@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1998, 1999 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/characters
@node Non-ASCII Characters, Searching and Matching, Text, Top
-@chapter Non-ASCII Characters
+@chapter Non-@acronym{ASCII} Characters
@cindex multibyte characters
-@cindex non-ASCII characters
+@cindex non-@acronym{ASCII} characters
- This chapter covers the special issues relating to non-@sc{ascii}
+ This chapter covers the special issues relating to non-@acronym{ASCII}
characters and how they are stored in strings and buffers.
@menu
-* Text Representations::
-* Converting Representations::
-* Selecting a Representation::
-* Character Codes::
-* Character Sets::
-* Chars and Bytes::
-* Splitting Characters::
-* Scanning Charsets::
-* Translation of Characters::
-* Coding Systems::
-* Input Methods::
+* Text Representations:: Unibyte and multibyte representations
+* Converting Representations:: Converting unibyte to multibyte and vice versa.
+* Selecting a Representation:: Treating a byte sequence as unibyte or multi.
+* Character Codes:: How unibyte and multibyte relate to
+ codes of individual characters.
+* Character Sets:: The space of possible character codes
+ is divided into various character sets.
+* Chars and Bytes:: More information about multibyte encodings.
+* Splitting Characters:: Converting a character to its byte sequence.
+* Scanning Charsets:: Which character sets are used in a buffer?
+* Translation of Characters:: Translation tables are used for conversion.
+* Coding Systems:: Coding systems are conversions for saving files.
+* Input Methods:: Input methods allow users to enter various
+ non-ASCII characters without special keyboards.
+* Locales:: Interacting with the POSIX locale.
@end menu
@node Text Representations
@cindex unibyte text
In unibyte representation, each character occupies one byte and
therefore the possible character codes range from 0 to 255. Codes 0
-through 127 are @sc{ascii} characters; the codes from 128 through 255
-are used for one non-@sc{ascii} character set (you can choose which
+through 127 are @acronym{ASCII} characters; the codes from 128 through 255
+are used for one non-@acronym{ASCII} character set (you can choose which
character set by setting the variable @code{nonascii-insert-offset}).
@cindex leading code
character are always in the range 160 through 255 (octal 0240 through
0377); these values are @dfn{trailing codes}.
- Some sequences of bytes do not form meaningful multibyte characters:
-for example, a single isolated byte in the range 128 through 255 is
-never meaningful. Such byte sequences are not entirely valid, and never
-appear in proper multibyte text (since that consists of a sequence of
-@emph{characters}); but they can appear as part of ``raw bytes''
-(@pxref{Explicit Encoding}).
+ Some sequences of bytes are not valid in multibyte text: for example,
+a single isolated byte in the range 128 through 159 is not allowed. But
+character codes 128 through 159 can appear in multibyte text,
+represented as two-byte sequences. All the character codes 128 through
+255 are possible (though slightly abnormal) in multibyte text; they
+appear in multibyte buffers and strings when you do explicit encoding
+and decoding (@pxref{Explicit Encoding}).
In a buffer, the buffer-local value of the variable
@code{enable-multibyte-characters} specifies the representation used.
when the string is constructed.
@defvar enable-multibyte-characters
-@tindex enable-multibyte-characters
This variable specifies the current buffer's text representation.
If it is non-@code{nil}, the buffer contains multibyte text; otherwise,
it contains unibyte text.
@end defvar
@defvar default-enable-multibyte-characters
-@tindex default-enable-multibyte-characters
This variable's value is entirely equivalent to @code{(default-value
'enable-multibyte-characters)}, and setting this variable changes that
default value. Setting the local binding of
@defun position-bytes position
@tindex position-bytes
-Return the byte-position corresponding to buffer position @var{position}
-in the current buffer.
+Return the byte-position corresponding to buffer position
+@var{position} in the current buffer. This is 1 at the start of the
+buffer, and counts upward in bytes. If @var{position} is out of
+range, the value is @code{nil}.
@end defun
@defun byte-to-position byte-position
@tindex byte-to-position
Return the buffer position corresponding to byte-position
-@var{byte-position} in the current buffer.
+@var{byte-position} in the current buffer. If @var{byte-position} is
+out of range, the value is @code{nil}.
@end defun
@defun multibyte-string-p string
-@tindex multibyte-string-p
Return @code{t} if @var{string} is a multibyte string.
@end defun
acceptable because the buffer's representation is a choice made by the
user that cannot be overridden automatically.
- Converting unibyte text to multibyte text leaves @sc{ascii} characters
-unchanged, and likewise 128 through 159. It converts the non-@sc{ascii}
-codes 160 through 255 by adding the value @code{nonascii-insert-offset}
-to each character code. By setting this variable, you specify which
-character set the unibyte characters correspond to (@pxref{Character
-Sets}). For example, if @code{nonascii-insert-offset} is 2048, which is
-@code{(- (make-char 'latin-iso8859-1) 128)}, then the unibyte
-non-@sc{ascii} characters correspond to Latin 1. If it is 2688, which
-is @code{(- (make-char 'greek-iso8859-7) 128)}, then they correspond to
-Greek letters.
+ Converting unibyte text to multibyte text leaves @acronym{ASCII} characters
+unchanged, and likewise character codes 128 through 159. It converts
+the non-@acronym{ASCII} codes 160 through 255 by adding the value
+@code{nonascii-insert-offset} to each character code. By setting this
+variable, you specify which character set the unibyte characters
+correspond to (@pxref{Character Sets}). For example, if
+@code{nonascii-insert-offset} is 2048, which is @code{(- (make-char
+'latin-iso8859-1) 128)}, then the unibyte non-@acronym{ASCII} characters
+correspond to Latin 1. If it is 2688, which is @code{(- (make-char
+'greek-iso8859-7) 128)}, then they correspond to Greek letters.
Converting multibyte text to unibyte is simpler: it discards all but
the low 8 bits of each character code. If @code{nonascii-insert-offset}
text.
@defvar nonascii-insert-offset
-@tindex nonascii-insert-offset
-This variable specifies the amount to add to a non-@sc{ascii} character
+This variable specifies the amount to add to a non-@acronym{ASCII} character
when converting unibyte text to multibyte. It also applies when
@code{self-insert-command} inserts a character in the unibyte
-non-@sc{ascii} range, 128 through 255. However, the function
-@code{insert-char} does not perform this conversion.
+non-@acronym{ASCII} range, 128 through 255. However, the functions
+@code{insert} and @code{insert-char} do not perform this conversion.
The right value to use to select character set @var{cs} is @code{(-
(make-char @var{cs}) 128)}. If the value of
@end defvar
@defvar nonascii-translation-table
-@tindex nonascii-translation-table
This variable provides a more general alternative to
@code{nonascii-insert-offset}. You can use it to specify independently
how to translate each code in the range of 128 through 255 into a
-multibyte character. The value should be a vector, or @code{nil}.
