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(Visiting Functions): `find-file-hook' is now a normal hook. (File Name Expansion): Explain difference between the way that `expand-file-name' and `file-truename' treat `..'. (Contents of Directories): Mention optional ID-FORMAT argument to `directory-files-and-attributes'. (Format Conversion): Mention new optional CONFIRM argument to `format-write-file'.
2818 lines
104 KiB
Plaintext
2818 lines
104 KiB
Plaintext
@c -*-texinfo-*-
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@c This is part of the GNU Emacs Lisp Reference Manual.
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@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2004
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@c Free Software Foundation, Inc.
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@c See the file elisp.texi for copying conditions.
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@setfilename ../info/files
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@node Files, Backups and Auto-Saving, Documentation, Top
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@comment node-name, next, previous, up
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@chapter Files
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In Emacs, you can find, create, view, save, and otherwise work with
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files and file directories. This chapter describes most of the
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file-related functions of Emacs Lisp, but a few others are described in
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@ref{Buffers}, and those related to backups and auto-saving are
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described in @ref{Backups and Auto-Saving}.
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Many of the file functions take one or more arguments that are file
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names. A file name is actually a string. Most of these functions
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expand file name arguments by calling @code{expand-file-name}, so that
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@file{~} is handled correctly, as are relative file names (including
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@samp{../}). These functions don't recognize environment variable
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substitutions such as @samp{$HOME}. @xref{File Name Expansion}.
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When file I/O functions signal Lisp errors, they usually use the
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condition @code{file-error} (@pxref{Handling Errors}). The error
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message is in most cases obtained from the operating system, according
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to locale @code{system-message-locale}, and decoded using coding system
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@code{locale-coding-system} (@pxref{Locales}).
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@menu
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* Visiting Files:: Reading files into Emacs buffers for editing.
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* Saving Buffers:: Writing changed buffers back into files.
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* Reading from Files:: Reading files into buffers without visiting.
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* Writing to Files:: Writing new files from parts of buffers.
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* File Locks:: Locking and unlocking files, to prevent
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simultaneous editing by two people.
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* Information about Files:: Testing existence, accessibility, size of files.
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* Changing Files:: Renaming files, changing protection, etc.
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* File Names:: Decomposing and expanding file names.
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* Contents of Directories:: Getting a list of the files in a directory.
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* Create/Delete Dirs:: Creating and Deleting Directories.
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* Magic File Names:: Defining "magic" special handling
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for certain file names.
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* Format Conversion:: Conversion to and from various file formats.
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@end menu
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@node Visiting Files
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@section Visiting Files
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@cindex finding files
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@cindex visiting files
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Visiting a file means reading a file into a buffer. Once this is
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done, we say that the buffer is @dfn{visiting} that file, and call the
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file ``the visited file'' of the buffer.
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A file and a buffer are two different things. A file is information
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recorded permanently in the computer (unless you delete it). A buffer,
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on the other hand, is information inside of Emacs that will vanish at
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the end of the editing session (or when you kill the buffer). Usually,
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a buffer contains information that you have copied from a file; then we
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say the buffer is visiting that file. The copy in the buffer is what
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you modify with editing commands. Such changes to the buffer do not
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change the file; therefore, to make the changes permanent, you must
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@dfn{save} the buffer, which means copying the altered buffer contents
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back into the file.
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In spite of the distinction between files and buffers, people often
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refer to a file when they mean a buffer and vice-versa. Indeed, we say,
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``I am editing a file,'' rather than, ``I am editing a buffer that I
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will soon save as a file of the same name.'' Humans do not usually need
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to make the distinction explicit. When dealing with a computer program,
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however, it is good to keep the distinction in mind.
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@menu
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* Visiting Functions:: The usual interface functions for visiting.
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* Subroutines of Visiting:: Lower-level subroutines that they use.
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@end menu
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@node Visiting Functions
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@subsection Functions for Visiting Files
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This section describes the functions normally used to visit files.
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For historical reasons, these functions have names starting with
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@samp{find-} rather than @samp{visit-}. @xref{Buffer File Name}, for
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functions and variables that access the visited file name of a buffer or
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that find an existing buffer by its visited file name.
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In a Lisp program, if you want to look at the contents of a file but
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not alter it, the fastest way is to use @code{insert-file-contents} in a
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temporary buffer. Visiting the file is not necessary and takes longer.
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@xref{Reading from Files}.
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@deffn Command find-file filename &optional wildcards
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This command selects a buffer visiting the file @var{filename},
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using an existing buffer if there is one, and otherwise creating a
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new buffer and reading the file into it. It also returns that buffer.
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Aside from some technical details, the body of the @code{find-file}
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function is basically equivalent to:
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@example
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(switch-to-buffer (find-file-noselect filename nil nil wildcards))
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@end example
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@noindent
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(See @code{switch-to-buffer} in @ref{Displaying Buffers}.)
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If @var{wildcards} is non-@code{nil}, which is always true in an
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interactive call, then @code{find-file} expands wildcard characters in
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@var{filename} and visits all the matching files.
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When @code{find-file} is called interactively, it prompts for
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@var{filename} in the minibuffer.
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@end deffn
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@defun find-file-noselect filename &optional nowarn rawfile wildcards
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This function is the guts of all the file-visiting functions. It finds
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or creates a buffer visiting the file @var{filename}, and returns it.
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It uses an existing buffer if there is one, and otherwise creates a new
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buffer and reads the file into it. You may make the buffer current or
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display it in a window if you wish, but this function does not do so.
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If @var{wildcards} is non-@code{nil},
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then @code{find-file-noselect} expands wildcard
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characters in @var{filename} and visits all the matching files.
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When @code{find-file-noselect} uses an existing buffer, it first
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verifies that the file has not changed since it was last visited or
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saved in that buffer. If the file has changed, then this function asks
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the user whether to reread the changed file. If the user says
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@samp{yes}, any changes previously made in the buffer are lost.
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This function displays warning or advisory messages in various peculiar
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cases, unless the optional argument @var{nowarn} is non-@code{nil}. For
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example, if it needs to create a buffer, and there is no file named
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@var{filename}, it displays the message @samp{(New file)} in the echo
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area, and leaves the buffer empty.
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The @code{find-file-noselect} function normally calls
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@code{after-find-file} after reading the file (@pxref{Subroutines of
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Visiting}). That function sets the buffer major mode, parses local
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variables, warns the user if there exists an auto-save file more recent
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than the file just visited, and finishes by running the functions in
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@code{find-file-hook}.
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If the optional argument @var{rawfile} is non-@code{nil}, then
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@code{after-find-file} is not called, and the
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@code{find-file-not-found-functions} are not run in case of failure. What's
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more, a non-@code{nil} @var{rawfile} value suppresses coding system
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conversion (@pxref{Coding Systems}) and format conversion (@pxref{Format
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Conversion}).
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The @code{find-file-noselect} function usually returns the buffer that
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is visiting the file @var{filename}. But, if wildcards are actually
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used and expanded, it returns a list of buffers that are visiting the
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various files.
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@example
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@group
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(find-file-noselect "/etc/fstab")
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@result{} #<buffer fstab>
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@end group
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@end example
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@end defun
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@deffn Command find-file-other-window filename &optional wildcards
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This command selects a buffer visiting the file @var{filename}, but
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does so in a window other than the selected window. It may use another
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existing window or split a window; see @ref{Displaying Buffers}.
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When this command is called interactively, it prompts for
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@var{filename}.
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@end deffn
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@deffn Command find-file-read-only filename &optional wildcards
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This command selects a buffer visiting the file @var{filename}, like
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@code{find-file}, but it marks the buffer as read-only. @xref{Read Only
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Buffers}, for related functions and variables.
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When this command is called interactively, it prompts for
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@var{filename}.
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@end deffn
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@deffn Command view-file filename
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This command visits @var{filename} using View mode, returning to the
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previous buffer when you exit View mode. View mode is a minor mode that
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provides commands to skim rapidly through the file, but does not let you
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modify the text. Entering View mode runs the normal hook
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@code{view-mode-hook}. @xref{Hooks}.
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When @code{view-file} is called interactively, it prompts for
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@var{filename}.
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@end deffn
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@tindex find-file-wildcards
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@defopt find-file-wildcards
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If this variable is non-@code{nil}, then the various @code{find-file}
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commands check for wildcard characters and visit all the files that
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match them (when invoked interactively or when their @var{wildcards}
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argument is non-@code{nil}). If this option is @code{nil}, then
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the @code{find-file} commands ignore their @var{wildcards} argument
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and never treat wildcard characters specially.
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@end defopt
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@defvar find-file-hook
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The value of this variable is a list of functions to be called after a
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file is visited. The file's local-variables specification (if any) will
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have been processed before the hooks are run. The buffer visiting the
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file is current when the hook functions are run.
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This variable is a normal hook. @xref{Hooks}.
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@end defvar
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@defvar find-file-not-found-functions
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The value of this variable is a list of functions to be called when
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@code{find-file} or @code{find-file-noselect} is passed a nonexistent
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file name. @code{find-file-noselect} calls these functions as soon as
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it detects a nonexistent file. It calls them in the order of the list,
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until one of them returns non-@code{nil}. @code{buffer-file-name} is
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already set up.
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This is not a normal hook because the values of the functions are
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used, and in many cases only some of the functions are called.
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@end defvar
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@node Subroutines of Visiting
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@comment node-name, next, previous, up
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@subsection Subroutines of Visiting
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The @code{find-file-noselect} function uses two important subroutines
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which are sometimes useful in user Lisp code: @code{create-file-buffer}
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and @code{after-find-file}. This section explains how to use them.
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@defun create-file-buffer filename
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This function creates a suitably named buffer for visiting
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@var{filename}, and returns it. It uses @var{filename} (sans directory)
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as the name if that name is free; otherwise, it appends a string such as
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@samp{<2>} to get an unused name. See also @ref{Creating Buffers}.
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@strong{Please note:} @code{create-file-buffer} does @emph{not}
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associate the new buffer with a file and does not select the buffer.
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It also does not use the default major mode.
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@example
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@group
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(create-file-buffer "foo")
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@result{} #<buffer foo>
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@end group
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@group
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(create-file-buffer "foo")
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@result{} #<buffer foo<2>>
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@end group
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@group
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(create-file-buffer "foo")
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@result{} #<buffer foo<3>>
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@end group
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@end example
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This function is used by @code{find-file-noselect}.
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It uses @code{generate-new-buffer} (@pxref{Creating Buffers}).
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@end defun
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@defun after-find-file &optional error warn noauto after-find-file-from-revert-buffer nomodes
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This function sets the buffer major mode, and parses local variables
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(@pxref{Auto Major Mode}). It is called by @code{find-file-noselect}
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and by the default revert function (@pxref{Reverting}).
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@cindex new file message
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@cindex file open error
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If reading the file got an error because the file does not exist, but
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its directory does exist, the caller should pass a non-@code{nil} value
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for @var{error}. In that case, @code{after-find-file} issues a warning:
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@samp{(New file)}. For more serious errors, the caller should usually not
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call @code{after-find-file}.
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If @var{warn} is non-@code{nil}, then this function issues a warning
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if an auto-save file exists and is more recent than the visited file.
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If @var{noauto} is non-@code{nil}, that says not to enable or disable
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Auto-Save mode. The mode remains enabled if it was enabled before.
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If @var{after-find-file-from-revert-buffer} is non-@code{nil}, that
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means this call was from @code{revert-buffer}. This has no direct
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effect, but some mode functions and hook functions check the value
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of this variable.
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If @var{nomodes} is non-@code{nil}, that means don't alter the buffer's
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major mode, don't process local variables specifications in the file,
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and don't run @code{find-file-hook}. This feature is used by
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@code{revert-buffer} in some cases.
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The last thing @code{after-find-file} does is call all the functions
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in the list @code{find-file-hook}.
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@end defun
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@node Saving Buffers
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@section Saving Buffers
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When you edit a file in Emacs, you are actually working on a buffer
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that is visiting that file---that is, the contents of the file are
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copied into the buffer and the copy is what you edit. Changes to the
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buffer do not change the file until you @dfn{save} the buffer, which
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means copying the contents of the buffer into the file.
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@deffn Command save-buffer &optional backup-option
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This function saves the contents of the current buffer in its visited
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file if the buffer has been modified since it was last visited or saved.
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Otherwise it does nothing.
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@code{save-buffer} is responsible for making backup files. Normally,
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@var{backup-option} is @code{nil}, and @code{save-buffer} makes a backup
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file only if this is the first save since visiting the file. Other
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values for @var{backup-option} request the making of backup files in
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other circumstances:
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@itemize @bullet
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@item
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With an argument of 4 or 64, reflecting 1 or 3 @kbd{C-u}'s, the
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@code{save-buffer} function marks this version of the file to be
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backed up when the buffer is next saved.
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@item
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With an argument of 16 or 64, reflecting 2 or 3 @kbd{C-u}'s, the
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@code{save-buffer} function unconditionally backs up the previous
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version of the file before saving it.
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@item
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With an argument of 0, unconditionally do @emph{not} make any backup file.
