locale-language-names}
403 (the former overrides the latter),
404 and selects the corresponding language environment if a match is found.
405 It also adjusts the display
406 table and terminal coding system, the locale coding system, the
407 preferred coding system as needed for the locale, and---last but not
408 least---the way Emacs decodes non-@acronym{ASCII} characters sent by your keyboard.
410 @c This seems unlikely, doesn't it?
411 If you modify the @env{LC_ALL}, @env{LC_CTYPE}, or @env{LANG}
412 environment variables while running Emacs (by using @kbd{M-x setenv}),
413 you may want to invoke the @code{set-locale-environment}
414 function afterwards to readjust the language environment from the new
417 @vindex locale-preferred-coding-systems
418 The @code{set-locale-environment} function normally uses the preferred
419 coding system established by the language environment to decode system
420 messages. But if your locale matches an entry in the variable
421 @code{locale-preferred-coding-systems}, Emacs uses the corresponding
422 coding system instead. For example, if the locale @samp{ja_JP.PCK}
423 matches @code{japanese-shift-jis} in
424 @code{locale-preferred-coding-systems}, Emacs uses that encoding even
425 though it might normally use @code{japanese-iso-8bit}.
427 You can override the language environment chosen at startup with
428 explicit use of the command @code{set-language-environment}, or with
429 customization of @code{current-language-environment} in your init
433 @findex describe-language-environment
434 @anchor{Describe Language Environment}
435 To display information about the effects of a certain language
436 environment @var{lang-env}, use the command @kbd{C-h L @var{lang-env}
437 @key{RET}} (@code{describe-language-environment}). This tells you
438 which languages this language environment is useful for, and lists the
439 character sets, coding systems, and input methods that go with it. It
440 also shows some sample text to illustrate scripts used in this
441 language environment. If you give an empty input for @var{lang-env},
442 this command describes the chosen language environment.
444 @vindex set-language-environment-hook
445 You can customize any language environment with the normal hook
446 @code{set-language-environment-hook}. The command
447 @code{set-language-environment} runs that hook after setting up the new
448 language environment. The hook functions can test for a specific
449 language environment by checking the variable
450 @code{current-language-environment}. This hook is where you should
451 put non-default settings for specific language environments, such as
452 coding systems for keyboard input and terminal output, the default
455 @vindex exit-language-environment-hook
456 Before it starts to set up the new language environment,
457 @code{set-language-environment} first runs the hook
458 @code{exit-language-environment-hook}. This hook is useful for undoing
459 customizations that were made with @code{set-language-environment-hook}.
460 For instance, if you set up a special key binding in a specific language
461 environment using @code{set-language-environment-hook}, you should set
462 up @code{exit-language-environment-hook} to restore the normal binding
466 @section Input Methods
468 @cindex input methods
469 An @dfn{input method} is a kind of character conversion designed
470 specifically for interactive input. In Emacs, typically each language
471 has its own input method; sometimes several languages that use the same
472 characters can share one input method. A few languages support several
475 The simplest kind of input method works by mapping @acronym{ASCII} letters
476 into another alphabet; this allows you to use one other alphabet
477 instead of @acronym{ASCII}. The Greek and Russian input methods
480 A more powerful technique is composition: converting sequences of
481 characters into one letter. Many European input methods use composition
482 to produce a single non-@acronym{ASCII} letter from a sequence that consists of a
483 letter followed by accent characters (or vice versa). For example, some
484 methods convert the sequence @kbd{o ^} into a single accented letter.
485 These input methods have no special commands of their own; all they do
486 is compose sequences of printing characters.
488 The input methods for syllabic scripts typically use mapping followed
489 by composition. The input methods for Thai and Korean work this way.
490 First, letters are mapped into symbols for particular sounds or tone
491 marks; then, sequences of these that make up a whole syllable are
492 mapped into one syllable sign.
494 Chinese and Japanese require more complex methods. In Chinese input
495 methods, first you enter the phonetic spelling of a Chinese word (in
496 input method @code{chinese-py}, among others), or a sequence of
497 portions of the character (input methods @code{chinese-4corner} and
498 @code{chinese-sw}, and others). One input sequence typically
499 corresponds to many possible Chinese characters. You select the one
500 you mean using keys such as @kbd{C-f}, @kbd{C-b}, @kbd{C-n},
501 @kbd{C-p} (or the arrow keys), and digits, which have special meanings
504 The possible characters are conceptually arranged in several rows,
505 with each row holding up to 10 alternatives. Normally, Emacs displays
506 just one row at a time, in the echo area; @code{(@var{i}/@var{j})}
507 appears at the beginning, to indicate that this is the @var{i}th row
508 out of a total of @var{j} rows. Type @kbd{C-n} or @kbd{C-p} to
509 display the next row or the previous row.
511 Type @kbd{C-f} and @kbd{C-b} to move forward and backward among
512 the alternatives in the current row. As you do this, Emacs highlights
513 the current alternative with a special color; type @code{C-@key{SPC}}
514 to select the current alternative and use it as input. The
515 alternatives in the row are also numbered; the number appears before
516 the alternative. Typing a number selects the associated alternative
517 of the current row and uses it as input.
519 @key{TAB} in these Chinese input methods displays a buffer showing
520 all the possible characters at once; then clicking @kbd{Mouse-2} on
521 one of them selects that alternative. The keys @kbd{C-f}, @kbd{C-b},
522 @kbd{C-n}, @kbd{C-p}, and digits continue to work as usual, but they
523 do the highlighting in the buffer showing the possible characters,
524 rather than in the echo area.
526 In Japanese input methods, first you input a whole word using
527 phonetic spelling; then, after the word is in the buffer, Emacs
528 converts it into one or more characters using a large dictionary. One
529 phonetic spelling corresponds to a number of different Japanese words;
530 to select one of them, use @kbd{C-n} and @kbd{C-p} to cycle through
533 Sometimes it is useful to cut off input method processing so that the
534 characters you have just entered will not combine with subsequent
535 characters. For example, in input method @code{latin-1-postfix}, the
536 sequence @kbd{o ^} combines to form an @samp{o} with an accent. What if
537 you want to enter them as separate characters?
539 One way is to type the accent twice; this is a special feature for
540 entering the separate letter and accent. For example, @kbd{o ^ ^} gives
541 you the two characters @samp{o^}. Another way is to type another letter
542 after the @kbd{o}---something that won't combine with that---and
543 immediately delete it. For example, you could type @kbd{o o @key{DEL}
544 ^} to get separate @samp{o} and @samp{^}.
546 Another method, more general but not quite as easy to type, is to use
547 @kbd{C-\ C-\} between two characters to stop them from combining. This
548 is the command @kbd{C-\} (@code{toggle-input-method}) used twice.
550 @xref{Select Input Method}.
553 @cindex incremental search, input method interference
554 @kbd{C-\ C-\} is especially useful inside an incremental search,
555 because it stops waiting for more characters to combine, and starts
556 searching for what you have already entered.
558 To find out how to input the character after point using the current
559 input method, type @kbd{C-u C-x =}. @xref{Position Info}.
561 @vindex input-method-verbose-flag
562 @vindex input-method-highlight-flag
563 The variables @code{input-method-highlight-flag} and
564 @code{input-method-verbose-flag} control how input methods explain
565 what is happening. If @code{input-method-highlight-flag} is
566 non-@code{nil}, the partial sequence is highlighted in the buffer (for
567 most input methods---some disable this feature). If
568 @code{input-method-verbose-flag} is non-@code{nil}, the list of
569 possible characters to type next is displayed in the echo area (but
570 not when you are in the minibuffer).
