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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
651f374c | 3 | @c Copyright (C) 1998, 1999, 2002, 2003, 2004, |
ceb4c4d3 | 4 | @c 2005, 2006 Free Software Foundation, Inc. |
cc6d0d2c RS |
5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/characters | |
7 | @node Non-ASCII Characters, Searching and Matching, Text, Top | |
ad800164 | 8 | @chapter Non-@acronym{ASCII} Characters |
cc6d0d2c | 9 | @cindex multibyte characters |
ad800164 | 10 | @cindex non-@acronym{ASCII} characters |
cc6d0d2c | 11 | |
ad800164 | 12 | This chapter covers the special issues relating to non-@acronym{ASCII} |
cc6d0d2c RS |
13 | characters and how they are stored in strings and buffers. |
14 | ||
15 | @menu | |
5557b83b RS |
16 | * Text Representations:: Unibyte and multibyte representations |
17 | * Converting Representations:: Converting unibyte to multibyte and vice versa. | |
18 | * Selecting a Representation:: Treating a byte sequence as unibyte or multi. | |
19 | * Character Codes:: How unibyte and multibyte relate to | |
20 | codes of individual characters. | |
a3d3f60d | 21 | * Character Sets:: The space of possible character codes |
5557b83b RS |
22 | is divided into various character sets. |
23 | * Chars and Bytes:: More information about multibyte encodings. | |
24 | * Splitting Characters:: Converting a character to its byte sequence. | |
25 | * Scanning Charsets:: Which character sets are used in a buffer? | |
26 | * Translation of Characters:: Translation tables are used for conversion. | |
27 | * Coding Systems:: Coding systems are conversions for saving files. | |
28 | * Input Methods:: Input methods allow users to enter various | |
8a9e355c | 29 | non-ASCII characters without special keyboards. |
5557b83b | 30 | * Locales:: Interacting with the POSIX locale. |
cc6d0d2c RS |
31 | @end menu |
32 | ||
33 | @node Text Representations | |
34 | @section Text Representations | |
35 | @cindex text representations | |
36 | ||
37 | Emacs has two @dfn{text representations}---two ways to represent text | |
38 | in a string or buffer. These are called @dfn{unibyte} and | |
39 | @dfn{multibyte}. Each string, and each buffer, uses one of these two | |
40 | representations. For most purposes, you can ignore the issue of | |
41 | representations, because Emacs converts text between them as | |
42 | appropriate. Occasionally in Lisp programming you will need to pay | |
43 | attention to the difference. | |
44 | ||
45 | @cindex unibyte text | |
46 | In unibyte representation, each character occupies one byte and | |
47 | therefore the possible character codes range from 0 to 255. Codes 0 | |
ad800164 EZ |
48 | through 127 are @acronym{ASCII} characters; the codes from 128 through 255 |
49 | are used for one non-@acronym{ASCII} character set (you can choose which | |
969fe9b5 | 50 | character set by setting the variable @code{nonascii-insert-offset}). |
cc6d0d2c RS |
51 | |
52 | @cindex leading code | |
53 | @cindex multibyte text | |
1911e6e5 | 54 | @cindex trailing codes |
cc6d0d2c RS |
55 | In multibyte representation, a character may occupy more than one |
56 | byte, and as a result, the full range of Emacs character codes can be | |
57 | stored. The first byte of a multibyte character is always in the range | |
58 | 128 through 159 (octal 0200 through 0237). These values are called | |
a9f0a989 RS |
59 | @dfn{leading codes}. The second and subsequent bytes of a multibyte |
60 | character are always in the range 160 through 255 (octal 0240 through | |
1911e6e5 | 61 | 0377); these values are @dfn{trailing codes}. |
cc6d0d2c | 62 | |
0ace421a | 63 | Some sequences of bytes are not valid in multibyte text: for example, |
1e4d32f8 GM |
64 | a single isolated byte in the range 128 through 159 is not allowed. But |
65 | character codes 128 through 159 can appear in multibyte text, | |
66 | represented as two-byte sequences. All the character codes 128 through | |
67 | 255 are possible (though slightly abnormal) in multibyte text; they | |
0ace421a GM |
68 | appear in multibyte buffers and strings when you do explicit encoding |
69 | and decoding (@pxref{Explicit Encoding}). | |
b6954afd | 70 | |
cc6d0d2c RS |
71 | In a buffer, the buffer-local value of the variable |
72 | @code{enable-multibyte-characters} specifies the representation used. | |
08f0f5e9 KH |
73 | The representation for a string is determined and recorded in the string |
74 | when the string is constructed. | |
cc6d0d2c | 75 | |
cc6d0d2c RS |
76 | @defvar enable-multibyte-characters |
77 | This variable specifies the current buffer's text representation. | |
78 | If it is non-@code{nil}, the buffer contains multibyte text; otherwise, | |
79 | it contains unibyte text. | |
80 | ||
969fe9b5 RS |
81 | You cannot set this variable directly; instead, use the function |
82 | @code{set-buffer-multibyte} to change a buffer's representation. | |
cc6d0d2c RS |
83 | @end defvar |
84 | ||
cc6d0d2c | 85 | @defvar default-enable-multibyte-characters |
a9f0a989 | 86 | This variable's value is entirely equivalent to @code{(default-value |
cc6d0d2c | 87 | 'enable-multibyte-characters)}, and setting this variable changes that |
a9f0a989 RS |
88 | default value. Setting the local binding of |
89 | @code{enable-multibyte-characters} in a specific buffer is not allowed, | |
90 | but changing the default value is supported, and it is a reasonable | |
91 | thing to do, because it has no effect on existing buffers. | |
cc6d0d2c RS |
92 | |
93 | The @samp{--unibyte} command line option does its job by setting the | |
94 | default value to @code{nil} early in startup. | |
95 | @end defvar | |
96 | ||
b6954afd RS |
97 | @defun position-bytes position |
98 | @tindex position-bytes | |
5ac343ac RS |
99 | Return the byte-position corresponding to buffer position |
100 | @var{position} in the current buffer. This is 1 at the start of the | |
101 | buffer, and counts upward in bytes. If @var{position} is out of | |
102 | range, the value is @code{nil}. | |
b6954afd RS |
103 | @end defun |
104 | ||
105 | @defun byte-to-position byte-position | |
106 | @tindex byte-to-position | |
107 | Return the buffer position corresponding to byte-position | |
35864124 LT |
108 | @var{byte-position} in the current buffer. If @var{byte-position} is |
109 | out of range, the value is @code{nil}. | |
b6954afd RS |
110 | @end defun |
111 | ||
cc6d0d2c | 112 | @defun multibyte-string-p string |
b6954afd | 113 | Return @code{t} if @var{string} is a multibyte string. |
cc6d0d2c RS |
114 | @end defun |
115 | ||
116 | @node Converting Representations | |
117 | @section Converting Text Representations | |
118 | ||
119 | Emacs can convert unibyte text to multibyte; it can also convert | |
120 | multibyte text to unibyte, though this conversion loses information. In | |
121 | general these conversions happen when inserting text into a buffer, or | |
122 | when putting text from several strings together in one string. You can | |
123 | also explicitly convert a string's contents to either representation. | |
124 | ||
125 | Emacs chooses the representation for a string based on the text that | |
126 | it is constructed from. The general rule is to convert unibyte text to | |
127 | multibyte text when combining it with other multibyte text, because the | |
128 | multibyte representation is more general and can hold whatever | |
129 | characters the unibyte text has. | |
130 | ||
131 | When inserting text into a buffer, Emacs converts the text to the | |
132 | buffer's representation, as specified by | |
133 | @code{enable-multibyte-characters} in that buffer. In particular, when | |
134 | you insert multibyte text into a unibyte buffer, Emacs converts the text | |
135 | to unibyte, even though this conversion cannot in general preserve all | |
136 | the characters that might be in the multibyte text. The other natural | |
137 | alternative, to convert the buffer contents to multibyte, is not | |
138 | acceptable because the buffer's representation is a choice made by the | |
969fe9b5 | 139 | user that cannot be overridden automatically. |
cc6d0d2c | 140 | |
ad800164 | 141 | Converting unibyte text to multibyte text leaves @acronym{ASCII} characters |
1e4d32f8 | 142 | unchanged, and likewise character codes 128 through 159. It converts |
ad800164 | 143 | the non-@acronym{ASCII} codes 160 through 255 by adding the value |
1e4d32f8 GM |
144 | @code{nonascii-insert-offset} to each character code. By setting this |
145 | variable, you specify which character set the unibyte characters | |
146 | correspond to (@pxref{Character Sets}). For example, if | |
147 | @code{nonascii-insert-offset} is 2048, which is @code{(- (make-char | |
ad800164 | 148 | 'latin-iso8859-1) 128)}, then the unibyte non-@acronym{ASCII} characters |
1e4d32f8 GM |
149 | correspond to Latin 1. If it is 2688, which is @code{(- (make-char |
150 | 'greek-iso8859-7) 128)}, then they correspond to Greek letters. | |
cc6d0d2c | 151 | |
8241495d RS |
152 | Converting multibyte text to unibyte is simpler: it discards all but |
153 | the low 8 bits of each character code. If @code{nonascii-insert-offset} | |
154 | has a reasonable value, corresponding to the beginning of some character | |
155 | set, this conversion is the inverse of the other: converting unibyte | |
156 | text to multibyte and back to unibyte reproduces the original unibyte | |
157 | text. | |
cc6d0d2c | 158 | |
cc6d0d2c | 159 | @defvar nonascii-insert-offset |
ad800164 | 160 | This variable specifies the amount to add to a non-@acronym{ASCII} character |
cc6d0d2c | 161 | when converting unibyte text to multibyte. It also applies when |
a9f0a989 | 162 | @code{self-insert-command} inserts a character in the unibyte |
ad800164 | 163 | non-@acronym{ASCII} range, 128 through 255. However, the functions |
7a063989 | 164 | @code{insert} and @code{insert-char} do not perform this conversion. |
cc6d0d2c RS |
165 | |
166 | The right value to use to select character set @var{cs} is @code{(- | |
a9f0a989 | 167 | (make-char @var{cs}) 128)}. If the value of |
cc6d0d2c RS |
168 | @code{nonascii-insert-offset} is zero, then conversion actually uses the |
169 | value for the Latin 1 character set, rather than zero. | |
170 | @end defvar | |
171 | ||
a9f0a989 | 172 | @defvar nonascii-translation-table |