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@end itemize
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@end deffn
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@anchor{Definition of save-some-buffers}
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@deffn Command save-some-buffers &optional save-silently-p pred
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This command saves some modified file-visiting buffers. Normally it
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asks the user about each buffer. But if @var{save-silently-p} is
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non-@code{nil}, it saves all the file-visiting buffers without querying
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the user.
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The optional @var{pred} argument controls which buffers to ask about
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(or to save silently if @var{save-silently-p} is non-@code{nil}).
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If it is @code{nil}, that means to ask only about file-visiting buffers.
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If it is @code{t}, that means also offer to save certain other non-file
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buffers---those that have a non-@code{nil} buffer-local value of
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@code{buffer-offer-save}. (A user who says @samp{yes} to saving a
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non-file buffer is asked to specify the file name to use.) The
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@code{save-buffers-kill-emacs} function passes the value @code{t} for
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@var{pred}.
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If @var{pred} is neither @code{t} nor @code{nil}, then it should be
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a function of no arguments. It will be called in each buffer to decide
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whether to offer to save that buffer. If it returns a non-@code{nil}
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value in a certain buffer, that means do offer to save that buffer.
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@end deffn
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@anchor{Definition of write-file}
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@deffn Command write-file filename &optional confirm
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This function writes the current buffer into file @var{filename}, makes
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the buffer visit that file, and marks it not modified. Then it renames
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the buffer based on @var{filename}, appending a string like @samp{<2>}
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if necessary to make a unique buffer name. It does most of this work by
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calling @code{set-visited-file-name} (@pxref{Buffer File Name}) and
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@code{save-buffer}.
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If @var{confirm} is non-@code{nil}, that means to ask for confirmation
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before overwriting an existing file. Interactively, confirmation is
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required, unless the user supplies a prefix argument.
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If @var{filename} is an existing directory, or a symbolic link to one,
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@code{write-file} uses the name of the visited file, in directory
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@var{filename}. If the buffer is not visiting a file, it uses the
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buffer name instead.
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@end deffn
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Saving a buffer runs several hooks. It also performs format
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conversion (@pxref{Format Conversion}), and may save text properties in
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``annotations'' (@pxref{Saving Properties}).
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@defvar write-file-functions
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The value of this variable is a list of functions to be called before
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writing out a buffer to its visited file. If one of them returns
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non-@code{nil}, the file is considered already written and the rest of
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the functions are not called, nor is the usual code for writing the file
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executed.
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If a function in @code{write-file-functions} returns non-@code{nil}, it
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is responsible for making a backup file (if that is appropriate).
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To do so, execute the following code:
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@example
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(or buffer-backed-up (backup-buffer))
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@end example
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You might wish to save the file modes value returned by
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@code{backup-buffer} and use that (if non-@code{nil}) to set the mode
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bits of the file that you write. This is what @code{save-buffer}
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normally does. @xref{Making Backups,, Making Backup Files}.
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The hook functions in @code{write-file-functions} are also responsible for
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encoding the data (if desired): they must choose a suitable coding
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system (@pxref{Lisp and Coding Systems}), perform the encoding
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(@pxref{Explicit Encoding}), and set @code{last-coding-system-used} to
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the coding system that was used (@pxref{Encoding and I/O}).
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If you set this hook locally in a buffer, it is assumed to be
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associated with the file or the way the contents of the buffer were
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obtained. Thus the variable is marked as a permanent local, so that
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changing the major mode does not alter a buffer-local value. On the
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other hand, calling @code{set-visited-file-name} will reset it.
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If this is not what you want, you might like to use
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@code{write-contents-functions} instead.
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Even though this is not a normal hook, you can use @code{add-hook} and
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@code{remove-hook} to manipulate the list. @xref{Hooks}.
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@end defvar
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@c Emacs 19 feature
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@defvar write-contents-functions
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This works just like @code{write-file-functions}, but it is intended for
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hooks that pertain to the contents of the file, as opposed to hooks that
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pertain to where the file came from. Such hooks are usually set up by
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major modes, as buffer-local bindings for this variable. If any of the
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functions in this hook returns non-@code{nil}, @code{write-file-functions}
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is not run.
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This variable automatically becomes buffer-local whenever it is set;
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switching to a new major mode always resets this variable, but
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calling @code{set-visited-file-name} does not.
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@end defvar
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@defopt before-save-hook
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This normal hook runs before a buffer is saved in its visited file,
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regardless of whether that is done normally or by one of the hooks
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described above. For instance, the @file{copyright.el} program uses
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|
this hook to make sure the file you are saving has the current year in
|
|
its copyright notice.
|
|
@end defopt
|
|
|
|
@c Emacs 19 feature
|
|
@defopt after-save-hook
|
|
This normal hook runs after a buffer has been saved in its visited file.
|
|
One use of this hook is in Fast Lock mode; it uses this hook to save the
|
|
highlighting information in a cache file.
|
|
@end defopt
|
|
|
|
@defopt file-precious-flag
|
|
If this variable is non-@code{nil}, then @code{save-buffer} protects
|
|
against I/O errors while saving by writing the new file to a temporary
|
|
name instead of the name it is supposed to have, and then renaming it to
|
|
the intended name after it is clear there are no errors. This procedure
|
|
prevents problems such as a lack of disk space from resulting in an
|
|
invalid file.
|
|
|
|
As a side effect, backups are necessarily made by copying. @xref{Rename
|
|
or Copy}. Yet, at the same time, saving a precious file always breaks
|
|
all hard links between the file you save and other file names.
|
|
|
|
Some modes give this variable a non-@code{nil} buffer-local value
|
|
in particular buffers.
|
|
@end defopt
|
|
|
|
@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.
|
|
|
|
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
|
|
major modes set it to @code{t} in particular buffers.
|
|
@end defopt
|
|
|
|
See also the function @code{set-visited-file-name} (@pxref{Buffer File
|
|
Name}).
|
|
|
|
@node Reading from Files
|
|
@comment node-name, next, previous, up
|
|
@section Reading from Files
|
|
|
|
You can copy a file from the disk and insert it into a buffer
|
|
using the @code{insert-file-contents} function. Don't use the user-level
|
|
command @code{insert-file} in a Lisp program, as that sets the mark.
|
|
|
|
@defun insert-file-contents filename &optional visit beg end replace
|
|
This function inserts the contents of file @var{filename} into the
|
|
current buffer after point. It returns a list of the absolute file name
|
|
and the length of the data inserted. An error is signaled if
|
|
@var{filename} is not the name of a file that can be read.
|
|
|
|
The function @code{insert-file-contents} checks the file contents
|
|
against the defined file formats, and converts the file contents if
|
|
appropriate. @xref{Format Conversion}. It also calls the functions in
|
|
the list @code{after-insert-file-functions}; see @ref{Saving
|
|
Properties}. Normally, one of the functions in the
|
|
@code{after-insert-file-functions} list determines the coding system
|
|
(@pxref{Coding Systems}) used for decoding the file's contents.
|
|
|
|
If @var{visit} is non-@code{nil}, this function additionally marks the
|
|
buffer as unmodified and sets up various fields in the buffer so that it
|
|
is visiting the file @var{filename}: these include the buffer's visited
|
|
file name and its last save file modtime. This feature is used by
|
|
@code{find-file-noselect} and you probably should not use it yourself.
|
|
|
|
If @var{beg} and @var{end} are non-@code{nil}, they should be integers
|
|
specifying the portion of the file to insert. In this case, @var{visit}
|
|
must be @code{nil}. For example,
|
|
|
|
@example
|
|
(insert-file-contents filename nil 0 500)
|
|
@end example
|
|
|
|
@noindent
|
|
inserts the first 500 characters of a file.
|
|
|
|
If the argument @var{replace} is non-@code{nil}, it means to replace the
|
|
contents of the buffer (actually, just the accessible portion) with the
|
|
contents of the file. This is better than simply deleting the buffer
|
|
contents and inserting the whole file, because (1) it preserves some
|
|
marker positions and (2) it puts less data in the undo list.
|
|
|
|
It is possible to read a special file (such as a FIFO or an I/O device)
|
|
with @code{insert-file-contents}, as long as @var{replace} and
|
|
@var{visit} are @code{nil}.
|
|
@end defun
|
|
|
|
@defun insert-file-contents-literally filename &optional visit beg end replace
|
|
This function works like @code{insert-file-contents} except that it does
|
|
not do format decoding (@pxref{Format Conversion}), does not do
|
|
character code conversion (@pxref{Coding Systems}), does not run
|
|
@code{find-file-hook}, does not perform automatic uncompression, and so
|
|
on.
|
|
@end defun
|
|
|
|
If you want to pass a file name to another process so that another
|
|
program can read the file, use the function @code{file-local-copy}; see
|
|
@ref{Magic File Names}.
|
|
|
|
@node Writing to Files
|
|
@comment node-name, next, previous, up
|
|
@section Writing to Files
|
|
|
|
You can write the contents of a buffer, or part of a buffer, directly
|
|
to a file on disk using the @code{append-to-file} and
|
|
@code{write-region} functions. Don't use these functions to write to
|
|
files that are being visited; that could cause confusion in the
|
|
mechanisms for visiting.
|
|
|
|
@deffn Command append-to-file start end filename
|
|
This function appends the contents of the region delimited by
|
|
@var{start} and @var{end} in the current buffer to the end of file
|
|
@var{filename}. If that file does not exist, it is created. This
|
|
function returns @code{nil}.
|
|
|
|
An error is signaled if @var{filename} specifies a nonwritable file,
|
|
or a nonexistent file in a directory where files cannot be created.
|
|
|
|
When called from Lisp, this function is completely equivalent to:
|
|
|
|
@example
|
|
(write-region start end filename t)
|
|
@end example
|
|
@end deffn
|
|
|
|
@deffn Command write-region start end filename &optional append visit lockname mustbenew
|
|
This function writes the region delimited by @var{start} and @var{end}
|
|
in the current buffer into the file specified by @var{filename}.
|
|
|
|
If @var{start} is @code{nil}, then the command writes the entire buffer
|
|
contents (@emph{not} just the accessible portion) to the file and
|
|
ignores @var{end}.
|
|
|
|
@c Emacs 19 feature
|
|
If @var{start} is a string, then @code{write-region} writes or appends
|
|
that string, rather than text from the buffer. @var{end} is ignored in
|
|
this case.
|
|
|
|
If @var{append} is non-@code{nil}, then the specified text is appended
|
|
to the existing file contents (if any). Starting in Emacs 21, if
|
|
@var{append} is an integer, then @code{write-region} seeks to that byte
|
|
offset from the start of the file and writes the data from there.
|
|
|
|
If @var{mustbenew} is non-@code{nil}, then @code{write-region} asks
|
|
for confirmation if @var{filename} names an existing file.
|
|
Starting in Emacs 21, if @var{mustbenew} is the symbol @code{excl},
|
|
then @code{write-region} does not ask for confirmation, but instead
|
|
it signals an error @code{file-already-exists} if the file already
|
|
exists.
|
|
|
|
The test for an existing file, when @var{mustbenew} is @code{excl}, uses
|
|
a special system feature. At least for files on a local disk, there is
|
|
no chance that some other program could create a file of the same name
|
|
before Emacs does, without Emacs's noticing.
|
|
|
|
If @var{visit} is @code{t}, then Emacs establishes an association
|
|
between the buffer and the file: the buffer is then visiting that file.
|
|
It also sets the last file modification time for the current buffer to
|
|
@var{filename}'s modtime, and marks the buffer as not modified. This
|
|
feature is used by @code{save-buffer}, but you probably should not use
|
|
it yourself.
|
|
|
|
@c Emacs 19 feature
|
|
If @var{visit} is a string, it specifies the file name to visit. This
|
|
way, you can write the data to one file (@var{filename}) while recording
|
|
the buffer as visiting another file (@var{visit}). The argument
|
|
@var{visit} is used in the echo area message and also for file locking;
|
|
@var{visit} is stored in @code{buffer-file-name}. This feature is used
|
|
to implement @code{file-precious-flag}; don't use it yourself unless you
|
|
really know what you're doing.
|
|
|
|
The optional argument @var{lockname}, if non-@code{nil}, specifies the
|
|
file name to use for purposes of locking and unlocking, overriding
|
|
@var{filename} and @var{visit} for that purpose.
|
|
|
|
The function @code{write-region} converts the data which it writes to
|
|
the appropriate file formats specified by @code{buffer-file-format}.
|
|
@xref{Format Conversion}. It also calls the functions in the list
|
|
@code{write-region-annotate-functions}; see @ref{Saving Properties}.
|
|
|
|
Normally, @code{write-region} displays the message @samp{Wrote
|
|
@var{filename}} in the echo area. If @var{visit} is neither @code{t}
|
|
nor @code{nil} nor a string, then this message is inhibited. This
|
|
feature is useful for programs that use files for internal purposes,
|
|
files that the user does not need to know about.
|
|
@end deffn
|
|
|
|
@anchor{Definition of with-temp-file}
|
|
@defmac with-temp-file file body...
|
|
The @code{with-temp-file} macro evaluates the @var{body} forms with a
|
|
temporary buffer as the current buffer; then, at the end, it writes the
|
|
buffer contents into file @var{file}. It kills the temporary buffer
|
|
when finished, restoring the buffer that was current before the
|
|
@code{with-temp-file} form. Then it returns the value of the last form
|
|
in @var{body}.
