@c Copyright (C) 1990-1995, 1998-1999, 2001-2012
@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
-@setfilename ../../info/files
@node Files, Backups and Auto-Saving, Documentation, Top
@comment node-name, next, previous, up
@chapter Files
In spite of the distinction between files and buffers, people often
refer to a file when they mean a buffer and vice-versa. Indeed, we say,
-``I am editing a file,'' rather than, ``I am editing a buffer that I
-will soon save as a file of the same name.'' Humans do not usually need
+``I am editing a file'', rather than, ``I am editing a buffer that I
+will soon save as a file of the same name''. Humans do not usually need
to make the distinction explicit. When dealing with a computer program,
however, it is good to keep the distinction in mind.
@defopt require-final-newline
This variable determines whether files may be written out that do
@emph{not} end with a newline. If the value of the variable is
-@code{t}, then @code{save-buffer} silently adds a newline at the end of
-the file whenever the buffer being saved does not already end in one.
-If the value of the variable is non-@code{nil}, but not @code{t}, then
-@code{save-buffer} asks the user whether to add a newline each time the
-case arises.
+@code{t}, then @code{save-buffer} silently adds a newline at the end
+of the buffer whenever it does not already end in one. If the value
+is @code{visit}, Emacs adds a missing newline just after it visits the
+file. If the value is @code{visit-save}, Emacs adds a missing newline
+both on visiting and on saving. For any other non-@code{nil} value,
+@code{save-buffer} asks the user whether to add a newline each time
+the case arises.
If the value of the variable is @code{nil}, then @code{save-buffer}
doesn't add newlines at all. @code{nil} is the default value, but a few
stored in the same directory as the file you are editing.
When you access files using NFS, there may be a small probability that
-you and another user will both lock the same file ``simultaneously.''
+you and another user will both lock the same file ``simultaneously''.
If this happens, it is possible for the two users to make changes
simultaneously, but Emacs will still warn the user who saves second.
Also, the detection of modification of a buffer visiting a file changed
File locking is not supported on some systems. On systems that do not
support it, the functions @code{lock-buffer}, @code{unlock-buffer} and
-@code{file-locked-p} do nothing and return @code{nil}.
+@code{file-locked-p} do nothing and return @code{nil}. It is also
+possible to disable locking, by setting the variable @code{create-lockfiles}.
+
+@defopt create-lockfiles
+If this variable is @code{nil}, Emacs does not lock files.
+@end defopt
@defun ask-user-about-lock file other-user
This function is called when the user tries to modify @var{file}, but it
other I/O device).
@end defun
+@defun file-equal-p file1 file2
+This function returns @code{t} if the files @var{file1} and
+@var{file2} name the same file. If @var{file1} or @var{file2} does
+not exist, the return value is unspecified.
+@end defun
+
+@defun file-in-directory-p file dir
+This function returns @code{t} if @var{file} is a file in directory
+@var{dir}, or in a subdirectory of @var{dir}. It also returns
+@code{t} if @var{file} and @var{dir} are the same directory. It
+compares the @code{file-truename} values of the two directories
+(@pxref{Truenames}). If @var{dir} does not name an existing
+directory, the return value is @code{nil}.
+@end defun
+
@node Truenames
@subsection Truenames
@cindex truename (of file)
@xref{Changing Files}, for functions that change file permissions,
such as @code{set-file-modes}.
+
+@cindex MS-DOS and file modes
+@cindex file modes and MS-DOS
+@strong{MS-DOS note:} On MS-DOS, there is no such thing as an
+``executable'' file mode bit. So @code{file-modes} considers a file
+executable if its name ends in one of the standard executable
+extensions, such as @file{.com}, @file{.bat}, @file{.exe}, and some
+others. Files that begin with the Unix-standard @samp{#!} signature,
+such as shell and Perl scripts, are also considered executable.
+Directories are also reported as executable, for compatibility with
+Unix. These conventions are also followed by @code{file-attributes},
+below.
@end defun
If the @var{filename} argument to the next two functions is a
@end table
@end defun
-@cindex MS-DOS and file modes
-@cindex file modes and MS-DOS
- On MS-DOS, there is no such thing as an ``executable'' file mode bit.
-So Emacs considers a file executable if its name ends in one of the
-standard executable extensions, such as @file{.com}, @file{.bat},
-@file{.exe}, and some others. Files that begin with the Unix-standard
-@samp{#!} signature, such as shell and Perl scripts, are also considered
-as executable files. This is reflected in the values returned by
-@code{file-modes} and @code{file-attributes}. Directories are also
-reported with executable bit set, for compatibility with Unix.
+@cindex SELinux context
+ SELinux is a Linux kernel feature which provides more sophisticated
+file access controls than ordinary ``Unix-style'' file permissions.