cc6d0d2c RS |
173 | This variable provides a more general alternative to |
174 | @code{nonascii-insert-offset}. You can use it to specify independently | |
175 | how to translate each code in the range of 128 through 255 into a | |
7a063989 | 176 | multibyte character. The value should be a char-table, or @code{nil}. |
969fe9b5 | 177 | If this is non-@code{nil}, it overrides @code{nonascii-insert-offset}. |
cc6d0d2c RS |
178 | @end defvar |
179 | ||
35864124 LT |
180 | The next three functions either return the argument @var{string}, or a |
181 | newly created string with no text properties. | |
182 | ||
cc6d0d2c RS |
183 | @defun string-make-unibyte string |
184 | This function converts the text of @var{string} to unibyte | |
1911e6e5 | 185 | representation, if it isn't already, and returns the result. If |
38eee91c EZ |
186 | @var{string} is a unibyte string, it is returned unchanged. Multibyte |
187 | character codes are converted to unibyte according to | |
188 | @code{nonascii-translation-table} or, if that is @code{nil}, using | |
189 | @code{nonascii-insert-offset}. If the lookup in the translation table | |
190 | fails, this function takes just the low 8 bits of each character. | |
cc6d0d2c RS |
191 | @end defun |
192 | ||
cc6d0d2c RS |
193 | @defun string-make-multibyte string |
194 | This function converts the text of @var{string} to multibyte | |
1911e6e5 | 195 | representation, if it isn't already, and returns the result. If |
35864124 LT |
196 | @var{string} is a multibyte string or consists entirely of |
197 | @acronym{ASCII} characters, it is returned unchanged. In particular, | |
198 | if @var{string} is unibyte and entirely @acronym{ASCII}, the returned | |
199 | string is unibyte. (When the characters are all @acronym{ASCII}, | |
200 | Emacs primitives will treat the string the same way whether it is | |
201 | unibyte or multibyte.) If @var{string} is unibyte and contains | |
202 | non-@acronym{ASCII} characters, the function | |
203 | @code{unibyte-char-to-multibyte} is used to convert each unibyte | |
204 | character to a multibyte character. | |
cc6d0d2c RS |
205 | @end defun |
206 | ||
131bf943 RS |
207 | @defun string-to-multibyte string |
208 | This function returns a multibyte string containing the same sequence | |
35864124 LT |
209 | of character codes as @var{string}. Unlike |
210 | @code{string-make-multibyte}, this function unconditionally returns a | |
211 | multibyte string. If @var{string} is a multibyte string, it is | |
212 | returned unchanged. | |
131bf943 RS |
213 | @end defun |
214 | ||
1ee89891 RS |
215 | @defun multibyte-char-to-unibyte char |
216 | This convert the multibyte character @var{char} to a unibyte | |
217 | character, based on @code{nonascii-translation-table} and | |
218 | @code{nonascii-insert-offset}. | |
219 | @end defun | |
220 | ||
221 | @defun unibyte-char-to-multibyte char | |
222 | This convert the unibyte character @var{char} to a multibyte | |
223 | character, based on @code{nonascii-translation-table} and | |
224 | @code{nonascii-insert-offset}. | |
225 | @end defun | |
226 | ||
cc6d0d2c RS |
227 | @node Selecting a Representation |
228 | @section Selecting a Representation | |
229 | ||
230 | Sometimes it is useful to examine an existing buffer or string as | |
231 | multibyte when it was unibyte, or vice versa. | |
232 | ||
cc6d0d2c RS |
233 | @defun set-buffer-multibyte multibyte |
234 | Set the representation type of the current buffer. If @var{multibyte} | |
235 | is non-@code{nil}, the buffer becomes multibyte. If @var{multibyte} | |
236 | is @code{nil}, the buffer becomes unibyte. | |
237 | ||
238 | This function leaves the buffer contents unchanged when viewed as a | |
239 | sequence of bytes. As a consequence, it can change the contents viewed | |
240 | as characters; a sequence of two bytes which is treated as one character | |
241 | in multibyte representation will count as two characters in unibyte | |
7a063989 KH |
242 | representation. Character codes 128 through 159 are an exception. They |
243 | are represented by one byte in a unibyte buffer, but when the buffer is | |
244 | set to multibyte, they are converted to two-byte sequences, and vice | |
245 | versa. | |
cc6d0d2c RS |
246 | |
247 | This function sets @code{enable-multibyte-characters} to record which | |
248 | representation is in use. It also adjusts various data in the buffer | |
969fe9b5 RS |
249 | (including overlays, text properties and markers) so that they cover the |
250 | same text as they did before. | |
b6954afd RS |
251 | |
252 | You cannot use @code{set-buffer-multibyte} on an indirect buffer, | |
253 | because indirect buffers always inherit the representation of the | |
254 | base buffer. | |
cc6d0d2c RS |
255 | @end defun |
256 | ||
cc6d0d2c RS |
257 | @defun string-as-unibyte string |
258 | This function returns a string with the same bytes as @var{string} but | |
259 | treating each byte as a character. This means that the value may have | |
260 | more characters than @var{string} has. | |
261 | ||
b6954afd | 262 | If @var{string} is already a unibyte string, then the value is |
7f84d9ae DL |
263 | @var{string} itself. Otherwise it is a newly created string, with no |
264 | text properties. If @var{string} is multibyte, any characters it | |
686ffe28 | 265 | contains of charset @code{eight-bit-control} or @code{eight-bit-graphic} |
7f84d9ae | 266 | are converted to the corresponding single byte. |
cc6d0d2c RS |
267 | @end defun |
268 | ||
cc6d0d2c RS |
269 | @defun string-as-multibyte string |
270 | This function returns a string with the same bytes as @var{string} but | |
271 | treating each multibyte sequence as one character. This means that the | |
272 | value may have fewer characters than @var{string} has. | |
273 | ||
b6954afd | 274 | If @var{string} is already a multibyte string, then the value is |
7f84d9ae DL |
275 | @var{string} itself. Otherwise it is a newly created string, with no |
276 | text properties. If @var{string} is unibyte and contains any individual | |
277 | 8-bit bytes (i.e.@: not part of a multibyte form), they are converted to | |
686ffe28 RS |
278 | the corresponding multibyte character of charset @code{eight-bit-control} |
279 | or @code{eight-bit-graphic}. | |
cc6d0d2c RS |
280 | @end defun |
281 | ||
282 | @node Character Codes | |
283 | @section Character Codes | |
284 | @cindex character codes | |
285 | ||
286 | The unibyte and multibyte text representations use different character | |
287 | codes. The valid character codes for unibyte representation range from | |
288 | 0 to 255---the values that can fit in one byte. The valid character | |
289 | codes for multibyte representation range from 0 to 524287, but not all | |
0ace421a | 290 | values in that range are valid. The values 128 through 255 are not |
1e4d32f8 | 291 | entirely proper in multibyte text, but they can occur if you do explicit |
0ace421a | 292 | encoding and decoding (@pxref{Explicit Encoding}). Some other character |
ad800164 | 293 | codes cannot occur at all in multibyte text. Only the @acronym{ASCII} codes |
1e4d32f8 | 294 | 0 through 127 are completely legitimate in both representations. |
cc6d0d2c | 295 | |
7a063989 | 296 | @defun char-valid-p charcode &optional genericp |
0a58afcd RS |
297 | This returns @code{t} if @var{charcode} is valid (either for unibyte |
298 | text or for multibyte text). | |
cc6d0d2c RS |
299 | |
300 | @example | |
301 | (char-valid-p 65) | |
302 | @result{} t | |
303 | (char-valid-p 256) | |
304 | @result{} nil | |
305 | (char-valid-p 2248) | |
306 | @result{} t | |
307 | @end example | |
7a063989 | 308 | |
6fe50867 | 309 | If the optional argument @var{genericp} is non-@code{nil}, this |
35864124 LT |
310 | function also returns @code{t} if @var{charcode} is a generic |
311 | character (@pxref{Splitting Characters}). | |
cc6d0d2c RS |
312 | @end defun |
313 | ||
314 | @node Character Sets | |
315 | @section Character Sets | |
316 | @cindex character sets | |
317 | ||
318 | Emacs classifies characters into various @dfn{character sets}, each of | |
319 | which has a name which is a symbol. Each character belongs to one and | |
320 | only one character set. | |
321 | ||
322 | In general, there is one character set for each distinct script. For | |
323 | example, @code{latin-iso8859-1} is one character set, | |
324 | @code{greek-iso8859-7} is another, and @code{ascii} is another. An | |
969fe9b5 RS |
325 | Emacs character set can hold at most 9025 characters; therefore, in some |
326 | cases, characters that would logically be grouped together are split | |
a9f0a989 RS |
327 | into several character sets. For example, one set of Chinese |
328 | characters, generally known as Big 5, is divided into two Emacs | |
329 | character sets, @code{chinese-big5-1} and @code{chinese-big5-2}. | |
cc6d0d2c | 330 | |
ad800164 EZ |
331 | @acronym{ASCII} characters are in character set @code{ascii}. The |
332 | non-@acronym{ASCII} characters 128 through 159 are in character set | |
4240c779 GM |
333 | @code{eight-bit-control}, and codes 160 through 255 are in character set |
334 | @code{eight-bit-graphic}. | |
335 | ||
cc6d0d2c | 336 | @defun charsetp object |
8241495d | 337 | Returns @code{t} if @var{object} is a symbol that names a character set, |
cc6d0d2c RS |
338 | @code{nil} otherwise. |
339 | @end defun | |
340 | ||
35864124 LT |
341 | @defvar charset-list |
342 | The value is a list of all defined character set names. | |
343 | @end defvar | |
344 | ||
cc6d0d2c | 345 | @defun charset-list |
35864124 LT |
346 | This function returns the value of @code{charset-list}. It is only |
347 | provided for backward compatibility. | |
cc6d0d2c RS |
348 | @end defun |
349 | ||
cc6d0d2c | 350 | @defun char-charset character |
b6954afd | 351 | This function returns the name of the character set that @var{character} |
35864124 LT |
352 | belongs to, or the symbol @code{unknown} if @var{character} is not a |
353 | valid character. | |
cc6d0d2c RS |
354 | @end defun |
355 | ||
8241495d RS |
356 | @defun charset-plist charset |
357 | @tindex charset-plist | |
358 | This function returns the charset property list of the character set | |
359 | @var{charset}. Although @var{charset} is a symbol, this is not the same | |
360 | as the property list of that symbol. Charset properties are used for | |