572 Another facility for typing characters not on your keyboard is by
573 using @kbd{C-x 8 @key{RET}} (@code{insert-char}) to insert a single
574 character based on its Unicode name or code-point; see @ref{Inserting
577 @node Select Input Method
578 @section Selecting an Input Method
582 Enable or disable use of the selected input method (@code{toggle-input-method}).
584 @item C-x @key{RET} C-\ @var{method} @key{RET}
585 Select a new input method for the current buffer (@code{set-input-method}).
587 @item C-h I @var{method} @key{RET}
588 @itemx C-h C-\ @var{method} @key{RET}
589 @findex describe-input-method
592 Describe the input method @var{method} (@code{describe-input-method}).
593 By default, it describes the current input method (if any). This
594 description should give you the full details of how to use any
595 particular input method.
597 @item M-x list-input-methods
598 Display a list of all the supported input methods.
601 @findex set-input-method
602 @vindex current-input-method
604 To choose an input method for the current buffer, use @kbd{C-x
605 @key{RET} C-\} (@code{set-input-method}). This command reads the
606 input method name from the minibuffer; the name normally starts with the
607 language environment that it is meant to be used with. The variable
608 @code{current-input-method} records which input method is selected.
610 @findex toggle-input-method
612 Input methods use various sequences of @acronym{ASCII} characters to
613 stand for non-@acronym{ASCII} characters. Sometimes it is useful to
614 turn off the input method temporarily. To do this, type @kbd{C-\}
615 (@code{toggle-input-method}). To reenable the input method, type
618 If you type @kbd{C-\} and you have not yet selected an input method,
619 it prompts you to specify one. This has the same effect as using
620 @kbd{C-x @key{RET} C-\} to specify an input method.
622 When invoked with a numeric argument, as in @kbd{C-u C-\},
623 @code{toggle-input-method} always prompts you for an input method,
624 suggesting the most recently selected one as the default.
626 @vindex default-input-method
627 Selecting a language environment specifies a default input method for
628 use in various buffers. When you have a default input method, you can
629 select it in the current buffer by typing @kbd{C-\}. The variable
630 @code{default-input-method} specifies the default input method
631 (@code{nil} means there is none).
633 In some language environments, which support several different input
634 methods, you might want to use an input method different from the
635 default chosen by @code{set-language-environment}. You can instruct
636 Emacs to select a different default input method for a certain
637 language environment, if you wish, by using
638 @code{set-language-environment-hook} (@pxref{Language Environments,
639 set-language-environment-hook}). For example:
642 (defun my-chinese-setup ()
643 "Set up my private Chinese environment."
644 (if (equal current-language-environment "Chinese-GB")
645 (setq default-input-method "chinese-tonepy")))
646 (add-hook 'set-language-environment-hook 'my-chinese-setup)
650 This sets the default input method to be @code{chinese-tonepy}
651 whenever you choose a Chinese-GB language environment.
653 You can instruct Emacs to activate a certain input method
654 automatically. For example:
657 (add-hook 'text-mode-hook
658 (lambda () (set-input-method "german-prefix")))
662 This automatically activates the input method ``german-prefix'' in
665 @findex quail-set-keyboard-layout
666 Some input methods for alphabetic scripts work by (in effect)
667 remapping the keyboard to emulate various keyboard layouts commonly used
668 for those scripts. How to do this remapping properly depends on your
669 actual keyboard layout. To specify which layout your keyboard has, use
670 the command @kbd{M-x quail-set-keyboard-layout}.
672 @findex quail-show-key
673 You can use the command @kbd{M-x quail-show-key} to show what key (or
674 key sequence) to type in order to input the character following point,
675 using the selected keyboard layout. The command @kbd{C-u C-x =} also
676 shows that information, in addition to other information about the
679 @findex list-input-methods
680 @kbd{M-x list-input-methods} displays a list of all the supported
681 input methods. The list gives information about each input method,
682 including the string that stands for it in the mode line.
685 @section Coding Systems
686 @cindex coding systems
688 Users of various languages have established many more-or-less standard
689 coding systems for representing them. Emacs does not use these coding
690 systems internally; instead, it converts from various coding systems to
691 its own system when reading data, and converts the internal coding
692 system to other coding systems when writing data. Conversion is
693 possible in reading or writing files, in sending or receiving from the
694 terminal, and in exchanging data with subprocesses.
696 Emacs assigns a name to each coding system. Most coding systems are
697 used for one language, and the name of the coding system starts with
698 the language name. Some coding systems are used for several
699 languages; their names usually start with @samp{iso}. There are also
700 special coding systems, such as @code{no-conversion}, @code{raw-text},
701 and @code{emacs-internal}.
703 @cindex international files from DOS/Windows systems
704 A special class of coding systems, collectively known as
705 @dfn{codepages}, is designed to support text encoded by MS-Windows and
706 MS-DOS software. The names of these coding systems are
707 @code{cp@var{nnnn}}, where @var{nnnn} is a 3- or 4-digit number of the
708 codepage. You can use these encodings just like any other coding
709 system; for example, to visit a file encoded in codepage 850, type
710 @kbd{C-x @key{RET} c cp850 @key{RET} C-x C-f @var{filename}
713 In addition to converting various representations of non-@acronym{ASCII}
714 characters, a coding system can perform end-of-line conversion. Emacs
715 handles three different conventions for how to separate lines in a file:
716 newline (``unix''), carriage-return linefeed (``dos''), and just
717 carriage-return (``mac'').
720 @item C-h C @var{coding} @key{RET}
721 Describe coding system @var{coding} (@code{describe-coding-system}).
723 @item C-h C @key{RET}
724 Describe the coding systems currently in use.
726 @item M-x list-coding-systems
727 Display a list of all the supported coding systems.
731 @findex describe-coding-system
732 The command @kbd{C-h C} (@code{describe-coding-system}) displays
733 information about particular coding systems, including the end-of-line
734 conversion specified by those coding systems. You can specify a coding
735 system name as the argument; alternatively, with an empty argument, it
736 describes the coding systems currently selected for various purposes,
737 both in the current buffer and as the defaults, and the priority list
738 for recognizing coding systems (@pxref{Recognize Coding}).
740 @findex list-coding-systems
741 To display a list of all the supported coding systems, type @kbd{M-x
742 list-coding-systems}. The list gives information about each coding
743 system, including the letter that stands for it in the mode line
746 @cindex end-of-line conversion
748 @cindex MS-DOS end-of-line conversion
749 @cindex Macintosh end-of-line conversion
750 Each of the coding systems that appear in this list---except for
751 @code{no-conversion}, which means no conversion of any kind---specifies
752 how and whether to convert printing characters, but leaves the choice of
753 end-of-line conversion to be decided based on the contents of each file.
754 For example, if the file appears to use the sequence carriage-return
755 linefeed to separate lines, DOS end-of-line conversion will be used.
757 Each of the listed coding systems has three variants, which specify
758 exactly what to do for end-of-line conversion:
762 Don't do any end-of-line conversion; assume the file uses
763 newline to separate lines. (This is the convention normally used
764 on Unix and GNU systems, and Mac OS X.)
767 Assume the file uses carriage-return linefeed to separate lines, and do
768 the appropriate conversion. (This is the convention normally used on
769 Microsoft systems.@footnote{It is also specified for MIME @samp{text/*}
770 bodies and in other network transport contexts. It is different
771 from the SGML reference syntax record-start/record-end format, which
772 Emacs doesn't support directly.})
775 Assume the file uses carriage-return to separate lines, and do the
776 appropriate conversion. (This was the convention used on the
777 Macintosh system prior to OS X.)
780 These variant coding systems are omitted from the
781 @code{list-coding-systems} display for brevity, since they are entirely
782 predictable. For example, the coding system @code{iso-latin-1} has
783 variants @code{iso-latin-1-unix}, @code{iso-latin-1-dos} and
784 @code{iso-latin-1-mac}.