|
|
|
|
The current buffer is restored even in case of an abnormal exit via
|
|
@code{throw} or error (@pxref{Nonlocal Exits}).
|
|
|
|
See also @code{with-temp-buffer} in @ref{Definition of
|
|
with-temp-buffer,, The Current Buffer}.
|
|
@end defmac
|
|
|
|
@node File Locks
|
|
@section File Locks
|
|
@cindex file locks
|
|
|
|
When two users edit the same file at the same time, they are likely to
|
|
interfere with each other. Emacs tries to prevent this situation from
|
|
arising by recording a @dfn{file lock} when a file is being modified.
|
|
Emacs can then detect the first attempt to modify a buffer visiting a
|
|
file that is locked by another Emacs job, and ask the user what to do.
|
|
The file lock is really a file, a symbolic link with a special name,
|
|
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''.
|
|
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
|
|
on disk catches some cases of simultaneous editing; see
|
|
@ref{Modification Time}.
|
|
|
|
@defun file-locked-p filename
|
|
This function returns @code{nil} if the file @var{filename} is not
|
|
locked. It returns @code{t} if it is locked by this Emacs process, and
|
|
it returns the name of the user who has locked it if it is locked by
|
|
some other job.
|
|
|
|
@example
|
|
@group
|
|
(file-locked-p "foo")
|
|
@result{} nil
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun lock-buffer &optional filename
|
|
This function locks the file @var{filename}, if the current buffer is
|
|
modified. The argument @var{filename} defaults to the current buffer's
|
|
visited file. Nothing is done if the current buffer is not visiting a
|
|
file, or is not modified.
|
|
@end defun
|
|
|
|
@defun unlock-buffer
|
|
This function unlocks the file being visited in the current buffer,
|
|
if the buffer is modified. If the buffer is not modified, then
|
|
the file should not be locked, so this function does nothing. It also
|
|
does nothing if the current buffer is not visiting a file.
|
|
@end defun
|
|
|
|
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}.
|
|
|
|
@defun ask-user-about-lock file other-user
|
|
This function is called when the user tries to modify @var{file}, but it
|
|
is locked by another user named @var{other-user}. The default
|
|
definition of this function asks the user to say what to do. The value
|
|
this function returns determines what Emacs does next:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
A value of @code{t} says to grab the lock on the file. Then
|
|
this user may edit the file and @var{other-user} loses the lock.
|
|
|
|
@item
|
|
A value of @code{nil} says to ignore the lock and let this
|
|
user edit the file anyway.
|
|
|
|
@item
|
|
@kindex file-locked
|
|
This function may instead signal a @code{file-locked} error, in which
|
|
case the change that the user was about to make does not take place.
|
|
|
|
The error message for this error looks like this:
|
|
|
|
@example
|
|
@error{} File is locked: @var{file} @var{other-user}
|
|
@end example
|
|
|
|
@noindent
|
|
where @code{file} is the name of the file and @var{other-user} is the
|
|
name of the user who has locked the file.
|
|
@end itemize
|
|
|
|
If you wish, you can replace the @code{ask-user-about-lock} function
|
|
with your own version that makes the decision in another way. The code
|
|
for its usual definition is in @file{userlock.el}.
|
|
@end defun
|
|
|
|
@node Information about Files
|
|
@section Information about Files
|
|
|
|
The functions described in this section all operate on strings that
|
|
designate file names. All the functions have names that begin with the
|
|
word @samp{file}. These functions all return information about actual
|
|
files or directories, so their arguments must all exist as actual files
|
|
or directories unless otherwise noted.
|
|
|
|
@menu
|
|
* Testing Accessibility:: Is a given file readable? Writable?
|
|
* Kinds of Files:: Is it a directory? A symbolic link?
|
|
* Truenames:: Eliminating symbolic links from a file name.
|
|
* File Attributes:: How large is it? Any other names? Etc.
|
|
@end menu
|
|
|
|
@node Testing Accessibility
|
|
@comment node-name, next, previous, up
|
|
@subsection Testing Accessibility
|
|
@cindex accessibility of a file
|
|
@cindex file accessibility
|
|
|
|
These functions test for permission to access a file in specific
|
|
ways. Unless explicitly stated otherwise, they recursively follow
|
|
symbolic links for their file name arguments, at all levels (at the
|
|
level of the file itself and at all levels of parent directories).
|
|
|
|
@defun file-exists-p filename
|
|
This function returns @code{t} if a file named @var{filename} appears
|
|
to exist. This does not mean you can necessarily read the file, only
|
|
that you can find out its attributes. (On Unix and GNU/Linux, this is
|
|
true if the file exists and you have execute permission on the
|
|
containing directories, regardless of the protection of the file
|
|
itself.)
|
|
|
|
If the file does not exist, or if fascist access control policies
|
|
prevent you from finding the attributes of the file, this function
|
|
returns @code{nil}.
|
|
|
|
Directories are files, so @code{file-exists-p} returns @code{t} when
|
|
given a directory name. However, symbolic links are treated
|
|
specially; @code{file-exists-p} returns @code{t} for a symbolic link
|
|
name only if the target file exists.
|
|
@end defun
|
|
|
|
@defun file-readable-p filename
|
|
This function returns @code{t} if a file named @var{filename} exists
|
|
and you can read it. It returns @code{nil} otherwise.
|
|
|
|
@example
|
|
@group
|
|
(file-readable-p "files.texi")
|
|
@result{} t
|
|
@end group
|
|
@group
|
|
(file-exists-p "/usr/spool/mqueue")
|
|
@result{} t
|
|
@end group
|
|
@group
|
|
(file-readable-p "/usr/spool/mqueue")
|
|
@result{} nil
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@c Emacs 19 feature
|
|
@defun file-executable-p filename
|
|
This function returns @code{t} if a file named @var{filename} exists and
|
|
you can execute it. It returns @code{nil} otherwise. On Unix and
|
|
GNU/Linux, if the file is a directory, execute permission means you can
|
|
check the existence and attributes of files inside the directory, and
|
|
open those files if their modes permit.
|
|
@end defun
|
|
|
|
@defun file-writable-p filename
|
|
This function returns @code{t} if the file @var{filename} can be written
|
|
or created by you, and @code{nil} otherwise. A file is writable if the
|
|
file exists and you can write it. It is creatable if it does not exist,
|
|
but the specified directory does exist and you can write in that
|
|
directory.
|
|
|
|
In the third example below, @file{foo} is not writable because the
|
|
parent directory does not exist, even though the user could create such
|
|
a directory.
|
|
|
|
@example
|
|
@group
|
|
(file-writable-p "~/foo")
|
|
@result{} t
|
|
@end group
|
|
@group
|
|
(file-writable-p "/foo")
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-writable-p "~/no-such-dir/foo")
|
|
@result{} nil
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@c Emacs 19 feature
|
|
@defun file-accessible-directory-p dirname
|
|
This function returns @code{t} if you have permission to open existing
|
|
files in the directory whose name as a file is @var{dirname}; otherwise
|
|
(or if there is no such directory), it returns @code{nil}. The value
|
|
of @var{dirname} may be either a directory name or the file name of a
|
|
file which is a directory.
|
|
|
|
Example: after the following,
|
|
|
|
@example
|
|
(file-accessible-directory-p "/foo")
|
|
@result{} nil
|
|
@end example
|
|
|
|
@noindent
|
|
we can deduce that any attempt to read a file in @file{/foo/} will
|
|
give an error.
|
|
@end defun
|
|
|
|
@defun access-file filename string
|
|
This function opens file @var{filename} for reading, then closes it and
|
|
returns @code{nil}. However, if the open fails, it signals an error
|
|
using @var{string} as the error message text.
|
|
@end defun
|
|
|
|
@defun file-ownership-preserved-p filename
|
|
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 @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
|
|
follow symbolic links at all levels of parent directories.
|
|
@end defun
|
|
|
|
@defun file-newer-than-file-p filename1 filename2
|
|
@cindex file age
|
|
@cindex file modification time
|
|
This function returns @code{t} if the file @var{filename1} is
|
|
newer than file @var{filename2}. If @var{filename1} does not
|
|
exist, it returns @code{nil}. If @var{filename1} does exist, but
|
|
@var{filename2} does not, it returns @code{t}.
|
|
|
|
In the following example, assume that the file @file{aug-19} was written
|
|
on the 19th, @file{aug-20} was written on the 20th, and the file
|
|
@file{no-file} doesn't exist at all.
|
|
|
|
@example
|
|
@group
|
|
(file-newer-than-file-p "aug-19" "aug-20")
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-newer-than-file-p "aug-20" "aug-19")
|
|
@result{} t
|
|
@end group
|
|
@group
|
|
(file-newer-than-file-p "aug-19" "no-file")
|
|
@result{} t
|
|
@end group
|
|
@group
|
|
(file-newer-than-file-p "no-file" "aug-19")
|
|
@result{} nil
|
|
@end group
|
|
@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}.
|
|
@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
|
|
as directories, symbolic links, and ordinary files.
|
|
|
|
@defun file-symlink-p filename
|
|
@cindex file symbolic links
|
|
If the file @var{filename} is a symbolic link, the
|
|
@code{file-symlink-p} function returns the (non-recursive) link target
|
|
as a string. (Determining the file name that the link points to from
|
|
the target is nontrivial.) First, this function recursively follows
|
|
symbolic links at all levels of parent directories.
|
|
|
|
If the file @var{filename} is not a symbolic link (or there is no such file),
|
|
@code{file-symlink-p} returns @code{nil}.
|
|
|
|
@example
|
|
@group
|
|
(file-symlink-p "foo")
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-symlink-p "sym-link")
|
|
@result{} "foo"
|
|
@end group
|
|
@group
|
|
(file-symlink-p "sym-link2")
|
|
@result{} "sym-link"
|
|
@end group
|
|
@group
|
|
(file-symlink-p "/bin")
|
|
@result{} "/pub/bin"
|
|
@end group
|
|
@end example
|
|
|
|
@c !!! file-symlink-p: should show output of ls -l for comparison
|
|
@end defun
|
|
|
|
The next two functions recursively follow symbolic links at
|
|
all levels for @var{filename}.
|
|
|
|
@defun file-directory-p filename
|
|
This function returns @code{t} if @var{filename} is the name of an
|
|
existing directory, @code{nil} otherwise.
|
|
|
|
@example
|
|
@group
|
|
(file-directory-p "~rms")
|
|
@result{} t
|
|
@end group
|
|
@group
|
|
(file-directory-p "~rms/lewis/files.texi")
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-directory-p "~rms/lewis/no-such-file")
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-directory-p "$HOME")
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-directory-p
|
|
(substitute-in-file-name "$HOME"))
|
|
@result{} t
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun file-regular-p filename
|
|
This function returns @code{t} if the file @var{filename} exists and is
|
|
a regular file (not a directory, named pipe, terminal, or
|
|
other I/O device).
|
|
@end defun
|
|
|
|
@node Truenames
|
|
@subsection Truenames
|
|
@cindex truename (of file)
|
|
|
|
@c Emacs 19 features
|
|
The @dfn{truename} of a file is the name that you get by following
|
|
symbolic links at all levels until none remain, then simplifying away
|
|
@samp{.}@: and @samp{..}@: appearing as name components. This results
|
|
in a sort of canonical name for the file. A file does not always have a
|
|
unique truename; the number of distinct truenames a file has is equal to
|
|
the number of hard links to the file. However, truenames are useful
|
|
because they eliminate symbolic links as a cause of name variation.
|
|
|
|
@defun file-truename filename
|
|
The function @code{file-truename} returns the truename of the file
|
|
@var{filename}. The argument must be an absolute file name.
|
|
|
|
This function does not expand environment variables. Only
|
|
@code{substitute-in-file-name} does that. @xref{Definition of
|
|
substitute-in-file-name}.
|
|
|
|
If you may need to follow symbolic links preceding @samp{..}@:
|
|
appearing as a name component, you should make sure to call
|
|
@code{file-truename} without prior direct or indirect calls to
|
|
@code{expand-file-name}, as otherwise the file name component
|
|
immediately preceding @samp{..} will be ``simplified away'' before
|
|
@code{file-truename} is called. To eliminate the need for a call to
|
|
@code{expand-file-name}, @code{file-truename} handles @samp{~} in the
|
|
same way that @code{expand-file-name} does. @xref{File Name
|
|
Expansion,, Functions that Expand Filenames}.
|
|
@end defun
|
|
|
|
@defun file-chase-links filename &optional limit
|
|
This function follows symbolic links, starting with @var{filename},
|
|
until it finds a file name which is not the name of a symbolic link.
|
|
Then it returns that file name. This function does @emph{not} follow
|
|
symbolic links at the level of parent directories.
|
|
|
|
If you specify a number for @var{limit}, then after chasing through
|
|
that many links, the function just returns what it has even if that is
|
|
still a symbolic link.