0f4da9ce | 361 | special purposes within Emacs. |
8241495d RS |
362 | @end defun |
363 | ||
5ac343ac RS |
364 | @deffn Command list-charset-chars charset |
365 | This command displays a list of characters in the character set | |
366 | @var{charset}. | |
367 | @end deffn | |
368 | ||
cc6d0d2c RS |
369 | @node Chars and Bytes |
370 | @section Characters and Bytes | |
371 | @cindex bytes and characters | |
372 | ||
a9f0a989 RS |
373 | @cindex introduction sequence |
374 | @cindex dimension (of character set) | |
cc6d0d2c | 375 | In multibyte representation, each character occupies one or more |
a9f0a989 | 376 | bytes. Each character set has an @dfn{introduction sequence}, which is |
ad800164 EZ |
377 | normally one or two bytes long. (Exception: the @code{ascii} character |
378 | set and the @code{eight-bit-graphic} character set have a zero-length | |
7a063989 KH |
379 | introduction sequence.) The introduction sequence is the beginning of |
380 | the byte sequence for any character in the character set. The rest of | |
381 | the character's bytes distinguish it from the other characters in the | |
382 | same character set. Depending on the character set, there are either | |
383 | one or two distinguishing bytes; the number of such bytes is called the | |
384 | @dfn{dimension} of the character set. | |
a9f0a989 RS |
385 | |
386 | @defun charset-dimension charset | |
b6954afd RS |
387 | This function returns the dimension of @var{charset}; at present, the |
388 | dimension is always 1 or 2. | |
389 | @end defun | |
390 | ||
391 | @defun charset-bytes charset | |
392 | @tindex charset-bytes | |
393 | This function returns the number of bytes used to represent a character | |
394 | in character set @var{charset}. | |
a9f0a989 RS |
395 | @end defun |
396 | ||
397 | This is the simplest way to determine the byte length of a character | |
398 | set's introduction sequence: | |
399 | ||
400 | @example | |
b6954afd | 401 | (- (charset-bytes @var{charset}) |
a9f0a989 RS |
402 | (charset-dimension @var{charset})) |
403 | @end example | |
404 | ||
405 | @node Splitting Characters | |
406 | @section Splitting Characters | |
407 | ||
408 | The functions in this section convert between characters and the byte | |
409 | values used to represent them. For most purposes, there is no need to | |
410 | be concerned with the sequence of bytes used to represent a character, | |
969fe9b5 | 411 | because Emacs translates automatically when necessary. |
cc6d0d2c | 412 | |
cc6d0d2c RS |
413 | @defun split-char character |
414 | Return a list containing the name of the character set of | |
a9f0a989 RS |
415 | @var{character}, followed by one or two byte values (integers) which |
416 | identify @var{character} within that character set. The number of byte | |
417 | values is the character set's dimension. | |
cc6d0d2c | 418 | |
35864124 LT |
419 | If @var{character} is invalid as a character code, @code{split-char} |
420 | returns a list consisting of the symbol @code{unknown} and @var{character}. | |
421 | ||
cc6d0d2c RS |
422 | @example |
423 | (split-char 2248) | |
424 | @result{} (latin-iso8859-1 72) | |
425 | (split-char 65) | |
426 | @result{} (ascii 65) | |
7a063989 KH |
427 | (split-char 128) |
428 | @result{} (eight-bit-control 128) | |
cc6d0d2c RS |
429 | @end example |
430 | @end defun | |
431 | ||
e8262f40 DL |
432 | @defun make-char charset &optional code1 code2 |
433 | This function returns the character in character set @var{charset} whose | |
434 | position codes are @var{code1} and @var{code2}. This is roughly the | |
435 | inverse of @code{split-char}. Normally, you should specify either one | |
436 | or both of @var{code1} and @var{code2} according to the dimension of | |
437 | @var{charset}. For example, | |
cc6d0d2c RS |
438 | |
439 | @example | |
440 | (make-char 'latin-iso8859-1 72) | |
441 | @result{} 2248 | |
442 | @end example | |
0f4da9ce DL |
443 | |
444 | Actually, the eighth bit of both @var{code1} and @var{code2} is zeroed | |
445 | before they are used to index @var{charset}. Thus you may use, for | |
446 | instance, an ISO 8859 character code rather than subtracting 128, as | |
447 | is necessary to index the corresponding Emacs charset. | |
cc6d0d2c RS |
448 | @end defun |
449 | ||
a9f0a989 RS |
450 | @cindex generic characters |
451 | If you call @code{make-char} with no @var{byte-values}, the result is | |
452 | a @dfn{generic character} which stands for @var{charset}. A generic | |
453 | character is an integer, but it is @emph{not} valid for insertion in the | |
454 | buffer as a character. It can be used in @code{char-table-range} to | |
455 | refer to the whole character set (@pxref{Char-Tables}). | |
456 | @code{char-valid-p} returns @code{nil} for generic characters. | |
457 | For example: | |
458 | ||
459 | @example | |
460 | (make-char 'latin-iso8859-1) | |
461 | @result{} 2176 | |
462 | (char-valid-p 2176) | |
463 | @result{} nil | |
7a063989 KH |
464 | (char-valid-p 2176 t) |
465 | @result{} t | |
a9f0a989 RS |
466 | (split-char 2176) |
467 | @result{} (latin-iso8859-1 0) | |
468 | @end example | |
469 | ||
ad800164 EZ |
470 | The character sets @code{ascii}, @code{eight-bit-control}, and |
471 | @code{eight-bit-graphic} don't have corresponding generic characters. If | |
e8262f40 DL |
472 | @var{charset} is one of them and you don't supply @var{code1}, |
473 | @code{make-char} returns the character code corresponding to the | |
474 | smallest code in @var{charset}. | |
7a063989 | 475 | |
a9f0a989 RS |
476 | @node Scanning Charsets |
477 | @section Scanning for Character Sets | |
478 | ||
479 | Sometimes it is useful to find out which character sets appear in a | |
480 | part of a buffer or a string. One use for this is in determining which | |
481 | coding systems (@pxref{Coding Systems}) are capable of representing all | |
482 | of the text in question. | |
483 | ||
5ac343ac RS |
484 | @defun charset-after &optional pos |
485 | This function return the charset of a character in the current buffer | |
486 | at position @var{pos}. If @var{pos} is omitted or @code{nil}, it | |
5a36d834 | 487 | defaults to the current value of point. If @var{pos} is out of range, |
5ac343ac RS |
488 | the value is @code{nil}. |
489 | @end defun | |
490 | ||
a9f0a989 | 491 | @defun find-charset-region beg end &optional translation |
a9f0a989 RS |
492 | This function returns a list of the character sets that appear in the |
493 | current buffer between positions @var{beg} and @var{end}. | |
494 | ||
495 | The optional argument @var{translation} specifies a translation table to | |
496 | be used in scanning the text (@pxref{Translation of Characters}). If it | |
497 | is non-@code{nil}, then each character in the region is translated | |
498 | through this table, and the value returned describes the translated | |
499 | characters instead of the characters actually in the buffer. | |
a265079f | 500 | @end defun |
a9f0a989 RS |
501 | |
502 | @defun find-charset-string string &optional translation | |
b6954afd RS |
503 | This function returns a list of the character sets that appear in the |
504 | string @var{string}. It is just like @code{find-charset-region}, except | |
505 | that it applies to the contents of @var{string} instead of part of the | |
506 | current buffer. | |
a9f0a989 RS |
507 | @end defun |
508 | ||
509 | @node Translation of Characters | |
510 | @section Translation of Characters | |
511 | @cindex character translation tables | |
512 | @cindex translation tables | |
513 | ||
35864124 LT |
514 | A @dfn{translation table} is a char-table that specifies a mapping |
515 | of characters into characters. These tables are used in encoding and | |
516 | decoding, and for other purposes. Some coding systems specify their | |
517 | own particular translation tables; there are also default translation | |
518 | tables which apply to all other coding systems. | |
a9f0a989 | 519 | |
a3d3f60d RS |
520 | For instance, the coding-system @code{utf-8} has a translation table |
521 | that maps characters of various charsets (e.g., | |
522 | @code{latin-iso8859-@var{x}}) into Unicode character sets. This way, | |
523 | it can encode Latin-2 characters into UTF-8. Meanwhile, | |
524 | @code{unify-8859-on-decoding-mode} operates by specifying | |
525 | @code{standard-translation-table-for-decode} to translate | |
526 | Latin-@var{x} characters into corresponding Unicode characters. | |
527 | ||
8241495d RS |
528 | @defun make-translation-table &rest translations |
529 | This function returns a translation table based on the argument | |
f57b6e64 DL |
530 | @var{translations}. Each element of @var{translations} should be a |
531 | list of elements of the form @code{(@var{from} . @var{to})}; this says | |
532 | to translate the character @var{from} into @var{to}. | |
a9f0a989 | 533 | |
c04c052b DL |
534 | The arguments and the forms in each argument are processed in order, |
535 | and if a previous form already translates @var{to} to some other | |
536 | character, say @var{to-alt}, @var{from} is also translated to | |
537 | @var{to-alt}. | |
538 | ||
a9f0a989 RS |
539 | You can also map one whole character set into another character set with |
540 | the same dimension. To do this, you specify a generic character (which | |
541 | designates a character set) for @var{from} (@pxref{Splitting Characters}). | |
35864124 LT |
542 | In this case, if @var{to} is also a generic character, its character |
543 | set should have the same dimension as @var{from}'s. Then the | |
544 | translation table translates each character of @var{from}'s character | |
545 | set into the corresponding character of @var{to}'s character set. If | |
546 | @var{from} is a generic character and @var{to} is an ordinary | |
547 | character, then the translation table translates every character of | |
548 | @var{from}'s character set into @var{to}. | |
a9f0a989 RS |
549 | @end defun |
550 | ||
551 | In decoding, the translation table's translations are applied to the | |
552 | characters that result from ordinary decoding. If a coding system has | |
35864124 LT |
553 | property @code{translation-table-for-decode}, that specifies the |
554 | translation table to use. (This is a property of the coding system, | |
555 | as returned by @code{coding-system-get}, not a property of the symbol | |