+multibyte character. The value should be a char-table, or @code{nil}.
If this is non-@code{nil}, it overrides @code{nonascii-insert-offset}.
@end defvar
+The next three functions either return the argument @var{string}, or a
+newly created string with no text properties.
+
@defun string-make-unibyte string
-@tindex string-make-unibyte
This function converts the text of @var{string} to unibyte
representation, if it isn't already, and returns the result. If
-@var{string} is a unibyte string, it is returned unchanged.
+@var{string} is a unibyte string, it is returned unchanged. Multibyte
+character codes are converted to unibyte according to
+@code{nonascii-translation-table} or, if that is @code{nil}, using
+@code{nonascii-insert-offset}. If the lookup in the translation table
+fails, this function takes just the low 8 bits of each character.
@end defun
@defun string-make-multibyte string
-@tindex string-make-multibyte
This function converts the text of @var{string} to multibyte
representation, if it isn't already, and returns the result. If
-@var{string} is a multibyte string, it is returned unchanged.
+@var{string} is a multibyte string or consists entirely of
+@acronym{ASCII} characters, it is returned unchanged. In particular,
+if @var{string} is unibyte and entirely @acronym{ASCII}, the returned
+string is unibyte. (When the characters are all @acronym{ASCII},
+Emacs primitives will treat the string the same way whether it is
+unibyte or multibyte.) If @var{string} is unibyte and contains
+non-@acronym{ASCII} characters, the function
+@code{unibyte-char-to-multibyte} is used to convert each unibyte
+character to a multibyte character.
+@end defun
+
+@defun string-to-multibyte string
+This function returns a multibyte string containing the same sequence
+of character codes as @var{string}. Unlike
+@code{string-make-multibyte}, this function unconditionally returns a
+multibyte string. If @var{string} is a multibyte string, it is
+returned unchanged.
+@end defun
+
+@defun multibyte-char-to-unibyte char
+This convert the multibyte character @var{char} to a unibyte
+character, based on @code{nonascii-translation-table} and
+@code{nonascii-insert-offset}.
+@end defun
+
+@defun unibyte-char-to-multibyte char
+This convert the unibyte character @var{char} to a multibyte
+character, based on @code{nonascii-translation-table} and
+@code{nonascii-insert-offset}.
@end defun
@node Selecting a Representation
multibyte when it was unibyte, or vice versa.
@defun set-buffer-multibyte multibyte
-@tindex set-buffer-multibyte
Set the representation type of the current buffer. If @var{multibyte}
is non-@code{nil}, the buffer becomes multibyte. If @var{multibyte}
is @code{nil}, the buffer becomes unibyte.
sequence of bytes. As a consequence, it can change the contents viewed
as characters; a sequence of two bytes which is treated as one character
in multibyte representation will count as two characters in unibyte
-representation.
+representation. Character codes 128 through 159 are an exception. They
+are represented by one byte in a unibyte buffer, but when the buffer is
+set to multibyte, they are converted to two-byte sequences, and vice
+versa.
This function sets @code{enable-multibyte-characters} to record which
representation is in use. It also adjusts various data in the buffer
@end defun
@defun string-as-unibyte string
-@tindex string-as-unibyte
This function returns a string with the same bytes as @var{string} but
treating each byte as a character. This means that the value may have
more characters than @var{string} has.
If @var{string} is already a unibyte string, then the value is
-@var{string} itself.
+@var{string} itself. Otherwise it is a newly created string, with no
+text properties. If @var{string} is multibyte, any characters it
+contains of charset @code{eight-bit-control} or @code{eight-bit-graphic}
+are converted to the corresponding single byte.
@end defun
@defun string-as-multibyte string
-@tindex string-as-multibyte
This function returns a string with the same bytes as @var{string} but
treating each multibyte sequence as one character. This means that the
value may have fewer characters than @var{string} has.
If @var{string} is already a multibyte string, then the value is
-@var{string} itself.
+@var{string} itself. Otherwise it is a newly created string, with no
+text properties. If @var{string} is unibyte and contains any individual
+8-bit bytes (i.e.@: not part of a multibyte form), they are converted to
+the corresponding multibyte character of charset @code{eight-bit-control}
+or @code{eight-bit-graphic}.
@end defun
@node Character Codes
codes. The valid character codes for unibyte representation range from
0 to 255---the values that can fit in one byte. The valid character
codes for multibyte representation range from 0 to 524287, but not all
-values in that range are valid. In particular, the values 128 through
-255 are not legitimate in multibyte text (though they can occur in ``raw
-bytes''; @pxref{Explicit Encoding}). Only the @sc{ascii} codes 0
-through 127 are fully legitimate in both representations.
+values in that range are valid. The values 128 through 255 are not
+entirely proper in multibyte text, but they can occur if you do explicit
+encoding and decoding (@pxref{Explicit Encoding}). Some other character
+codes cannot occur at all in multibyte text. Only the @acronym{ASCII} codes
+0 through 127 are completely legitimate in both representations.
-@defun char-valid-p charcode
-This returns @code{t} if @var{charcode} is valid for either one of the two
-text representations.
+@defun char-valid-p charcode &optional genericp
+This returns @code{t} if @var{charcode} is valid (either for unibyte
+text or for multibyte text).
@example
(char-valid-p 65)
(char-valid-p 2248)
@result{} t
@end example
+
+If the optional argument @var{genericp} is non-@code{nil}, this
+function also returns @code{t} if @var{charcode} is a generic
+character (@pxref{Splitting Characters}).
@end defun
@node Character Sets
characters, generally known as Big 5, is divided into two Emacs
character sets, @code{chinese-big5-1} and @code{chinese-big5-2}.
+ @acronym{ASCII} characters are in character set @code{ascii}. The
+non-@acronym{ASCII} characters 128 through 159 are in character set
+@code{eight-bit-control}, and codes 160 through 255 are in character set
+@code{eight-bit-graphic}.
+
@defun charsetp object
-@tindex charsetp
Returns @code{t} if @var{object} is a symbol that names a character set,
@code{nil} otherwise.
@end defun
+@defvar charset-list
+The value is a list of all defined character set names.
+@end defvar
+
@defun charset-list
-@tindex charset-list
-This function returns a list of all defined character set names.
+This function returns the value of @code{charset-list}. It is only
+provided for backward compatibility.
@end defun
@defun char-charset character
-@tindex char-charset
This function returns the name of the character set that @var{character}
-belongs to.
+belongs to, or the symbol @code{unknown} if @var{character} is not a
+valid character.
@end defun
@defun charset-plist charset
This function returns the charset property list of the character set
@var{charset}. Although @var{charset} is a symbol, this is not the same
as the property list of that symbol. Charset properties are used for
-special purposes within Emacs; for example, @code{x-charset-registry}
-helps determine which fonts to use (@pxref{Font Selection}).