|
|
@end defun
|
|
|
|
To illustrate the difference between @code{file-chase-links} and
|
|
@code{file-truename}, suppose that @file{/usr/foo} is a symbolic link to
|
|
the directory @file{/home/foo}, and @file{/home/foo/hello} is an
|
|
ordinary file (or at least, not a symbolic link) or nonexistent. Then
|
|
we would have:
|
|
|
|
@example
|
|
(file-chase-links "/usr/foo/hello")
|
|
;; @r{This does not follow the links in the parent directories.}
|
|
@result{} "/usr/foo/hello"
|
|
(file-truename "/usr/foo/hello")
|
|
;; @r{Assuming that @file{/home} is not a symbolic link.}
|
|
@result{} "/home/foo/hello"
|
|
@end example
|
|
|
|
@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 information
|
|
about a file, other than its contents. This information includes the
|
|
mode bits that control access permission, the owner and group numbers,
|
|
the number of names, the inode number, the size, and the times of access
|
|
and modification.
|
|
|
|
@defun file-modes filename
|
|
@cindex permission
|
|
@cindex file attributes
|
|
This function returns the mode bits of @var{filename}, as an integer.
|
|
The mode bits are also called the file permissions, and they specify
|
|
access control in the usual Unix fashion. If the low-order bit is 1,
|
|
then the file is executable by all users, if the second-lowest-order bit
|
|
is 1, then the file is writable by all users, etc.
|
|
|
|
The highest value returnable is 4095 (7777 octal), meaning that
|
|
everyone has read, write, and execute permission, that the @acronym{SUID} bit
|
|
is set for both others and group, and that the sticky bit is set.
|
|
|
|
If @var{filename} does not exist, @code{file-modes} returns @code{nil}.
|
|
|
|
This function recursively follows symbolic links at all levels.
|
|
|
|
@example
|
|
@group
|
|
(file-modes "~/junk/diffs")
|
|
@result{} 492 ; @r{Decimal integer.}
|
|
@end group
|
|
@group
|
|
(format "%o" 492)
|
|
@result{} "754" ; @r{Convert to octal.}
|
|
@end group
|
|
|
|
@group
|
|
(set-file-modes "~/junk/diffs" 438)
|
|
@result{} nil
|
|
@end group
|
|
|
|
@group
|
|
(format "%o" 438)
|
|
@result{} "666" ; @r{Convert to octal.}
|
|
@end group
|
|
|
|
@group
|
|
% ls -l diffs
|
|
-rw-rw-rw- 1 lewis 0 3063 Oct 30 16:00 diffs
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
If the @var{filename} argument to the next two functions is a symbolic
|
|
link, then these function do @emph{not} replace it with its target.
|
|
However, they both recursively follow symbolic links at all levels of
|
|
parent directories.
|
|
|
|
@defun file-nlinks filename
|
|
This functions returns the number of names (i.e., hard links) that
|
|
file @var{filename} has. If the file does not exist, then this function
|
|
returns @code{nil}. Note that symbolic links have no effect on this
|
|
function, because they are not considered to be names of the files they
|
|
link to.
|
|
|
|
@example
|
|
@group
|
|
% ls -l foo*
|
|
-rw-rw-rw- 2 rms 4 Aug 19 01:27 foo
|
|
-rw-rw-rw- 2 rms 4 Aug 19 01:27 foo1
|
|
@end group
|
|
|
|
@group
|
|
(file-nlinks "foo")
|
|
@result{} 2
|
|
@end group
|
|
@group
|
|
(file-nlinks "doesnt-exist")
|
|
@result{} nil
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@anchor{Definition of file-attributes}
|
|
@defun file-attributes filename &optional id-format
|
|
This function returns a list of attributes of file @var{filename}. If
|
|
the specified file cannot be opened, it returns @code{nil}.
|
|
The optional parameter @var{id-format} specifies the preferred format
|
|
of attributes @acronym{UID} and @acronym{GID} (see below)---the
|
|
valid values are @code{'string} and @code{'integer}. The latter is
|
|
the default, but we plan to change that, so you should specify a
|
|
non-@code{nil} value for @var{id-format} if you use the returned
|
|
@acronym{UID} or @acronym{GID}.
|
|
|
|
The elements of the list, in order, are:
|
|
|
|
@enumerate 0
|
|
@item
|
|
@code{t} for a directory, a string for a symbolic link (the name
|
|
linked to), or @code{nil} for a text file.
|
|
|
|
@c Wordy so as to prevent an overfull hbox. --rjc 15mar92
|
|
@item
|
|
The number of names the file has. Alternate names, also known as hard
|
|
links, can be created by using the @code{add-name-to-file} function
|
|
(@pxref{Changing Files}).
|
|
|
|
@item
|
|
The file's @acronym{UID} as a string or an integer. If a string
|
|
value cannot be looked up, the integer value is returned.
|
|
|
|
@item
|
|
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
|
|
value of @code{current-time}; see @ref{Time of Day}.)
|
|
|
|
@item
|
|
The time of last modification as a list of two integers (as above).
|
|
|
|
@item
|
|
The time of last status change as a list of two integers (as above).
|
|
|
|
@item
|
|
The size of the file in bytes. If the size is too large to fit in a
|
|
Lisp integer, this is a floating point number.
|
|
|
|
@item
|
|
The file's modes, as a string of ten letters or dashes,
|
|
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.
|
|
|
|
@item
|
|
The file's inode number. If possible, this is an integer. If the inode
|
|
number is too large to be represented as an integer in Emacs Lisp, then
|
|
the value has the form @code{(@var{high} . @var{low})}, where @var{low}
|
|
holds the low 16 bits.
|
|
|
|
@item
|
|
The file system number of the file system that the file is in.
|
|
Depending on the magnitude of the value, this can be either an integer
|
|
or a cons cell, in the same manner as the inode number. This element
|
|
and the file's inode number together give enough information to
|
|
distinguish any two files on the system---no two files can have the same
|
|
values for both of these numbers.
|
|
@end enumerate
|
|
|
|
For example, here are the file attributes for @file{files.texi}:
|
|
|
|
@example
|
|
@group
|
|
(file-attributes "files.texi" 'string)
|
|
@result{} (nil 1 "lh" "users"
|
|
(8489 20284)
|
|
(8489 20284)
|
|
(8489 20285)
|
|
14906 "-rw-rw-rw-"
|
|
nil 129500 -32252)
|
|
@end group
|
|
@end example
|
|
|
|
@noindent
|
|
and here is how the result is interpreted:
|
|
|
|
@table @code
|
|
@item nil
|
|
is neither a directory nor a symbolic link.
|
|
|
|
@item 1
|
|
has only one name (the name @file{files.texi} in the current default
|
|
directory).
|
|
|
|
@item "lh"
|
|
is owned by the user with name "lh".
|
|
|
|
@item "users"
|
|
is in the group with name "users".
|
|
|
|
@item (8489 20284)
|
|
was last accessed on Aug 19 00:09.
|
|
|
|
@item (8489 20284)
|
|
was last modified on Aug 19 00:09.
|
|
|
|
@item (8489 20285)
|
|
last had its inode changed on Aug 19 00:09.
|
|
|
|
@item 14906
|
|
is 14906 bytes long. (It may not contain 14906 characters, though,
|
|
if some of the bytes belong to multibyte sequences.)
|
|
|
|
@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 129500
|
|
has an inode number of 129500.
|
|
@item -32252
|
|
is on file system number -32252.
|
|
@end table
|
|
@end defun
|
|
|
|
@node Changing Files
|
|
@section Changing File Names and Attributes
|
|
@cindex renaming files
|
|
@cindex copying files
|
|
@cindex deleting files
|
|
@cindex linking files
|
|
@cindex setting modes of files
|
|
|
|
The functions in this section rename, copy, delete, link, and set the
|
|
modes of files.
|
|
|
|
In the functions that have an argument @var{newname}, if a file by the
|
|
name of @var{newname} already exists, the actions taken depend on the
|
|
value of the argument @var{ok-if-already-exists}:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
Signal a @code{file-already-exists} error if
|
|
@var{ok-if-already-exists} is @code{nil}.
|
|
|
|
@item
|
|
Request confirmation if @var{ok-if-already-exists} is a number.
|
|
|
|
@item
|
|
Replace the old file without confirmation if @var{ok-if-already-exists}
|
|
is any other value.
|
|
@end itemize
|
|
|
|
The next four commands all recursively follow symbolic links at all
|
|
levels of parent directories for their first argument, but, if that
|
|
argument is itself a symbolic link, then only @code{copy-file}
|
|
replaces it with its (recursive) target.
|
|
|
|
@deffn Command add-name-to-file oldname newname &optional ok-if-already-exists
|
|
@cindex file with multiple names
|
|
@cindex file hard link
|
|
This function gives the file named @var{oldname} the additional name
|
|
@var{newname}. This means that @var{newname} becomes a new ``hard
|
|
link'' to @var{oldname}.
|
|
|
|
In the first part of the following example, we list two files,
|
|
@file{foo} and @file{foo3}.
|
|
|
|
@example
|
|
@group
|
|
% ls -li fo*
|
|
81908 -rw-rw-rw- 1 rms 29 Aug 18 20:32 foo
|
|
84302 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3
|
|
@end group
|
|
@end example
|
|
|
|
Now we create a hard link, by calling @code{add-name-to-file}, then list
|
|
the files again. This shows two names for one file, @file{foo} and
|
|
@file{foo2}.
|
|
|
|
@example
|
|
@group
|
|
(add-name-to-file "foo" "foo2")
|
|
@result{} nil
|
|
@end group
|
|
|
|
@group
|
|
% ls -li fo*
|
|
81908 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo
|
|
81908 -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo2
|
|
84302 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3
|
|
@end group
|
|
@end example
|
|
|
|
Finally, we evaluate the following:
|
|
|
|
@example
|
|
(add-name-to-file "foo" "foo3" t)
|
|
@end example
|
|
|
|
@noindent
|
|
and list the files again. Now there are three names
|
|
for one file: @file{foo}, @file{foo2}, and @file{foo3}. The old
|
|
contents of @file{foo3} are lost.
|
|
|
|
@example
|
|
@group
|
|
(add-name-to-file "foo1" "foo3")
|
|
@result{} nil
|
|
@end group
|
|
|
|
@group
|
|
% ls -li fo*
|
|
81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo
|
|
81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo2
|
|
81908 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo3
|
|
@end group
|
|
@end example
|
|
|
|
This function is meaningless on operating systems where multiple names
|
|
for one file are not allowed. Some systems implement multiple names
|
|
by copying the file instead.
|
|
|
|
See also @code{file-nlinks} in @ref{File Attributes}.
|
|
@end deffn
|
|
|
|
@deffn Command rename-file filename newname &optional ok-if-already-exists
|
|
This command renames the file @var{filename} as @var{newname}.
|
|
|
|
If @var{filename} has additional names aside from @var{filename}, it
|
|
continues to have those names. In fact, adding the name @var{newname}
|
|
with @code{add-name-to-file} and then deleting @var{filename} has the
|
|
same effect as renaming, aside from momentary intermediate states.
|
|
@end deffn
|
|
|
|
@deffn Command copy-file oldname newname &optional ok-if-exists time
|
|
This command copies the file @var{oldname} to @var{newname}. An
|
|
error is signaled if @var{oldname} does not exist. If @var{newname}
|
|
names a directory, it copies @var{oldname} into that directory,
|
|
preserving its final name component.
|
|
|
|
If @var{time} is non-@code{nil}, then this function gives the new file
|
|
the same last-modified time that the old one has. (This works on only
|
|
some operating systems.) If setting the time gets an error,
|
|
@code{copy-file} signals a @code{file-date-error} error.
|
|
|
|
This function copies the file modes, too.
|
|
|
|
In an interactive call, a prefix argument specifies a non-@code{nil}
|
|
value for @var{time}.
|
|
@end deffn
|
|
|
|
@deffn Command make-symbolic-link filename newname &optional ok-if-exists
|
|
@pindex ln
|
|
@kindex file-already-exists
|
|
This command makes a symbolic link to @var{filename}, named
|
|
@var{newname}. This is like the shell command @samp{ln -s
|
|
@var{filename} @var{newname}}.
|
|
|
|
This function is not available on systems that don't support symbolic
|
|
links.
|
|
@end deffn
|
|
|
|
@deffn Command delete-file filename
|
|
@pindex rm
|
|
This command deletes the file @var{filename}, like the shell command
|
|
@samp{rm @var{filename}}. If the file has multiple names, it continues
|
|
to exist under the other names.
|
|
|
|
A suitable kind of @code{file-error} error is signaled if the file does
|
|
not exist, or is not deletable. (On Unix and GNU/Linux, a file is
|
|
deletable if its directory is writable.)
|
|
|
|
If @var{filename} is a symbolic link, @code{delete-file} does not
|
|
replace it with its target, but it does follow symbolic links at all
|
|
levels of parent directories.
|
|
|
|
See also @code{delete-directory} in @ref{Create/Delete Dirs}.
|
|
@end deffn
|
|
|
|
@defun define-logical-name varname string
|
|
This function defines the logical name @var{varname} to have the value
|
|
@var{string}. It is available only on VMS.
|
|
@end defun
|
|
|
|
@defun set-file-modes filename mode
|
|
This function sets mode bits of @var{filename} to @var{mode} (which
|
|
must be an integer). Only the low 12 bits of @var{mode} are used.
|
|
This function recursively follows symbolic links at all levels for
|
|
@var{filename}.