556 | that is the coding system's name. @xref{Coding System Basics,, Basic | |
557 | Concepts of Coding Systems}.) Otherwise, if | |
558 | @code{standard-translation-table-for-decode} is non-@code{nil}, | |
559 | decoding uses that table. | |
a9f0a989 RS |
560 | |
561 | In encoding, the translation table's translations are applied to the | |
562 | characters in the buffer, and the result of translation is actually | |
563 | encoded. If a coding system has property | |
35864124 LT |
564 | @code{translation-table-for-encode}, that specifies the translation |
565 | table to use. Otherwise the variable | |
b1f687a2 RS |
566 | @code{standard-translation-table-for-encode} specifies the translation |
567 | table. | |
a9f0a989 | 568 | |
b1f687a2 | 569 | @defvar standard-translation-table-for-decode |
a9f0a989 RS |
570 | This is the default translation table for decoding, for |
571 | coding systems that don't specify any other translation table. | |
572 | @end defvar | |
573 | ||
b1f687a2 | 574 | @defvar standard-translation-table-for-encode |
a9f0a989 RS |
575 | This is the default translation table for encoding, for |
576 | coding systems that don't specify any other translation table. | |
577 | @end defvar | |
578 | ||
131bf943 RS |
579 | @defvar translation-table-for-input |
580 | Self-inserting characters are translated through this translation | |
fa27fb28 RS |
581 | table before they are inserted. Search commands also translate their |
582 | input through this table, so they can compare more reliably with | |
583 | what's in the buffer. | |
a3d3f60d RS |
584 | |
585 | @code{set-buffer-file-coding-system} sets this variable so that your | |
586 | keyboard input gets translated into the character sets that the buffer | |
fa27fb28 RS |
587 | is likely to contain. This variable automatically becomes |
588 | buffer-local when set. | |
131bf943 RS |
589 | @end defvar |
590 | ||
cc6d0d2c RS |
591 | @node Coding Systems |
592 | @section Coding Systems | |
593 | ||
594 | @cindex coding system | |
595 | When Emacs reads or writes a file, and when Emacs sends text to a | |
596 | subprocess or receives text from a subprocess, it normally performs | |
597 | character code conversion and end-of-line conversion as specified | |
598 | by a particular @dfn{coding system}. | |
599 | ||
8241495d RS |
600 | How to define a coding system is an arcane matter, and is not |
601 | documented here. | |
b6954afd | 602 | |
a9f0a989 | 603 | @menu |
5557b83b RS |
604 | * Coding System Basics:: Basic concepts. |
605 | * Encoding and I/O:: How file I/O functions handle coding systems. | |
606 | * Lisp and Coding Systems:: Functions to operate on coding system names. | |
607 | * User-Chosen Coding Systems:: Asking the user to choose a coding system. | |
608 | * Default Coding Systems:: Controlling the default choices. | |
609 | * Specifying Coding Systems:: Requesting a particular coding system | |
610 | for a single file operation. | |
611 | * Explicit Encoding:: Encoding or decoding text without doing I/O. | |
612 | * Terminal I/O Encoding:: Use of encoding for terminal I/O. | |
613 | * MS-DOS File Types:: How DOS "text" and "binary" files | |
614 | relate to coding systems. | |
a9f0a989 RS |
615 | @end menu |
616 | ||
617 | @node Coding System Basics | |
618 | @subsection Basic Concepts of Coding Systems | |
619 | ||
cc6d0d2c RS |
620 | @cindex character code conversion |
621 | @dfn{Character code conversion} involves conversion between the encoding | |
622 | used inside Emacs and some other encoding. Emacs supports many | |
623 | different encodings, in that it can convert to and from them. For | |
624 | example, it can convert text to or from encodings such as Latin 1, Latin | |
625 | 2, Latin 3, Latin 4, Latin 5, and several variants of ISO 2022. In some | |
626 | cases, Emacs supports several alternative encodings for the same | |
627 | characters; for example, there are three coding systems for the Cyrillic | |
628 | (Russian) alphabet: ISO, Alternativnyj, and KOI8. | |
629 | ||
cc6d0d2c | 630 | Most coding systems specify a particular character code for |
8241495d RS |
631 | conversion, but some of them leave the choice unspecified---to be chosen |
632 | heuristically for each file, based on the data. | |
cc6d0d2c | 633 | |
aa945b59 RS |
634 | In general, a coding system doesn't guarantee roundtrip identity: |
635 | decoding a byte sequence using coding system, then encoding the | |
636 | resulting text in the same coding system, can produce a different byte | |
637 | sequence. However, the following coding systems do guarantee that the | |
638 | byte sequence will be the same as what you originally decoded: | |
6fa88620 KH |
639 | |
640 | @quotation | |
641 | chinese-big5 chinese-iso-8bit cyrillic-iso-8bit emacs-mule | |
642 | greek-iso-8bit hebrew-iso-8bit iso-latin-1 iso-latin-2 iso-latin-3 | |
643 | iso-latin-4 iso-latin-5 iso-latin-8 iso-latin-9 iso-safe | |
644 | japanese-iso-8bit japanese-shift-jis korean-iso-8bit raw-text | |
645 | @end quotation | |
646 | ||
aa945b59 RS |
647 | Encoding buffer text and then decoding the result can also fail to |
648 | reproduce the original text. For instance, if you encode Latin-2 | |
8b918214 RS |
649 | characters with @code{utf-8} and decode the result using the same |
650 | coding system, you'll get Unicode characters (of charset | |
aa945b59 RS |
651 | @code{mule-unicode-0100-24ff}). If you encode Unicode characters with |
652 | @code{iso-latin-2} and decode the result with the same coding system, | |
653 | you'll get Latin-2 characters. | |
6fa88620 | 654 | |
969fe9b5 RS |
655 | @cindex end of line conversion |
656 | @dfn{End of line conversion} handles three different conventions used | |
657 | on various systems for representing end of line in files. The Unix | |
658 | convention is to use the linefeed character (also called newline). The | |
8241495d RS |
659 | DOS convention is to use a carriage-return and a linefeed at the end of |
660 | a line. The Mac convention is to use just carriage-return. | |
969fe9b5 | 661 | |
cc6d0d2c RS |
662 | @cindex base coding system |
663 | @cindex variant coding system | |
664 | @dfn{Base coding systems} such as @code{latin-1} leave the end-of-line | |
665 | conversion unspecified, to be chosen based on the data. @dfn{Variant | |
666 | coding systems} such as @code{latin-1-unix}, @code{latin-1-dos} and | |
667 | @code{latin-1-mac} specify the end-of-line conversion explicitly as | |
a9f0a989 | 668 | well. Most base coding systems have three corresponding variants whose |
cc6d0d2c RS |
669 | names are formed by adding @samp{-unix}, @samp{-dos} and @samp{-mac}. |
670 | ||
a9f0a989 RS |
671 | The coding system @code{raw-text} is special in that it prevents |
672 | character code conversion, and causes the buffer visited with that | |
673 | coding system to be a unibyte buffer. It does not specify the | |
674 | end-of-line conversion, allowing that to be determined as usual by the | |
675 | data, and has the usual three variants which specify the end-of-line | |
676 | conversion. @code{no-conversion} is equivalent to @code{raw-text-unix}: | |
677 | it specifies no conversion of either character codes or end-of-line. | |
678 | ||
679 | The coding system @code{emacs-mule} specifies that the data is | |
680 | represented in the internal Emacs encoding. This is like | |
681 | @code{raw-text} in that no code conversion happens, but different in | |
682 | that the result is multibyte data. | |
683 | ||
684 | @defun coding-system-get coding-system property | |
a9f0a989 RS |
685 | This function returns the specified property of the coding system |
686 | @var{coding-system}. Most coding system properties exist for internal | |
687 | purposes, but one that you might find useful is @code{mime-charset}. | |
688 | That property's value is the name used in MIME for the character coding | |
689 | which this coding system can read and write. Examples: | |
690 | ||
691 | @example | |
692 | (coding-system-get 'iso-latin-1 'mime-charset) | |
693 | @result{} iso-8859-1 | |
694 | (coding-system-get 'iso-2022-cn 'mime-charset) | |
695 | @result{} iso-2022-cn | |
696 | (coding-system-get 'cyrillic-koi8 'mime-charset) | |
697 | @result{} koi8-r | |
698 | @end example | |
699 | ||
700 | The value of the @code{mime-charset} property is also defined | |
701 | as an alias for the coding system. | |
702 | @end defun | |
703 | ||
704 | @node Encoding and I/O | |
705 | @subsection Encoding and I/O | |
706 | ||
1911e6e5 | 707 | The principal purpose of coding systems is for use in reading and |
a9f0a989 RS |
708 | writing files. The function @code{insert-file-contents} uses |
709 | a coding system for decoding the file data, and @code{write-region} | |
710 | uses one to encode the buffer contents. | |
711 | ||
712 | You can specify the coding system to use either explicitly | |
5ac343ac | 713 | (@pxref{Specifying Coding Systems}), or implicitly using a default |
a9f0a989 RS |
714 | mechanism (@pxref{Default Coding Systems}). But these methods may not |
715 | completely specify what to do. For example, they may choose a coding | |
716 | system such as @code{undefined} which leaves the character code | |
717 | conversion to be determined from the data. In these cases, the I/O | |
718 | operation finishes the job of choosing a coding system. Very often | |
719 | you will want to find out afterwards which coding system was chosen. | |
720 | ||
721 | @defvar buffer-file-coding-system | |
475aab0d CY |
722 | This buffer-local variable records the coding system that was used to visit |
723 | the current buffer. It is used for saving the buffer, and for writing part | |
1b02d12c EZ |
724 | of the buffer with @code{write-region}. If the text to be written |
725 | cannot be safely encoded using the coding system specified by this | |
726 | variable, these operations select an alternative encoding by calling | |
727 | the function @code{select-safe-coding-system} (@pxref{User-Chosen | |
728 | Coding Systems}). If selecting a different encoding requires to ask | |
729 | the user to specify a coding system, @code{buffer-file-coding-system} | |
730 | is updated to the newly selected coding system. | |
731 | ||
732 | @code{buffer-file-coding-system} does @emph{not} affect sending text | |