786 @cindex @code{undecided}, coding system
787 The coding systems @code{unix}, @code{dos}, and @code{mac} are
788 aliases for @code{undecided-unix}, @code{undecided-dos}, and
789 @code{undecided-mac}, respectively. These coding systems specify only
790 the end-of-line conversion, and leave the character code conversion to
791 be deduced from the text itself.
793 @cindex @code{raw-text}, coding system
794 The coding system @code{raw-text} is good for a file which is mainly
795 @acronym{ASCII} text, but may contain byte values above 127 that are
796 not meant to encode non-@acronym{ASCII} characters. With
797 @code{raw-text}, Emacs copies those byte values unchanged, and sets
798 @code{enable-multibyte-characters} to @code{nil} in the current buffer
799 so that they will be interpreted properly. @code{raw-text} handles
800 end-of-line conversion in the usual way, based on the data
801 encountered, and has the usual three variants to specify the kind of
802 end-of-line conversion to use.
804 @cindex @code{no-conversion}, coding system
805 In contrast, the coding system @code{no-conversion} specifies no
806 character code conversion at all---none for non-@acronym{ASCII} byte values and
807 none for end of line. This is useful for reading or writing binary
808 files, tar files, and other files that must be examined verbatim. It,
809 too, sets @code{enable-multibyte-characters} to @code{nil}.
811 The easiest way to edit a file with no conversion of any kind is with
812 the @kbd{M-x find-file-literally} command. This uses
813 @code{no-conversion}, and also suppresses other Emacs features that
814 might convert the file contents before you see them. @xref{Visiting}.
816 @cindex @code{emacs-internal}, coding system
817 The coding system @code{emacs-internal} (or @code{utf-8-emacs},
818 which is equivalent) means that the file contains non-@acronym{ASCII}
819 characters stored with the internal Emacs encoding. This coding
820 system handles end-of-line conversion based on the data encountered,
821 and has the usual three variants to specify the kind of end-of-line
824 @node Recognize Coding
825 @section Recognizing Coding Systems
827 Whenever Emacs reads a given piece of text, it tries to recognize
828 which coding system to use. This applies to files being read, output
829 from subprocesses, text from X selections, etc. Emacs can select the
830 right coding system automatically most of the time---once you have
831 specified your preferences.
833 Some coding systems can be recognized or distinguished by which byte
834 sequences appear in the data. However, there are coding systems that
835 cannot be distinguished, not even potentially. For example, there is no
836 way to distinguish between Latin-1 and Latin-2; they use the same byte
837 values with different meanings.
839 Emacs handles this situation by means of a priority list of coding
840 systems. Whenever Emacs reads a file, if you do not specify the coding
841 system to use, Emacs checks the data against each coding system,
842 starting with the first in priority and working down the list, until it
843 finds a coding system that fits the data. Then it converts the file
844 contents assuming that they are represented in this coding system.
846 The priority list of coding systems depends on the selected language
847 environment (@pxref{Language Environments}). For example, if you use
848 French, you probably want Emacs to prefer Latin-1 to Latin-2; if you use
849 Czech, you probably want Latin-2 to be preferred. This is one of the
850 reasons to specify a language environment.
852 @findex prefer-coding-system
853 However, you can alter the coding system priority list in detail
854 with the command @kbd{M-x prefer-coding-system}. This command reads
855 the name of a coding system from the minibuffer, and adds it to the
856 front of the priority list, so that it is preferred to all others. If
857 you use this command several times, each use adds one element to the
858 front of the priority list.
860 If you use a coding system that specifies the end-of-line conversion
861 type, such as @code{iso-8859-1-dos}, what this means is that Emacs
862 should attempt to recognize @code{iso-8859-1} with priority, and should
863 use DOS end-of-line conversion when it does recognize @code{iso-8859-1}.
865 @vindex file-coding-system-alist
866 Sometimes a file name indicates which coding system to use for the
867 file. The variable @code{file-coding-system-alist} specifies this
868 correspondence. There is a special function
869 @code{modify-coding-system-alist} for adding elements to this list. For
870 example, to read and write all @samp{.txt} files using the coding system
871 @code{chinese-iso-8bit}, you can execute this Lisp expression:
874 (modify-coding-system-alist 'file "\\.txt\\'" 'chinese-iso-8bit)
878 The first argument should be @code{file}, the second argument should be
879 a regular expression that determines which files this applies to, and
880 the third argument says which coding system to use for these files.
882 @vindex inhibit-eol-conversion
883 @cindex DOS-style end-of-line display
884 Emacs recognizes which kind of end-of-line conversion to use based on
885 the contents of the file: if it sees only carriage-returns, or only
886 carriage-return linefeed sequences, then it chooses the end-of-line
887 conversion accordingly. You can inhibit the automatic use of
888 end-of-line conversion by setting the variable @code{inhibit-eol-conversion}
889 to non-@code{nil}. If you do that, DOS-style files will be displayed
890 with the @samp{^M} characters visible in the buffer; some people
891 prefer this to the more subtle @samp{(DOS)} end-of-line type
892 indication near the left edge of the mode line (@pxref{Mode Line,
895 @vindex inhibit-iso-escape-detection
896 @cindex escape sequences in files
897 By default, the automatic detection of coding system is sensitive to
898 escape sequences. If Emacs sees a sequence of characters that begin
899 with an escape character, and the sequence is valid as an ISO-2022
900 code, that tells Emacs to use one of the ISO-2022 encodings to decode
903 However, there may be cases that you want to read escape sequences
904 in a file as is. In such a case, you can set the variable
905 @code{inhibit-iso-escape-detection} to non-@code{nil}. Then the code
906 detection ignores any escape sequences, and never uses an ISO-2022
907 encoding. The result is that all escape sequences become visible in
910 The default value of @code{inhibit-iso-escape-detection} is
911 @code{nil}. We recommend that you not change it permanently, only for
912 one specific operation. That's because some Emacs Lisp source files
913 in the Emacs distribution contain non-@acronym{ASCII} characters encoded in the
914 coding system @code{iso-2022-7bit}, and they won't be
915 decoded correctly when you visit those files if you suppress the
916 escape sequence detection.
917 @c I count a grand total of 3 such files, so is the above really true?
919 @vindex auto-coding-alist
920 @vindex auto-coding-regexp-alist
921 The variables @code{auto-coding-alist} and
922 @code{auto-coding-regexp-alist} are
923 the strongest way to specify the coding system for certain patterns of
924 file names, or for files containing certain patterns, respectively.
925 These variables even override @samp{-*-coding:-*-} tags in the file
926 itself (@pxref{Specify Coding}). For example, Emacs
927 uses @code{auto-coding-alist} for tar and archive files, to prevent it
928 from being confused by a @samp{-*-coding:-*-} tag in a member of the
929 archive and thinking it applies to the archive file as a whole.
931 @c This describes old-style BABYL files, which are no longer relevant.
932 Likewise, Emacs uses @code{auto-coding-regexp-alist} to ensure that
933 RMAIL files, whose names in general don't match any particular
934 pattern, are decoded correctly.
937 @vindex auto-coding-functions
938 Another way to specify a coding system is with the variable
939 @code{auto-coding-functions}. For example, one of the builtin
940 @code{auto-coding-functions} detects the encoding for XML files.
941 Unlike the previous two, this variable does not override any
942 @samp{-*-coding:-*-} tag.
945 @section Specifying a File's Coding System
947 If Emacs recognizes the encoding of a file incorrectly, you can
948 reread the file using the correct coding system with @kbd{C-x
949 @key{RET} r} (@code{revert-buffer-with-coding-system}). This command
950 prompts for the coding system to use. To see what coding system Emacs
951 actually used to decode the file, look at the coding system mnemonic
952 letter near the left edge of the mode line (@pxref{Mode Line}), or
953 type @kbd{C-h C} (@code{describe-coding-system}).