|
|
@end defun
|
|
|
|
@c Emacs 19 feature
|
|
@defun set-default-file-modes mode
|
|
@cindex umask
|
|
This function sets the default file protection for new files created by
|
|
Emacs and its subprocesses. Every file created with Emacs initially has
|
|
this protection, or a subset of it (@code{write-region} will not give a
|
|
file execute permission even if the default file protection allows
|
|
execute permission). On Unix and GNU/Linux, the default protection is
|
|
the bitwise complement of the ``umask'' value.
|
|
|
|
The argument @var{mode} must be an integer. On most systems, only the
|
|
low 9 bits of @var{mode} are meaningful. You can use the Lisp construct
|
|
for octal character codes to enter @var{mode}; for example,
|
|
|
|
@example
|
|
(set-default-file-modes ?\644)
|
|
@end example
|
|
|
|
Saving a modified version of an existing file does not count as creating
|
|
the file; it preserves the existing file's mode, whatever that is. So
|
|
the default file protection has no effect.
|
|
@end defun
|
|
|
|
@defun default-file-modes
|
|
This function returns the current default protection value.
|
|
@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.
|
|
|
|
@node File Names
|
|
@section File Names
|
|
@cindex file names
|
|
|
|
Files are generally referred to by their names, in Emacs as elsewhere.
|
|
File names in Emacs are represented as strings. The functions that
|
|
operate on a file all expect a file name argument.
|
|
|
|
In addition to operating on files themselves, Emacs Lisp programs
|
|
often need to operate on file names; i.e., to take them apart and to use
|
|
part of a name to construct related file names. This section describes
|
|
how to manipulate file names.
|
|
|
|
The functions in this section do not actually access files, so they
|
|
can operate on file names that do not refer to an existing file or
|
|
directory.
|
|
|
|
On MS-DOS and MS-Windows, these functions (like the function that
|
|
actually operate on files) accept MS-DOS or MS-Windows file-name syntax,
|
|
where backslashes separate the components, as well as Unix syntax; but
|
|
they always return Unix syntax. On VMS, these functions (and the ones
|
|
that operate on files) understand both VMS file-name syntax and Unix
|
|
syntax. This enables Lisp programs to specify file names in Unix syntax
|
|
and work properly on all systems without change.
|
|
|
|
@menu
|
|
* File Name Components:: The directory part of a file name, and the rest.
|
|
* Relative File Names:: Some file names are relative to a current directory.
|
|
* Directory Names:: A directory's name as a directory
|
|
is different from its name as a file.
|
|
* File Name Expansion:: Converting relative file names to absolute ones.
|
|
* Unique File Names:: Generating names for temporary files.
|
|
* File Name Completion:: Finding the completions for a given file name.
|
|
* Standard File Names:: If your package uses a fixed file name,
|
|
how to handle various operating systems simply.
|
|
@end menu
|
|
|
|
@node File Name Components
|
|
@subsection File Name Components
|
|
@cindex directory part (of file name)
|
|
@cindex nondirectory part (of file name)
|
|
@cindex version number (in file name)
|
|
|
|
The operating system groups files into directories. To specify a
|
|
file, you must specify the directory and the file's name within that
|
|
directory. Therefore, Emacs considers a file name as having two main
|
|
parts: the @dfn{directory name} part, and the @dfn{nondirectory} part
|
|
(or @dfn{file name within the directory}). Either part may be empty.
|
|
Concatenating these two parts reproduces the original file name.
|
|
|
|
On most systems, the directory part is everything up to and including
|
|
the last slash (backslash is also allowed in input on MS-DOS or
|
|
MS-Windows); the nondirectory part is the rest. The rules in VMS syntax
|
|
are complicated.
|
|
|
|
For some purposes, the nondirectory part is further subdivided into
|
|
the name proper and the @dfn{version number}. On most systems, only
|
|
backup files have version numbers in their names. On VMS, every file
|
|
has a version number, but most of the time the file name actually used
|
|
in Emacs omits the version number, so that version numbers in Emacs are
|
|
found mostly in directory lists.
|
|
|
|
@defun file-name-directory filename
|
|
This function returns the directory part of @var{filename}, as a
|
|
directory name (@pxref{Directory Names}), or @code{nil} if
|
|
@var{filename} does not include a directory part.
|
|
|
|
On GNU and Unix systems, a string returned by this function always
|
|
ends in a slash. On MSDOS it can also end in a colon. On VMS, it
|
|
returns a string ending in one of the three characters @samp{:},
|
|
@samp{]}, or @samp{>}.
|
|
|
|
@example
|
|
@group
|
|
(file-name-directory "lewis/foo") ; @r{Unix example}
|
|
@result{} "lewis/"
|
|
@end group
|
|
@group
|
|
(file-name-directory "foo") ; @r{Unix example}
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-name-directory "[X]FOO.TMP") ; @r{VMS example}
|
|
@result{} "[X]"
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun file-name-nondirectory filename
|
|
This function returns the nondirectory part of @var{filename}.
|
|
|
|
@example
|
|
@group
|
|
(file-name-nondirectory "lewis/foo")
|
|
@result{} "foo"
|
|
@end group
|
|
@group
|
|
(file-name-nondirectory "foo")
|
|
@result{} "foo"
|
|
@end group
|
|
@group
|
|
(file-name-nondirectory "lewis/")
|
|
@result{} ""
|
|
@end group
|
|
@group
|
|
;; @r{The following example is accurate only on VMS.}
|
|
(file-name-nondirectory "[X]FOO.TMP")
|
|
@result{} "FOO.TMP"
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun file-name-sans-versions filename &optional keep-backup-version
|
|
This function returns @var{filename} with any file version numbers,
|
|
backup version numbers, or trailing tildes discarded.
|
|
|
|
If @var{keep-backup-version} is non-@code{nil}, then true file version
|
|
numbers understood as such by the file system are discarded from the
|
|
return value, but backup version numbers are kept.
|
|
|
|
@example
|
|
@group
|
|
(file-name-sans-versions "~rms/foo.~1~")
|
|
@result{} "~rms/foo"
|
|
@end group
|
|
@group
|
|
(file-name-sans-versions "~rms/foo~")
|
|
@result{} "~rms/foo"
|
|
@end group
|
|
@group
|
|
(file-name-sans-versions "~rms/foo")
|
|
@result{} "~rms/foo"
|
|
@end group
|
|
@group
|
|
;; @r{The following example applies to VMS only.}
|
|
(file-name-sans-versions "foo;23")
|
|
@result{} "foo"
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun file-name-extension filename &optional period
|
|
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
|
|
starts with the last @samp{.} in the last name component (minus
|
|
any version/backup part).
|
|
|
|
This function returns @code{nil} for extensionless file names such as
|
|
@file{foo}. It returns @code{""} for null extensions, as in
|
|
@file{foo.}. If the last component of a file name begins with a
|
|
@samp{.}, that @samp{.} doesn't count as the beginning of an
|
|
extension. Thus, @file{.emacs}'s ``extension'' is @code{nil}, not
|
|
@samp{.emacs}.
|
|
|
|
If @var{period} is non-@code{nil}, then the returned value includes
|
|
the period that delimits the extension, and if @var{filename} has no
|
|
extension, the value is @code{""}.
|
|
@end defun
|
|
|
|
@defun file-name-sans-extension filename
|
|
This function returns @var{filename} minus its extension, if any. The
|
|
version/backup part, if present, is only removed if the file has an
|
|
extension. For example,
|
|
|
|
@example
|
|
(file-name-sans-extension "foo.lose.c")
|
|
@result{} "foo.lose"
|
|
(file-name-sans-extension "big.hack/foo")
|
|
@result{} "big.hack/foo"
|
|
(file-name-sans-extension "/my/home/.emacs")
|
|
@result{} "/my/home/.emacs"
|
|
(file-name-sans-extension "/my/home/.emacs.el")
|
|
@result{} "/my/home/.emacs"
|
|
(file-name-sans-extension "~/foo.el.~3~")
|
|
@result{} "~/foo"
|
|
(file-name-sans-extension "~/foo.~3~")
|
|
@result{} "~/foo.~3~"
|
|
@end example
|
|
|
|
Note that the @samp{.~3~} in the two last examples is the backup part,
|
|
not an extension.
|
|
@end defun
|
|
|
|
@ignore
|
|
Andrew Innes says that this
|
|
|
|
@c @defvar directory-sep-char
|
|
@c @tindex directory-sep-char
|
|
This variable holds the character that Emacs normally uses to separate
|
|
file name components. The default value is @code{?/}, but on MS-Windows
|
|
you can set it to @code{?\\}; then the functions that transform file names
|
|
use backslashes in their output.
|
|
|
|
File names using backslashes work as input to Lisp primitives even on
|
|
MS-DOS and MS-Windows, even if @code{directory-sep-char} has its default
|
|
value of @code{?/}.
|
|
@end defvar
|
|
@end ignore
|
|
|
|
@node Relative File Names
|
|
@subsection Absolute and Relative File Names
|
|
@cindex absolute file name
|
|
@cindex relative file name
|
|
|
|
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}. The rules on VMS are complicated.
|
|
|
|
@defun file-name-absolute-p filename
|
|
This function returns @code{t} if file @var{filename} is an absolute
|
|
file name, @code{nil} otherwise. On VMS, this function understands both
|
|
Unix syntax and VMS syntax.
|
|
|
|
@example
|
|
@group
|
|
(file-name-absolute-p "~rms/foo")
|
|
@result{} t
|
|
@end group
|
|
@group
|
|
(file-name-absolute-p "rms/foo")
|
|
@result{} nil
|
|
@end group
|
|
@group
|
|
(file-name-absolute-p "/user/rms/foo")
|
|
@result{} t
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@node Directory Names
|
|
@comment node-name, next, previous, up
|
|
@subsection Directory Names
|
|
@cindex directory name
|
|
@cindex file name of directory
|
|
|
|
A @dfn{directory name} is the name of a directory. A directory is
|
|
actually a kind of file, so it has a file name, which is related to
|
|
the directory name but not identical to it. (This is not quite the
|
|
same as the usual Unix terminology.) These two different names for
|
|
the same entity are related by a syntactic transformation. On GNU and
|
|
Unix systems, this is simple: a directory name ends in a slash,
|
|
whereas the directory's name as a file lacks that slash. On MSDOS and
|
|
VMS, the relationship is more complicated.
|
|
|
|
The difference between a directory name and its name as a file is
|
|
subtle but crucial. When an Emacs variable or function argument is
|
|
described as being a directory name, a file name of a directory is not
|
|
acceptable. When @code{file-name-directory} returns a string, that is
|
|
always a directory name.
|
|
|
|
The following two functions convert between directory names and file
|
|
names. They do nothing special with environment variable substitutions
|
|
such as @samp{$HOME}, and the constructs @samp{~}, @samp{.} and @samp{..}.
|
|
|
|
@defun file-name-as-directory filename
|
|
This function returns a string representing @var{filename} in a form
|
|
that the operating system will interpret as the name of a directory. On
|
|
most systems, this means appending a slash to the string (if it does not
|
|
already end in one). On VMS, the function converts a string of the form
|
|
@file{[X]Y.DIR.1} to the form @file{[X.Y]}.
|
|
|
|
@example
|
|
@group
|
|
(file-name-as-directory "~rms/lewis")
|
|
@result{} "~rms/lewis/"
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun directory-file-name dirname
|
|
This function returns a string representing @var{dirname} in a form that
|
|
the operating system will interpret as the name of a file. On most
|
|
systems, this means removing the final slash (or backslash) from the
|
|
string. On VMS, the function converts a string of the form @file{[X.Y]}
|
|
to @file{[X]Y.DIR.1}.
|
|
|
|
@example
|
|
@group
|
|
(directory-file-name "~lewis/")
|
|
@result{} "~lewis"
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
Given a directory name, you can combine it with a relative file name
|
|
using @code{concat}:
|
|
|
|
@example
|
|
(concat @var{dirname} @var{relfile})
|
|
@end example
|
|
|
|
@noindent
|
|
Be sure to verify that the file name is relative before doing that.
|
|
If you use an absolute file name, the results could be syntactically
|
|
invalid or refer to the wrong file.
|
|
|
|
If you want to use a directory file name in making such a
|
|
combination, you must first convert it to a directory name using
|
|
@code{file-name-as-directory}:
|
|
|
|
@example
|
|
(concat (file-name-as-directory @var{dirfile}) @var{relfile})
|
|
@end example
|
|
|
|
@noindent
|
|
Don't try concatenating a slash by hand, as in
|
|
|
|
@example
|
|
;;; @r{Wrong!}
|
|
(concat @var{dirfile} "/" @var{relfile})
|
|
@end example
|
|
|
|
@noindent
|
|
because this is not portable. Always use
|
|
@code{file-name-as-directory}.
|
|
|
|
@cindex directory name abbreviation
|
|
Directory name abbreviations are useful for directories that are
|
|
normally accessed through symbolic links. Sometimes the users recognize
|
|
primarily the link's name as ``the name'' of the directory, and find it
|
|
annoying to see the directory's ``real'' name. If you define the link
|
|
name as an abbreviation for the ``real'' name, Emacs shows users the
|
|
abbreviation instead.
|
|
|
|
@defvar directory-abbrev-alist
|
|
The variable @code{directory-abbrev-alist} contains an alist of
|
|
abbreviations to use for file directories. Each element has the form
|
|
@code{(@var{from} . @var{to})}, and says to replace @var{from} with
|
|
@var{to} when it appears in a directory name. The @var{from} string is
|
|
actually a regular expression; it should always start with @samp{^}.
