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This section describes variables that specify the default coding system for certain files or when running certain subprograms, and the function that I/O operations use to access them.
The idea of these variables is that you set them once and for all to the
defaults you want, and then do not change them again. To specify a
particular coding system for a particular operation in a Lisp program, don't
change these variables; instead, override them using
coding-system-for-read and coding-system-for-write
(voir la section Specifying a Coding System for One Operation).
This variable is an alist of text patterns and corresponding coding
systems. Each element has the form (regexp
. coding-system); a file whose first few kilobytes match regexp
is decoded with coding-system when its contents are read into a
buffer. The settings in this alist take priority over coding: tags
in the files and the contents of 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.
This variable is an alist that specifies the coding systems to use for
reading and writing particular files. Each element has the form
(pattern . coding), where pattern is a regular
expression that matches certain file names. The element applies to file
names that match pattern.
The CDR of the element, coding, should be either a coding system, a cons cell containing two coding systems, or a function name (a symbol with a function definition). If coding is a coding system, that coding system is used for both reading the file and writing it. If coding is a cons cell containing two coding systems, its CAR specifies the coding system for decoding, and its CDR specifies the coding system for encoding.
If coding is a function name, the function should take one argument, a
list of all arguments passed to 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.
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 file-coding-system-alist, except that pattern is
matched against the program name used to start the subprocess. The coding
system or systems specified in this alist are used to initialize the coding
systems used for I/O to the subprocess, but you can specify other coding
systems later using set-process-coding-system.
Warning: Coding systems such as undecided, which determine
the coding system from the data, do not work entirely reliably with
asynchronous subprocess output. This is because Emacs handles asynchronous
subprocess output in batches, as it arrives. If the coding system leaves
the character code conversion unspecified, or leaves the end-of-line
conversion unspecified, Emacs must try to detect the proper conversion from
one batch at a time, and this does not always work.
Therefore, with an asynchronous subprocess, if at all possible, use a coding
system which determines both the character code conversion and the end of
line conversion—that is, one like latin-1-unix, rather than
undecided or latin-1.
This variable is an alist that specifies the coding system to use for
network streams. It works much like file-coding-system-alist, with
the difference that the pattern in an element may be either a port
number or a regular expression. If it is a regular expression, it is
matched against the network service name used to open the network stream.
This variable specifies the coding systems to use for subprocess (and network stream) input and output, when nothing else specifies what to do.
The value should be a cons cell of the form (input-coding
. output-coding). Here input-coding applies to input from the
subprocess, and output-coding applies to output to it.
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, 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 nil.
If a file has a ‘coding:’ tag, that takes precedence, so these functions won't be called.
This function returns the coding system to use (by default) for performing operation with arguments. The value has this form:
(decoding-system . encoding-system) |
The first element, decoding-system, is the coding system to use for decoding (in case operation does decoding), and encoding-system is the coding system for encoding (in case operation does encoding).
The argument operation is a symbol, one of write-region,
start-process, call-process, call-process-region,
insert-file-contents, or open-network-stream. These are the
names of the Emacs I/O primitives that can do character code and eol
conversion.
The remaining arguments should be the same arguments that might be given to
the corresponding I/O primitive. Depending on the primitive, one of those
arguments is selected as the target. For example, if operation
does file I/O, whichever argument specifies the file name is the target.
For subprocess primitives, the process name is the target. For
open-network-stream, the target is the service name or port number.
Depending on operation, this function looks up the target in
file-coding-system-alist, process-coding-system-alist, or
network-coding-system-alist. If the target is found in the alist,
find-operation-coding-system returns its association in the alist;
otherwise it returns nil.
If operation is insert-file-contents, the argument
corresponding to the target may be a cons cell of the form
(filename . buffer)). In that case, filename is a
file name to look up in file-coding-system-alist, and buffer is
a buffer that contains the file's contents (not yet decoded). If
file-coding-system-alist specifies a function to call for this file,
and that function needs to examine the file's contents (as it usually does),
it should examine the contents of buffer instead of reading the file.
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Ce document a été généré par Eric Reinbold le 13 Octobre 2007 en utilisant texi2html 1.78.