+++ /dev/null
-This is Info file ../../info/lispref.info, produced by Makeinfo version
-1.68 from the input file lispref.texi.
-
-INFO-DIR-SECTION XEmacs Editor
-START-INFO-DIR-ENTRY
-* Lispref: (lispref). XEmacs Lisp Reference Manual.
-END-INFO-DIR-ENTRY
-
- Edition History:
-
- GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU
-Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid
-Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994
-XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995
-GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp
-Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp
-Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp
-Reference Manual (for 19.15 and 20.1, 20.2, 20.3) v3.2, April, May,
-November 1997 XEmacs Lisp Reference Manual (for 21.0) v3.3, April 1998
-
- Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software
-Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc.
-Copyright (C) 1995, 1996 Ben Wing.
-
- Permission is granted to make and distribute verbatim copies of this
-manual provided the copyright notice and this permission notice are
-preserved on all copies.
-
- Permission is granted to copy and distribute modified versions of
-this manual under the conditions for verbatim copying, provided that the
-entire resulting derived work is distributed under the terms of a
-permission notice identical to this one.
-
- Permission is granted to copy and distribute translations of this
-manual into another language, under the above conditions for modified
-versions, except that this permission notice may be stated in a
-translation approved by the Foundation.
-
- Permission is granted to copy and distribute modified versions of
-this manual under the conditions for verbatim copying, provided also
-that the section entitled "GNU General Public License" is included
-exactly as in the original, and provided that the entire resulting
-derived work is distributed under the terms of a permission notice
-identical to this one.
-
- Permission is granted to copy and distribute translations of this
-manual into another language, under the above conditions for modified
-versions, except that the section entitled "GNU General Public License"
-may be included in a translation approved by the Free Software
-Foundation instead of in the original English.
-
-\1f
-File: lispref.info, Node: Keys in Documentation, Next: Describing Characters, Prev: Accessing Documentation, Up: Documentation
-
-Substituting Key Bindings in Documentation
-==========================================
-
- When documentation strings refer to key sequences, they should use
-the current, actual key bindings. They can do so using certain special
-text sequences described below. Accessing documentation strings in the
-usual way substitutes current key binding information for these special
-sequences. This works by calling `substitute-command-keys'. You can
-also call that function yourself.
-
- Here is a list of the special sequences and what they mean:
-
-`\[COMMAND]'
- stands for a key sequence that will invoke COMMAND, or `M-x
- COMMAND' if COMMAND has no key bindings.
-
-`\{MAPVAR}'
- stands for a summary of the value of MAPVAR, which should be a
- keymap. The summary is made by `describe-bindings'.
-
-`\<MAPVAR>'
- stands for no text itself. It is used for a side effect: it
- specifies MAPVAR as the keymap for any following `\[COMMAND]'
- sequences in this documentation string.
-
-`\='
- quotes the following character and is discarded; this `\=\=' puts
- `\=' into the output, and `\=\[' puts `\[' into the output.
-
- *Please note:* Each `\' must be doubled when written in a string in
-XEmacs Lisp.
-
- - Function: substitute-command-keys STRING
- This function scans STRING for the above special sequences and
- replaces them by what they stand for, returning the result as a
- string. This permits display of documentation that refers
- accurately to the user's own customized key bindings.
-
- Here are examples of the special sequences:
-
- (substitute-command-keys
- "To abort recursive edit, type: \\[abort-recursive-edit]")
- => "To abort recursive edit, type: C-]"
-
- (substitute-command-keys
- "The keys that are defined for the minibuffer here are:
- \\{minibuffer-local-must-match-map}")
- => "The keys that are defined for the minibuffer here are:
-
- ? minibuffer-completion-help
- SPC minibuffer-complete-word
- TAB minibuffer-complete
- LFD minibuffer-complete-and-exit
- RET minibuffer-complete-and-exit
- C-g abort-recursive-edit
- "
- (substitute-command-keys
- "To abort a recursive edit from the minibuffer, type\
- \\<minibuffer-local-must-match-map>\\[abort-recursive-edit].")
- => "To abort a recursive edit from the minibuffer, type C-g."
-
- (substitute-command-keys
- "Substrings of the form \\=\\{MAPVAR} are replaced by summaries
- \(made by describe-bindings) of the value of MAPVAR, taken as a keymap.