b6954afd | 733 | to a subprocess. |
a9f0a989 RS |
734 | @end defvar |
735 | ||
736 | @defvar save-buffer-coding-system | |
7a063989 KH |
737 | This variable specifies the coding system for saving the buffer (by |
738 | overriding @code{buffer-file-coding-system}). Note that it is not used | |
739 | for @code{write-region}. | |
8241495d RS |
740 | |
741 | When a command to save the buffer starts out to use | |
7a063989 KH |
742 | @code{buffer-file-coding-system} (or @code{save-buffer-coding-system}), |
743 | and that coding system cannot handle | |
8241495d | 744 | the actual text in the buffer, the command asks the user to choose |
1b02d12c EZ |
745 | another coding system (by calling @code{select-safe-coding-system}). |
746 | After that happens, the command also updates | |
747 | @code{buffer-file-coding-system} to represent the coding system that | |
748 | the user specified. | |
a9f0a989 RS |
749 | @end defvar |
750 | ||
751 | @defvar last-coding-system-used | |
a9f0a989 RS |
752 | I/O operations for files and subprocesses set this variable to the |
753 | coding system name that was used. The explicit encoding and decoding | |
754 | functions (@pxref{Explicit Encoding}) set it too. | |
755 | ||
756 | @strong{Warning:} Since receiving subprocess output sets this variable, | |
8241495d RS |
757 | it can change whenever Emacs waits; therefore, you should copy the |
758 | value shortly after the function call that stores the value you are | |
a9f0a989 RS |
759 | interested in. |
760 | @end defvar | |
761 | ||
2eb4136f RS |
762 | The variable @code{selection-coding-system} specifies how to encode |
763 | selections for the window system. @xref{Window System Selections}. | |
764 | ||
1ee89891 RS |
765 | @defvar file-name-coding-system |
766 | The variable @code{file-name-coding-system} specifies the coding | |
767 | system to use for encoding file names. Emacs encodes file names using | |
768 | that coding system for all file operations. If | |
769 | @code{file-name-coding-system} is @code{nil}, Emacs uses a default | |
770 | coding system determined by the selected language environment. In the | |
771 | default language environment, any non-@acronym{ASCII} characters in | |
772 | file names are not encoded specially; they appear in the file system | |
773 | using the internal Emacs representation. | |
774 | @end defvar | |
775 | ||
776 | @strong{Warning:} if you change @code{file-name-coding-system} (or | |
777 | the language environment) in the middle of an Emacs session, problems | |
778 | can result if you have already visited files whose names were encoded | |
779 | using the earlier coding system and are handled differently under the | |
780 | new coding system. If you try to save one of these buffers under the | |
781 | visited file name, saving may use the wrong file name, or it may get | |
782 | an error. If such a problem happens, use @kbd{C-x C-w} to specify a | |
783 | new file name for that buffer. | |
784 | ||
969fe9b5 RS |
785 | @node Lisp and Coding Systems |
786 | @subsection Coding Systems in Lisp | |
787 | ||
8241495d | 788 | Here are the Lisp facilities for working with coding systems: |
cc6d0d2c | 789 | |
cc6d0d2c RS |
790 | @defun coding-system-list &optional base-only |
791 | This function returns a list of all coding system names (symbols). If | |
792 | @var{base-only} is non-@code{nil}, the value includes only the | |
7a063989 KH |
793 | base coding systems. Otherwise, it includes alias and variant coding |
794 | systems as well. | |
cc6d0d2c RS |
795 | @end defun |
796 | ||
cc6d0d2c RS |
797 | @defun coding-system-p object |
798 | This function returns @code{t} if @var{object} is a coding system | |
35864124 | 799 | name or @code{nil}. |
cc6d0d2c RS |
800 | @end defun |
801 | ||
cc6d0d2c RS |
802 | @defun check-coding-system coding-system |
803 | This function checks the validity of @var{coding-system}. | |
804 | If that is valid, it returns @var{coding-system}. | |
805 | Otherwise it signals an error with condition @code{coding-system-error}. | |
806 | @end defun | |
807 | ||
a9f0a989 | 808 | @defun coding-system-change-eol-conversion coding-system eol-type |
a9f0a989 | 809 | This function returns a coding system which is like @var{coding-system} |
1911e6e5 | 810 | except for its eol conversion, which is specified by @code{eol-type}. |
a9f0a989 RS |
811 | @var{eol-type} should be @code{unix}, @code{dos}, @code{mac}, or |
812 | @code{nil}. If it is @code{nil}, the returned coding system determines | |
813 | the end-of-line conversion from the data. | |
35864124 LT |
814 | |
815 | @var{eol-type} may also be 0, 1 or 2, standing for @code{unix}, | |
070b546b | 816 | @code{dos} and @code{mac}, respectively. |
a9f0a989 | 817 | @end defun |
969fe9b5 | 818 | |
a9f0a989 | 819 | @defun coding-system-change-text-conversion eol-coding text-coding |
a9f0a989 RS |
820 | This function returns a coding system which uses the end-of-line |
821 | conversion of @var{eol-coding}, and the text conversion of | |
822 | @var{text-coding}. If @var{text-coding} is @code{nil}, it returns | |
823 | @code{undecided}, or one of its variants according to @var{eol-coding}. | |
969fe9b5 RS |
824 | @end defun |
825 | ||
a9f0a989 | 826 | @defun find-coding-systems-region from to |
a9f0a989 RS |
827 | This function returns a list of coding systems that could be used to |
828 | encode a text between @var{from} and @var{to}. All coding systems in | |
829 | the list can safely encode any multibyte characters in that portion of | |
830 | the text. | |
831 | ||
832 | If the text contains no multibyte characters, the function returns the | |
833 | list @code{(undecided)}. | |
834 | @end defun | |
835 | ||
836 | @defun find-coding-systems-string string | |
a9f0a989 RS |
837 | This function returns a list of coding systems that could be used to |
838 | encode the text of @var{string}. All coding systems in the list can | |
839 | safely encode any multibyte characters in @var{string}. If the text | |
840 | contains no multibyte characters, this returns the list | |
841 | @code{(undecided)}. | |
842 | @end defun | |
843 | ||
844 | @defun find-coding-systems-for-charsets charsets | |
a9f0a989 RS |
845 | This function returns a list of coding systems that could be used to |
846 | encode all the character sets in the list @var{charsets}. | |
847 | @end defun | |
848 | ||
849 | @defun detect-coding-region start end &optional highest | |
cc6d0d2c | 850 | This function chooses a plausible coding system for decoding the text |
0ace421a | 851 | from @var{start} to @var{end}. This text should be a byte sequence |
969fe9b5 | 852 | (@pxref{Explicit Encoding}). |
cc6d0d2c | 853 | |
a9f0a989 | 854 | Normally this function returns a list of coding systems that could |
cc6d0d2c | 855 | handle decoding the text that was scanned. They are listed in order of |
a9f0a989 RS |
856 | decreasing priority. But if @var{highest} is non-@code{nil}, then the |
857 | return value is just one coding system, the one that is highest in | |
858 | priority. | |
859 | ||
ad800164 | 860 | If the region contains only @acronym{ASCII} characters, the value |
35864124 LT |
861 | is @code{undecided} or @code{(undecided)}, or a variant specifying |
862 | end-of-line conversion, if that can be deduced from the text. | |
cc6d0d2c RS |
863 | @end defun |
864 | ||
35864124 | 865 | @defun detect-coding-string string &optional highest |
cc6d0d2c RS |
866 | This function is like @code{detect-coding-region} except that it |
867 | operates on the contents of @var{string} instead of bytes in the buffer. | |
1911e6e5 RS |
868 | @end defun |
869 | ||
35864124 LT |
870 | @xref{Coding systems for a subprocess,, Process Information}, in |
871 | particular the description of the functions | |
872 | @code{process-coding-system} and @code{set-process-coding-system}, for | |
873 | how to examine or set the coding systems used for I/O to a subprocess. | |
1911e6e5 RS |
874 | |
875 | @node User-Chosen Coding Systems | |
876 | @subsection User-Chosen Coding Systems | |
877 | ||
1b02d12c | 878 | @cindex select safe coding system |
35864124 | 879 | @defun select-safe-coding-system from to &optional default-coding-system accept-default-p file |
bf23b477 EZ |
880 | This function selects a coding system for encoding specified text, |
881 | asking the user to choose if necessary. Normally the specified text | |
35864124 LT |
882 | is the text in the current buffer between @var{from} and @var{to}. If |
883 | @var{from} is a string, the string specifies the text to encode, and | |
884 | @var{to} is ignored. | |
bf23b477 EZ |
885 | |
886 | If @var{default-coding-system} is non-@code{nil}, that is the first | |
887 | coding system to try; if that can handle the text, | |
888 | @code{select-safe-coding-system} returns that coding system. It can | |
889 | also be a list of coding systems; then the function tries each of them | |
35864124 LT |
890 | one by one. After trying all of them, it next tries the current |
891 | buffer's value of @code{buffer-file-coding-system} (if it is not | |
892 | @code{undecided}), then the value of | |
893 | @code{default-buffer-file-coding-system} and finally the user's most | |
894 | preferred coding system, which the user can set using the command | |
895 | @code{prefer-coding-system} (@pxref{Recognize Coding,, Recognizing | |
896 | Coding Systems, emacs, The GNU Emacs Manual}). | |
bf23b477 EZ |
897 | |
898 | If one of those coding systems can safely encode all the specified | |
899 | text, @code{select-safe-coding-system} chooses it and returns it. | |
900 | Otherwise, it asks the user to choose from a list of coding systems | |
901 | which can encode all the text, and returns the user's choice. | |
902 | ||
35864124 LT |
903 | @var{default-coding-system} can also be a list whose first element is |
904 | t and whose other elements are coding systems. Then, if no coding | |
905 | system in the list can handle the text, @code{select-safe-coding-system} | |
906 | queries the user immediately, without trying any of the three | |
907 | alternatives described above. | |
908 | ||
bf23b477 | 909 | The optional argument @var{accept-default-p}, if non-@code{nil}, |
35864124 LT |
910 | should be a function to determine whether a coding system selected |
911 | without user interaction is acceptable. @code{select-safe-coding-system} | |