+special purposes within Emacs.
@end defun
+@deffn Command list-charset-chars charset
+This command displays a list of characters in the character set
+@var{charset}.
+@end deffn
+
@node Chars and Bytes
@section Characters and Bytes
@cindex bytes and characters
@cindex dimension (of character set)
In multibyte representation, each character occupies one or more
bytes. Each character set has an @dfn{introduction sequence}, which is
-normally one or two bytes long. (Exception: the @sc{ascii} character
-set has a zero-length introduction sequence.) The introduction sequence
-is the beginning of the byte sequence for any character in the character
-set. The rest of the character's bytes distinguish it from the other
-characters in the same character set. Depending on the character set,
-there are either one or two distinguishing bytes; the number of such
-bytes is called the @dfn{dimension} of the character set.
+normally one or two bytes long. (Exception: the @code{ascii} character
+set and the @code{eight-bit-graphic} character set have a zero-length
+introduction sequence.) The introduction sequence is the beginning of
+the byte sequence for any character in the character set. The rest of
+the character's bytes distinguish it from the other characters in the
+same character set. Depending on the character set, there are either
+one or two distinguishing bytes; the number of such bytes is called the
+@dfn{dimension} of the character set.
@defun charset-dimension charset
-@tindex charset-dimension
This function returns the dimension of @var{charset}; at present, the
dimension is always 1 or 2.
@end defun
because Emacs translates automatically when necessary.
@defun split-char character
-@tindex split-char
Return a list containing the name of the character set of
@var{character}, followed by one or two byte values (integers) which
identify @var{character} within that character set. The number of byte
values is the character set's dimension.
+If @var{character} is invalid as a character code, @code{split-char}
+returns a list consisting of the symbol @code{unknown} and @var{character}.
+
@example
(split-char 2248)
@result{} (latin-iso8859-1 72)
(split-char 65)
@result{} (ascii 65)
-@end example
-
-Unibyte non-@sc{ascii} characters are considered as part of
-the @code{ascii} character set:
-
-@example
-(split-char 192)
- @result{} (ascii 192)
+(split-char 128)
+ @result{} (eight-bit-control 128)
@end example
@end defun
-@defun make-char charset &rest byte-values
-@tindex make-char
-This function returns the character in character set @var{charset}
-identified by @var{byte-values}. This is roughly the inverse of
-@code{split-char}. Normally, you should specify either one or two
-@var{byte-values}, according to the dimension of @var{charset}. For
-example,
+@defun make-char charset &optional code1 code2
+This function returns the character in character set @var{charset} whose
+position codes are @var{code1} and @var{code2}. This is roughly the
+inverse of @code{split-char}. Normally, you should specify either one
+or both of @var{code1} and @var{code2} according to the dimension of
+@var{charset}. For example,
@example
(make-char 'latin-iso8859-1 72)
@result{} 2248
@end example
+
+Actually, the eighth bit of both @var{code1} and @var{code2} is zeroed
+before they are used to index @var{charset}. Thus you may use, for
+instance, an ISO 8859 character code rather than subtracting 128, as
+is necessary to index the corresponding Emacs charset.
@end defun
@cindex generic characters
@result{} 2176
(char-valid-p 2176)
@result{} nil
+(char-valid-p 2176 t)
+ @result{} t
(split-char 2176)
@result{} (latin-iso8859-1 0)
@end example
+The character sets @code{ascii}, @code{eight-bit-control}, and
+@code{eight-bit-graphic} don't have corresponding generic characters. If
+@var{charset} is one of them and you don't supply @var{code1},
+@code{make-char} returns the character code corresponding to the
+smallest code in @var{charset}.
+
@node Scanning Charsets
@section Scanning for Character Sets
coding systems (@pxref{Coding Systems}) are capable of representing all
of the text in question.
+@defun charset-after &optional pos
+This function return the charset of a character in the current buffer
+at position @var{pos}. If @var{pos} is omitted or @code{nil}, it
+defauls to the current value of point. If @var{pos} is out of range,
+the value is @code{nil}.
+@end defun
+
@defun find-charset-region beg end &optional translation
-@tindex find-charset-region
This function returns a list of the character sets that appear in the
current buffer between positions @var{beg} and @var{end}.
is non-@code{nil}, then each character in the region is translated
through this table, and the value returned describes the translated
characters instead of the characters actually in the buffer.
-
-In two peculiar cases, the value includes the symbol @code{unknown}:
-
-@itemize @bullet
-@item
-When a unibyte buffer contains non-@sc{ascii} characters.
-
-@item
-When a multibyte buffer contains invalid byte-sequences (raw bytes).
-@xref{Explicit Encoding}.
-@end itemize
@end defun
@defun find-charset-string string &optional translation
-@tindex find-charset-string
This function returns a list of the character sets that appear in the
string @var{string}. It is just like @code{find-charset-region}, except
that it applies to the contents of @var{string} instead of part of the
@cindex character translation tables
@cindex translation tables
- A @dfn{translation table} specifies a mapping of characters
-into characters. These tables are used in encoding and decoding, and
-for other purposes. Some coding systems specify their own particular
-translation tables; there are also default translation tables which
-apply to all other coding systems.
+ A @dfn{translation table} is a char-table that specifies a mapping
+of characters into characters. These tables are used in encoding and
+decoding, and for other purposes. Some coding systems specify their
+own particular translation tables; there are also default translation
+tables which apply to all other coding systems.
+
+ For instance, the coding-system @code{utf-8} has a translation table
+that maps characters of various charsets (e.g.,
+@code{latin-iso8859-@var{x}}) into Unicode character sets. This way,
+it can encode Latin-2 characters into UTF-8. Meanwhile,
+@code{unify-8859-on-decoding-mode} operates by specifying
+@code{standard-translation-table-for-decode} to translate
+Latin-@var{x} characters into corresponding Unicode characters.
@defun make-translation-table &rest translations
This function returns a translation table based on the argument
-@var{translations}. Each element of
-@var{translations} should be a list of the form @code{(@var{from}
-. @var{to})}; this says to translate the character @var{from} into
-@var{to}.
+@var{translations}. Each element of @var{translations} should be a
+list of elements of the form @code{(@var{from} . @var{to})}; this says
+to translate the character @var{from} into @var{to}.
+
+The arguments and the forms in each argument are processed in order,
+and if a previous form already translates @var{to} to some other
+character, say @var{to-alt}, @var{from} is also translated to
+@var{to-alt}.
You can also map one whole character set into another character set with
the same dimension. To do this, you specify a generic character (which
designates a character set) for @var{from} (@pxref{Splitting Characters}).
-In this case, @var{to} should also be a generic character, for another
-character set of the same dimension. Then the translation table
-translates each character of @var{from}'s character set into the
-corresponding character of @var{to}'s character set.