- Substrings of the form \\=\\<MAPVAR> specify to use the value of MAPVAR
- as the keymap for future \\=\\[COMMAND] substrings.
- \\=\\= quotes the following character and is discarded;
- thus, \\=\\=\\=\\= puts \\=\\= into the output,
- and \\=\\=\\=\\[ puts \\=\\[ into the output.")
- => "Substrings of the form \{MAPVAR} are replaced by summaries
- (made by describe-bindings) of the value of MAPVAR, taken as a keymap.
- Substrings of the form \<MAPVAR> specify to use the value of MAPVAR
- as the keymap for future \[COMMAND] substrings.
- \= quotes the following character and is discarded;
- thus, \=\= puts \= into the output,
- and \=\[ puts \[ into the output."
-
-\1f
-File: lispref.info, Node: Describing Characters, Next: Help Functions, Prev: Keys in Documentation, Up: Documentation
-
-Describing Characters for Help Messages
-=======================================
-
- These functions convert events, key sequences or characters to
-textual descriptions. These descriptions are useful for including
-arbitrary text characters or key sequences in messages, because they
-convert non-printing and whitespace characters to sequences of printing
-characters. The description of a non-whitespace printing character is
-the character itself.
-
- - Function: key-description SEQUENCE
- This function returns a string containing the XEmacs standard
- notation for the input events in SEQUENCE. The argument SEQUENCE
- may be a string, vector or list. *Note Events::, for more
- information about valid events. See also the examples for
- `single-key-description', below.
-
- - Function: single-key-description KEY
- This function returns a string describing KEY in the standard
- XEmacs notation for keyboard input. A normal printing character
- appears as itself, but a control character turns into a string
- starting with `C-', a meta character turns into a string starting
- with `M-', and space, linefeed, etc. appear as `SPC', `LFD', etc.
- A symbol appears as the name of the symbol. An event that is a
- list appears as the name of the symbol in the CAR of the list.
-
- (single-key-description ?\C-x)
- => "C-x"
-
- (key-description "\C-x \M-y \n \t \r \f123")
- => "C-x SPC M-y SPC LFD SPC TAB SPC RET SPC C-l 1 2 3"
-
- (single-key-description 'kp_next)
- => "kp_next"
-
- (single-key-description '(shift button1))
- => "Sh-button1"
-
- - Function: text-char-description CHARACTER
- This function returns a string describing CHARACTER in the
- standard XEmacs notation for characters that appear in text--like
- `single-key-description', except that control characters are
- represented with a leading caret (which is how control characters
- in XEmacs buffers are usually displayed).
-
- (text-char-description ?\C-c)
- => "^C"
-
- (text-char-description ?\M-m)
- => "M-m"
-
- (text-char-description ?\C-\M-m)
- => "M-^M"
-
-\1f
-File: lispref.info, Node: Help Functions, Next: Obsoleteness, Prev: Describing Characters, Up: Documentation
-
-Help Functions
-==============
-
- XEmacs provides a variety of on-line help functions, all accessible
-to the user as subcommands of the prefix `C-h', or on some keyboards,
-`help'. For more information about them, see *Note Help: (emacs)Help.
-Here we describe some program-level interfaces to the same information.
-
- - Command: apropos REGEXP &optional DO-ALL PREDICATE
- This function finds all symbols whose names contain a match for the
- regular expression REGEXP, and returns a list of them (*note
- Regular Expressions::.). It also displays the symbols in a buffer
- named `*Help*', each with a one-line description.
-
- If DO-ALL is non-`nil', then `apropos' also shows key bindings for
- the functions that are found.
-
- If PREDICATE is non-`nil', it should be a function to be called on
- each symbol that has matched REGEXP. Only symbols for which
- PREDICATE returns a non-`nil' value are listed or displayed.
-
- In the first of the following examples, `apropos' finds all the
- symbols with names containing `exec'. In the second example, it
- finds and returns only those symbols that are also commands. (We
- don't show the output that results in the `*Help*' buffer.)