+If Emacs has been compiled with SELinux support on a system with
+SELinux enabled, you can use the function @code{file-selinux-context}
+to retrieve a file's SELinux security context. For the function
+@code{set-file-selinux-context}, see @ref{Changing Files}.
+
+@defun file-selinux-context filename
+This function returns the SELinux security context of the file
+@var{filename}. This return value is a list of the form
+@code{(@var{user} @var{role} @var{type} @var{range})}, whose elements
+are the context's user, role, type, and range respectively, as Lisp
+strings. See the SELinux documentation for details about what these
+actually mean.
+
+If the file does not exist or is inaccessible, or if the system does
+not support SELinux, or if Emacs was not compiled with SELinux
+support, then the return value is @code{(nil nil nil nil)}.
+@end defun
@node Locating Files
@subsection How to Locate Files in Standard Places
This section explains how to search for a file in a list of
directories (a @dfn{path}), or for an executable file in the standard
-list of executable file directories, or for an Emacs-specific user
-configuration file.
+list of executable file directories.
+
+ To search for a user-specific configuration file, @xref{Standard
+File Names}, for the @code{locate-user-emacs-file} function.
@defun locate-file filename path &optional suffixes predicate
This function searches for a file whose name is @var{filename} in a
@code{exec-suffixes} (@pxref{Subprocess Creation}).
@end defun
-@defun locate-user-emacs-file base-name &optional old-name
-This function returns an absolute file name for an Emacs-specific
-configuration or data file. The argument @file{base-name} should be a
-relative file name. The return value is the absolute name of a file
-in the directory specified by @code{user-emacs-directory}; if that
-directory does not exist, this function creates it.
-
-If the optional argument @var{old-name} is non-@code{nil}, it
-specifies a file in the user's home directory,
-@file{~/@var{old-name}}. If such a file exists, the return value is
-the absolute name of that file, instead of the file specified by
-@var{base-name}. This argument is intended to be used by Emacs
-packages to provide backward compatibility. For instance, prior to
-the introduction of @code{user-emacs-directory}, the abbrev file was
-located in @file{~/.abbrev_defs}, so the definition of
-@code{abbrev-file-name} is
-
-@example
-(defcustom abbrev-file-name
- (locate-user-emacs-file "abbrev_defs" ".abbrev_defs")
- "Default name of file from which to read abbrevs."
- @dots{}
- :type 'file)
-@end example
-@end defun
-
@node Changing Files
@section Changing File Names and Attributes
@c @cindex renaming files Duplicates rename-file
file. This works only on some operating systems, and only if you have
the correct permissions to do so.
-@cindex SELinux
-If the optional argument @var{preserve-selinux} is non-@code{nil}, we
-attempt to copy the SELinux@footnote{@samp{Security-Enhanced Linux}
-is a kernel feature that allows for finer access controls to be set on
-files, and a system security policy to define who can access what.
-The functions @code{file-selinux-context} and @code{set-file-selinux-context}
-get and set, respectively, the SELinux properties of a file.}
-context of the file. For this to work, Emacs must have been built
-with libselinux support.
+If the optional argument @var{preserve-selinux} is non-@code{nil}, and
+Emacs has been compiled with SELinux support, this function attempts
+to copy the file's SELinux context (@pxref{File Attributes}).
@end deffn
@deffn Command make-symbolic-link filename newname &optional ok-if-exists
(@pxref{Time of Day}).
@end defun
+@defun set-file-selinux-context filename context
+This function sets the SELinux security context of the file
+@var{filename} to @var{context}. @xref{File Attributes}, for a brief
+description of SELinux contexts. The @var{context} argument should be
+a list @code{(@var{user} @var{role} @var{type} @var{range})}, like the
+return value of @code{file-selinux-context}. The function does
+nothing if SELinux is disabled, or if Emacs was compiled without
+SELinux support.
+@end defun
+
@node File Names
@section File Names
@cindex file names
@end defun
@defun file-name-extension filename &optional period
-This function returns @var{filename}'s final ``extension,'' if any,
+This function returns @var{filename}'s final ``extension'', if any,
after applying @code{file-name-sans-versions} to remove any
version/backup part. The extension, in a file name, is the part that
follows the last @samp{.} in the last name component (minus any
All the directories in the file system form a tree starting at the
root directory. A file name can specify all the directory names
-starting from the root of the tree; then it is called an @dfn{absolute}
-file name. Or it can specify the position of the file in the tree
-relative to a default directory; then it is called a @dfn{relative} file
-name. On Unix and GNU/Linux, an absolute file name starts with a slash
-or a tilde (@samp{~}), and a relative one does not. On MS-DOS and
-MS-Windows, an absolute file name starts with a slash or a backslash, or
-with a drive specification @samp{@var{x}:/}, where @var{x} is the
-@dfn{drive letter}.