956 You can specify the coding system for a particular file in the file
957 itself, using the @w{@samp{-*-@dots{}-*-}} construct at the beginning,
958 or a local variables list at the end (@pxref{File Variables}). You do
959 this by defining a value for the ``variable'' named @code{coding}.
960 Emacs does not really have a variable @code{coding}; instead of
961 setting a variable, this uses the specified coding system for the
962 file. For example, @samp{-*-mode: C; coding: latin-1;-*-} specifies
963 use of the Latin-1 coding system, as well as C mode. When you specify
964 the coding explicitly in the file, that overrides
965 @code{file-coding-system-alist}.
968 @section Choosing Coding Systems for Output
970 @vindex buffer-file-coding-system
971 Once Emacs has chosen a coding system for a buffer, it stores that
972 coding system in @code{buffer-file-coding-system}. That makes it the
973 default for operations that write from this buffer into a file, such
974 as @code{save-buffer} and @code{write-region}. You can specify a
975 different coding system for further file output from the buffer using
976 @code{set-buffer-file-coding-system} (@pxref{Text Coding}).
978 You can insert any character Emacs supports into any Emacs buffer,
979 but most coding systems can only handle a subset of these characters.
980 Therefore, it's possible that the characters you insert cannot be
981 encoded with the coding system that will be used to save the buffer.
982 For example, you could visit a text file in Polish, encoded in
983 @code{iso-8859-2}, and add some Russian words to it. When you save
984 that buffer, Emacs cannot use the current value of
985 @code{buffer-file-coding-system}, because the characters you added
986 cannot be encoded by that coding system.
988 When that happens, Emacs tries the most-preferred coding system (set
989 by @kbd{M-x prefer-coding-system} or @kbd{M-x
990 set-language-environment}). If that coding system can safely encode
991 all of the characters in the buffer, Emacs uses it, and stores its
992 value in @code{buffer-file-coding-system}. Otherwise, Emacs displays
993 a list of coding systems suitable for encoding the buffer's contents,
994 and asks you to choose one of those coding systems.
996 If you insert the unsuitable characters in a mail message, Emacs
997 behaves a bit differently. It additionally checks whether the
998 @c What determines this?
999 most-preferred coding system is recommended for use in MIME messages;
1000 if not, it informs you of this fact and prompts you for another coding
1001 system. This is so you won't inadvertently send a message encoded in
1002 a way that your recipient's mail software will have difficulty
1003 decoding. (You can still use an unsuitable coding system if you enter
1004 its name at the prompt.)
1006 @c It seems that select-message-coding-system does this.
1007 @c Both sendmail.el and smptmail.el call it; i.e., smtpmail.el still
1008 @c obeys sendmail-coding-system.
1009 @vindex sendmail-coding-system
1010 When you send a mail message (@pxref{Sending Mail}),
1011 Emacs has four different ways to determine the coding system to use
1012 for encoding the message text. It tries the buffer's own value of
1013 @code{buffer-file-coding-system}, if that is non-@code{nil}.
1014 Otherwise, it uses the value of @code{sendmail-coding-system}, if that
1015 is non-@code{nil}. The third way is to use the default coding system
1016 for new files, which is controlled by your choice of language
1017 @c i.e., default-sendmail-coding-system
1018 environment, if that is non-@code{nil}. If all of these three values
1019 are @code{nil}, Emacs encodes outgoing mail using the Latin-1 coding
1021 @c FIXME? Where does the Latin-1 default come in?
1024 @section Specifying a Coding System for File Text
1026 In cases where Emacs does not automatically choose the right coding
1027 system for a file's contents, you can use these commands to specify
1031 @item C-x @key{RET} f @var{coding} @key{RET}
1032 Use coding system @var{coding} to save or revisit the file in
1033 the current buffer (@code{set-buffer-file-coding-system}).
1035 @item C-x @key{RET} c @var{coding} @key{RET}
1036 Specify coding system @var{coding} for the immediately following
1037 command (@code{universal-coding-system-argument}).
1039 @item C-x @key{RET} r @var{coding} @key{RET}
1040 Revisit the current file using the coding system @var{coding}
1041 (@code{revert-buffer-with-coding-system}).
1043 @item M-x recode-region @key{RET} @var{right} @key{RET} @var{wrong} @key{RET}
1044 Convert a region that was decoded using coding system @var{wrong},
1045 decoding it using coding system @var{right} instead.
1049 @findex set-buffer-file-coding-system
1050 The command @kbd{C-x @key{RET} f}
1051 (@code{set-buffer-file-coding-system}) sets the file coding system for
1052 the current buffer (i.e., the coding system to use when saving or
1053 reverting the file). You specify which coding system using the
1054 minibuffer. You can also invoke this command by clicking with
1055 @kbd{Mouse-3} on the coding system indicator in the mode line
1056 (@pxref{Mode Line}).
1058 If you specify a coding system that cannot handle all the characters
1059 in the buffer, Emacs will warn you about the troublesome characters,
1060 and ask you to choose another coding system, when you try to save the
1061 buffer (@pxref{Output Coding}).
1063 @cindex specify end-of-line conversion
1064 You can also use this command to specify the end-of-line conversion
1065 (@pxref{Coding Systems, end-of-line conversion}) for encoding the
1066 current buffer. For example, @kbd{C-x @key{RET} f dos @key{RET}} will
1067 cause Emacs to save the current buffer's text with DOS-style
1068 carriage-return linefeed line endings.
1071 @findex universal-coding-system-argument
1072 Another way to specify the coding system for a file is when you visit
1073 the file. First use the command @kbd{C-x @key{RET} c}
1074 (@code{universal-coding-system-argument}); this command uses the
1075 minibuffer to read a coding system name. After you exit the minibuffer,
1076 the specified coding system is used for @emph{the immediately following
1079 So if the immediately following command is @kbd{C-x C-f}, for example,
1080 it reads the file using that coding system (and records the coding
1081 system for when you later save the file). Or if the immediately following
1082 command is @kbd{C-x C-w}, it writes the file using that coding system.
1083 When you specify the coding system for saving in this way, instead
1084 of with @kbd{C-x @key{RET} f}, there is no warning if the buffer
1085 contains characters that the coding system cannot handle.
1087 Other file commands affected by a specified coding system include
1088 @kbd{C-x i} and @kbd{C-x C-v}, as well as the other-window variants
1089 of @kbd{C-x C-f}. @kbd{C-x @key{RET} c} also affects commands that
1090 start subprocesses, including @kbd{M-x shell} (@pxref{Shell}). If the
1091 immediately following command does not use the coding system, then
1092 @kbd{C-x @key{RET} c} ultimately has no effect.
1094 An easy way to visit a file with no conversion is with the @kbd{M-x
1095 find-file-literally} command. @xref{Visiting}.
1097 The default value of the variable @code{buffer-file-coding-system}
1098 specifies the choice of coding system to use when you create a new file.
1099 It applies when you find a new file, and when you create a buffer and
1100 then save it in a file. Selecting a language environment typically sets
1101 this variable to a good choice of default coding system for that language
1105 @findex revert-buffer-with-coding-system
1106 If you visit a file with a wrong coding system, you can correct this
1107 with @kbd{C-x @key{RET} r} (@code{revert-buffer-with-coding-system}).
1108 This visits the current file again, using a coding system you specify.
1110 @findex recode-region
1111 If a piece of text has already been inserted into a buffer using the
1112 wrong coding system, you can redo the decoding of it using @kbd{M-x
1113 recode-region}. This prompts you for the proper coding system, then
1114 for the wrong coding system that was actually used, and does the
1115 conversion. It first encodes the region using the wrong coding system,
1116 then decodes it again using the proper coding system.