912 | calls this function with one argument, the base coding system of the | |
913 | selected coding system. If @var{accept-default-p} returns @code{nil}, | |
914 | @code{select-safe-coding-system} rejects the silently selected coding | |
915 | system, and asks the user to select a coding system from a list of | |
916 | possible candidates. | |
bf23b477 EZ |
917 | |
918 | @vindex select-safe-coding-system-accept-default-p | |
919 | If the variable @code{select-safe-coding-system-accept-default-p} is | |
920 | non-@code{nil}, its value overrides the value of | |
921 | @var{accept-default-p}. | |
35864124 LT |
922 | |
923 | As a final step, before returning the chosen coding system, | |
924 | @code{select-safe-coding-system} checks whether that coding system is | |
925 | consistent with what would be selected if the contents of the region | |
926 | were read from a file. (If not, this could lead to data corruption in | |
927 | a file subsequently re-visited and edited.) Normally, | |
928 | @code{select-safe-coding-system} uses @code{buffer-file-name} as the | |
929 | file for this purpose, but if @var{file} is non-@code{nil}, it uses | |
930 | that file instead (this can be relevant for @code{write-region} and | |
931 | similar functions). If it detects an apparent inconsistency, | |
932 | @code{select-safe-coding-system} queries the user before selecting the | |
933 | coding system. | |
969fe9b5 RS |
934 | @end defun |
935 | ||
936 | Here are two functions you can use to let the user specify a coding | |
937 | system, with completion. @xref{Completion}. | |
938 | ||
a9f0a989 | 939 | @defun read-coding-system prompt &optional default |
969fe9b5 RS |
940 | This function reads a coding system using the minibuffer, prompting with |
941 | string @var{prompt}, and returns the coding system name as a symbol. If | |
942 | the user enters null input, @var{default} specifies which coding system | |
943 | to return. It should be a symbol or a string. | |
944 | @end defun | |
945 | ||
969fe9b5 RS |
946 | @defun read-non-nil-coding-system prompt |
947 | This function reads a coding system using the minibuffer, prompting with | |
a9f0a989 | 948 | string @var{prompt}, and returns the coding system name as a symbol. If |
969fe9b5 RS |
949 | the user tries to enter null input, it asks the user to try again. |
950 | @xref{Coding Systems}. | |
cc6d0d2c RS |
951 | @end defun |
952 | ||
953 | @node Default Coding Systems | |
a9f0a989 | 954 | @subsection Default Coding Systems |
cc6d0d2c | 955 | |
a9f0a989 RS |
956 | This section describes variables that specify the default coding |
957 | system for certain files or when running certain subprograms, and the | |
1911e6e5 | 958 | function that I/O operations use to access them. |
a9f0a989 RS |
959 | |
960 | The idea of these variables is that you set them once and for all to the | |
961 | defaults you want, and then do not change them again. To specify a | |
962 | particular coding system for a particular operation in a Lisp program, | |
963 | don't change these variables; instead, override them using | |
964 | @code{coding-system-for-read} and @code{coding-system-for-write} | |
965 | (@pxref{Specifying Coding Systems}). | |
cc6d0d2c | 966 | |
bf23b477 EZ |
967 | @defvar auto-coding-regexp-alist |
968 | This variable is an alist of text patterns and corresponding coding | |
969 | systems. Each element has the form @code{(@var{regexp} | |
970 | . @var{coding-system})}; a file whose first few kilobytes match | |
971 | @var{regexp} is decoded with @var{coding-system} when its contents are | |
972 | read into a buffer. The settings in this alist take priority over | |
973 | @code{coding:} tags in the files and the contents of | |
974 | @code{file-coding-system-alist} (see below). The default value is set | |
975 | so that Emacs automatically recognizes mail files in Babyl format and | |
976 | reads them with no code conversions. | |
977 | @end defvar | |
978 | ||
cc6d0d2c RS |
979 | @defvar file-coding-system-alist |
980 | This variable is an alist that specifies the coding systems to use for | |
981 | reading and writing particular files. Each element has the form | |
982 | @code{(@var{pattern} . @var{coding})}, where @var{pattern} is a regular | |
983 | expression that matches certain file names. The element applies to file | |
984 | names that match @var{pattern}. | |
985 | ||
35864124 | 986 | The @sc{cdr} of the element, @var{coding}, should be either a coding |
8241495d RS |
987 | system, a cons cell containing two coding systems, or a function name (a |
988 | symbol with a function definition). If @var{coding} is a coding system, | |
989 | that coding system is used for both reading the file and writing it. If | |
35864124 LT |
990 | @var{coding} is a cons cell containing two coding systems, its @sc{car} |
991 | specifies the coding system for decoding, and its @sc{cdr} specifies the | |
8241495d RS |
992 | coding system for encoding. |
993 | ||
35864124 LT |
994 | If @var{coding} is a function name, the function should take one |
995 | argument, a list of all arguments passed to | |
996 | @code{find-operation-coding-system}. It must return a coding system | |
997 | or a cons cell containing two coding systems. This value has the same | |
998 | meaning as described above. | |
cc6d0d2c RS |
999 | @end defvar |
1000 | ||
cc6d0d2c RS |
1001 | @defvar process-coding-system-alist |
1002 | This variable is an alist specifying which coding systems to use for a | |
1003 | subprocess, depending on which program is running in the subprocess. It | |
1004 | works like @code{file-coding-system-alist}, except that @var{pattern} is | |
1005 | matched against the program name used to start the subprocess. The coding | |
1006 | system or systems specified in this alist are used to initialize the | |
1007 | coding systems used for I/O to the subprocess, but you can specify | |
1008 | other coding systems later using @code{set-process-coding-system}. | |
1009 | @end defvar | |
1010 | ||
8241495d RS |
1011 | @strong{Warning:} Coding systems such as @code{undecided}, which |
1012 | determine the coding system from the data, do not work entirely reliably | |
1911e6e5 | 1013 | with asynchronous subprocess output. This is because Emacs handles |
a9f0a989 RS |
1014 | asynchronous subprocess output in batches, as it arrives. If the coding |
1015 | system leaves the character code conversion unspecified, or leaves the | |
1016 | end-of-line conversion unspecified, Emacs must try to detect the proper | |
1017 | conversion from one batch at a time, and this does not always work. | |
1018 | ||
1019 | Therefore, with an asynchronous subprocess, if at all possible, use a | |
1020 | coding system which determines both the character code conversion and | |
1021 | the end of line conversion---that is, one like @code{latin-1-unix}, | |
1022 | rather than @code{undecided} or @code{latin-1}. | |
1023 | ||
cc6d0d2c RS |
1024 | @defvar network-coding-system-alist |
1025 | This variable is an alist that specifies the coding system to use for | |
1026 | network streams. It works much like @code{file-coding-system-alist}, | |
969fe9b5 | 1027 | with the difference that the @var{pattern} in an element may be either a |
cc6d0d2c RS |
1028 | port number or a regular expression. If it is a regular expression, it |
1029 | is matched against the network service name used to open the network | |
1030 | stream. | |
1031 | @end defvar | |
1032 | ||
cc6d0d2c RS |
1033 | @defvar default-process-coding-system |
1034 | This variable specifies the coding systems to use for subprocess (and | |
1035 | network stream) input and output, when nothing else specifies what to | |
1036 | do. | |
1037 | ||
a9f0a989 RS |
1038 | The value should be a cons cell of the form @code{(@var{input-coding} |
1039 | . @var{output-coding})}. Here @var{input-coding} applies to input from | |
1040 | the subprocess, and @var{output-coding} applies to output to it. | |
cc6d0d2c RS |
1041 | @end defvar |
1042 | ||
131bf943 RS |
1043 | @defvar auto-coding-functions |
1044 | This variable holds a list of functions that try to determine a | |
1045 | coding system for a file based on its undecoded contents. | |
1046 | ||
1047 | Each function in this list should be written to look at text in the | |
1048 | current buffer, but should not modify it in any way. The buffer will | |
1049 | contain undecoded text of parts of the file. Each function should | |
1050 | take one argument, @var{size}, which tells it how many characters to | |
1051 | look at, starting from point. If the function succeeds in determining | |
1052 | a coding system for the file, it should return that coding system. | |
1053 | Otherwise, it should return @code{nil}. | |
1054 | ||
1055 | If a file has a @samp{coding:} tag, that takes precedence, so these | |
1056 | functions won't be called. | |
1057 | @end defvar | |
1058 | ||
a9f0a989 | 1059 | @defun find-operation-coding-system operation &rest arguments |
a9f0a989 RS |
1060 | This function returns the coding system to use (by default) for |
1061 | performing @var{operation} with @var{arguments}. The value has this | |
1062 | form: | |
1063 | ||
1064 | @example | |
35864124 | 1065 | (@var{decoding-system} . @var{encoding-system}) |
a9f0a989 RS |
1066 | @end example |
1067 | ||
1068 | The first element, @var{decoding-system}, is the coding system to use | |
1069 | for decoding (in case @var{operation} does decoding), and | |
1070 | @var{encoding-system} is the coding system for encoding (in case | |
1071 | @var{operation} does encoding). | |
1072 | ||
342fd6cd RS |
1073 | The argument @var{operation} should be a symbol, any one of |
1074 | @code{insert-file-contents}, @code{write-region}, | |
1075 | @code{start-process}, @code{call-process}, @code{call-process-region}, | |
1076 | or @code{open-network-stream}. These are the names of the Emacs I/O | |
1077 | primitives that can do coding system conversion. | |
a9f0a989 RS |
1078 | |
1079 | The remaining arguments should be the same arguments that might be given | |
8241495d | 1080 | to that I/O primitive. Depending on the primitive, one of those |
a9f0a989 RS |
1081 | arguments is selected as the @dfn{target}. For example, if |
1082 | @var{operation} does file I/O, whichever argument specifies the file | |