+In this case, if @var{to} is also a generic character, its character
+set should have the same dimension as @var{from}'s. Then the
+translation table translates each character of @var{from}'s character
+set into the corresponding character of @var{to}'s character set. If
+@var{from} is a generic character and @var{to} is an ordinary
+character, then the translation table translates every character of
+@var{from}'s character set into @var{to}.
@end defun
In decoding, the translation table's translations are applied to the
characters that result from ordinary decoding. If a coding system has
-property @code{character-translation-table-for-decode}, that specifies
-the translation table to use. Otherwise, if
-@code{standard-translation-table-for-decode} is non-@code{nil}, decoding
-uses that table.
+property @code{translation-table-for-decode}, that specifies the
+translation table to use. (This is a property of the coding system,
+as returned by @code{coding-system-get}, not a property of the symbol
+that is the coding system's name. @xref{Coding System Basics,, Basic
+Concepts of Coding Systems}.) Otherwise, if
+@code{standard-translation-table-for-decode} is non-@code{nil},
+decoding uses that table.
In encoding, the translation table's translations are applied to the
characters in the buffer, and the result of translation is actually
encoded. If a coding system has property
-@code{character-translation-table-for-encode}, that specifies the
-translation table to use. Otherwise the variable
+@code{translation-table-for-encode}, that specifies the translation
+table to use. Otherwise the variable
@code{standard-translation-table-for-encode} specifies the translation
table.
coding systems that don't specify any other translation table.
@end defvar
+@defvar translation-table-for-input
+Self-inserting characters are translated through this translation
+table before they are inserted. This variable automatically becomes
+buffer-local when set.
+
+@code{set-buffer-file-coding-system} sets this variable so that your
+keyboard input gets translated into the character sets that the buffer
+is likely to contain.
+@end defvar
+
@node Coding Systems
@section Coding Systems
documented here.
@menu
-* Coding System Basics::
-* Encoding and I/O::
-* Lisp and Coding Systems::
-* User-Chosen Coding Systems::
-* Default Coding Systems::
-* Specifying Coding Systems::
-* Explicit Encoding::
-* Terminal I/O Encoding::
-* MS-DOS File Types::
+* Coding System Basics:: Basic concepts.
+* Encoding and I/O:: How file I/O functions handle coding systems.
+* Lisp and Coding Systems:: Functions to operate on coding system names.
+* User-Chosen Coding Systems:: Asking the user to choose a coding system.
+* Default Coding Systems:: Controlling the default choices.
+* Specifying Coding Systems:: Requesting a particular coding system
+ for a single file operation.
+* Explicit Encoding:: Encoding or decoding text without doing I/O.
+* Terminal I/O Encoding:: Use of encoding for terminal I/O.
+* MS-DOS File Types:: How DOS "text" and "binary" files
+ relate to coding systems.
@end menu
@node Coding System Basics
conversion, but some of them leave the choice unspecified---to be chosen
heuristically for each file, based on the data.
+ In general, a coding system doesn't guarantee roundtrip identity:
+decoding a byte sequence using coding system, then encoding the
+resulting text in the same coding system, can produce a different byte
+sequence. However, the following coding systems do guarantee that the
+byte sequence will be the same as what you originally decoded:
+
+@quotation
+chinese-big5 chinese-iso-8bit cyrillic-iso-8bit emacs-mule
+greek-iso-8bit hebrew-iso-8bit iso-latin-1 iso-latin-2 iso-latin-3
+iso-latin-4 iso-latin-5 iso-latin-8 iso-latin-9 iso-safe
+japanese-iso-8bit japanese-shift-jis korean-iso-8bit raw-text
+@end quotation
+
+ Encoding buffer text and then decoding the result can also fail to
+reproduce the original text. For instance, if you encode Latin-2
+characters with @code{utf-8} and decode the result using the same
+coding system, you'll get Unicode characters (of charset
+@code{mule-unicode-0100-24ff}). If you encode Unicode characters with
+@code{iso-latin-2} and decode the result with the same coding system,
+you'll get Latin-2 characters.
+
@cindex end of line conversion
@dfn{End of line conversion} handles three different conventions used
on various systems for representing end of line in files. The Unix
that the result is multibyte data.
@defun coding-system-get coding-system property
-@tindex coding-system-get
This function returns the specified property of the coding system
@var{coding-system}. Most coding system properties exist for internal
purposes, but one that you might find useful is @code{mime-charset}.
uses one to encode the buffer contents.
You can specify the coding system to use either explicitly
-(@pxref{Specifying Coding Systems}), or implicitly using the defaulting
+(@pxref{Specifying Coding Systems}), or implicitly using a default
mechanism (@pxref{Default Coding Systems}). But these methods may not
completely specify what to do. For example, they may choose a coding
system such as @code{undefined} which leaves the character code
you will want to find out afterwards which coding system was chosen.
@defvar buffer-file-coding-system
-@tindex buffer-file-coding-system
This variable records the coding system that was used for visiting the
current buffer. It is used for saving the buffer, and for writing part
-of the buffer with @code{write-region}. When those operations ask the
-user to specify a different coding system,
-@code{buffer-file-coding-system} is updated to the coding system
-specified.
-
-However, @code{buffer-file-coding-system} does not affect sending text
+of the buffer with @code{write-region}. If the text to be written
+cannot be safely encoded using the coding system specified by this
+variable, these operations select an alternative encoding by calling
+the function @code{select-safe-coding-system} (@pxref{User-Chosen
+Coding Systems}). If selecting a different encoding requires to ask
+the user to specify a coding system, @code{buffer-file-coding-system}
+is updated to the newly selected coding system.
+
+@code{buffer-file-coding-system} does @emph{not} affect sending text
to a subprocess.
@end defvar
@defvar save-buffer-coding-system
-@tindex save-buffer-coding-system
-This variable specifies the coding system for saving the buffer---but it
-is not used for @code{write-region}.
+This variable specifies the coding system for saving the buffer (by
+overriding @code{buffer-file-coding-system}). Note that it is not used
+for @code{write-region}.
When a command to save the buffer starts out to use
-@code{save-buffer-coding-system}, and that coding system cannot handle
+@code{buffer-file-coding-system} (or @code{save-buffer-coding-system}),
+and that coding system cannot handle
the actual text in the buffer, the command asks the user to choose
-another coding system. After that happens, the command also updates
-@code{save-buffer-coding-system} to represent the coding system that the
-user specified.
+another coding system (by calling @code{select-safe-coding-system}).
+After that happens, the command also updates
+@code{buffer-file-coding-system} to represent the coding system that
+the user specified.
@end defvar
@defvar last-coding-system-used
-@tindex last-coding-system-used
I/O operations for files and subprocesses set this variable to the
coding system name that was used. The explicit encoding and decoding
functions (@pxref{Explicit Encoding}) set it too.