1118 @node Communication Coding
1119 @section Coding Systems for Interprocess Communication
1121 This section explains how to specify coding systems for use
1122 in communication with other processes.
1125 @item C-x @key{RET} x @var{coding} @key{RET}
1126 Use coding system @var{coding} for transferring selections to and from
1127 other graphical applications (@code{set-selection-coding-system}).
1129 @item C-x @key{RET} X @var{coding} @key{RET}
1130 Use coding system @var{coding} for transferring @emph{one}
1131 selection---the next one---to or from another graphical application
1132 (@code{set-next-selection-coding-system}).
1134 @item C-x @key{RET} p @var{input-coding} @key{RET} @var{output-coding} @key{RET}
1135 Use coding systems @var{input-coding} and @var{output-coding} for
1136 subprocess input and output in the current buffer
1137 (@code{set-buffer-process-coding-system}).
1142 @findex set-selection-coding-system
1143 @findex set-next-selection-coding-system
1144 The command @kbd{C-x @key{RET} x} (@code{set-selection-coding-system})
1145 specifies the coding system for sending selected text to other windowing
1146 applications, and for receiving the text of selections made in other
1147 applications. This command applies to all subsequent selections, until
1148 you override it by using the command again. The command @kbd{C-x
1149 @key{RET} X} (@code{set-next-selection-coding-system}) specifies the
1150 coding system for the next selection made in Emacs or read by Emacs.
1152 @vindex x-select-request-type
1153 The variable @code{x-select-request-type} specifies the data type to
1154 request from the X Window System for receiving text selections from
1155 other applications. If the value is @code{nil} (the default), Emacs
1156 tries @code{UTF8_STRING} and @code{COMPOUND_TEXT}, in this order, and
1157 uses various heuristics to choose the more appropriate of the two
1158 results; if none of these succeed, Emacs falls back on @code{STRING}.
1159 If the value of @code{x-select-request-type} is one of the symbols
1160 @code{COMPOUND_TEXT}, @code{UTF8_STRING}, @code{STRING}, or
1161 @code{TEXT}, Emacs uses only that request type. If the value is a
1162 list of some of these symbols, Emacs tries only the request types in
1163 the list, in order, until one of them succeeds, or until the list is
1167 @findex set-buffer-process-coding-system
1168 The command @kbd{C-x @key{RET} p} (@code{set-buffer-process-coding-system})
1169 specifies the coding system for input and output to a subprocess. This
1170 command applies to the current buffer; normally, each subprocess has its
1171 own buffer, and thus you can use this command to specify translation to
1172 and from a particular subprocess by giving the command in the
1173 corresponding buffer.
1175 You can also use @kbd{C-x @key{RET} c}
1176 (@code{universal-coding-system-argument}) just before the command that
1177 runs or starts a subprocess, to specify the coding system for
1178 communicating with that subprocess. @xref{Text Coding}.
1180 The default for translation of process input and output depends on the
1181 current language environment.
1183 @vindex locale-coding-system
1184 @cindex decoding non-@acronym{ASCII} keyboard input on X
1185 The variable @code{locale-coding-system} specifies a coding system
1186 to use when encoding and decoding system strings such as system error
1187 messages and @code{format-time-string} formats and time stamps. That
1188 coding system is also used for decoding non-@acronym{ASCII} keyboard
1189 input on the X Window System. You should choose a coding system that is compatible
1190 with the underlying system's text representation, which is normally
1191 specified by one of the environment variables @env{LC_ALL},
1192 @env{LC_CTYPE}, and @env{LANG}. (The first one, in the order
1193 specified above, whose value is nonempty is the one that determines
1194 the text representation.)
1196 @node File Name Coding
1197 @section Coding Systems for File Names
1200 @item C-x @key{RET} F @var{coding} @key{RET}
1201 Use coding system @var{coding} for encoding and decoding file
1202 names (@code{set-file-name-coding-system}).
1205 @findex set-file-name-coding-system
1206 @kindex C-x @key{RET} F
1207 @cindex file names with non-@acronym{ASCII} characters
1208 The command @kbd{C-x @key{RET} F} (@code{set-file-name-coding-system})
1209 specifies a coding system to use for encoding file @emph{names}. It
1210 has no effect on reading and writing the @emph{contents} of files.
1212 @vindex file-name-coding-system
1213 In fact, all this command does is set the value of the variable
1214 @code{file-name-coding-system}. If you set the variable to a coding
1215 system name (as a Lisp symbol or a string), Emacs encodes file names
1216 using that coding system for all file operations. This makes it
1217 possible to use non-@acronym{ASCII} characters in file names---or, at
1218 least, those non-@acronym{ASCII} characters that the specified coding
1221 If @code{file-name-coding-system} is @code{nil}, Emacs uses a
1222 default coding system determined by the selected language environment,
1223 and stored in the @code{default-file-name-coding-system} variable.
1224 @c FIXME? Is this correct? What is the "default language environment"?
1225 In the default language environment, non-@acronym{ASCII} characters in
1226 file names are not encoded specially; they appear in the file system
1227 using the internal Emacs representation.
1229 @cindex file-name encoding, MS-Windows
1230 @vindex w32-unicode-filenames
1231 When Emacs runs on MS-Windows versions that are descendants of the
1232 NT family (Windows 2000, XP, Vista, Windows 7, and Windows 8), the
1233 value of @code{file-name-coding-system} is largely ignored, as Emacs
1234 by default uses APIs that allow to pass Unicode file names directly.
1235 By contrast, on Windows 9X, file names are encoded using
1236 @code{file-name-coding-system}, which should be set to the codepage
1237 (@pxref{Coding Systems, codepage}) pertinent for the current system
1238 locale. The value of the variable @code{w32-unicode-filenames}
1239 controls whether Emacs uses the Unicode APIs when it calls OS
1240 functions that accept file names. This variable is set by the startup
1241 code to @code{nil} on Windows 9X, and to @code{t} on newer versions of
1244 @strong{Warning:} if you change @code{file-name-coding-system} (or the
1245 language environment) in the middle of an Emacs session, problems can
1246 result if you have already visited files whose names were encoded using
1247 the earlier coding system and cannot be encoded (or are encoded
1248 differently) under the new coding system. If you try to save one of
1249 these buffers under the visited file name, saving may use the wrong file
1250 name, or it may encounter an error. If such a problem happens, use @kbd{C-x
1251 C-w} to specify a new file name for that buffer.
1253 @findex recode-file-name
1254 If a mistake occurs when encoding a file name, use the command
1255 @kbd{M-x recode-file-name} to change the file name's coding
1256 system. This prompts for an existing file name, its old coding
1257 system, and the coding system to which you wish to convert.
1259 @node Terminal Coding
1260 @section Coding Systems for Terminal I/O
1263 @item C-x @key{RET} t @var{coding} @key{RET}
1264 Use coding system @var{coding} for terminal output
1265 (@code{set-terminal-coding-system}).
1267 @item C-x @key{RET} k @var{coding} @key{RET}
1268 Use coding system @var{coding} for keyboard input
1269 (@code{set-keyboard-coding-system}).
1273 @findex set-terminal-coding-system
1274 The command @kbd{C-x @key{RET} t} (@code{set-terminal-coding-system})
1275 specifies the coding system for terminal output. If you specify a
1276 character code for terminal output, all characters output to the
1277 terminal are translated into that coding system.
1279 This feature is useful for certain character-only terminals built to
1280 support specific languages or character sets---for example, European
1281 terminals that support one of the ISO Latin character sets. You need to
1282 specify the terminal coding system when using multibyte text, so that
1283 Emacs knows which characters the terminal can actually handle.
1285 By default, output to the terminal is not translated at all, unless
1286 Emacs can deduce the proper coding system from your terminal type or
1287 your locale specification (@pxref{Language Environments}).
