When Emacs visits a file, it automatically selects a major mode for the buffer based on information in the file name or in the file itself. It also processes local variables specified in the file text.
This function establishes the proper major mode and buffer-local variable bindings for the current buffer. First it calls
set-auto-mode(see below), then it runs
hack-local-variablesto parse, and bind or evaluate as appropriate, the file's local variables (see File Local Variables).
If the find-file argument to
normal-modeassumes that the
find-filefunction is calling it. In this case, it may process local variables in the ‘-*-’ line or at the end of the file. The variable
enable-local-variablescontrols whether to do so. See Local Variables in Files, for the syntax of the local variables section of a file.
If you run
normal-modeinteractively, the argument find-file is normally
nil. In this case,
normal-modeunconditionally processes any file local variables.
The function calls
set-auto-modeto choose a major mode. If this does not specify a mode, the buffer stays in the major mode determined by the default value of
This function selects the major mode that is appropriate for the current buffer. It bases its decision (in order of precedence) on the ‘-*-’ line, on any ‘mode:’ local variable near the end of a file, on the ‘#!’ line (using
interpreter-mode-alist), on the text at the beginning of the buffer (using
magic-mode-alist), and finally on the visited file name (using
auto-mode-alist). See How Major Modes are Chosen. If
set-auto-modedoes not check the ‘-*-’ line, or near the end of the file, for any mode tag.
There are some file types where it is not appropriate to scan the file contents for a mode specifier. For example, a tar archive may happen to contain, near the end of the file, a member file that has a local variables section specifying a mode for that particular file. This should not be applied to the containing tar file. Similarly, a tiff image file might just happen to contain a first line that seems to match the ‘-*-’ pattern. For these reasons, both these file extensions are members of the list
inhibit-local-variables-regexps. Add patterns to this list to prevent Emacs searching them for local variables of any kind (not just mode specifiers).
If keep-mode-if-same is non-
nil, this function does not call the mode command if the buffer is already in the proper major mode. For instance,
set-visited-file-namesets this to
tto avoid killing buffer local variables that the user may have set.
This function sets the major mode of buffer to the default value of
major-mode; if that is
nil, it uses the current buffer's major mode (if that is suitable). As an exception, if buffer's name is *scratch*, it sets the mode to
The low-level primitives for creating buffers do not use this function, but medium-level commands such as
find-file-noselectuse it whenever they create buffers.
This variable specifies major modes to use for scripts that specify a command interpreter in a ‘#!’ line. Its value is an alist with elements of the form
); this says to use mode mode if the file specifies an interpreter which matches
\\'. For example, one of the default elements is
("python[0-9.]*" . python-mode).
This variable's value is an alist with elements of the form
), where regexp is a regular expression and function is a function or
nil. After visiting a file,
set-auto-modecalls function if the text at the beginning of the buffer matches regexp and function is non-
nil; if function is
auto-mode-alistgets to decide the mode.
This works like
magic-mode-alist, except that it is handled only if
auto-mode-alistdoes not specify a mode for this file.
This variable contains an association list of file name patterns (regular expressions) and corresponding major mode commands. Usually, the file name patterns test for suffixes, such as ‘.el’ and ‘.c’, but this need not be the case. An ordinary element of the alist looks like
For example,(("\\`/tmp/fol/" . text-mode) ("\\.texinfo\\'" . texinfo-mode) ("\\.texi\\'" . texinfo-mode) ("\\.el\\'" . emacs-lisp-mode) ("\\.c\\'" . c-mode) ("\\.h\\'" . c-mode) ...)
When you visit a file whose expanded file name (see File Name Expansion), with version numbers and backup suffixes removed using
file-name-sans-versions(see File Name Components), matches a regexp,
set-auto-modecalls the corresponding mode-function. This feature enables Emacs to select the proper major mode for most files.
If an element of
auto-mode-alisthas the form
t), then after calling function, Emacs searches
auto-mode-alistagain for a match against the portion of the file name that did not match before. This feature is useful for uncompression packages: an entry of the form
t)can uncompress the file and then put the uncompressed file in the proper mode according to the name sans ‘.gz’.
Here is an example of how to prepend several pattern pairs to
auto-mode-alist. (You might use this sort of expression in your init file.)(setq auto-mode-alist (append ;; File name (within directory) starts with a dot. '(("/\\.[^/]*\\'" . fundamental-mode) ;; File name has no dot. ("/[^\\./]*\\'" . fundamental-mode) ;; File name ends in ‘.C’. ("\\.C\\'" . c++-mode)) auto-mode-alist))