The variable @code{selection-coding-system} specifies how to encode
selections for the window system. @xref{Window System Selections}.
+@defvar file-name-coding-system
+The variable @code{file-name-coding-system} specifies the coding
+system to use for encoding file names. Emacs encodes file names using
+that coding system for all file operations. If
+@code{file-name-coding-system} is @code{nil}, Emacs uses a default
+coding system determined by the selected language environment. In the
+default language environment, any non-@acronym{ASCII} characters in
+file names are not encoded specially; they appear in the file system
+using the internal Emacs representation.
+@end defvar
+
+ @strong{Warning:} if you change @code{file-name-coding-system} (or
+the language environment) in the middle of an Emacs session, problems
+can result if you have already visited files whose names were encoded
+using the earlier coding system and are handled differently under the
+new coding system. If you try to save one of these buffers under the
+visited file name, saving may use the wrong file name, or it may get
+an error. If such a problem happens, use @kbd{C-x C-w} to specify a
+new file name for that buffer.
+
@node Lisp and Coding Systems
@subsection Coding Systems in Lisp
Here are the Lisp facilities for working with coding systems:
@defun coding-system-list &optional base-only
-@tindex coding-system-list
This function returns a list of all coding system names (symbols). If
@var{base-only} is non-@code{nil}, the value includes only the
-base coding systems. Otherwise, it includes variant coding systems as well.
+base coding systems. Otherwise, it includes alias and variant coding
+systems as well.
@end defun
@defun coding-system-p object
-@tindex coding-system-p
This function returns @code{t} if @var{object} is a coding system
-name.
+name or @code{nil}.
@end defun
@defun check-coding-system coding-system
-@tindex check-coding-system
This function checks the validity of @var{coding-system}.
If that is valid, it returns @var{coding-system}.
Otherwise it signals an error with condition @code{coding-system-error}.
@end defun
@defun coding-system-change-eol-conversion coding-system eol-type
-@tindex coding-system-change-eol-conversion
This function returns a coding system which is like @var{coding-system}
except for its eol conversion, which is specified by @code{eol-type}.
@var{eol-type} should be @code{unix}, @code{dos}, @code{mac}, or
@code{nil}. If it is @code{nil}, the returned coding system determines
the end-of-line conversion from the data.
+
+@var{eol-type} may also be 0, 1 or 2, standing for @code{unix},
+@code{dos} and @code{mac}, respectively.
@end defun
@defun coding-system-change-text-conversion eol-coding text-coding
-@tindex coding-system-change-text-conversion
This function returns a coding system which uses the end-of-line
conversion of @var{eol-coding}, and the text conversion of
@var{text-coding}. If @var{text-coding} is @code{nil}, it returns
@end defun
@defun find-coding-systems-region from to
-@tindex find-coding-systems-region
This function returns a list of coding systems that could be used to
encode a text between @var{from} and @var{to}. All coding systems in
the list can safely encode any multibyte characters in that portion of
@end defun
@defun find-coding-systems-string string
-@tindex find-coding-systems-string
This function returns a list of coding systems that could be used to
encode the text of @var{string}. All coding systems in the list can
safely encode any multibyte characters in @var{string}. If the text
@end defun
@defun find-coding-systems-for-charsets charsets
-@tindex find-coding-systems-for-charsets
This function returns a list of coding systems that could be used to
encode all the character sets in the list @var{charsets}.
@end defun
@defun detect-coding-region start end &optional highest
-@tindex detect-coding-region
This function chooses a plausible coding system for decoding the text
-from @var{start} to @var{end}. This text should be ``raw bytes''
+from @var{start} to @var{end}. This text should be a byte sequence
(@pxref{Explicit Encoding}).
Normally this function returns a list of coding systems that could
return value is just one coding system, the one that is highest in
priority.
-If the region contains only @sc{ascii} characters, the value
-is @code{undecided} or @code{(undecided)}.
+If the region contains only @acronym{ASCII} characters, the value
+is @code{undecided} or @code{(undecided)}, or a variant specifying
+end-of-line conversion, if that can be deduced from the text.
@end defun
-@defun detect-coding-string string highest
-@tindex detect-coding-string
+@defun detect-coding-string string &optional highest
This function is like @code{detect-coding-region} except that it
operates on the contents of @var{string} instead of bytes in the buffer.
@end defun
- @xref{Process Information}, for how to examine or set the coding
-systems used for I/O to a subprocess.
+ @xref{Coding systems for a subprocess,, Process Information}, in
+particular the description of the functions
+@code{process-coding-system} and @code{set-process-coding-system}, for
+how to examine or set the coding systems used for I/O to a subprocess.
@node User-Chosen Coding Systems
@subsection User-Chosen Coding Systems
-@tindex select-safe-coding-system
-@defun select-safe-coding-system from to &optional preferred-coding-system
-This function selects a coding system for encoding the text between
-@var{from} and @var{to}, asking the user to choose if necessary.
-
-The optional argument @var{preferred-coding-system} specifies a coding
-system to try first. If that one can handle the text in the specified
-region, then it is used. If this argument is omitted, the current
-buffer's value of @code{buffer-file-coding-system} is tried first.
-
-If the region contains some multibyte characters that the preferred
-coding system cannot encode, this function asks the user to choose from
-a list of coding systems which can encode the text, and returns the
-user's choice.
-
-One other kludgy feature: if @var{from} is a string, the string is the
-target text, and @var{to} is ignored.
+@cindex select safe coding system
+@defun select-safe-coding-system from to &optional default-coding-system accept-default-p file
+This function selects a coding system for encoding specified text,
+asking the user to choose if necessary. Normally the specified text
+is the text in the current buffer between @var{from} and @var{to}. If
+@var{from} is a string, the string specifies the text to encode, and
+@var{to} is ignored.
+
+If @var{default-coding-system} is non-@code{nil}, that is the first
+coding system to try; if that can handle the text,
+@code{select-safe-coding-system} returns that coding system. It can
+also be a list of coding systems; then the function tries each of them
+one by one. After trying all of them, it next tries the current
+buffer's value of @code{buffer-file-coding-system} (if it is not
+@code{undecided}), then the value of
+@code{default-buffer-file-coding-system} and finally the user's most
+preferred coding system, which the user can set using the command
+@code{prefer-coding-system} (@pxref{Recognize Coding,, Recognizing
+Coding Systems, emacs, The GNU Emacs Manual}).
+
+If one of those coding systems can safely encode all the specified
+text, @code{select-safe-coding-system} chooses it and returns it.
+Otherwise, it asks the user to choose from a list of coding systems
+which can encode all the text, and returns the user's choice.
+
+@var{default-coding-system} can also be a list whose first element is
+t and whose other elements are coding systems. Then, if no coding
+system in the list can handle the text, @code{select-safe-coding-system}
+queries the user immediately, without trying any of the three
+alternatives described above.