1290 @findex set-keyboard-coding-system
1291 @vindex keyboard-coding-system
1292 The command @kbd{C-x @key{RET} k} (@code{set-keyboard-coding-system}),
1293 or the variable @code{keyboard-coding-system}, specifies the coding
1294 system for keyboard input. Character-code translation of keyboard
1295 input is useful for terminals with keys that send non-@acronym{ASCII}
1296 graphic characters---for example, some terminals designed for ISO
1297 Latin-1 or subsets of it.
1299 By default, keyboard input is translated based on your system locale
1300 setting. If your terminal does not really support the encoding
1301 implied by your locale (for example, if you find it inserts a
1302 non-@acronym{ASCII} character if you type @kbd{M-i}), you will need to set
1303 @code{keyboard-coding-system} to @code{nil} to turn off encoding.
1304 You can do this by putting
1307 (set-keyboard-coding-system nil)
1313 There is a similarity between using a coding system translation for
1314 keyboard input, and using an input method: both define sequences of
1315 keyboard input that translate into single characters. However, input
1316 methods are designed to be convenient for interactive use by humans, and
1317 the sequences that are translated are typically sequences of @acronym{ASCII}
1318 printing characters. Coding systems typically translate sequences of
1319 non-graphic characters.
1325 A font typically defines shapes for a single alphabet or script.
1326 Therefore, displaying the entire range of scripts that Emacs supports
1327 requires a collection of many fonts. In Emacs, such a collection is
1328 called a @dfn{fontset}. A fontset is defined by a list of font specifications,
1329 each assigned to handle a range of character codes, and may fall back
1330 on another fontset for characters that are not covered by the fonts
1333 @cindex fonts for various scripts
1334 @cindex Intlfonts package, installation
1335 Each fontset has a name, like a font. However, while fonts are
1336 stored in the system and the available font names are defined by the
1337 system, fontsets are defined within Emacs itself. Once you have
1338 defined a fontset, you can use it within Emacs by specifying its name,
1339 anywhere that you could use a single font. Of course, Emacs fontsets
1340 can use only the fonts that the system supports. If some characters
1341 appear on the screen as empty boxes or hex codes, this means that the
1342 fontset in use for them has no font for those characters. In this
1343 case, or if the characters are shown, but not as well as you would
1344 like, you may need to install extra fonts. Your operating system may
1345 have optional fonts that you can install; or you can install the GNU
1346 Intlfonts package, which includes fonts for most supported
1347 scripts.@footnote{If you run Emacs on X, you may need to inform the X
1348 server about the location of the newly installed fonts with commands
1350 @c FIXME? I feel like this may be out of date.
1351 @c E.g., the intlfonts tarfile is ~ 10 years old.
1354 xset fp+ /usr/local/share/emacs/fonts
1359 Emacs creates three fontsets automatically: the @dfn{standard
1360 fontset}, the @dfn{startup fontset} and the @dfn{default fontset}.
1361 @c FIXME? The doc of *standard*-fontset-spec says:
1362 @c "You have the biggest chance to display international characters
1363 @c with correct glyphs by using the *standard* fontset." (my emphasis)
1364 @c See http://lists.gnu.org/archive/html/emacs-devel/2012-04/msg00430.html
1365 The default fontset is most likely to have fonts for a wide variety of
1366 non-@acronym{ASCII} characters, and is the default fallback for the
1367 other two fontsets, and if you set a default font rather than fontset.
1368 However, it does not specify font family names, so results can be
1369 somewhat random if you use it directly. You can specify use of a
1370 particular fontset by starting Emacs with the @samp{-fn} option.
1374 emacs -fn fontset-standard
1378 You can also specify a fontset with the @samp{Font} resource (@pxref{X
1381 If no fontset is specified for use, then Emacs uses an
1382 @acronym{ASCII} font, with @samp{fontset-default} as a fallback for
1383 characters the font does not cover. The standard fontset is only used if
1384 explicitly requested, despite its name.
1386 A fontset does not necessarily specify a font for every character
1387 code. If a fontset specifies no font for a certain character, or if
1388 it specifies a font that does not exist on your system, then it cannot
1389 display that character properly. It will display that character as a
1390 hex code or thin space or an empty box instead. (@xref{Text Display, ,
1391 glyphless characters}, for details.)
1393 @node Defining Fontsets
1394 @section Defining fontsets
1396 @vindex standard-fontset-spec
1397 @vindex w32-standard-fontset-spec
1398 @vindex ns-standard-fontset-spec
1399 @cindex standard fontset
1400 When running on X, Emacs creates a standard fontset automatically according to the value
1401 of @code{standard-fontset-spec}. This fontset's name is
1404 -*-fixed-medium-r-normal-*-16-*-*-*-*-*-fontset-standard
1408 or just @samp{fontset-standard} for short.
1410 On GNUstep and Mac OS X, the standard fontset is created using the value of
1411 @code{ns-standard-fontset-spec}, and on MS Windows it is
1412 created using the value of @code{w32-standard-fontset-spec}.
1414 @c FIXME? How does one access these, or do anything with them?
1416 Bold, italic, and bold-italic variants of the standard fontset are
1417 created automatically. Their names have @samp{bold} instead of
1418 @samp{medium}, or @samp{i} instead of @samp{r}, or both.
1420 @cindex startup fontset
1421 Emacs generates a fontset automatically, based on any default
1422 @acronym{ASCII} font that you specify with the @samp{Font} resource or
1423 the @samp{-fn} argument, or the default font that Emacs found when it
1424 started. This is the @dfn{startup fontset} and its name is
1425 @code{fontset-startup}. It does this by replacing the
1426 @var{charset_registry} field with @samp{fontset}, and replacing
1427 @var{charset_encoding} field with @samp{startup}, then using the
1428 resulting string to specify a fontset.
1430 For instance, if you start Emacs with a font of this form,
1432 @c FIXME? I think this is a little misleading, because you cannot (?)
1433 @c actually specify a font with wildcards, it has to be a complete spec.
1434 @c Also, an X font specification of this form hasn't (?) been
1435 @c mentioned before now, and is somewhat obsolete these days.
1436 @c People are more likely to use a form like
1437 @c emacs -fn "DejaVu Sans Mono-12"
1438 @c How does any of this apply in that case?
1440 emacs -fn "*courier-medium-r-normal--14-140-*-iso8859-1"
1444 Emacs generates the following fontset and uses it for the initial X
1448 -*-courier-medium-r-normal-*-14-140-*-*-*-*-fontset-startup
1451 The startup fontset will use the font that you specify, or a variant
1452 with a different registry and encoding, for all the characters that
1453 are supported by that font, and fallback on @samp{fontset-default} for
1456 With the X resource @samp{Emacs.Font}, you can specify a fontset name
1457 just like an actual font name. But be careful not to specify a fontset
1458 name in a wildcard resource like @samp{Emacs*Font}---that wildcard
1459 specification matches various other resources, such as for menus, and
1460 @c FIXME is this still true?
1461 menus cannot handle fontsets. @xref{X Resources}.
1463 You can specify additional fontsets using X resources named
1464 @samp{Fontset-@var{n}}, where @var{n} is an integer starting from 0.
1465 The resource value should have this form:
1468 @var{fontpattern}, @r{[}@var{charset}:@var{font}@r{]@dots{}}
1472 @var{fontpattern} should have the form of a standard X font name (see
1473 the previous fontset-startup example), except
1474 for the last two fields. They should have the form
1475 @samp{fontset-@var{alias}}.
1477 The fontset has two names, one long and one short. The long name is
1478 @var{fontpattern}. The short name is @samp{fontset-@var{alias}}. You
1479 can refer to the fontset by either name.
