@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
+@node Files
@chapter Files
This chapter describes the Emacs Lisp functions and variables to
When file I/O functions signal Lisp errors, they usually use the
condition @code{file-error} (@pxref{Handling Errors}). The error
message is in most cases obtained from the operating system, according
-to locale @code{system-message-locale}, and decoded using coding system
+to locale @code{system-messages-locale}, and decoded using coding system
@code{locale-coding-system} (@pxref{Locales}).
@menu
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.
@defvar find-file-literally
This buffer-local variable, if set to a non-@code{nil} value, makes
@code{save-buffer} behave as if the buffer were visiting its file
-literally, i.e. without conversions of any kind. The command
+literally, i.e., without conversions of any kind. The command
@code{find-file-literally} sets this variable's local value, but other
-equivalent functions and commands can do that as well, e.g.@: to avoid
+equivalent functions and commands can do that as well, e.g., to avoid
automatic addition of a newline at the end of the file. This variable
is permanent local, so it is unaffected by changes of major modes.
@end defvar
@node Subroutines of Visiting
-@comment node-name, next, previous, up
@subsection Subroutines of Visiting
The @code{find-file-noselect} function uses two important subroutines
@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
Name}).
@node Reading from Files
-@comment node-name, next, previous, up
@section Reading from Files
@cindex reading from files
@ref{Magic File Names}.
@node Writing to Files
-@comment node-name, next, previous, up
@section Writing to Files
@cindex writing to files
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
@end menu
@node Testing Accessibility
-@comment node-name, next, previous, up
@subsection Testing Accessibility
@cindex accessibility of a file
@cindex file accessibility
using @var{string} as the error message text.
@end defun
-@defun file-ownership-preserved-p filename
+@defun file-ownership-preserved-p filename &optional group
This function returns @code{t} if deleting the file @var{filename} and
then creating it anew would keep the file's owner unchanged. It also
returns @code{t} for nonexistent files.
+If the optional argument @var{group} is non-@code{nil}, this function
+also checks that the file's group would be unchanged.
+
If @var{filename} is a symbolic link, then, unlike the other functions
discussed here, @code{file-ownership-preserved-p} does @emph{not}
replace @var{filename} with its target. However, it does recursively
@end example
You can use @code{file-attributes} to get a file's last modification
-time as a list of two numbers. @xref{File Attributes}.
+time as a list of four integers. @xref{File Attributes}.
@end defun
@node Kinds of Files
-@comment node-name, next, previous, up
@subsection Distinguishing Kinds of Files
This section describes how to distinguish various kinds of files, such
other I/O device).
@end defun
-@defun files-equal-p file1 file2
+@defun file-equal-p file1 file2
This function returns @code{t} if the files @var{file1} and
-@var{file2} name the same file. Two ordinary files are considered to
-be the same if the function @code{file-attributes} (@xref{File
-Attributes}) returns @code{equal} values for them.
+@var{file2} name the same file. If @var{file1} or @var{file2} does
+not exist, the return value is unspecified.
@end defun
-@defun file-subdir-of-p dir1 dir2
-This function returns @code{t} if directory @var{dir1} is a
-subdirectory of @var{dir2}, or if @var{dir1} and @var{dir2} are the
-same directory. It compares the @code{file-truename} values of the
-two directories (@pxref{Truenames}). If either @var{dir1} or
-@var{dir2} do not name existing directories, the return value is
-@code{nil}.
+@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
@xref{Buffer File Name}, for related information.
@node File Attributes
-@comment node-name, next, previous, up
@subsection Other Information about Files
This section describes the functions for getting detailed
The file's @acronym{GID}, likewise.
@item
-The time of last access, as a list of two integers.
-The first integer has the high-order 16 bits of time,
-the second has the low 16 bits. (This is similar to the
+The time of last access, as a list of four integers @code{(@var{sec-high}
+@var{sec-low} @var{microsec} @var{picosec})}. (This is similar to the
value of @code{current-time}; see @ref{Time of Day}.) Note that on
some FAT-based filesystems, only the date of last access is recorded,
so this time will always hold the midnight of the day of last access.
@cindex modification time of file
@item
-The time of last modification as a list of two integers (as above).
+The time of last modification as a list of four integers (as above).
This is the last time when the file's contents were modified.
@item
-The time of last status change as a list of two integers (as above).
+The time of last status change as a list of four integers (as above).
This is the time of the last change to the file's access mode bits,
its owner and group, and other information recorded in the filesystem
for the file, beyond the file's contents.
as in @samp{ls -l}.
@item
-@code{t} if the file's @acronym{GID} would change if file were
-deleted and recreated; @code{nil} otherwise.
+An unspecified value, present for backward compatibility.
@item
The file's inode number. If possible, this is an integer. If the
@group
(file-attributes "files.texi" 'string)
@result{} (nil 1 "lh" "users"
- (19145 42977)
- (19141 59576)
- (18340 17300)
+ (20614 64019 50040 152000)
+ (20000 23 0 0)
+ (20614 64555 902289 872000)
122295 "-rw-rw-rw-"
- nil (5888 2 . 43978)
+ t (5888 2 . 43978)
(15479 . 46724))
@end group
@end example
@item "users"
is in the group with name "users".
-@item (19145 42977)
-was last accessed on Oct 5 2009, at 10:01:37.
+@item (20614 64019 50040 152000)
+was last accessed on October 23, 2012, at 20:12:03.050040152 UTC.
-@item (19141 59576)
-last had its contents modified on Oct 2 2009, at 13:49:12.
+@item (20000 23 0 0)
+was last modified on July 15, 2001, at 08:53:43 UTC.
-@item (18340 17300)
-last had its status changed on Feb 2 2008, at 12:19:00.
+@item (20614 64555 902289 872000)
+last had its status changed on October 23, 2012, at 20:20:59.902289872 UTC.
@item 122295
is 122295 bytes long. (It may not contain 122295 characters, though,
@item "-rw-rw-rw-"
has a mode of read and write access for the owner, group, and world.
-@item nil
-would retain the same @acronym{GID} if it were recreated.
+@item t
+is merely a placeholder; it carries no information.
@item (5888 2 . 43978)
has an inode number of 6473924464520138.
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
The predicate is passed the candidate file name as its single
argument. If @var{predicate} is @code{nil} or omitted,
@code{locate-file} uses @code{file-readable-p} as the predicate.
-@xref{Kinds of Files}, for other useful predicates, e.g.@:
+@xref{Kinds of Files}, for other useful predicates, e.g.,
@code{file-executable-p} and @code{file-directory-p}.
For compatibility, @var{predicate} can also be one of the symbols
@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
@var{modes} into the equivalent integer value. If the symbolic
specification is based on an existing file, that file's mode bits are
taken from the optional argument @var{base-modes}; if that argument is
-omitted or @code{nil}, it defaults to 0, i.e.@: no access rights at
+omitted or @code{nil}, it defaults to 0, i.e., no access rights at
all.
@end defun
@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
not an extension.
@end defun
+@defun file-name-base &optional filename
+This function is the composition of @code{file-name-sans-extension}
+and @code{file-name-nondirectory}. For example,
+
+@example
+(file-name-base "/my/home/foo.c")
+ @result{} "foo"
+@end example
+
+The @var{filename} argument defaults to @code{buffer-file-name}.
+@end defun
@node Relative File Names
@subsection Absolute and Relative File Names
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
@end defun
@node Directory Names
-@comment node-name, next, previous, up
@subsection Directory Names
@cindex directory name
@cindex file name of directory
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)))))))
+ (< 0 (nth 7 (file-attributes
+ (file-chase-links file)))))))
@end example
@end defopt
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