+
+The optional argument @var{accept-default-p}, if non-@code{nil},
+should be a function to determine whether a coding system selected
+without user interaction is acceptable. @code{select-safe-coding-system}
+calls this function with one argument, the base coding system of the
+selected coding system. If @var{accept-default-p} returns @code{nil},
+@code{select-safe-coding-system} rejects the silently selected coding
+system, and asks the user to select a coding system from a list of
+possible candidates.
+
+@vindex select-safe-coding-system-accept-default-p
+If the variable @code{select-safe-coding-system-accept-default-p} is
+non-@code{nil}, its value overrides the value of
+@var{accept-default-p}.
+
+As a final step, before returning the chosen coding system,
+@code{select-safe-coding-system} checks whether that coding system is
+consistent with what would be selected if the contents of the region
+were read from a file. (If not, this could lead to data corruption in
+a file subsequently re-visited and edited.) Normally,
+@code{select-safe-coding-system} uses @code{buffer-file-name} as the
+file for this purpose, but if @var{file} is non-@code{nil}, it uses
+that file instead (this can be relevant for @code{write-region} and
+similar functions). If it detects an apparent inconsistency,
+@code{select-safe-coding-system} queries the user before selecting the
+coding system.
@end defun
Here are two functions you can use to let the user specify a coding
system, with completion. @xref{Completion}.
@defun read-coding-system prompt &optional default
-@tindex read-coding-system
This function reads a coding system using the minibuffer, prompting with
string @var{prompt}, and returns the coding system name as a symbol. If
the user enters null input, @var{default} specifies which coding system
@end defun
@defun read-non-nil-coding-system prompt
-@tindex read-non-nil-coding-system
This function reads a coding system using the minibuffer, prompting with
string @var{prompt}, and returns the coding system name as a symbol. If
the user tries to enter null input, it asks the user to try again.
@code{coding-system-for-read} and @code{coding-system-for-write}
(@pxref{Specifying Coding Systems}).
+@defvar auto-coding-regexp-alist
+This variable is an alist of text patterns and corresponding coding
+systems. Each element has the form @code{(@var{regexp}
+. @var{coding-system})}; a file whose first few kilobytes match
+@var{regexp} is decoded with @var{coding-system} when its contents are
+read into a buffer. The settings in this alist take priority over
+@code{coding:} tags in the files and the contents of
+@code{file-coding-system-alist} (see below). The default value is set
+so that Emacs automatically recognizes mail files in Babyl format and
+reads them with no code conversions.
+@end defvar
+
@defvar file-coding-system-alist
-@tindex file-coding-system-alist
This variable is an alist that specifies the coding systems to use for
reading and writing particular files. Each element has the form
@code{(@var{pattern} . @var{coding})}, where @var{pattern} is a regular
specifies the coding system for decoding, and its @sc{cdr} specifies the
coding system for encoding.
-If @var{coding} is a function name, the function must return a coding
-system or a cons cell containing two coding systems. This value is used
-as described above.
+If @var{coding} is a function name, the function should take one
+argument, a list of all arguments passed to
+@code{find-operation-coding-system}. It must return a coding system
+or a cons cell containing two coding systems. This value has the same
+meaning as described above.
@end defvar
@defvar process-coding-system-alist
-@tindex process-coding-system-alist
This variable is an alist specifying which coding systems to use for a
subprocess, depending on which program is running in the subprocess. It
works like @code{file-coding-system-alist}, except that @var{pattern} is
rather than @code{undecided} or @code{latin-1}.
@defvar network-coding-system-alist
-@tindex network-coding-system-alist
This variable is an alist that specifies the coding system to use for
network streams. It works much like @code{file-coding-system-alist},
with the difference that the @var{pattern} in an element may be either a
@end defvar
@defvar default-process-coding-system
-@tindex default-process-coding-system
This variable specifies the coding systems to use for subprocess (and
network stream) input and output, when nothing else specifies what to
do.
the subprocess, and @var{output-coding} applies to output to it.
@end defvar
+@defvar auto-coding-functions
+This variable holds a list of functions that try to determine a
+coding system for a file based on its undecoded contents.
+
+Each function in this list should be written to look at text in the
+current buffer, but should not modify it in any way. The buffer will
+contain undecoded text of parts of the file. Each function should
+take one argument, @var{size}, which tells it how many characters to
+look at, starting from point. If the function succeeds in determining
+a coding system for the file, it should return that coding system.
+Otherwise, it should return @code{nil}.
+
+If a file has a @samp{coding:} tag, that takes precedence, so these
+functions won't be called.
+@end defvar
+
@defun find-operation-coding-system operation &rest arguments
-@tindex find-operation-coding-system
This function returns the coding system to use (by default) for
performing @var{operation} with @var{arguments}. The value has this
form:
@example
-(@var{decoding-system} @var{encoding-system})
+(@var{decoding-system} . @var{encoding-system})
@end example
The first element, @var{decoding-system}, is the coding system to use
@var{encoding-system} is the coding system for encoding (in case
@var{operation} does encoding).
-The argument @var{operation} should be a symbol, one of
-@code{insert-file-contents}, @code{write-region}, @code{call-process},
-@code{call-process-region}, @code{start-process}, or
-@code{open-network-stream}. These are the names of the Emacs I/O primitives
-that can do coding system conversion.
+The argument @var{operation} should be a symbol, any one of
+@code{insert-file-contents}, @code{write-region},
+@code{start-process}, @code{call-process}, @code{call-process-region},
+or @code{open-network-stream}. These are the names of the Emacs I/O
+primitives that can do coding system conversion.
The remaining arguments should be the same arguments that might be given
to that I/O primitive. Depending on the primitive, one of those
target. For @code{open-network-stream}, the target is the service name
or port number.
-This function looks up the target in @code{file-coding-system-alist},
-@code{process-coding-system-alist}, or
-@code{network-coding-system-alist}, depending on @var{operation}.
-@xref{Default Coding Systems}.
+Depending on @var{operation}, this function looks up the target in
+@code{file-coding-system-alist}, @code{process-coding-system-alist},
+or @code{network-coding-system-alist}.
@end defun
@node Specifying Coding Systems
@code{coding-system-for-write}.
@defvar coding-system-for-read
-@tindex coding-system-for-read
If this variable is non-@code{nil}, it specifies the coding system to
use for reading a file, or for input from a synchronous subprocess.
@example
;; @r{Read the file with no character code conversion.}
-;; @r{Assume @sc{crlf} represents end-of-line.}
-(let ((coding-system-for-write 'emacs-mule-dos))
+;; @r{Assume @acronym{crlf} represents end-of-line.}
+(let ((coding-system-for-read 'emacs-mule-dos))
(insert-file-contents filename))
@end example
@end defvar
@defvar coding-system-for-write
-@tindex coding-system-for-write
This works much like @code{coding-system-for-read}, except that it
applies to output rather than input. It affects writing to files,
as well as sending output to subprocesses and net connections.
