Commit 2b2ea6db authored by Richard M. Stallman's avatar Richard M. Stallman
Browse files

(Safe File Variables): Lots of clarification.

Renamed from Unsafe File Variables.
parent 9ca66103
2006-02-14 Richard M. Stallman <rms@gnu.org>
* custom.texi (Safe File Variables): Lots of clarification.
Renamed from Unsafe File Variables.
2006-02-14 Chong Yidong <cyd@stupidchicken.com>
* custom.texi (Unsafe File Variables): File variable confirmation
......
......@@ -1045,14 +1045,13 @@ buffer, and sets them to the values specified in the file.
@menu
* Specifying File Variables:: Specifying file local variables.
* Unsafe File Variables:: Handling local variables that may not
be safe.
* Safe File Variables:: Making sure file local variables are safe.
@end menu
@node Specifying File Variables
@subsubsection Specifying File Variables
There are two ways to specify local variable values: in the first
There are two ways to specify file local variable values: in the first
line, or with a local variables list. Here's how to specify them in the
first line:
......@@ -1098,7 +1097,7 @@ variables list and a @samp{-*-} line, Emacs processes @emph{everything}
in the @samp{-*-} line first, and @emph{everything} in the local
variables list afterward.
Here is an example of a local variables list:
Here is an example of a local variables list:
@example
;;; Local Variables: ***
......@@ -1179,52 +1178,52 @@ list need not take the time to search the whole file.
major mode of a buffer according to the file name and contents,
including the local variables list if any. @xref{Choosing Modes}.
@node Unsafe File Variables
@subsubsection Unsafe File Variables
File variables create a certain amount of risk; when you visit
someone else's file, its variables could affect your Emacs in
arbitrary ways. A special risk is posed by the @code{eval}
``variable,'' which can potentially execute arbitrary code, and
certain actual variables such as @code{load-path}.
Therefore, whenever Emacs encounters file variables that are not
known to be safe, it displays the entire list of variables defined in
that file, and asks you for confirmation before setting them. You can
type @samp{y} or @samp{SPC} to apply the local variables list, or
@samp{n} to ignore it.
When Emacs is run in batch mode (@pxref{Initial Options}), it
assumes that the answer is @samp{n}.
There is a set of file variables and values that are known to be
safe. For instance, it is safe to give @code{comment-column} or
@node Safe File Variables
@subsubsection Safety of File Variables
File-local variables can be dangerous; when you visit someone else's
file, there's no telling what its local variables list could do to
your Emacs. Improper values of the @code{eval} ``variable,'' and
other variables such as @code{load-path}, could execute Lisp code you
didn't intend to run.
Therefore, whenever Emacs encounters file local variable values that
are not known to be safe, it displays the file's entire local
variables list, and asks you for confirmation before setting them.
You can type @kbd{y} or @key{SPC} to put the local variables list into
effect, or @kbd{n} to ignore it. When Emacs is run in batch mode
(@pxref{Initial Options}), it can't really ask you, so it assumes the
answer @samp{n}.
Emacs normally recognizes certain variables/value pairs as safe.
For instance, it is safe to give @code{comment-column} or
@code{fill-column} any integer value. If a file specifies only safe
variable-value pairs, Emacs will not ask for confirmation before
setting them. You can also tell Emacs that a set of variable-value
pairs is safe, by entering @samp{!} at the file variables confirmation
prompt. In that case, Emacs will not ask for confirmation if it
encounters these variable-value pairs in the future. You can directly
edit the list of safe variable-value pairs by customizing
variable/value pairs, Emacs does not ask for confirmation before
setting them. Otherwise, you can tell Emacs to record that all the
variable/value pairs in the file are safe, by typing @kbd{!} at the
confirmation prompt. When Emacs encounters these variable/value pairs
subsequently, in the same file or others, it will assume they are
safe.
@vindex safe-local-variable-values
@cindex risky variable
Some variables, such as @code{load-path}, are considered
particularly @dfn{risky}: there is seldom any reason to specify them
as local variables, and changing them can be dangerous. Even if you
enter @kbd{!} at the confirmation prompt, Emacs will not record any
values as safe for these variables. If you really want to record safe
values for these variables, do it directly by customizing
@samp{safe-local-variable-values} (@pxref{Easy Customization}).
Some variables, such as @code{load-path}, are considered
@dfn{risky}: there is seldom any reason to specify them as file
variables, and changing them can be dangerous. Even if you enter
@samp{!} at the confirmation prompt, Emacs will not save these values
for the future. Therefore, you will be prompted each time the
variable is encountered. If you really want to allow such a variable,
you can avoid the prompt by editing @samp{safe-local-variable-values}.
@findex enable-local-variables
@vindex enable-local-variables
The variable @code{enable-local-variables} allows you to change the
way Emacs processes local variables. Its default value is @code{t},
which means the behavior described above. If you set the value to
@code{nil}, Emacs simply ignores local variables in files. Any other
value says to query you about each file that has local variables, even
if the variables are known to be safe.
which specifies the behavior described above. If it is @code{nil},
Emacs simply ignores all file local variables. Any other value says
to query you about each file that has local variables, without trying
to determine whether the values are known to be safe.
@findex enable-local-eval
@vindex enable-local-eval
The variable @code{enable-local-eval} controls whether Emacs
processes @code{eval} variables. The three possibilities for the
variable's value are @code{t}, @code{nil}, and anything else, just as
......@@ -1232,7 +1231,7 @@ for @code{enable-local-variables}. The default is @code{maybe}, which
is neither @code{t} nor @code{nil}, so normally Emacs does ask for
confirmation about processes @code{eval} variables.
@findex safe-local-eval-forms
@vindex safe-local-eval-forms
The @code{safe-local-eval-forms} is a customizable list of eval
forms which are safe to eval, so Emacs should not ask for
confirmation to evaluate these forms.
......
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