|
|
The @var{to} string should be an ordinary absolute directory name. Do
|
|
not use @samp{~} to stand for a home directory in that string. The
|
|
function @code{abbreviate-file-name} performs these substitutions.
|
|
|
|
You can set this variable in @file{site-init.el} to describe the
|
|
abbreviations appropriate for your site.
|
|
|
|
Here's an example, from a system on which file system @file{/home/fsf}
|
|
and so on are normally accessed through symbolic links named @file{/fsf}
|
|
and so on.
|
|
|
|
@example
|
|
(("^/home/fsf" . "/fsf")
|
|
("^/home/gp" . "/gp")
|
|
("^/home/gd" . "/gd"))
|
|
@end example
|
|
@end defvar
|
|
|
|
To convert a directory name to its abbreviation, use this
|
|
function:
|
|
|
|
@anchor{Definition of abbreviate-file-name}
|
|
@defun abbreviate-file-name filename
|
|
This function applies abbreviations from @code{directory-abbrev-alist}
|
|
to its argument, and substitutes @samp{~} for the user's home
|
|
directory. You can use it for directory names and for file names,
|
|
because it recognizes abbreviations even as part of the name.
|
|
@end defun
|
|
|
|
@node File Name Expansion
|
|
@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}/../}.
|
|
|
|
In the next two functions, the @var{directory} argument can be either
|
|
a directory name or a directory file name. @xref{Directory Names}.
|
|
|
|
@defun expand-file-name filename &optional directory
|
|
This function converts @var{filename} to an absolute file name. If
|
|
@var{directory} is supplied, it is the default directory to start with
|
|
if @var{filename} is relative. (The value of @var{directory} should
|
|
itself be an absolute directory name; it may start with @samp{~}.)
|
|
Otherwise, the current buffer's value of @code{default-directory} is
|
|
used. For example:
|
|
|
|
@example
|
|
@group
|
|
(expand-file-name "foo")
|
|
@result{} "/xcssun/users/rms/lewis/foo"
|
|
@end group
|
|
@group
|
|
(expand-file-name "../foo")
|
|
@result{} "/xcssun/users/rms/foo"
|
|
@end group
|
|
@group
|
|
(expand-file-name "foo" "/usr/spool/")
|
|
@result{} "/usr/spool/foo"
|
|
@end group
|
|
@group
|
|
(expand-file-name "$HOME/foo")
|
|
@result{} "/xcssun/users/rms/lewis/$HOME/foo"
|
|
@end group
|
|
@end example
|
|
|
|
If the part of the combined file name before the first slash is
|
|
@samp{~}, it expands to the value of the @env{HOME} environment
|
|
variable (usually your home directory). If the part before the first
|
|
slash is @samp{~@var{user}} and if @var{user} is a valid login name,
|
|
it expands to @var{user}'s home directory.
|
|
|
|
Filenames containing @samp{.} or @samp{..} are simplified to their
|
|
canonical form:
|
|
|
|
@example
|
|
@group
|
|
(expand-file-name "bar/../foo")
|
|
@result{} "/xcssun/users/rms/lewis/foo"
|
|
@end group
|
|
@end example
|
|
|
|
Note that @code{expand-file-name} does @emph{not} expand environment
|
|
variables; only @code{substitute-in-file-name} does that.
|
|
|
|
Note also that @code{expand-file-name} does not follow symbolic links
|
|
at any level. This results in a difference between the way
|
|
@code{file-truename} and @code{expand-file-name} treat @samp{..}.
|
|
Assuming that @samp{/tmp/bar} is a symbolic link to the directory
|
|
@samp{/tmp/foo/bar} we get:
|
|
|
|
@example
|
|
@group
|
|
(file-truename "/tmp/bar/../myfile")
|
|
@result{} "/tmp/foo/myfile"
|
|
@end group
|
|
@group
|
|
(expand-file-name "/tmp/bar/../myfile")
|
|
@result{} "/tmp/myfile"
|
|
@end group
|
|
@end example
|
|
|
|
If you may need to follow symbolic links preceding @samp{..}, you
|
|
should make sure to call @code{file-truename} without prior direct or
|
|
indirect calls to @code{expand-file-name}. @xref{Truenames}.
|
|
@end defun
|
|
|
|
@c Emacs 19 feature
|
|
@defun file-relative-name filename &optional directory
|
|
This function does the inverse of expansion---it tries to return a
|
|
relative name that is equivalent to @var{filename} when interpreted
|
|
relative to @var{directory}. If @var{directory} is omitted or
|
|
@code{nil}, it defaults to the current buffer's default directory.
|
|
|
|
On some operating systems, an absolute file name begins with a device
|
|
name. On such systems, @var{filename} has no relative equivalent based
|
|
on @var{directory} if they start with two different device names. In
|
|
this case, @code{file-relative-name} returns @var{filename} in absolute
|
|
form.
|
|
|
|
@example
|
|
(file-relative-name "/foo/bar" "/foo/")
|
|
@result{} "bar"
|
|
(file-relative-name "/foo/bar" "/hack/")
|
|
@result{} "../foo/bar"
|
|
@end example
|
|
@end defun
|
|
|
|
@defvar default-directory
|
|
The value of this buffer-local variable is the default directory for the
|
|
current buffer. It should be an absolute directory name; it may start
|
|
with @samp{~}. This variable is buffer-local in every buffer.
|
|
|
|
@code{expand-file-name} uses the default directory when its second
|
|
argument is @code{nil}.
|
|
|
|
Aside from VMS, the value is always a string ending with a slash.
|
|
|
|
@example
|
|
@group
|
|
default-directory
|
|
@result{} "/user/lewis/manual/"
|
|
@end group
|
|
@end example
|
|
@end defvar
|
|
|
|
@anchor{Definition of substitute-in-file-name}
|
|
@defun substitute-in-file-name filename
|
|
This function replaces environment variable references in
|
|
@var{filename} with the environment variable values. Following
|
|
standard Unix shell syntax, @samp{$} is the prefix to substitute an
|
|
environment variable value. If the input contains @samp{$$}, that is
|
|
converted to @samp{$}; this gives the user a way to ``quote'' a
|
|
@samp{$}.
|
|
|
|
The environment variable name is the series of alphanumeric characters
|
|
(including underscores) that follow the @samp{$}. If the character following
|
|
the @samp{$} is a @samp{@{}, then the variable name is everything up to the
|
|
matching @samp{@}}.
|
|
|
|
Calling @code{substitute-in-file-name} on output produced by
|
|
@code{substitute-in-file-name} tends to give incorrect results. For
|
|
instance, use of @samp{$$} to quote a single @samp{$} won't work
|
|
properly, and @samp{$} in an environment variable's value could lead
|
|
to repeated substitution. Therefore, programs that call this function
|
|
and put the output where it will be passed to this function need to
|
|
double all @samp{$} characters to prevent subsequent incorrect
|
|
results.
|
|
|
|
@c Wordy to avoid overfull hbox. --rjc 15mar92
|
|
Here we assume that the environment variable @code{HOME}, which holds
|
|
the user's home directory name, has value @samp{/xcssun/users/rms}.
|
|
|
|
@example
|
|
@group
|
|
(substitute-in-file-name "$HOME/foo")
|
|
@result{} "/xcssun/users/rms/foo"
|
|
@end group
|
|
@end example
|
|
|
|
After substitution, if a @samp{~} or a @samp{/} appears immediately
|
|
after another @samp{/}, the function discards everything before it (up
|
|
through the immediately preceding @samp{/}).
|
|
|
|
@example
|
|
@group
|
|
(substitute-in-file-name "bar/~/foo")
|
|
@result{} "~/foo"
|
|
@end group
|
|
@group
|
|
(substitute-in-file-name "/usr/local/$HOME/foo")
|
|
@result{} "/xcssun/users/rms/foo"
|
|
;; @r{@file{/usr/local/} has been discarded.}
|
|
@end group
|
|
@end example
|
|
|
|
On VMS, @samp{$} substitution is not done, so this function does nothing
|
|
on VMS except discard superfluous initial components as shown above.
|
|
@end defun
|
|
|
|
@node Unique File Names
|
|
@subsection Generating Unique File Names
|
|
|
|
Some programs need to write temporary files. Here is the usual way to
|
|
construct a name for such a file, starting in Emacs 21:
|
|
|
|
@example
|
|
(make-temp-file @var{name-of-application})
|
|
@end example
|
|
|
|
@noindent
|
|
The job of @code{make-temp-file} is to prevent two different users or
|
|
two different jobs from trying to use the exact same file name.
|
|
|
|
@defun make-temp-file prefix &optional dir-flag suffix
|
|
@tindex make-temp-file
|
|
This function creates a temporary file and returns its name.
|
|
The name starts with @var{prefix}; it also contains a number that is
|
|
different in each Emacs job. If @var{prefix} is a relative file name,
|
|
it is expanded against @code{temporary-file-directory}.
|
|
|
|
@example
|
|
@group
|
|
(make-temp-file "foo")
|
|
@result{} "/tmp/foo232J6v"
|
|
@end group
|
|
@end example
|
|
|
|
When @code{make-temp-file} returns, the file has been created and is
|
|
empty. At that point, you should write the intended contents into the
|
|
file.
|
|
|
|
If @var{dir-flag} is non-@code{nil}, @code{make-temp-file} creates an
|
|
empty directory instead of an empty file. It returns the file name,
|
|
not the directory name, of that directory. @xref{Directory Names}.
|
|
|
|
If @var{suffix} is non-@code{nil}, @code{make-temp-file} adds it at
|
|
the end of the file name.
|
|
|
|
To prevent conflicts among different libraries running in the same
|
|
Emacs, each Lisp program that uses @code{make-temp-file} should have its
|
|
own @var{prefix}. The number added to the end of @var{prefix}
|
|
distinguishes between the same application running in different Emacs
|
|
jobs. Additional added characters permit a large number of distinct
|
|
names even in one Emacs job.
|
|
@end defun
|
|
|
|
The default directory for temporary files is controlled by the
|
|
variable @code{temporary-file-directory}. This variable gives the user
|
|
a uniform way to specify the directory for all temporary files. Some
|
|
programs use @code{small-temporary-file-directory} instead, if that is
|
|
non-@code{nil}. To use it, you should expand the prefix against
|
|
the proper directory before calling @code{make-temp-file}.
|
|
|
|
In older Emacs versions where @code{make-temp-file} does not exist,
|
|
you should use @code{make-temp-name} instead:
|
|
|
|
@example
|
|
(make-temp-name
|
|
(expand-file-name @var{name-of-application}
|
|
temporary-file-directory))
|
|
@end example
|
|
|
|
@defun make-temp-name string
|
|
This function generates a string that can be used as a unique file name.
|
|
The name starts with @var{string}, and contains a number that is
|
|
different in each Emacs job. It is like @code{make-temp-file} except
|
|
that it just constructs a name, and does not create a file. Another
|
|
difference is that @var{string} should be an absolute file name. On
|
|
MS-DOS, this function can truncate the @var{string} prefix to fit into
|
|
the 8+3 file-name limits.
|
|
@end defun
|
|
|
|
@defvar temporary-file-directory
|
|
@cindex @code{TMPDIR} environment variable
|
|
@cindex @code{TMP} environment variable
|
|
@cindex @code{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
|
|
name instead. Using the value as the second argument to
|
|
@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}
|
|
environment variables, with a fall-back to a system-dependent name if
|
|
none of these variables is defined.
|
|
|
|
Even if you do not use @code{make-temp-file} to create the temporary
|
|
file, you should still use this variable to decide which directory to
|
|
put the file in. However, if you expect the file to be small, you
|
|
should use @code{small-temporary-file-directory} first if that is
|
|
non-@code{nil}.
|
|
@end defvar
|
|
|
|
@tindex small-temporary-file-directory
|
|
@defvar small-temporary-file-directory
|
|
This variable (new in Emacs 21) specifies the directory name for
|
|
creating certain temporary files, which are likely to be small.
|
|
|
|
If you want to write a temporary file which is likely to be small, you
|
|
should compute the directory like this:
|
|
|
|
@example
|
|
(make-temp-file
|
|
(expand-file-name @var{prefix}
|
|
(or small-temporary-file-directory
|
|
temporary-file-directory)))
|
|
@end example
|
|
@end defvar
|
|
|
|
@node File Name Completion
|
|
@subsection File Name Completion
|
|
@cindex file name completion subroutines
|
|
@cindex completion, file name
|
|
|
|
This section describes low-level subroutines for completing a file
|
|
name. For other completion functions, see @ref{Completion}.
|
|
|
|
@defun file-name-all-completions partial-filename directory
|
|
This function returns a list of all possible completions for a file
|
|
whose name starts with @var{partial-filename} in directory
|
|
@var{directory}. The order of the completions is the order of the files
|
|
in the directory, which is unpredictable and conveys no useful
|
|
information.
|
|
|
|
The argument @var{partial-filename} must be a file name containing no
|
|
directory part and no slash (or backslash on some systems). The current
|
|
buffer's default directory is prepended to @var{directory}, if
|
|
@var{directory} is not absolute.