@end defvar
@defvar inhibit-eol-conversion
-@tindex inhibit-eol-conversion
When this variable is non-@code{nil}, no end-of-line conversion is done,
no matter which coding system is specified. This applies to all the
Emacs I/O and subprocess primitives, and to the explicit encoding and
You can also explicitly encode and decode text using the functions
in this section.
-@cindex raw bytes
The result of encoding, and the input to decoding, are not ordinary
-text. They are ``raw bytes''---bytes that represent text in the same
-way that an external file would. When a buffer contains raw bytes, it
-is most natural to mark that buffer as using unibyte representation,
-using @code{set-buffer-multibyte} (@pxref{Selecting a Representation}),
-but this is not required. If the buffer's contents are only temporarily
-raw, leave the buffer multibyte, which will be correct after you decode
-them.
-
- The usual way to get raw bytes in a buffer, for explicit decoding, is
-to read them from a file with @code{insert-file-contents-literally}
-(@pxref{Reading from Files}) or specify a non-@code{nil} @var{rawfile}
-argument when visiting a file with @code{find-file-noselect}.
-
- The usual way to use the raw bytes that result from explicitly
-encoding text is to copy them to a file or process---for example, to
-write them with @code{write-region} (@pxref{Writing to Files}), and
-suppress encoding for that @code{write-region} call by binding
-@code{coding-system-for-write} to @code{no-conversion}.
-
- Raw bytes typically contain stray individual bytes with values in the
-range 128 through 255, that are legitimate only as part of multibyte
-sequences. Even if the buffer is multibyte, Emacs treats each such
-individual byte as a character and uses the byte value as its character
-code. In this way, character codes 128 through 255 can be found in a
-multibyte buffer, even though they are not legitimate multibyte
-character codes.
-
- Raw bytes sometimes contain overlong byte-sequences that look like a
-proper multibyte character plus extra superfluous trailing codes. For
-most purposes, Emacs treats such a sequence in a buffer or string as a
-single character, and if you look at its character code, you get the
-value that corresponds to the multibyte character
-sequence---disregarding the extra trailing codes. This is not quite
-clean, but raw bytes are used only in limited ways, so as a practical
-matter it is not worth the trouble to treat this case differently.
-
- When a multibyte buffer contains illegitimate byte sequences,
-sometimes insertion or deletion can cause them to coalesce into a
-legitimate multibyte character. For example, suppose the buffer
-contains the sequence 129 68 192, 68 being the character @samp{D}. If
-you delete the @samp{D}, the bytes 129 and 192 become adjacent, and thus
-become one multibyte character (Latin-1 A with grave accent). Point
-moves to one side or the other of the character, since it cannot be
-within a character. Don't be alarmed by this.
-
- Some really peculiar situations prevent proper coalescence. For
-example, if you narrow the buffer so that the accessible portion begins
-just before the @samp{D}, then delete the @samp{D}, the two surrounding
-bytes cannot coalesce because one of them is outside the accessible
-portion of the buffer. In this case, the deletion cannot be done, so
-@code{delete-region} signals an error.
+text. They logically consist of a series of byte values; that is, a
+series of characters whose codes are in the range 0 through 255. In a
+multibyte buffer or string, character codes 128 through 159 are
+represented by multibyte sequences, but this is invisible to Lisp
+programs.
+
+ The usual way to read a file into a buffer as a sequence of bytes, so
+you can decode the contents explicitly, is with
+@code{insert-file-contents-literally} (@pxref{Reading from Files});
+alternatively, specify a non-@code{nil} @var{rawfile} argument when
+visiting a file with @code{find-file-noselect}. These methods result in
+a unibyte buffer.
+
+ The usual way to use the byte sequence that results from explicitly
+encoding text is to copy it to a file or process---for example, to write
+it with @code{write-region} (@pxref{Writing to Files}), and suppress
+encoding by binding @code{coding-system-for-write} to
+@code{no-conversion}.
Here are the functions to perform explicit encoding or decoding. The
-decoding functions produce ``raw bytes''; the encoding functions are
-meant to operate on ``raw bytes''. All of these functions discard text
-properties.
+decoding functions produce sequences of bytes; the encoding functions
+are meant to operate on sequences of bytes. All of these functions
+discard text properties.
-@defun encode-coding-region start end coding-system
-@tindex encode-coding-region
-This function encodes the text from @var{start} to @var{end} according
+@deffn Command encode-coding-region start end coding-system
+This command encodes the text from @var{start} to @var{end} according
to coding system @var{coding-system}. The encoded text replaces the
-original text in the buffer. The result of encoding is ``raw bytes,''
-but the buffer remains multibyte if it was multibyte before.
-@end defun
+original text in the buffer. The result of encoding is logically a
+sequence of bytes, but the buffer remains multibyte if it was multibyte
+before.
-@defun encode-coding-string string coding-system
-@tindex encode-coding-string
+This command returns the length of the encoded text.
+@end deffn
+
+@defun encode-coding-string string coding-system &optional nocopy
This function encodes the text in @var{string} according to coding
system @var{coding-system}. It returns a new string containing the
-encoded text. The result of encoding is a unibyte string of ``raw bytes.''
+encoded text, except when @var{nocopy} is non-@code{nil}, in which
+case the function may return @var{string} itself if the encoding
+operation is trivial. The result of encoding is a unibyte string.
@end defun
-@defun decode-coding-region start end coding-system
-@tindex decode-coding-region
-This function decodes the text from @var{start} to @var{end} according
+@deffn Command decode-coding-region start end coding-system
+This command decodes the text from @var{start} to @var{end} according
to coding system @var{coding-system}. The decoded text replaces the
original text in the buffer. To make explicit decoding useful, the text
-before decoding ought to be ``raw bytes.''
-@end defun
+before decoding ought to be a sequence of byte values, but both
+multibyte and unibyte buffers are acceptable.
+
+This command returns the length of the decoded text.
+@end deffn
-@defun decode-coding-string string coding-system
-@tindex decode-coding-string
+@defun decode-coding-string string coding-system &optional nocopy
This function decodes the text in @var{string} according to coding
system @var{coding-system}. It returns a new string containing the
-decoded text. To make explicit decoding useful, the contents of
-@var{string} ought to be ``raw bytes.''
+decoded text, except when @var{nocopy} is non-@code{nil}, in which
+case the function may return @var{string} itself if the decoding
+operation is trivial. To make explicit decoding useful, the contents
+of @var{string} ought to be a sequence of byte values, but a multibyte
+string is acceptable.
+@end defun
+
+@defun decode-coding-inserted-region from to filename &optional visit beg end replace
+This function decodes the text from @var{from} to @var{to} as if
+it were being read from file @var{filename} using @code{insert-file-contents}
+using the rest of the arguments provided.