1481 The construct @samp{@var{charset}:@var{font}} specifies which font to
1482 use (in this fontset) for one particular character set. Here,
1483 @var{charset} is the name of a character set, and @var{font} is the
1484 font to use for that character set. You can use this construct any
1485 number of times in defining one fontset.
1487 For the other character sets, Emacs chooses a font based on
1488 @var{fontpattern}. It replaces @samp{fontset-@var{alias}} with values
1489 that describe the character set. For the @acronym{ASCII} character font,
1490 @samp{fontset-@var{alias}} is replaced with @samp{ISO8859-1}.
1492 In addition, when several consecutive fields are wildcards, Emacs
1493 collapses them into a single wildcard. This is to prevent use of
1494 auto-scaled fonts. Fonts made by scaling larger fonts are not usable
1495 for editing, and scaling a smaller font is not also useful, because it is
1496 better to use the smaller font in its own size, which is what Emacs
1499 Thus if @var{fontpattern} is this,
1502 -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24
1506 the font specification for @acronym{ASCII} characters would be this:
1509 -*-fixed-medium-r-normal-*-24-*-ISO8859-1
1513 and the font specification for Chinese GB2312 characters would be this:
1516 -*-fixed-medium-r-normal-*-24-*-gb2312*-*
1519 You may not have any Chinese font matching the above font
1520 specification. Most X distributions include only Chinese fonts that
1521 have @samp{song ti} or @samp{fangsong ti} in the @var{family} field. In
1522 such a case, @samp{Fontset-@var{n}} can be specified as:
1525 Emacs.Fontset-0: -*-fixed-medium-r-normal-*-24-*-*-*-*-*-fontset-24,\
1526 chinese-gb2312:-*-*-medium-r-normal-*-24-*-gb2312*-*
1530 Then, the font specifications for all but Chinese GB2312 characters have
1531 @samp{fixed} in the @var{family} field, and the font specification for
1532 Chinese GB2312 characters has a wild card @samp{*} in the @var{family}
1535 @findex create-fontset-from-fontset-spec
1536 The function that processes the fontset resource value to create the
1537 fontset is called @code{create-fontset-from-fontset-spec}. You can also
1538 call this function explicitly to create a fontset.
1540 @xref{Fonts}, for more information about font naming.
1542 @node Modifying Fontsets
1543 @section Modifying Fontsets
1544 @cindex fontsets, modifying
1545 @findex set-fontset-font
1547 Fontsets do not always have to be created from scratch. If only
1548 minor changes are required it may be easier to modify an existing
1549 fontset. Modifying @samp{fontset-default} will also affect other
1550 fontsets that use it as a fallback, so can be an effective way of
1551 fixing problems with the fonts that Emacs chooses for a particular
1554 Fontsets can be modified using the function @code{set-fontset-font},
1555 specifying a character, a charset, a script, or a range of characters
1556 to modify the font for, and a font specification for the font to be
1557 used. Some examples are:
1560 ;; Use Liberation Mono for latin-3 charset.
1561 (set-fontset-font "fontset-default" 'iso-8859-3
1564 ;; Prefer a big5 font for han characters
1565 (set-fontset-font "fontset-default"
1566 'han (font-spec :registry "big5")
1569 ;; Use DejaVu Sans Mono as a fallback in fontset-startup
1570 ;; before resorting to fontset-default.
1571 (set-fontset-font "fontset-startup" nil "DejaVu Sans Mono"
1574 ;; Use MyPrivateFont for the Unicode private use area.
1575 (set-fontset-font "fontset-default" '(#xe000 . #xf8ff)
1581 @node Undisplayable Characters
1582 @section Undisplayable Characters
1584 There may be some non-@acronym{ASCII} characters that your
1585 terminal cannot display. Most text terminals support just a single
1586 character set (use the variable @code{default-terminal-coding-system}
1587 to tell Emacs which one, @ref{Terminal Coding}); characters that
1588 can't be encoded in that coding system are displayed as @samp{?} by
1591 Graphical displays can display a broader range of characters, but
1592 you may not have fonts installed for all of them; characters that have
1593 no font appear as a hollow box.
1595 If you use Latin-1 characters but your terminal can't display
1596 Latin-1, you can arrange to display mnemonic @acronym{ASCII} sequences
1597 instead, e.g., @samp{"o} for o-umlaut. Load the library
1598 @file{iso-ascii} to do this.
1600 @vindex latin1-display
1601 If your terminal can display Latin-1, you can display characters
1602 from other European character sets using a mixture of equivalent
1603 Latin-1 characters and @acronym{ASCII} mnemonics. Customize the variable
1604 @code{latin1-display} to enable this. The mnemonic @acronym{ASCII}
1605 sequences mostly correspond to those of the prefix input methods.
1608 @section Unibyte Editing Mode
1610 @cindex European character sets
1611 @cindex accented characters
1612 @cindex ISO Latin character sets
1613 @cindex Unibyte operation
1614 The ISO 8859 Latin-@var{n} character sets define character codes in
1615 the range 0240 to 0377 octal (160 to 255 decimal) to handle the
1616 accented letters and punctuation needed by various European languages
1617 (and some non-European ones). Note that Emacs considers bytes with
1618 codes in this range as raw bytes, not as characters, even in a unibyte
1619 buffer, i.e., if you disable multibyte characters. However, Emacs can
1620 still handle these character codes as if they belonged to @emph{one}
1621 of the single-byte character sets at a time. To specify @emph{which}
1622 of these codes to use, invoke @kbd{M-x set-language-environment} and
1623 specify a suitable language environment such as @samp{Latin-@var{n}}.
1624 @xref{Disabling Multibyte, , Disabling Multibyte Characters, elisp,
1625 GNU Emacs Lisp Reference Manual}.
1627 @vindex unibyte-display-via-language-environment
1628 Emacs can also display bytes in the range 160 to 255 as readable
1629 characters, provided the terminal or font in use supports them. This
1630 works automatically. On a graphical display, Emacs can also display
1631 single-byte characters through fontsets, in effect by displaying the
1632 equivalent multibyte characters according to the current language
1633 environment. To request this, set the variable
1634 @code{unibyte-display-via-language-environment} to a non-@code{nil}
1635 value. Note that setting this only affects how these bytes are
1636 displayed, but does not change the fundamental fact that Emacs treats
1637 them as raw bytes, not as characters.
1639 @cindex @code{iso-ascii} library
1640 If your terminal does not support display of the Latin-1 character
1641 set, Emacs can display these characters as @acronym{ASCII} sequences which at
1642 least give you a clear idea of what the characters are. To do this,
1643 load the library @code{iso-ascii}. Similar libraries for other
1644 Latin-@var{n} character sets could be implemented, but have not been
1647 @findex standard-display-8bit
1648 @cindex 8-bit display
1649 Normally non-ISO-8859 characters (decimal codes between 128 and 159
1650 inclusive) are displayed as octal escapes. You can change this for
1651 non-standard ``extended'' versions of ISO-8859 character sets by using the
1652 function @code{standard-display-8bit} in the @code{disp-table} library.
1654 There are two ways to input single-byte non-@acronym{ASCII}
1660 You can use an input method for the selected language environment.
1661 @xref{Input Methods}. When you use an input method in a unibyte buffer,
1662 the non-@acronym{ASCII} character you specify with it is converted to unibyte.
1665 If your keyboard can generate character codes 128 (decimal) and up,
1666 representing non-@acronym{ASCII} characters, you can type those character codes
1669 On a graphical display, you should not need to do anything special to
1670 use these keys; they should simply work. On a text terminal, you
1671 should use the command @code{M-x set-keyboard-coding-system} or customize the
1672 variable @code{keyboard-coding-system} to specify which coding system
1673 your keyboard uses (@pxref{Terminal Coding}). Enabling this feature
1674 will probably require you to use @key{ESC} to type Meta characters;
1675 however, on a console terminal or in @code{xterm}, you can arrange for
1676 Meta to be converted to @key{ESC} and still be able type 8-bit
1677 characters present directly on the keyboard or using @key{Compose} or
1678 @key{AltGr} keys. @xref{User Input}.