1083 | name is the target. For subprocess primitives, the process name is the | |
1084 | target. For @code{open-network-stream}, the target is the service name | |
1085 | or port number. | |
1086 | ||
342fd6cd RS |
1087 | Depending on @var{operation}, this function looks up the target in |
1088 | @code{file-coding-system-alist}, @code{process-coding-system-alist}, | |
1089 | or @code{network-coding-system-alist}. | |
a9f0a989 RS |
1090 | @end defun |
1091 | ||
cc6d0d2c | 1092 | @node Specifying Coding Systems |
a9f0a989 | 1093 | @subsection Specifying a Coding System for One Operation |
cc6d0d2c RS |
1094 | |
1095 | You can specify the coding system for a specific operation by binding | |
1096 | the variables @code{coding-system-for-read} and/or | |
1097 | @code{coding-system-for-write}. | |
1098 | ||
cc6d0d2c RS |
1099 | @defvar coding-system-for-read |
1100 | If this variable is non-@code{nil}, it specifies the coding system to | |
1101 | use for reading a file, or for input from a synchronous subprocess. | |
1102 | ||
1103 | It also applies to any asynchronous subprocess or network stream, but in | |
1104 | a different way: the value of @code{coding-system-for-read} when you | |
1105 | start the subprocess or open the network stream specifies the input | |
1106 | decoding method for that subprocess or network stream. It remains in | |
1107 | use for that subprocess or network stream unless and until overridden. | |
1108 | ||
1109 | The right way to use this variable is to bind it with @code{let} for a | |
1110 | specific I/O operation. Its global value is normally @code{nil}, and | |
1111 | you should not globally set it to any other value. Here is an example | |
1112 | of the right way to use the variable: | |
1113 | ||
1114 | @example | |
1115 | ;; @r{Read the file with no character code conversion.} | |
ad800164 | 1116 | ;; @r{Assume @acronym{crlf} represents end-of-line.} |
a3d3f60d | 1117 | (let ((coding-system-for-read 'emacs-mule-dos)) |
cc6d0d2c RS |
1118 | (insert-file-contents filename)) |
1119 | @end example | |
1120 | ||
1121 | When its value is non-@code{nil}, @code{coding-system-for-read} takes | |
a9f0a989 | 1122 | precedence over all other methods of specifying a coding system to use for |
cc6d0d2c RS |
1123 | input, including @code{file-coding-system-alist}, |
1124 | @code{process-coding-system-alist} and | |
1125 | @code{network-coding-system-alist}. | |
1126 | @end defvar | |
1127 | ||
cc6d0d2c RS |
1128 | @defvar coding-system-for-write |
1129 | This works much like @code{coding-system-for-read}, except that it | |
1130 | applies to output rather than input. It affects writing to files, | |
b6954afd | 1131 | as well as sending output to subprocesses and net connections. |
cc6d0d2c RS |
1132 | |
1133 | When a single operation does both input and output, as do | |
1134 | @code{call-process-region} and @code{start-process}, both | |
1135 | @code{coding-system-for-read} and @code{coding-system-for-write} | |
1136 | affect it. | |
1137 | @end defvar | |
1138 | ||
cc6d0d2c RS |
1139 | @defvar inhibit-eol-conversion |
1140 | When this variable is non-@code{nil}, no end-of-line conversion is done, | |
1141 | no matter which coding system is specified. This applies to all the | |
1142 | Emacs I/O and subprocess primitives, and to the explicit encoding and | |
1143 | decoding functions (@pxref{Explicit Encoding}). | |
1144 | @end defvar | |
1145 | ||
cc6d0d2c | 1146 | @node Explicit Encoding |
a9f0a989 | 1147 | @subsection Explicit Encoding and Decoding |
cc6d0d2c RS |
1148 | @cindex encoding text |
1149 | @cindex decoding text | |
1150 | ||
1151 | All the operations that transfer text in and out of Emacs have the | |
1152 | ability to use a coding system to encode or decode the text. | |
1153 | You can also explicitly encode and decode text using the functions | |
1154 | in this section. | |
1155 | ||
cc6d0d2c | 1156 | The result of encoding, and the input to decoding, are not ordinary |
0ace421a GM |
1157 | text. They logically consist of a series of byte values; that is, a |
1158 | series of characters whose codes are in the range 0 through 255. In a | |
1159 | multibyte buffer or string, character codes 128 through 159 are | |
1160 | represented by multibyte sequences, but this is invisible to Lisp | |
1161 | programs. | |
1162 | ||
1163 | The usual way to read a file into a buffer as a sequence of bytes, so | |
1164 | you can decode the contents explicitly, is with | |
1165 | @code{insert-file-contents-literally} (@pxref{Reading from Files}); | |
1166 | alternatively, specify a non-@code{nil} @var{rawfile} argument when | |
1167 | visiting a file with @code{find-file-noselect}. These methods result in | |
1168 | a unibyte buffer. | |
1169 | ||
1170 | The usual way to use the byte sequence that results from explicitly | |
1171 | encoding text is to copy it to a file or process---for example, to write | |
1172 | it with @code{write-region} (@pxref{Writing to Files}), and suppress | |
1173 | encoding by binding @code{coding-system-for-write} to | |
1174 | @code{no-conversion}. | |
b6954afd RS |
1175 | |
1176 | Here are the functions to perform explicit encoding or decoding. The | |
0ace421a GM |
1177 | decoding functions produce sequences of bytes; the encoding functions |
1178 | are meant to operate on sequences of bytes. All of these functions | |
1179 | discard text properties. | |
1911e6e5 | 1180 | |
35864124 LT |
1181 | @deffn Command encode-coding-region start end coding-system |
1182 | This command encodes the text from @var{start} to @var{end} according | |
969fe9b5 | 1183 | to coding system @var{coding-system}. The encoded text replaces the |
0ace421a GM |
1184 | original text in the buffer. The result of encoding is logically a |
1185 | sequence of bytes, but the buffer remains multibyte if it was multibyte | |
1186 | before. | |
cc6d0d2c | 1187 | |
35864124 LT |
1188 | This command returns the length of the encoded text. |
1189 | @end deffn | |
1190 | ||
1191 | @defun encode-coding-string string coding-system &optional nocopy | |
cc6d0d2c RS |
1192 | This function encodes the text in @var{string} according to coding |
1193 | system @var{coding-system}. It returns a new string containing the | |
35864124 LT |
1194 | encoded text, except when @var{nocopy} is non-@code{nil}, in which |
1195 | case the function may return @var{string} itself if the encoding | |
1196 | operation is trivial. The result of encoding is a unibyte string. | |
cc6d0d2c RS |
1197 | @end defun |
1198 | ||
35864124 LT |
1199 | @deffn Command decode-coding-region start end coding-system |
1200 | This command decodes the text from @var{start} to @var{end} according | |
cc6d0d2c RS |
1201 | to coding system @var{coding-system}. The decoded text replaces the |
1202 | original text in the buffer. To make explicit decoding useful, the text | |
0ace421a GM |
1203 | before decoding ought to be a sequence of byte values, but both |
1204 | multibyte and unibyte buffers are acceptable. | |
cc6d0d2c | 1205 | |
35864124 LT |
1206 | This command returns the length of the decoded text. |
1207 | @end deffn | |
1208 | ||
1209 | @defun decode-coding-string string coding-system &optional nocopy | |
cc6d0d2c RS |
1210 | This function decodes the text in @var{string} according to coding |
1211 | system @var{coding-system}. It returns a new string containing the | |
35864124 LT |
1212 | decoded text, except when @var{nocopy} is non-@code{nil}, in which |
1213 | case the function may return @var{string} itself if the decoding | |
1214 | operation is trivial. To make explicit decoding useful, the contents | |
1215 | of @var{string} ought to be a sequence of byte values, but a multibyte | |
0ace421a | 1216 | string is acceptable. |
cc6d0d2c | 1217 | @end defun |
969fe9b5 | 1218 | |
131bf943 RS |
1219 | @defun decode-coding-inserted-region from to filename &optional visit beg end replace |
1220 | This function decodes the text from @var{from} to @var{to} as if | |
1221 | it were being read from file @var{filename} using @code{insert-file-contents} | |
1222 | using the rest of the arguments provided. | |
1223 | ||
1224 | The normal way to use this function is after reading text from a file | |
1225 | without decoding, if you decide you would rather have decoded it. | |
1226 | Instead of deleting the text and reading it again, this time with | |
1227 | decoding, you can call this function. | |
1228 | @end defun | |
1229 | ||
a9f0a989 RS |
1230 | @node Terminal I/O Encoding |
1231 | @subsection Terminal I/O Encoding | |
1232 | ||
1233 | Emacs can decode keyboard input using a coding system, and encode | |
2eb4136f RS |
1234 | terminal output. This is useful for terminals that transmit or display |
1235 | text using a particular encoding such as Latin-1. Emacs does not set | |
1236 | @code{last-coding-system-used} for encoding or decoding for the | |
1237 | terminal. | |
a9f0a989 RS |
1238 | |
1239 | @defun keyboard-coding-system | |
a9f0a989 RS |
1240 | This function returns the coding system that is in use for decoding |
1241 | keyboard input---or @code{nil} if no coding system is to be used. | |
1242 | @end defun | |
1243 | ||
35864124 LT |
1244 | @deffn Command set-keyboard-coding-system coding-system |
1245 | This command specifies @var{coding-system} as the coding system to | |
a9f0a989 RS |
1246 | use for decoding keyboard input. If @var{coding-system} is @code{nil}, |
1247 | that means do not decode keyboard input. | |
35864124 | 1248 | @end deffn |
a9f0a989 RS |
1249 | |
1250 | @defun terminal-coding-system | |
a9f0a989 RS |
1251 | This function returns the coding system that is in use for encoding |
1252 | terminal output---or @code{nil} for no encoding. | |
1253 | @end defun | |
1254 | ||
35864124 LT |
1255 | @deffn Command set-terminal-coding-system coding-system |
1256 | This command specifies @var{coding-system} as the coding system to use | |
a9f0a989 RS |
1257 | for encoding terminal output. If @var{coding-system} is @code{nil}, |
1258 | that means do not encode terminal output. | |
35864124 | 1259 | @end deffn |
a9f0a989 | 1260 | |
969fe9b5 | 1261 | @node MS-DOS File Types |
a9f0a989 | 1262 | @subsection MS-DOS File Types |
969fe9b5 RS |
1263 | @cindex DOS file types |
1264 | @cindex MS-DOS file types | |
1265 | @cindex Windows file types | |
1266 | @cindex file types on MS-DOS and Windows | |