|
|
|
|
In the following example, suppose that @file{~rms/lewis} is the current
|
|
default directory, and has five files whose names begin with @samp{f}:
|
|
@file{foo}, @file{file~}, @file{file.c}, @file{file.c.~1~}, and
|
|
@file{file.c.~2~}.@refill
|
|
|
|
@example
|
|
@group
|
|
(file-name-all-completions "f" "")
|
|
@result{} ("foo" "file~" "file.c.~2~"
|
|
"file.c.~1~" "file.c")
|
|
@end group
|
|
|
|
@group
|
|
(file-name-all-completions "fo" "")
|
|
@result{} ("foo")
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defun file-name-completion filename directory
|
|
This function completes the file name @var{filename} in directory
|
|
@var{directory}. It returns the longest prefix common to all file names
|
|
in directory @var{directory} that start with @var{filename}.
|
|
|
|
If only one match exists and @var{filename} matches it exactly, the
|
|
function returns @code{t}. The function returns @code{nil} if directory
|
|
@var{directory} contains no name starting with @var{filename}.
|
|
|
|
In the following example, suppose that the current default directory
|
|
has five files whose names begin with @samp{f}: @file{foo},
|
|
@file{file~}, @file{file.c}, @file{file.c.~1~}, and
|
|
@file{file.c.~2~}.@refill
|
|
|
|
@example
|
|
@group
|
|
(file-name-completion "fi" "")
|
|
@result{} "file"
|
|
@end group
|
|
|
|
@group
|
|
(file-name-completion "file.c.~1" "")
|
|
@result{} "file.c.~1~"
|
|
@end group
|
|
|
|
@group
|
|
(file-name-completion "file.c.~1~" "")
|
|
@result{} t
|
|
@end group
|
|
|
|
@group
|
|
(file-name-completion "file.c.~3" "")
|
|
@result{} nil
|
|
@end group
|
|
@end example
|
|
@end defun
|
|
|
|
@defopt completion-ignored-extensions
|
|
@code{file-name-completion} usually ignores file names that end in any
|
|
string in this list. It does not ignore them when all the possible
|
|
completions end in one of these suffixes. This variable has no effect
|
|
on @code{file-name-all-completions}.@refill
|
|
|
|
A typical value might look like this:
|
|
|
|
@example
|
|
@group
|
|
completion-ignored-extensions
|
|
@result{} (".o" ".elc" "~" ".dvi")
|
|
@end group
|
|
@end example
|
|
|
|
If an element of @code{completion-ignored-extensions} ends in a slash
|
|
@samp{/}, it signals a directory. The elements which do @emph{not} end
|
|
in a slash will never match a directory; thus, the above value will not
|
|
filter out a directory named @file{foo.elc}.
|
|
@end defopt
|
|
|
|
@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.
|
|
|
|
@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
|
|
|
|
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:
|
|
|
|
@example
|
|
(defvar save-completions-file-name
|
|
(convert-standard-filename "~/.completions")
|
|
"*The file name to save completions to.")
|
|
@end example
|
|
|
|
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.
|
|
|
|
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}.
|
|
|
|
@node Contents of Directories
|
|
@section Contents of Directories
|
|
@cindex directory-oriented functions
|
|
@cindex file names in directory
|
|
|
|
A directory is a kind of file that contains other files entered under
|
|
various names. Directories are a feature of the file system.
|
|
|
|
Emacs can list the names of the files in a directory as a Lisp list,
|
|
or display the names in a buffer using the @code{ls} shell command. In
|
|
the latter case, it can optionally display information about each file,
|
|
depending on the options passed to the @code{ls} command.
|
|
|
|
@defun directory-files directory &optional full-name match-regexp nosort
|
|
This function returns a list of the names of the files in the directory
|
|
@var{directory}. By default, the list is in alphabetical order.
|
|
|
|
If @var{full-name} is non-@code{nil}, the function returns the files'
|
|
absolute file names. Otherwise, it returns the names relative to
|
|
the specified directory.
|
|
|
|
If @var{match-regexp} is non-@code{nil}, this function returns only
|
|
those file names that contain a match for that regular expression---the
|
|
other file names are excluded from the list.
|
|
|
|
@c Emacs 19 feature
|
|
If @var{nosort} is non-@code{nil}, @code{directory-files} does not sort
|
|
the list, so you get the file names in no particular order. Use this if
|
|
you want the utmost possible speed and don't care what order the files
|
|
are processed in. If the order of processing is visible to the user,
|
|
then the user will probably be happier if you do sort the names.
|
|
|
|
@example
|
|
@group
|
|
(directory-files "~lewis")
|
|
@result{} ("#foo#" "#foo.el#" "." ".."
|
|
"dired-mods.el" "files.texi"
|
|
"files.texi.~1~")
|
|
@end group
|
|
@end example
|
|
|
|
An error is signaled if @var{directory} is not the name of a directory
|
|
that can be read.
|
|
@end defun
|
|
|
|
@defun directory-files-and-attributes directory &optional full-name match-regexp nosort id-format
|
|
This is similar to @code{directory-files} in deciding which files
|
|
to report on and how to report their names. However, instead
|
|
of returning a list of file names, it returns for each file a
|
|
list @code{(@var{filename} . @var{attributes})}, where @var{attributes}
|
|
is what @code{file-attributes} would return for that file.
|
|
The optional argument @var{id-format} has the same meaning as the
|
|
corresponding argument to @code{file-attributes} (@pxref{Definition
|
|
of file-attributes}).
|
|
@end defun
|
|
|
|
@defun file-name-all-versions file dirname
|
|
This function returns a list of all versions of the file named
|
|
@var{file} in directory @var{dirname}. It is only available on VMS.
|
|
@end defun
|
|
|
|
@tindex file-expand-wildcards
|
|
@defun file-expand-wildcards pattern &optional full
|
|
This function expands the wildcard pattern @var{pattern}, returning
|
|
a list of file names that match it.
|
|
|
|
If @var{pattern} is written as an absolute file name,
|
|
the values are absolute also.
|
|
|
|
If @var{pattern} is written as a relative file name, it is interpreted
|
|
relative to the current default directory. The file names returned are
|
|
normally also relative to the current default directory. However, if
|
|
@var{full} is non-@code{nil}, they are absolute.
|
|
@end defun
|
|
|
|
@defun insert-directory file switches &optional wildcard full-directory-p
|
|
This function inserts (in the current buffer) a directory listing for
|
|
directory @var{file}, formatted with @code{ls} according to
|
|
@var{switches}. It leaves point after the inserted text.
|
|
@var{switches} may be a string of options, or a list of strings
|
|
representing individual options.
|
|
|
|
The argument @var{file} may be either a directory name or a file
|
|
specification including wildcard characters. If @var{wildcard} is
|
|
non-@code{nil}, that means treat @var{file} as a file specification with
|
|
wildcards.
|
|
|
|
If @var{full-directory-p} is non-@code{nil}, that means the directory
|
|
listing is expected to show the full contents of a directory. You
|
|
should specify @code{t} when @var{file} is a directory and switches do
|
|
not contain @samp{-d}. (The @samp{-d} option to @code{ls} says to
|
|
describe a directory itself as a file, rather than showing its
|
|
contents.)
|
|
|
|
On most systems, this function works by running a directory listing
|
|
program whose name is in the variable @code{insert-directory-program}.
|
|
If @var{wildcard} is non-@code{nil}, it also runs the shell specified by
|
|
@code{shell-file-name}, to expand the wildcards.
|
|
|
|
MS-DOS and MS-Windows systems usually lack the standard Unix program
|
|
@code{ls}, so this function emulates the standard Unix program @code{ls}
|
|
with Lisp code.
|
|
|
|
As a technical detail, when @var{switches} contains the long
|
|
@samp{--dired} option, @code{insert-directory} treats it specially,
|
|
for the sake of dired. However, the normally equivalent short
|
|
@samp{-D} option is just passed on to @code{insert-directory-program},
|
|
as any other option.
|
|
@end defun
|
|
|
|
@defvar insert-directory-program
|
|
This variable's value is the program to run to generate a directory listing
|
|
for the function @code{insert-directory}. It is ignored on systems
|
|
which generate the listing with Lisp code.
|
|
@end defvar
|
|
|
|
@node Create/Delete Dirs
|
|
@section Creating and Deleting Directories
|
|
@c Emacs 19 features
|
|
|
|
Most Emacs Lisp file-manipulation functions get errors when used on
|
|
files that are directories. For example, you cannot delete a directory
|
|
with @code{delete-file}. These special functions exist to create and
|
|
delete directories.
|
|
|
|
@defun make-directory dirname &optional parents
|
|
This function creates a directory named @var{dirname}.
|
|
If @var{parents} is non-@code{nil}, as is always the case in an
|
|
interactive call, that means to create the parent directories first,
|
|
if they don't already exist.
|
|
@end defun
|
|
|
|
@defun delete-directory dirname
|
|
This function deletes the directory named @var{dirname}. The function
|
|
@code{delete-file} does not work for files that are directories; you
|
|
must use @code{delete-directory} for them. If the directory contains
|
|
any files, @code{delete-directory} signals an error.
|
|
|
|
This function only follows symbolic links at the level of parent
|
|
directories.
|
|
@end defun
|
|
|
|
@node Magic File Names
|
|
@section Making Certain File Names ``Magic''
|
|
@cindex magic file names
|
|
|
|
@c Emacs 19 feature
|
|
You can implement special handling for certain file names. This is
|
|
called making those names @dfn{magic}. The principal use for this
|
|
feature is in implementing remote file names (@pxref{Remote Files,,
|
|
Remote Files, emacs, The GNU Emacs Manual}).
|
|
|
|
To define a kind of magic file name, you must supply a regular
|
|
expression to define the class of names (all those that match the
|
|
regular expression), plus a handler that implements all the primitive
|
|
Emacs file operations for file names that do match.
|
|
|
|
The variable @code{file-name-handler-alist} holds a list of handlers,
|
|
together with regular expressions that determine when to apply each
|
|
handler. Each element has this form:
|
|
|
|
@example
|
|
(@var{regexp} . @var{handler})
|
|
@end example
|
|
|
|
@noindent
|
|
All the Emacs primitives for file access and file name transformation
|
|
check the given file name against @code{file-name-handler-alist}. If
|
|
the file name matches @var{regexp}, the primitives handle that file by
|
|
calling @var{handler}.
|
|
|
|
The first argument given to @var{handler} is the name of the
|
|
primitive, as a symbol; the remaining arguments are the arguments that
|
|
were passed to that primitive. (The first of these arguments is most
|
|
often the file name itself.) For example, if you do this:
|
|
|
|
@example
|
|
(file-exists-p @var{filename})
|
|
@end example
|
|
|
|
@noindent
|
|
and @var{filename} has handler @var{handler}, then @var{handler} is
|
|
called like this:
|
|
|
|
@example
|
|
(funcall @var{handler} 'file-exists-p @var{filename})
|
|
@end example
|
|
|
|
When a function takes two or more arguments that must be file names,
|
|
it checks each of those names for a handler. For example, if you do
|
|
this:
|
|
|
|
@example
|
|
(expand-file-name @var{filename} @var{dirname})
|
|
@end example
|
|
|
|
@noindent
|
|
then it checks for a handler for @var{filename} and then for a handler
|
|
for @var{dirname}. In either case, the @var{handler} is called like
|
|
this:
|
|
|
|
@example
|
|
(funcall @var{handler} 'expand-file-name @var{filename} @var{dirname})
|
|
@end example
|
|
|
|
@noindent
|
|
The @var{handler} then needs to figure out whether to handle
|
|
@var{filename} or @var{dirname}.
|
|
|
|
If the specified file name matches more than one handler, the one
|
|
whose match starts last in the file name gets precedence. This rule
|
|
is chosen so that handlers for jobs such as uncompression are handled
|
|
first, before handlers for jobs such as remote file access.
|
|
|
|
Here are the operations that a magic file name handler gets to handle:
|
|
|
|
@ifnottex
|
|
@noindent
|
|
@code{access-file}, @code{add-name-to-file},
|
|
@code{byte-compiler-base-file-name},@*
|
|
@code{copy-file}, @code{delete-directory},
|
|
@code{delete-file},
|
|
@code{diff-latest-backup-file},
|
|
@code{directory-file-name},
|
|
@code{directory-files},
|
|
@code{directory-files-and-attributes},
|
|
@code{dired-call-process},
|
|
@code{dired-compress-file}, @code{dired-uncache},@*
|
|
@code{expand-file-name},
|
|
@code{file-accessible-directory-p},
|
|
@code{file-attributes},
|
|
@code{file-directory-p},
|
|
@code{file-executable-p}, @code{file-exists-p},
|
|
@code{file-local-copy},
|
|
@code{file-modes}, @code{file-name-all-completions},
|
|
@code{file-name-as-directory},
|
|
@code{file-name-completion},
|
|
@code{file-name-directory},
|
|
@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{find-file-noselect},@*
|
|
@code{get-file-buffer},
|
|
@code{insert-directory},
|
|
@code{insert-file-contents},@*
|
|
@code{load}, @code{make-directory},
|
|
@code{make-directory-internal},
|
|
@code{make-symbolic-link},@*
|
|
@code{rename-file}, @code{set-file-modes},
|
|
@code{set-visited-file-modtime}, @code{shell-command},
|
|
@code{substitute-in-file-name},@*
|
|
@code{unhandled-file-name-directory},
|
|
@code{vc-registered},
|
|
@code{verify-visited-file-modtime},@*
|
|
@code{write-region}.