-
- (apropos "exec")
- => (Buffer-menu-execute command-execute exec-directory
- exec-path execute-extended-command execute-kbd-macro
- executing-kbd-macro executing-macro)
-
- (apropos "exec" nil 'commandp)
- => (Buffer-menu-execute execute-extended-command)
-
- `apropos' is used by various user-level commands, such as `C-h a'
- (`hyper-apropos'), a graphical front-end to `apropos'; and `C-h A'
- (`command-apropos'), which does an apropos over only those
- functions which are user commands. `command-apropos' calls
- `apropos', specifying a PREDICATE to restrict the output to
- symbols that are commands. The call to `apropos' looks like this:
-
- (apropos string t 'commandp)
-
- - Variable: help-map
- The value of this variable is a local keymap for characters
- following the Help key, `C-h'.
-
- - Prefix Command: help-command
- This symbol is not a function; its function definition is actually
- the keymap known as `help-map'. It is defined in `help.el' as
- follows:
-
- (define-key global-map "\C-h" 'help-command)
- (fset 'help-command help-map)
-
- - Function: print-help-return-message &optional FUNCTION
- This function builds a string that explains how to restore the
- previous state of the windows after a help command. After
- building the message, it applies FUNCTION to it if FUNCTION is
- non-`nil'. Otherwise it calls `message' to display it in the echo
- area.
-
- This function expects to be called inside a
- `with-output-to-temp-buffer' special form, and expects
- `standard-output' to have the value bound by that special form.
- For an example of its use, see the long example in *Note Accessing
- Documentation::.
-
- - Variable: help-char
- The value of this variable is the help character--the character
- that XEmacs recognizes as meaning Help. By default, it is the
- character `?\^H' (ASCII 8), which is `C-h'. When XEmacs reads this
- character, if `help-form' is non-`nil' Lisp expression, it
- evaluates that expression, and displays the result in a window if
- it is a string.
-
- `help-char' can be a character or a key description such as `help'
- or `(meta h)'.
-
- Usually the value of `help-form''s value is `nil'. Then the help
- character has no special meaning at the level of command input, and
- it becomes part of a key sequence in the normal way. The standard
- key binding of `C-h' is a prefix key for several general-purpose
- help features.
-
- The help character is special after prefix keys, too. If it has no
- binding as a subcommand of the prefix key, it runs
- `describe-prefix-bindings', which displays a list of all the
- subcommands of the prefix key.
-
- - Variable: help-form
- If this variable is non-`nil', its value is a form to evaluate
- whenever the character `help-char' is read. If evaluating the form
- produces a string, that string is displayed.
-
- A command that calls `next-command-event' or `next-event' probably
- should bind `help-form' to a non-`nil' expression while it does
- input. (The exception is when `C-h' is meaningful input.)
- Evaluating this expression should result in a string that explains
- what the input is for and how to enter it properly.
-
- Entry to the minibuffer binds this variable to the value of
- `minibuffer-help-form' (*note Minibuffer Misc::.).
-
- - Variable: prefix-help-command
- This variable holds a function to print help for a prefix
- character. The function is called when the user types a prefix
- key followed by the help character, and the help character has no
- binding after that prefix. The variable's default value is
- `describe-prefix-bindings'.
-
- - Function: describe-prefix-bindings
- This function calls `describe-bindings' to display a list of all
- the subcommands of the prefix key of the most recent key sequence.
- The prefix described consists of all but the last event of that
- key sequence. (The last event is, presumably, the help character.)
-
- The following two functions are found in the library `helper'. They
-are for modes that want to provide help without relinquishing control,
-such as the "electric" modes. You must load that library with
-`(require 'helper)' in order to use them. Their names begin with
-`Helper' to distinguish them from the ordinary help functions.
-
- - Command: Helper-describe-bindings
- This command pops up a window displaying a help buffer containing a
- listing of all of the key bindings from both the local and global
- keymaps. It works by calling `describe-bindings'.
-
- - Command: Helper-help
- This command provides help for the current mode. It prompts the
- user in the minibuffer with the message `Help (Type ? for further
- options)', and then provides assistance in finding out what the key
- bindings are, and what the mode is intended for. It returns `nil'.
-
- This can be customized by changing the map `Helper-help-map'.