1267 | @cindex text files and binary files | |
1268 | @cindex binary files and text files | |
1269 | ||
8241495d RS |
1270 | On MS-DOS and Microsoft Windows, Emacs guesses the appropriate |
1271 | end-of-line conversion for a file by looking at the file's name. This | |
0ace421a | 1272 | feature classifies files as @dfn{text files} and @dfn{binary files}. By |
8241495d RS |
1273 | ``binary file'' we mean a file of literal byte values that are not |
1274 | necessarily meant to be characters; Emacs does no end-of-line conversion | |
1275 | and no character code conversion for them. On the other hand, the bytes | |
1276 | in a text file are intended to represent characters; when you create a | |
1277 | new file whose name implies that it is a text file, Emacs uses DOS | |
1278 | end-of-line conversion. | |
969fe9b5 RS |
1279 | |
1280 | @defvar buffer-file-type | |
1281 | This variable, automatically buffer-local in each buffer, records the | |
a9f0a989 RS |
1282 | file type of the buffer's visited file. When a buffer does not specify |
1283 | a coding system with @code{buffer-file-coding-system}, this variable is | |
1284 | used to determine which coding system to use when writing the contents | |
1285 | of the buffer. It should be @code{nil} for text, @code{t} for binary. | |
1286 | If it is @code{t}, the coding system is @code{no-conversion}. | |
1287 | Otherwise, @code{undecided-dos} is used. | |
1288 | ||
1289 | Normally this variable is set by visiting a file; it is set to | |
1290 | @code{nil} if the file was visited without any actual conversion. | |
969fe9b5 RS |
1291 | @end defvar |
1292 | ||
1293 | @defopt file-name-buffer-file-type-alist | |
1294 | This variable holds an alist for recognizing text and binary files. | |
1295 | Each element has the form (@var{regexp} . @var{type}), where | |
1296 | @var{regexp} is matched against the file name, and @var{type} may be | |
1297 | @code{nil} for text, @code{t} for binary, or a function to call to | |
1298 | compute which. If it is a function, then it is called with a single | |
1299 | argument (the file name) and should return @code{t} or @code{nil}. | |
1300 | ||
8241495d | 1301 | When running on MS-DOS or MS-Windows, Emacs checks this alist to decide |
969fe9b5 RS |
1302 | which coding system to use when reading a file. For a text file, |
1303 | @code{undecided-dos} is used. For a binary file, @code{no-conversion} | |
1304 | is used. | |
1305 | ||
1306 | If no element in this alist matches a given file name, then | |
1307 | @code{default-buffer-file-type} says how to treat the file. | |
1308 | @end defopt | |
1309 | ||
1310 | @defopt default-buffer-file-type | |
1311 | This variable says how to handle files for which | |
1312 | @code{file-name-buffer-file-type-alist} says nothing about the type. | |
1313 | ||
1314 | If this variable is non-@code{nil}, then these files are treated as | |
a9f0a989 RS |
1315 | binary: the coding system @code{no-conversion} is used. Otherwise, |
1316 | nothing special is done for them---the coding system is deduced solely | |
1317 | from the file contents, in the usual Emacs fashion. | |
969fe9b5 RS |
1318 | @end defopt |
1319 | ||
a9f0a989 RS |
1320 | @node Input Methods |
1321 | @section Input Methods | |
1322 | @cindex input methods | |
1323 | ||
ad800164 | 1324 | @dfn{Input methods} provide convenient ways of entering non-@acronym{ASCII} |
a9f0a989 | 1325 | characters from the keyboard. Unlike coding systems, which translate |
ad800164 | 1326 | non-@acronym{ASCII} characters to and from encodings meant to be read by |
a9f0a989 RS |
1327 | programs, input methods provide human-friendly commands. (@xref{Input |
1328 | Methods,,, emacs, The GNU Emacs Manual}, for information on how users | |
1329 | use input methods to enter text.) How to define input methods is not | |
1330 | yet documented in this manual, but here we describe how to use them. | |
1331 | ||
1332 | Each input method has a name, which is currently a string; | |
1333 | in the future, symbols may also be usable as input method names. | |
1334 | ||
a9f0a989 RS |
1335 | @defvar current-input-method |
1336 | This variable holds the name of the input method now active in the | |
1337 | current buffer. (It automatically becomes local in each buffer when set | |
1338 | in any fashion.) It is @code{nil} if no input method is active in the | |
1339 | buffer now. | |
969fe9b5 RS |
1340 | @end defvar |
1341 | ||
35864124 | 1342 | @defopt default-input-method |
a9f0a989 RS |
1343 | This variable holds the default input method for commands that choose an |
1344 | input method. Unlike @code{current-input-method}, this variable is | |
1345 | normally global. | |
35864124 | 1346 | @end defopt |
a9f0a989 | 1347 | |
35864124 LT |
1348 | @deffn Command set-input-method input-method |
1349 | This command activates input method @var{input-method} for the current | |
a9f0a989 | 1350 | buffer. It also sets @code{default-input-method} to @var{input-method}. |
35864124 | 1351 | If @var{input-method} is @code{nil}, this command deactivates any input |
a9f0a989 | 1352 | method for the current buffer. |
35864124 | 1353 | @end deffn |
a9f0a989 | 1354 | |
a9f0a989 RS |
1355 | @defun read-input-method-name prompt &optional default inhibit-null |
1356 | This function reads an input method name with the minibuffer, prompting | |
1357 | with @var{prompt}. If @var{default} is non-@code{nil}, that is returned | |
1358 | by default, if the user enters empty input. However, if | |
1359 | @var{inhibit-null} is non-@code{nil}, empty input signals an error. | |
1360 | ||
1361 | The returned value is a string. | |
1362 | @end defun | |
1363 | ||
a9f0a989 RS |
1364 | @defvar input-method-alist |
1365 | This variable defines all the supported input methods. | |
1366 | Each element defines one input method, and should have the form: | |
1367 | ||
1368 | @example | |
1911e6e5 RS |
1369 | (@var{input-method} @var{language-env} @var{activate-func} |
1370 | @var{title} @var{description} @var{args}...) | |
a9f0a989 RS |
1371 | @end example |
1372 | ||
1911e6e5 RS |
1373 | Here @var{input-method} is the input method name, a string; |
1374 | @var{language-env} is another string, the name of the language | |
1375 | environment this input method is recommended for. (That serves only for | |
1376 | documentation purposes.) | |
a9f0a989 | 1377 | |
a9f0a989 RS |
1378 | @var{activate-func} is a function to call to activate this method. The |
1379 | @var{args}, if any, are passed as arguments to @var{activate-func}. All | |
1380 | told, the arguments to @var{activate-func} are @var{input-method} and | |
1381 | the @var{args}. | |
0ace421a GM |
1382 | |
1383 | @var{title} is a string to display in the mode line while this method is | |
1384 | active. @var{description} is a string describing this method and what | |
1385 | it is good for. | |
1911e6e5 | 1386 | @end defvar |
a9f0a989 | 1387 | |
2eb4136f | 1388 | The fundamental interface to input methods is through the |
35864124 LT |
1389 | variable @code{input-method-function}. @xref{Reading One Event}, |
1390 | and @ref{Invoking the Input Method}. | |
2468d0c0 DL |
1391 | |
1392 | @node Locales | |
1393 | @section Locales | |
1394 | @cindex locale | |
1395 | ||
1396 | POSIX defines a concept of ``locales'' which control which language | |
1397 | to use in language-related features. These Emacs variables control | |
1398 | how Emacs interacts with these features. | |
1399 | ||
1400 | @defvar locale-coding-system | |
1401 | @tindex locale-coding-system | |
a007679c | 1402 | @cindex keyboard input decoding on X |
2468d0c0 | 1403 | This variable specifies the coding system to use for decoding system |
a007679c EZ |
1404 | error messages and---on X Window system only---keyboard input, for |
1405 | encoding the format argument to @code{format-time-string}, and for | |
1406 | decoding the return value of @code{format-time-string}. | |
2468d0c0 DL |
1407 | @end defvar |
1408 | ||
1409 | @defvar system-messages-locale | |
1410 | @tindex system-messages-locale | |
1411 | This variable specifies the locale to use for generating system error | |
1412 | messages. Changing the locale can cause messages to come out in a | |
9c17f494 | 1413 | different language or in a different orthography. If the variable is |
2468d0c0 DL |
1414 | @code{nil}, the locale is specified by environment variables in the |
1415 | usual POSIX fashion. | |
1416 | @end defvar | |
1417 | ||
1418 | @defvar system-time-locale | |
1419 | @tindex system-time-locale | |
1420 | This variable specifies the locale to use for formatting time values. | |
1421 | Changing the locale can cause messages to appear according to the | |
1422 | conventions of a different language. If the variable is @code{nil}, the | |
1423 | locale is specified by environment variables in the usual POSIX fashion. | |
1424 | @end defvar | |
0ace421a | 1425 | |
131bf943 RS |
1426 | @defun locale-info item |
1427 | This function returns locale data @var{item} for the current POSIX | |
1428 | locale, if available. @var{item} should be one of these symbols: | |
1429 | ||
1430 | @table @code | |
1431 | @item codeset | |
1432 | Return the character set as a string (locale item @code{CODESET}). | |
1433 | ||
1434 | @item days | |
1435 | Return a 7-element vector of day names (locale items | |
1436 | @code{DAY_1} through @code{DAY_7}); | |
1437 | ||
1438 | @item months | |
1439 | Return a 12-element vector of month names (locale items @code{MON_1} | |
1440 | through @code{MON_12}). | |
1441 | ||
1442 | @item paper | |
1443 | Return a list @code{(@var{width} @var{height})} for the default paper | |
35864124 | 1444 | size measured in millimeters (locale items @code{PAPER_WIDTH} and |
131bf943 RS |
1445 | @code{PAPER_HEIGHT}). |
1446 | @end table | |
1447 | ||
1448 | If the system can't provide the requested information, or if | |
1449 | @var{item} is not one of those symbols, the value is @code{nil}. All | |
1450 | strings in the return value are decoded using | |
35864124 | 1451 | @code{locale-coding-system}. @xref{Locales,,, libc, The GNU Libc Manual}, |
131bf943 RS |
1452 | for more information about locales and locale items. |
1453 | @end defun | |
ab5796a9 MB |
1454 | |
1455 | @ignore | |
1456 | arch-tag: be705bf8-941b-4c35-84fc-ad7d20ddb7cb | |
1457 | @end ignore |