+starting from the root of the tree; then it is called an
+@dfn{absolute} file name. Or it can specify the position of the file
+in the tree relative to a default directory; then it is called a
+@dfn{relative} file name. On Unix and GNU/Linux, an absolute file
+name starts with a @samp{/} or a @samp{~}
+(@pxref{abbreviate-file-name}), and a relative one does not. On
+MS-DOS and MS-Windows, an absolute file name starts with a slash or a
+backslash, or with a drive specification @samp{@var{x}:/}, where
+@var{x} is the @dfn{drive letter}.
@defun file-name-absolute-p filename
This function returns @code{t} if file @var{filename} is an absolute
To convert a directory name to its abbreviation, use this
function:
+@cindex file name abbreviations
+@cindex abbreviated file names
@defun abbreviate-file-name filename
-@anchor{Definition of abbreviate-file-name}
+@anchor{abbreviate-file-name}
This function returns an abbreviated form of @var{filename}. It
applies the abbreviations specified in @code{directory-abbrev-alist}
(@pxref{File Aliases,,File Aliases, emacs, The GNU Emacs Manual}),
@subsection Functions that Expand Filenames
@cindex expansion of file names
- @dfn{Expansion} of a file name means converting a relative file name
-to an absolute one. Since this is done relative to a default directory,
-you must specify the default directory name as well as the file name to
-be expanded. Expansion also simplifies file names by eliminating
-redundancies such as @file{./} and @file{@var{name}/../}.
+ @dfn{Expanding} a file name means converting a relative file name to
+an absolute one. Since this is done relative to a default directory,
+you must specify the default directory name as well as the file name
+to be expanded. It also involves expanding abbreviations like
+@file{~/}
+@ifnottex
+(@pxref{abbreviate-file-name}),
+@end ifnottex
+and eliminating redundancies like @file{./} and @file{@var{name}/../}.
@defun expand-file-name filename &optional directory
This function converts @var{filename} to an absolute file name. If
results.
@c Wordy to avoid overfull hbox. --rjc 15mar92
-Here we assume that the environment variable @code{HOME}, which holds
+Here we assume that the environment variable @env{HOME}, which holds
the user's home directory name, has value @samp{/xcssun/users/rms}.
@example
the proper directory before calling @code{make-temp-file}.
@defopt temporary-file-directory
-@cindex @code{TMPDIR} environment variable
-@cindex @code{TMP} environment variable
-@cindex @code{TEMP} environment variable
+@cindex @env{TMPDIR} environment variable
+@cindex @env{TMP} environment variable
+@cindex @env{TEMP} environment variable
This variable specifies the directory name for creating temporary files.
Its value should be a directory name (@pxref{Directory Names}), but it
is good for Lisp programs to cope if the value is a directory's file
@code{expand-file-name} is a good way to achieve that.
The default value is determined in a reasonable way for your operating
-system; it is based on the @code{TMPDIR}, @code{TMP} and @code{TEMP}
+system; it is based on the @env{TMPDIR}, @env{TMP} and @env{TEMP}
environment variables, with a fall-back to a system-dependent name if
none of these variables is defined.
@node Standard File Names
@subsection Standard File Names
- Most of the file names used in Lisp programs are entered by the user.
-But occasionally a Lisp program needs to specify a standard file name
-for a particular use---typically, to hold customization information
-about each user. For example, abbrev definitions are stored (by
-default) in the file @file{~/.abbrev_defs}; the @code{completion}
-package stores completions in the file @file{~/.completions}. These are
-two of the many standard file names used by parts of Emacs for certain
-purposes.
-
- Various operating systems have their own conventions for valid file
-names and for which file names to use for user profile data. A Lisp
-program which reads a file using a standard file name ought to use, on
-each type of system, a file name suitable for that system. The function
-@code{convert-standard-filename} makes this easy to do.
+ Sometimes, an Emacs Lisp program needs to specify a standard file
+name for a particular use---typically, to hold configuration data
+specified by the current user. Usually, such files should be located
+in the directory specified by @code{user-emacs-directory}, which is
+@file{~/.emacs.d} by default (@pxref{Init File}). For example, abbrev
+definitions are stored by default in @file{~/.emacs.d/abbrev_defs}.
+The easiest way to specify such a file name is to use the function
+@code{locate-user-emacs-file}.
-@defun convert-standard-filename filename
-This function alters the file name @var{filename} to fit the conventions
-of the operating system in use, and returns the result as a new string.
-@end defun
+@defun locate-user-emacs-file base-name &optional old-name
+This function returns an absolute file name for an Emacs-specific
+configuration or data file. The argument @file{base-name} should be a
+relative file name. The return value is the absolute name of a file
+in the directory specified by @code{user-emacs-directory}; if that
+directory does not exist, this function creates it.