-
-\1f
-File: lispref.info, Node: Obsoleteness, Prev: Help Functions, Up: Documentation
-
-Obsoleteness
-============
-
- As you add functionality to a package, you may at times want to
-replace an older function with a new one. To preserve compatibility
-with existing code, the older function needs to still exist; but users
-of that function should be told to use the newer one instead. XEmacs
-Lisp lets you mark a function or variable as "obsolete", and indicate
-what should be used instead.
-
- - Function: make-obsolete FUNCTION NEW
- This function indicates that FUNCTION is an obsolete function, and
- the function NEW should be used instead. The byte compiler will
- issue a warning to this effect when it encounters a usage of the
- older function, and the help system will also note this in the
- function's documentation. NEW can also be a string (if there is
- not a single function with the same functionality any more), and
- should be a descriptive statement, such as "use FOO or BAR
- instead" or "this function is unnecessary".
-
- - Function: make-obsolete-variable VARIABLE NEW
- This is like `make-obsolete' but is for variables instead of
- functions.
-
- - Function: define-obsolete-function-alias OLDFUN NEWFUN
- This function combines `make-obsolete' and `define-function',
- declaring OLDFUN to be an obsolete variant of NEWFUN and defining
- OLDFUN as an alias for NEWFUN.
-
- - Function: define-obsolete-variable-alias OLDVAR NEWVAR
- This is like `define-obsolete-function-alias' but for variables.
-
- Note that you should not normally put obsoleteness information
-explicitly in a function or variable's doc string. The obsoleteness
-information that you specify using the above functions will be displayed
-whenever the doc string is displayed, and by adding it explicitly the
-result is redundancy.
-
- Also, if an obsolete function is substantially the same as a newer
-one but is not actually an alias, you should consider omitting the doc
-string entirely (use a null string `""' as the doc string). That way,
-the user is told about the obsoleteness and is forced to look at the
-documentation of the new function, making it more likely that he will
-use the new function.
-
- - Function: function-obsoleteness-doc FUNCTION
- If FUNCTION is obsolete, this function returns a string describing
- this. This is the message that is printed out during byte
- compilation or in the function's documentation. If FUNCTION is
- not obsolete, `nil' is returned.
-
- - Function: variable-obsoleteness-doc VARIABLE
- This is like `function-obsoleteness-doc' but for variables.
-
- The obsoleteness information is stored internally by putting a
-property `byte-obsolete-info' (for functions) or
-`byte-obsolete-variable' (for variables) on the symbol that specifies
-the obsolete function or variable. For more information, see the
-implementation of `make-obsolete' and `make-obsolete-variable' in
-`lisp/bytecomp/bytecomp-runtime.el'.
-
-\1f
-File: lispref.info, Node: Files, Next: Backups and Auto-Saving, Prev: Documentation, Up: Top
-
-Files
-*****
-
- In XEmacs, you can find, create, view, save, and otherwise work with
-files and file directories. This chapter describes most of the
-file-related functions of XEmacs Lisp, but a few others are described in
-*Note Buffers::, and those related to backups and auto-saving are
-described in *Note Backups and Auto-Saving::.
-
- Many of the file functions take one or more arguments that are file
-names. A file name is actually a string. Most of these functions
-expand file name arguments using `expand-file-name', so that `~' is
-handled correctly, as are relative file names (including `../'). These
-functions don't recognize environment variable substitutions such as
-`$HOME'. *Note File Name Expansion::.
-
-* Menu:
-
-* Visiting Files:: Reading files into Emacs buffers for editing.
-* Saving Buffers:: Writing changed buffers back into files.
-* Reading from Files:: Reading files into buffers without visiting.
-* Writing to Files:: Writing new files from parts of buffers.
-* File Locks:: Locking and unlocking files, to prevent
- simultaneous editing by two people.
-* Information about Files:: Testing existence, accessibility, size of files.
-* Changing File Attributes:: Renaming files, changing protection, etc.
-* File Names:: Decomposing and expanding file names.
-* Contents of Directories:: Getting a list of the files in a directory.
-* Create/Delete Dirs:: Creating and Deleting Directories.
-* Magic File Names:: Defining "magic" special handling
- for certain file names.
-* Partial Files:: Treating a section of a buffer as a file.
-* Format Conversion:: Conversion to and from various file formats.