+
+The normal way to use this function is after reading text from a file
+without decoding, if you decide you would rather have decoded it.
+Instead of deleting the text and reading it again, this time with
+decoding, you can call this function.
@end defun
@node Terminal I/O Encoding
terminal.
@defun keyboard-coding-system
-@tindex keyboard-coding-system
This function returns the coding system that is in use for decoding
keyboard input---or @code{nil} if no coding system is to be used.
@end defun
-@defun set-keyboard-coding-system coding-system
-@tindex set-keyboard-coding-system
-This function specifies @var{coding-system} as the coding system to
+@deffn Command set-keyboard-coding-system coding-system
+This command specifies @var{coding-system} as the coding system to
use for decoding keyboard input. If @var{coding-system} is @code{nil},
that means do not decode keyboard input.
-@end defun
+@end deffn
@defun terminal-coding-system
-@tindex terminal-coding-system
This function returns the coding system that is in use for encoding
terminal output---or @code{nil} for no encoding.
@end defun
-@defun set-terminal-coding-system coding-system
-@tindex set-terminal-coding-system
-This function specifies @var{coding-system} as the coding system to use
+@deffn Command set-terminal-coding-system coding-system
+This command specifies @var{coding-system} as the coding system to use
for encoding terminal output. If @var{coding-system} is @code{nil},
that means do not encode terminal output.
-@end defun
+@end deffn
@node MS-DOS File Types
@subsection MS-DOS File Types
On MS-DOS and Microsoft Windows, Emacs guesses the appropriate
end-of-line conversion for a file by looking at the file's name. This
-feature classifies fils as @dfn{text files} and @dfn{binary files}. By
+feature classifies files as @dfn{text files} and @dfn{binary files}. By
``binary file'' we mean a file of literal byte values that are not
necessarily meant to be characters; Emacs does no end-of-line conversion
and no character code conversion for them. On the other hand, the bytes
@section Input Methods
@cindex input methods
- @dfn{Input methods} provide convenient ways of entering non-@sc{ascii}
+ @dfn{Input methods} provide convenient ways of entering non-@acronym{ASCII}
characters from the keyboard. Unlike coding systems, which translate
-non-@sc{ascii} characters to and from encodings meant to be read by
+non-@acronym{ASCII} characters to and from encodings meant to be read by
programs, input methods provide human-friendly commands. (@xref{Input
Methods,,, emacs, The GNU Emacs Manual}, for information on how users
use input methods to enter text.) How to define input methods is not
Each input method has a name, which is currently a string;
in the future, symbols may also be usable as input method names.
-@tindex current-input-method
@defvar current-input-method
This variable holds the name of the input method now active in the
current buffer. (It automatically becomes local in each buffer when set
buffer now.
@end defvar
-@tindex default-input-method
-@defvar default-input-method
+@defopt default-input-method
This variable holds the default input method for commands that choose an
input method. Unlike @code{current-input-method}, this variable is
normally global.
-@end defvar
+@end defopt
-@tindex set-input-method
-@defun set-input-method input-method
-This function activates input method @var{input-method} for the current
+@deffn Command set-input-method input-method
+This command activates input method @var{input-method} for the current
buffer. It also sets @code{default-input-method} to @var{input-method}.
-If @var{input-method} is @code{nil}, this function deactivates any input
+If @var{input-method} is @code{nil}, this command deactivates any input
method for the current buffer.
-@end defun
+@end deffn
-@tindex read-input-method-name
@defun read-input-method-name prompt &optional default inhibit-null
This function reads an input method name with the minibuffer, prompting
with @var{prompt}. If @var{default} is non-@code{nil}, that is returned
The returned value is a string.
@end defun
-@tindex input-method-alist
@defvar input-method-alist
This variable defines all the supported input methods.
Each element defines one input method, and should have the form:
environment this input method is recommended for. (That serves only for
documentation purposes.)
-@var{title} is a string to display in the mode line while this method is
-active. @var{description} is a string describing this method and what
-it is good for.
-
@var{activate-func} is a function to call to activate this method. The
@var{args}, if any, are passed as arguments to @var{activate-func}. All
told, the arguments to @var{activate-func} are @var{input-method} and
the @var{args}.
+
+@var{title} is a string to display in the mode line while this method is
+active. @var{description} is a string describing this method and what
+it is good for.
@end defvar
The fundamental interface to input methods is through the
-variable @code{input-method-function}. @xref{Reading One Event}.
+variable @code{input-method-function}. @xref{Reading One Event},
+and @ref{Invoking the Input Method}.
+
+@node Locales
+@section Locales
+@cindex locale
+
+ POSIX defines a concept of ``locales'' which control which language
+to use in language-related features. These Emacs variables control
+how Emacs interacts with these features.
+
+@defvar locale-coding-system
+@tindex locale-coding-system
+@cindex keyboard input decoding on X
+This variable specifies the coding system to use for decoding system
+error messages and---on X Window system only---keyboard input, for
+encoding the format argument to @code{format-time-string}, and for
+decoding the return value of @code{format-time-string}.
+@end defvar
+
+@defvar system-messages-locale
+@tindex system-messages-locale
+This variable specifies the locale to use for generating system error
+messages. Changing the locale can cause messages to come out in a
+different language or in a different orthography. If the variable is
+@code{nil}, the locale is specified by environment variables in the
+usual POSIX fashion.
+@end defvar
+
+@defvar system-time-locale
+@tindex system-time-locale
+This variable specifies the locale to use for formatting time values.
+Changing the locale can cause messages to appear according to the
+conventions of a different language. If the variable is @code{nil}, the
+locale is specified by environment variables in the usual POSIX fashion.
+@end defvar
+
+@defun locale-info item
+This function returns locale data @var{item} for the current POSIX
+locale, if available. @var{item} should be one of these symbols:
+
+@table @code
+@item codeset
+Return the character set as a string (locale item @code{CODESET}).
+
+@item days
+Return a 7-element vector of day names (locale items
+@code{DAY_1} through @code{DAY_7});
+
+@item months
+Return a 12-element vector of month names (locale items @code{MON_1}
+through @code{MON_12}).
+
+@item paper
+Return a list @code{(@var{width} @var{height})} for the default paper
+size measured in millimeters (locale items @code{PAPER_WIDTH} and
+@code{PAPER_HEIGHT}).
+@end table
+
+If the system can't provide the requested information, or if
+@var{item} is not one of those symbols, the value is @code{nil}. All
+strings in the return value are decoded using
+@code{locale-coding-system}. @xref{Locales,,, libc, The GNU Libc Manual},
+for more information about locales and locale items.
+@end defun
+
+@ignore
+ arch-tag: be705bf8-941b-4c35-84fc-ad7d20ddb7cb
+@end ignore