|
|
@end ifnottex
|
|
@iftex
|
|
@noindent
|
|
@flushleft
|
|
@code{access-file}, @code{add-name-to-file},
|
|
@code{byte-com@discretionary{}{}{}piler-base-file-name},
|
|
@code{copy-file}, @code{delete-directory},
|
|
@code{delete-file},
|
|
@code{diff-latest-backup-file},
|
|
@code{directory-file-name},
|
|
@code{directory-files},
|
|
@code{directory-files-and-at@discretionary{}{}{}tributes},
|
|
@code{dired-call-process},
|
|
@code{dired-compress-file}, @code{dired-uncache},
|
|
@code{expand-file-name},
|
|
@code{file-accessible-direc@discretionary{}{}{}tory-p},
|
|
@code{file-attributes},
|
|
@code{file-direct@discretionary{}{}{}ory-p},
|
|
@code{file-executable-p}, @code{file-exists-p},
|
|
@code{file-local-copy},
|
|
@code{file-modes}, @code{file-name-all-completions},
|
|
@code{file-name-as-directory},
|
|
@code{file-name-completion},
|
|
@code{file-name-directory},
|
|
@code{file-name-nondirec@discretionary{}{}{}tory},
|
|
@code{file-name-sans-versions}, @code{file-newer-than-file-p},
|
|
@code{file-ownership-pre@discretionary{}{}{}served-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{find-file-noselect},
|
|
@code{get-file-buffer},
|
|
@code{insert-directory},
|
|
@code{insert-file-contents},
|
|
@code{load}, @code{make-direc@discretionary{}{}{}tory},
|
|
@code{make-direc@discretionary{}{}{}tory-internal},
|
|
@code{make-symbolic-link},
|
|
@code{rename-file}, @code{set-file-modes},
|
|
@code{set-visited-file-modtime}, @code{shell-command},
|
|
@code{substitute-in-file-name},
|
|
@code{unhandled-file-name-directory},
|
|
@code{vc-regis@discretionary{}{}{}tered},
|
|
@code{verify-visited-file-modtime},
|
|
@code{write-region}.
|
|
@end flushleft
|
|
@end iftex
|
|
|
|
Handlers for @code{insert-file-contents} typically need to clear the
|
|
buffer's modified flag, with @code{(set-buffer-modified-p nil)}, if the
|
|
@var{visit} argument is non-@code{nil}. This also has the effect of
|
|
unlocking the buffer if it is locked.
|
|
|
|
The handler function must handle all of the above operations, and
|
|
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
|
|
for an operation it does not recognize. Here's one way to do this:
|
|
|
|
@smallexample
|
|
(defun my-file-handler (operation &rest args)
|
|
;; @r{First check for the specific operations}
|
|
;; @r{that we have special handling for.}
|
|
(cond ((eq operation 'insert-file-contents) @dots{})
|
|
((eq operation 'write-region) @dots{})
|
|
@dots{}
|
|
;; @r{Handle any operation we don't know about.}
|
|
(t (let ((inhibit-file-name-handlers
|
|
(cons 'my-file-handler
|
|
(and (eq inhibit-file-name-operation operation)
|
|
inhibit-file-name-handlers)))
|
|
(inhibit-file-name-operation operation))
|
|
(apply operation args)))))
|
|
@end smallexample
|
|
|
|
When a handler function decides to call the ordinary Emacs primitive for
|
|
the operation at hand, it needs to prevent the primitive from calling
|
|
the same handler once again, thus leading to an infinite recursion. The
|
|
example above shows how to do this, with the variables
|
|
@code{inhibit-file-name-handlers} and
|
|
@code{inhibit-file-name-operation}. Be careful to use them exactly as
|
|
shown above; the details are crucial for proper behavior in the case of
|
|
multiple handlers, and for operations that have two file names that may
|
|
each have handlers.
|
|
|
|
@kindex safe-magic (@r{property})
|
|
Handlers that don't really do anything special for actual access to the
|
|
file---such as the ones that implement completion of host names for
|
|
remote file names---should have a non-@code{nil} @code{safe-magic}
|
|
property. For instance, Emacs normally ``protects'' directory names
|
|
it finds in @code{PATH} from becoming magic, if they look like magic
|
|
file names, by prefixing them with @samp{/:}. But if the handler that
|
|
would be used for them has a non-@code{nil} @code{safe-magic}
|
|
property, the @samp{/:} is not added.
|
|
|
|
@defvar inhibit-file-name-handlers
|
|
This variable holds a list of handlers whose use is presently inhibited
|
|
for a certain operation.
|
|
@end defvar
|
|
|
|
@defvar inhibit-file-name-operation
|
|
The operation for which certain handlers are presently inhibited.
|
|
@end defvar
|
|
|
|
@defun find-file-name-handler file operation
|
|
This function returns the handler function for file name @var{file}, or
|
|
@code{nil} if there is none. The argument @var{operation} should be the
|
|
operation to be performed on the file---the value you will pass to the
|
|
handler as its first argument when you call it. The operation is needed
|
|
for comparison with @code{inhibit-file-name-operation}.
|
|
@end defun
|
|
|
|
@defun file-local-copy filename
|
|
This function copies file @var{filename} to an ordinary non-magic file
|
|
on the local machine, if it isn't on the local machine already. Magic
|
|
file names should handle the @code{file-local-copy} operation if they
|
|
refer to files on other machines. A magic file name that is used for
|
|
other purposes than remote file access should not handle
|
|
@code{file-local-copy}; then this function will treat the file as
|
|
local.
|
|
|
|
If @var{filename} is local, whether magic or not, this function does
|
|
nothing and returns @code{nil}. Otherwise it returns the file name
|
|
of the local copy file.
|
|
@end defun
|
|
|
|
@defun file-remote-p filename
|
|
This function returns @code{t} if @var{filename} is a remote file---that is,
|
|
a magic file name that handles @code{file-local-copy}.
|
|
@end defun
|
|
|
|
@defun unhandled-file-name-directory filename
|
|
This function returns the name of a directory that is not magic. It
|
|
uses the directory part of @var{filename} if that is not magic. For a
|
|
magic file name, it invokes the file name handler, which therefore
|
|
decides what value to return.
|
|
|
|
This is useful for running a subprocess; every subprocess must have a
|
|
non-magic directory to serve as its current directory, and this function
|
|
is a good way to come up with one.
|
|
@end defun
|
|
|
|
@node Format Conversion
|
|
@section File Format Conversion
|
|
|
|
@cindex file format conversion
|
|
@cindex encoding file formats
|
|
@cindex decoding file formats
|
|
The variable @code{format-alist} defines a list of @dfn{file formats},
|
|
which describe textual representations used in files for the data (text,
|
|
text-properties, and possibly other information) in an Emacs buffer.
|
|
Emacs performs format conversion if appropriate when reading and writing
|
|
files.
|
|
|
|
@defvar format-alist
|
|
This list contains one format definition for each defined file format.
|
|
@end defvar
|
|
|
|
@cindex format definition
|
|
Each format definition is a list of this form:
|
|
|
|
@example
|
|
(@var{name} @var{doc-string} @var{regexp} @var{from-fn} @var{to-fn} @var{modify} @var{mode-fn})
|
|
@end example
|
|
|
|
Here is what the elements in a format definition mean:
|
|
|
|
@table @var
|
|
@item name
|
|
The name of this format.
|
|
|
|
@item doc-string
|
|
A documentation string for the format.
|
|
|
|
@item regexp
|
|
A regular expression which is used to recognize files represented in
|
|
this format.
|
|
|
|
@item from-fn
|
|
A shell command or function to decode data in this format (to convert
|
|
file data into the usual Emacs data representation).
|
|
|
|
A shell command is represented as a string; Emacs runs the command as a
|
|
filter to perform the conversion.
|
|
|
|
If @var{from-fn} is a function, it is called with two arguments, @var{begin}
|
|
and @var{end}, which specify the part of the buffer it should convert.
|
|
It should convert the text by editing it in place. Since this can
|
|
change the length of the text, @var{from-fn} should return the modified
|
|
end position.
|
|
|
|
One responsibility of @var{from-fn} is to make sure that the beginning
|
|
of the file no longer matches @var{regexp}. Otherwise it is likely to
|
|
get called again.
|
|
|
|
@item to-fn
|
|
A shell command or function to encode data in this format---that is, to
|
|
convert the usual Emacs data representation into this format.
|
|
|
|
If @var{to-fn} is a string, it is a shell command; Emacs runs the
|
|
command as a filter to perform the conversion.
|
|
|
|
If @var{to-fn} is a function, it is called with two arguments, @var{begin}
|
|
and @var{end}, which specify the part of the buffer it should convert.
|
|
There are two ways it can do the conversion:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
By editing the buffer in place. In this case, @var{to-fn} should
|
|
return the end-position of the range of text, as modified.
|
|
|
|
@item
|
|
By returning a list of annotations. This is a list of elements of the
|
|
form @code{(@var{position} . @var{string})}, where @var{position} is an
|
|
integer specifying the relative position in the text to be written, and
|
|
@var{string} is the annotation to add there. The list must be sorted in
|
|
order of position when @var{to-fn} returns it.
|
|
|
|
When @code{write-region} actually writes the text from the buffer to the
|
|
file, it intermixes the specified annotations at the corresponding
|
|
positions. All this takes place without modifying the buffer.
|
|
@end itemize
|
|
|
|
@item modify
|
|
A flag, @code{t} if the encoding function modifies the buffer, and
|
|
@code{nil} if it works by returning a list of annotations.
|
|
|
|
@item mode-fn
|
|
A minor-mode function to call after visiting a file converted from this
|
|
format. The function is called with one argument, the integer 1;
|
|
that tells a minor-mode function to enable the mode.
|
|
@end table
|
|
|
|
The function @code{insert-file-contents} automatically recognizes file
|
|
formats when it reads the specified file. It checks the text of the
|
|
beginning of the file against the regular expressions of the format
|
|
definitions, and if it finds a match, it calls the decoding function for
|
|
that format. Then it checks all the known formats over again.
|
|
It keeps checking them until none of them is applicable.
|
|
|
|
Visiting a file, with @code{find-file-noselect} or the commands that use
|
|
it, performs conversion likewise (because it calls
|
|
@code{insert-file-contents}); it also calls the mode function for each
|
|
format that it decodes. It stores a list of the format names in the
|
|
buffer-local variable @code{buffer-file-format}.
|
|
|
|
@defvar buffer-file-format
|
|
This variable states the format of the visited file. More precisely,
|
|
this is a list of the file format names that were decoded in the course
|
|
of visiting the current buffer's file. It is always buffer-local in all
|
|
buffers.
|
|
@end defvar
|
|
|
|
When @code{write-region} writes data into a file, it first calls the
|
|
encoding functions for the formats listed in @code{buffer-file-format},
|
|
in the order of appearance in the list.
|
|
|
|
@deffn Command format-write-file file format &optional confirm
|
|
This command writes the current buffer contents into the file
|
|
@var{file} in format @var{format}, and makes that format the default
|
|
for future saves of the buffer. The argument @var{format} is a list
|
|
of format names. 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 write-file}.
|
|
@end deffn
|
|
|
|
@deffn Command format-find-file file format
|
|
This command finds the file @var{file}, converting it according to
|
|
format @var{format}. It also makes @var{format} the default if the
|
|
buffer is saved later.
|
|
|
|
The argument @var{format} is a list of format names. If @var{format} is
|
|
@code{nil}, no conversion takes place. Interactively, typing just
|
|
@key{RET} for @var{format} specifies @code{nil}.
|
|
@end deffn
|
|
|
|
@deffn Command format-insert-file file format &optional beg end
|
|
This command inserts the contents of file @var{file}, converting it
|
|
according to format @var{format}. If @var{beg} and @var{end} are
|
|
non-@code{nil}, they specify which part of the file to read, as in
|
|
@code{insert-file-contents} (@pxref{Reading from Files}).
|
|
|
|
The return value is like what @code{insert-file-contents} returns: a
|
|
list of the absolute file name and the length of the data inserted
|
|
(after conversion).
|
|
|
|
The argument @var{format} is a list of format names. If @var{format} is
|
|
@code{nil}, no conversion takes place. Interactively, typing just
|
|
@key{RET} for @var{format} specifies @code{nil}.
|
|
@end deffn
|
|
|
|
@defvar auto-save-file-format
|
|
This variable specifies the format to use for auto-saving. Its value is
|
|
a list of format names, just like the value of
|
|
@code{buffer-file-format}; however, it is used instead of
|
|
@code{buffer-file-format} for writing auto-save files. If the value
|
|
is @code{t}, the default, auto-saving uses the same format as a
|
|
regular save in the same buffer. This variable is always buffer-local
|
|
in all buffers.
|
|
@end defvar
|
|
|
|
@ignore
|
|
arch-tag: 141f74ce-6ae3-40dc-a6c4-ef83fc4ec35c
|
|
@end ignore
|