- The recommended way to specify a standard file name in a Lisp program
-is to choose a name which fits the conventions of GNU and Unix systems,
-usually with a nondirectory part that starts with a period, and pass it
-to @code{convert-standard-filename} instead of using it directly. Here
-is an example from the @code{completion} package:
+If the optional argument @var{old-name} is non-@code{nil}, it
+specifies a file in the user's home directory,
+@file{~/@var{old-name}}. If such a file exists, the return value is
+the absolute name of that file, instead of the file specified by
+@var{base-name}. This argument is intended to be used by Emacs
+packages to provide backward compatibility. For instance, prior to
+the introduction of @code{user-emacs-directory}, the abbrev file was
+located in @file{~/.abbrev_defs}. Here is the definition of
+@code{abbrev-file-name}:
@example
-(defvar save-completions-file-name
- (convert-standard-filename "~/.completions")
- "*The file name to save completions to.")
+(defcustom abbrev-file-name
+ (locate-user-emacs-file "abbrev_defs" ".abbrev_defs")
+ "Default name of file from which to read abbrevs."
+ @dots{}
+ :type 'file)
@end example
+@end defun
- On GNU and Unix systems, and on some other systems as well,
-@code{convert-standard-filename} returns its argument unchanged. On
-some other systems, it alters the name to fit the system's conventions.
+ A lower-level function for standardizing file names, which
+@code{locate-user-emacs-file} uses as a subroutine, is
+@code{convert-standard-filename}.
- For example, on MS-DOS the alterations made by this function include
-converting a leading @samp{.} to @samp{_}, converting a @samp{_} in the
-middle of the name to @samp{.} if there is no other @samp{.}, inserting
-a @samp{.} after eight characters if there is none, and truncating to
-three characters after the @samp{.}. (It makes other changes as well.)
-Thus, @file{.abbrev_defs} becomes @file{_abbrev.def}, and
-@file{.completions} becomes @file{_complet.ion}.
+@defun convert-standard-filename filename
+This function returns a file name based on @var{filename}, which fits
+the conventions of the current operating system.
+
+On GNU and Unix systems, this simply returns @var{filename}. On other
+operating systems, it may enforce system-specific file name
+conventions; for example, on MS-DOS this function performs a variety
+of changes to enforce MS-DOS file name limitations, including
+converting any leading @samp{.} to @samp{_} and truncating to three
+characters after the @samp{.}.
+
+The recommended way to use this function is to specify a name which
+fits the conventions of GNU and Unix systems, and pass it to
+@code{convert-standard-filename}.
+@end defun
@node Contents of Directories
@section Contents of Directories
@code{file-name-nondirectory},
@code{file-name-sans-versions}, @code{file-newer-than-file-p},
@code{file-ownership-preserved-p},
-@code{file-readable-p}, @code{file-regular-p}, @code{file-symlink-p},
-@code{file-truename}, @code{file-writable-p},
-@code{find-backup-file-name},
+@code{file-readable-p}, @code{file-regular-p}, @code{file-in-directory-p},
+@code{file-symlink-p}, @code{file-truename}, @code{file-writable-p},
+@code{file-equal-p}, @code{find-backup-file-name},
@c Not sure why it was here: @code{find-file-noselect},@*
@code{get-file-buffer},
@code{insert-directory},
possibly others to be added in the future. It need not implement all
these operations itself---when it has nothing special to do for a
certain operation, it can reinvoke the primitive, to handle the
-operation ``in the usual way.'' It should always reinvoke the primitive
+operation ``in the usual way''. It should always reinvoke the primitive
for an operation it does not recognize. Here's one way to do this:
@smallexample
@example
(defun display-time-file-nonempty-p (file)
- (let ((remote-file-name-inhibit-cache (- display-time-interval 5)))
+ (let ((remote-file-name-inhibit-cache
+ (- display-time-interval 5)))
(and (file-exists-p file)
(< 0 (nth 7 (file-attributes (file-chase-links file)))))))
@end example
This command writes the current buffer contents into the file @var{file}
in a format based on @var{format}, which is a list of format names. It
constructs the actual format starting from @var{format}, then appending
-any elements from the value of @code{buffer-file-format} with a non-nil
-@var{preserve} flag (see above), if they are not already present in
-@var{format}. It then updates @code{buffer-file-format} with this
-format, making it the default for future saves. Except for the
+any elements from the value of @code{buffer-file-format} with a
+non-@code{nil} @var{preserve} flag (see above), if they are not already
+present in @var{format}. It then updates @code{buffer-file-format} with
+this format, making it the default for future saves. Except for the
@var{format} argument, this command is similar to @code{write-file}. In
particular, @var{confirm} has the same meaning and interactive treatment
as the corresponding argument to @code{write-file}. @xref{Definition of
HCoop / bpt / emacs.git / blobdiff