GNU Info
(emacs)Specify Coding
Specifying a Coding System
==========================
In cases where Emacs does not automatically choose the right coding
system, you can use these commands to specify one:
`C-x <RET> f CODING <RET>'
Use coding system CODING for the visited file in the current
buffer.
`C-x <RET> c CODING <RET>'
Specify coding system CODING for the immediately following command.
`C-x <RET> k CODING <RET>'
Use coding system CODING for keyboard input.
`C-x <RET> t CODING <RET>'
Use coding system CODING for terminal output.
`C-x <RET> p INPUT-CODING <RET> OUTPUT-CODING <RET>'
Use coding systems INPUT-CODING and OUTPUT-CODING for subprocess
input and output in the current buffer.
`C-x <RET> x CODING <RET>'
Use coding system CODING for transferring selections to and from
other programs through the window system.
`C-x <RET> X CODING <RET>'
Use coding system CODING for transferring _one_ selection--the
next one--to or from the window system.
The command `C-x <RET> f' (`set-buffer-file-coding-system')
specifies the file coding system for the current buffer--in other
words, which coding system to use when saving or rereading the visited
file. You specify which coding system using the minibuffer. Since this
command applies to a file you have already visited, it affects only the
way the file is saved.
Another way to specify the coding system for a file is when you visit
the file. First use the command `C-x <RET> c'
(`universal-coding-system-argument'); this command uses the minibuffer
to read a coding system name. After you exit the minibuffer, the
specified coding system is used for _the immediately following command_.
So if the immediately following command is `C-x C-f', for example,
it reads the file using that coding system (and records the coding
system for when the file is saved). Or if the immediately following
command is `C-x C-w', it writes the file using that coding system.
Other file commands affected by a specified coding system include `C-x
C-i' and `C-x C-v', as well as the other-window variants of `C-x C-f'.
`C-x <RET> c' also affects commands that start subprocesses,
including `M-x shell' (Note: Shell).
However, if the immediately following command does not use the coding
system, then `C-x <RET> c' ultimately has no effect.
An easy way to visit a file with no conversion is with the `M-x
find-file-literally' command. Note: Visiting.
The variable `default-buffer-file-coding-system' specifies the
choice of coding system to use when you create a new file. It applies
when you find a new file, and when you create a buffer and then save it
in a file. Selecting a language environment typically sets this
variable to a good choice of default coding system for that language
environment.
The command `C-x <RET> t' (`set-terminal-coding-system') specifies
the coding system for terminal output. If you specify a character code
for terminal output, all characters output to the terminal are
translated into that coding system.
This feature is useful for certain character-only terminals built to
support specific languages or character sets--for example, European
terminals that support one of the ISO Latin character sets. You need to
specify the terminal coding system when using multibyte text, so that
Emacs knows which characters the terminal can actually handle.
By default, output to the terminal is not translated at all, unless
Emacs can deduce the proper coding system from your terminal type or
your locale specification (Note: Language Environments).
The command `C-x <RET> k' (`set-keyboard-coding-system') or the
Custom option `keyboard-coding-system' specifies the coding system for
keyboard input. Character-code translation of keyboard input is useful
for terminals with keys that send non-ASCII graphic characters--for
example, some terminals designed for ISO Latin-1 or subsets of it.
By default, keyboard input is not translated at all.
There is a similarity between using a coding system translation for
keyboard input, and using an input method: both define sequences of
keyboard input that translate into single characters. However, input
methods are designed to be convenient for interactive use by humans, and
the sequences that are translated are typically sequences of ASCII
printing characters. Coding systems typically translate sequences of
non-graphic characters.
The command `C-x <RET> x' (`set-selection-coding-system') specifies
the coding system for sending selected text to the window system, and
for receiving the text of selections made in other applications. This
command applies to all subsequent selections, until you override it by
using the command again. The command `C-x <RET> X'
(`set-next-selection-coding-system') specifies the coding system for
the next selection made in Emacs or read by Emacs.
The command `C-x <RET> p' (`set-buffer-process-coding-system')
specifies the coding system for input and output to a subprocess. This
command applies to the current buffer; normally, each subprocess has its
own buffer, and thus you can use this command to specify translation to
and from a particular subprocess by giving the command in the
corresponding buffer.
The default for translation of process input and output depends on
the current language environment.
The variable `file-name-coding-system' specifies a coding system to
use for encoding file names. If you set the variable to a coding
system name (as a Lisp symbol or a string), Emacs encodes file names
using that coding system for all file operations. This makes it
possible to use non-ASCII characters in file names--or, at least, those
non-ASCII characters which the specified coding system can encode.
If `file-name-coding-system' is `nil', Emacs uses a default coding
system determined by the selected language environment. In the default
language environment, any non-ASCII characters in file names are not
encoded specially; they appear in the file system using the internal
Emacs representation.
*Warning:* if you change `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 cannot be encoded (or are encoded
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 `C-x C-w'
to specify a new file name for that buffer.
The variable `locale-coding-system' specifies a coding system to use
when encoding and decoding system strings such as system error messages
and `format-time-string' formats and time stamps. That coding system
is also used for decoding non-ASCII keyboard input on X Window systems.
You should choose a coding system that is compatible with the
underlying system's text representation, which is normally specified by
one of the environment variables `LC_ALL', `LC_CTYPE', and `LANG'.
(The first one, in the order specified above, whose value is nonempty
is the one that determines the text representation.)
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