1681 @cindex @code{iso-transl} library
1682 @cindex compose character
1683 @cindex dead character
1685 For Latin-1 only, you can use the key @kbd{C-x 8} as a ``compose
1686 character'' prefix for entry of non-@acronym{ASCII} Latin-1 printing
1687 characters. @kbd{C-x 8} is good for insertion (in the minibuffer as
1688 well as other buffers), for searching, and in any other context where
1689 a key sequence is allowed.
1691 @kbd{C-x 8} works by loading the @code{iso-transl} library. Once that
1692 library is loaded, the @key{Alt} modifier key, if the keyboard has
1693 one, serves the same purpose as @kbd{C-x 8}: use @key{Alt} together
1694 with an accent character to modify the following letter. In addition,
1695 if the keyboard has keys for the Latin-1 ``dead accent characters'',
1696 they too are defined to compose with the following character, once
1697 @code{iso-transl} is loaded.
1699 Use @kbd{C-x 8 C-h} to list all the available @kbd{C-x 8} translations.
1706 In Emacs, @dfn{charset} is short for ``character set''. Emacs
1707 supports most popular charsets (such as @code{ascii},
1708 @code{iso-8859-1}, @code{cp1250}, @code{big5}, and @code{unicode}), in
1709 addition to some charsets of its own (such as @code{emacs},
1710 @code{unicode-bmp}, and @code{eight-bit}). All supported characters
1711 belong to one or more charsets.
1713 Emacs normally ``does the right thing'' with respect to charsets, so
1714 that you don't have to worry about them. However, it is sometimes
1715 helpful to know some of the underlying details about charsets.
1717 One example is font selection (@pxref{Fonts}). Each language
1718 environment (@pxref{Language Environments}) defines a ``priority
1719 list'' for the various charsets. When searching for a font, Emacs
1720 initially attempts to find one that can display the highest-priority
1721 charsets. For instance, in the Japanese language environment, the
1722 charset @code{japanese-jisx0208} has the highest priority, so Emacs
1723 tries to use a font whose @code{registry} property is
1724 @samp{JISX0208.1983-0}.
1726 @findex list-charset-chars
1727 @cindex characters in a certain charset
1728 @findex describe-character-set
1729 There are two commands that can be used to obtain information about
1730 charsets. The command @kbd{M-x list-charset-chars} prompts for a
1731 charset name, and displays all the characters in that character set.
1732 The command @kbd{M-x describe-character-set} prompts for a charset
1733 name, and displays information about that charset, including its
1734 internal representation within Emacs.
1736 @findex list-character-sets
1737 @kbd{M-x list-character-sets} displays a list of all supported
1738 charsets. The list gives the names of charsets and additional
1739 information to identity each charset; see the
1740 @url{http://www.itscj.ipsj.or.jp/ISO-IR/, International Register of
1741 Coded Character Sets} for more details. In this list,
1742 charsets are divided into two categories: @dfn{normal charsets} are
1743 listed first, followed by @dfn{supplementary charsets}. A
1744 supplementary charset is one that is used to define another charset
1745 (as a parent or a subset), or to provide backward-compatibility for
1746 older Emacs versions.
1748 To find out which charset a character in the buffer belongs to, put
1749 point before it and type @kbd{C-u C-x =} (@pxref{International
1752 @node Bidirectional Editing
1753 @section Bidirectional Editing
1754 @cindex bidirectional editing
1755 @cindex right-to-left text
1757 Emacs supports editing text written in scripts, such as Arabic and
1758 Hebrew, whose natural ordering of horizontal text for display is from
1759 right to left. However, digits and Latin text embedded in these
1760 scripts are still displayed left to right. It is also not uncommon to
1761 have small portions of text in Arabic or Hebrew embedded in an otherwise
1762 Latin document; e.g., as comments and strings in a program source
1763 file. For these reasons, text that uses these scripts is actually
1764 @dfn{bidirectional}: a mixture of runs of left-to-right and
1765 right-to-left characters.
1767 This section describes the facilities and options provided by Emacs
1768 for editing bidirectional text.
1770 @cindex logical order
1771 @cindex visual order
1772 Emacs stores right-to-left and bidirectional text in the so-called
1773 @dfn{logical} (or @dfn{reading}) order: the buffer or string position
1774 of the first character you read precedes that of the next character.
1775 Reordering of bidirectional text into the @dfn{visual} order happens
1776 at display time. As result, character positions no longer increase
1777 monotonically with their positions on display. Emacs implements the
1778 Unicode Bidirectional Algorithm described in the Unicode Standard
1779 Annex #9, for reordering of bidirectional text for display.
1781 @vindex bidi-display-reordering
1782 The buffer-local variable @code{bidi-display-reordering} controls
1783 whether text in the buffer is reordered for display. If its value is
1784 non-@code{nil}, Emacs reorders characters that have right-to-left
1785 directionality when they are displayed. The default value is
1788 @cindex base direction of paragraphs
1789 @cindex paragraph, base direction
1790 Each paragraph of bidirectional text can have its own @dfn{base
1791 direction}, either right-to-left or left-to-right. (Paragraph
1792 @c paragraph-separate etc have no influence on this?
1793 boundaries are empty lines, i.e., lines consisting entirely of
1794 whitespace characters.) Text in left-to-right paragraphs begins on
1795 the screen at the left margin of the window and is truncated or
1796 continued when it reaches the right margin. By contrast, text in
1797 right-to-left paragraphs is displayed starting at the right margin and
1798 is continued or truncated at the left margin.
1800 @vindex bidi-paragraph-direction
1801 Emacs determines the base direction of each paragraph dynamically,
1802 based on the text at the beginning of the paragraph. However,
1803 sometimes a buffer may need to force a certain base direction for its
1804 paragraphs. The variable @code{bidi-paragraph-direction}, if
1805 non-@code{nil}, disables the dynamic determination of the base
1806 direction, and instead forces all paragraphs in the buffer to have the
1807 direction specified by its buffer-local value. The value can be either
1808 @code{right-to-left} or @code{left-to-right}. Any other value is
1809 interpreted as @code{nil}.
1813 Alternatively, you can control the base direction of a paragraph by
1814 inserting special formatting characters in front of the paragraph.
1815 The special character @code{RIGHT-TO-LEFT MARK}, or @sc{rlm}, forces
1816 the right-to-left direction on the following paragraph, while
1817 @code{LEFT-TO-RIGHT MARK}, or @sc{lrm} forces the left-to-right
1818 direction. (You can use @kbd{C-x 8 @key{RET}} to insert these characters.)
1819 In a GUI session, the @sc{lrm} and @sc{rlm} characters display as very
1820 thin blank characters; on text terminals they display as blanks.
1822 Because characters are reordered for display, Emacs commands that
1823 operate in the logical order or on stretches of buffer positions may
1824 produce unusual effects. For example, @kbd{C-f} and @kbd{C-b}
1825 commands move point in the logical order, so the cursor will sometimes
1826 jump when point traverses reordered bidirectional text. Similarly, a
1827 highlighted region covering a contiguous range of character positions
1828 may look discontinuous if the region spans reordered text. This is
1829 normal and similar to the behavior of other programs that support
1830 bidirectional text. If you set @code{visual-order-cursor-movement} to
1831 a non-@code{nil} value, cursor motion by the arrow keys follows the
1832 visual order on screen (@pxref{Moving Point, visual-order movement}).