@c This is part of the Emacs manual.
-@c Copyright (C) 1985, 86, 87, 93, 94, 95, 97, 2000 Free Software Foundation, Inc.
+@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2000, 2001,
+@c 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Major Modes, Indentation, International, Top
@chapter Major Modes
The least specialized major mode is called @dfn{Fundamental mode}.
This mode has no mode-specific redefinitions or variable settings, so
that each Emacs command behaves in its most general manner, and each
-option is in its default state. For editing text of a specific type
-that Emacs knows about, such as Lisp code or English text, you should
-switch to the appropriate major mode, such as Lisp mode or Text mode.
+user option variable is in its default state. For editing text of a
+specific type that Emacs knows about, such as Lisp code or English
+text, you should switch to the appropriate major mode, such as Lisp
+mode or Text mode.
Selecting a major mode changes the meanings of a few keys to become
more specifically adapted to the language being edited. The ones that
most of the time Emacs determines which mode to use based on the file
name or on special text in the file.
- Explicit selection of a new major mode is done with a @kbd{M-x} command.
-From the name of a major mode, add @code{-mode} to get the name of a
-command to select that mode. Thus, you can enter Lisp mode by executing
-@kbd{M-x lisp-mode}.
+ To explicitly select a new major, you use an @kbd{M-x} command.
+Take the name of a major mode and add @code{-mode} to get the name of
+the command to select that mode. Thus, you can enter Lisp mode by
+executing @kbd{M-x lisp-mode}.
@vindex auto-mode-alist
When you visit a file, Emacs usually chooses the right major mode based
@code{(@t{"\\.c\\'"} . c-mode)}, and it is responsible for selecting C
mode for files whose names end in @file{.c}. (Note that @samp{\\} is
needed in Lisp syntax to include a @samp{\} in the string, which must
-be used to suppress the special meaning of @samp{.} in regexps.) If the
-element has the form @code{(@var{regexp} @var{mode-function}
+be used to suppress the special meaning of @samp{.} in regexps.) If
+the element has the form @code{(@var{regexp} @var{mode-function}
@var{flag})} and @var{flag} is non-@code{nil}, then after calling
-@var{mode-function}, the suffix that matched @var{regexp} is discarded
-and the list is searched again for another match.
+@var{mode-function}, Emacs discards the suffix that matched
+@var{regexp} and searches the list again for another match.
- You can specify which major mode should be used for editing a certain
-file by a special sort of text in the first nonblank line of the file. The
+@vindex magic-mode-alist
+ Sometimes the major mode is determined from the way the file's text
+begins. The variable @code{magic-mode-alist} controls this. Its value
+is a list of elements of this form:
+
+@example
+(@var{regexp} . @var{mode-function})
+@end example
+
+@noindent
+This looks like an element of @code{auto-mode-alist}, but it doesn't work
+the same: this @var{regexp} is matched against the text at the start
+of the buffer, not against the file name. @code{magic-mode-alist}
+takes priority over @code{auto-mode-alist}.
+
+ You can specify the major mode to use for editing a certain file by
+special text in the first nonblank line of the file. The
mode name should appear in this line both preceded and followed by
@samp{-*-}. Other text may appear on the line as well. For example,
mode Emacs would choose automatically: use the command @kbd{M-x
normal-mode} to do this. This is the same function that
@code{find-file} calls to choose the major mode. It also processes
-the file's local variables list (if any).
+the file's @samp{-*-} line or local variables list (if any).
+@xref{File Variables}.
@vindex change-major-mode-with-file-name
The commands @kbd{C-x C-w} and @code{set-visited-file-name} change to
a new major mode if the new file name implies a mode (@pxref{Saving}).
+(@kbd{C-x C-s} does this too, if the buffer wasn't visiting a file.)
However, this does not happen if the buffer contents specify a major
mode, and certain ``special'' major modes do not allow the mode to
change. You can turn off this mode-changing feature by setting