-* Files and MS-DOS:: Distinguishing text and binary files on MS-DOS.
-
-\1f
-File: lispref.info, Node: Visiting Files, Next: Saving Buffers, Up: Files
-
-Visiting Files
-==============
-
- Visiting a file means reading a file into a buffer. Once this is
-done, we say that the buffer is "visiting" that file, and call the file
-"the visited file" of the buffer.
-
- A file and a buffer are two different things. A file is information
-recorded permanently in the computer (unless you delete it). A buffer,
-on the other hand, is information inside of XEmacs that will vanish at
-the end of the editing session (or when you kill the buffer). Usually,
-a buffer contains information that you have copied from a file; then we
-say the buffer is visiting that file. The copy in the buffer is what
-you modify with editing commands. Such changes to the buffer do not
-change the file; therefore, to make the changes permanent, you must
-"save" the buffer, which means copying the altered buffer contents back
-into the file.
-
- In spite of the distinction between files and buffers, people often
-refer to a file when they mean a buffer and vice-versa. Indeed, we say,
-"I am editing a file," rather than, "I am editing a buffer that I will
-soon save as a file of the same name." Humans do not usually need to
-make the distinction explicit. When dealing with a computer program,
-however, it is good to keep the distinction in mind.
-
-* Menu:
-
-* Visiting Functions:: The usual interface functions for visiting.
-* Subroutines of Visiting:: Lower-level subroutines that they use.
-
-\1f
-File: lispref.info, Node: Visiting Functions, Next: Subroutines of Visiting, Up: Visiting Files
-
-Functions for Visiting Files
-----------------------------
-
- This section describes the functions normally used to visit files.
-For historical reasons, these functions have names starting with
-`find-' rather than `visit-'. *Note Buffer File Name::, for functions
-and variables that access the visited file name of a buffer or that
-find an existing buffer by its visited file name.
-
- In a Lisp program, if you want to look at the contents of a file but
-not alter it, the fastest way is to use `insert-file-contents' in a
-temporary buffer. Visiting the file is not necessary and takes longer.
-*Note Reading from Files::.
-
- - Command: find-file FILENAME
- This command selects a buffer visiting the file FILENAME, using an
- existing buffer if there is one, and otherwise creating a new
- buffer and reading the file into it. It also returns that buffer.
-
- The body of the `find-file' function is very simple and looks like
- this:
-
- (switch-to-buffer (find-file-noselect filename))
-
- (See `switch-to-buffer' in *Note Displaying Buffers::.)
-
- When `find-file' is called interactively, it prompts for FILENAME
- in the minibuffer.
-
- - Function: find-file-noselect FILENAME &optional NOWARN
- This function is the guts of all the file-visiting functions. It
- finds or creates a buffer visiting the file FILENAME, and returns
- it. It uses an existing buffer if there is one, and otherwise
- creates a new buffer and reads the file into it. You may make the
- buffer current or display it in a window if you wish, but this
- function does not do so.
-
- When `find-file-noselect' uses an existing buffer, it first
- verifies that the file has not changed since it was last visited or
- saved in that buffer. If the file has changed, then this function
- asks the user whether to reread the changed file. If the user says
- `yes', any changes previously made in the buffer are lost.
-
- If `find-file-noselect' needs to create a buffer, and there is no
- file named FILENAME, it displays the message `New file' in the
- echo area, and leaves the buffer empty.
-
- If NO-WARN is non-`nil', various warnings that XEmacs normally
- gives (e.g. if another buffer is already visiting FILENAME but
- FILENAME has been removed from disk since that buffer was created)
- are suppressed.
-
- The `find-file-noselect' function calls `after-find-file' after
- reading the file (*note Subroutines of Visiting::.). That function
- sets the buffer major mode, parses local variables, warns the user
- if there exists an auto-save file more recent than the file just
- visited, and finishes by running the functions in
- `find-file-hooks'.
-
- The `find-file-noselect' function returns the buffer that is
- visiting the file FILENAME.
-
- (find-file-noselect "/etc/fstab")
- => #<buffer fstab>
-
- - Command: find-file-other-window FILENAME
- This command selects a buffer visiting the file FILENAME, but does
- so in a window other than the selected window. It may use another
- existing window or split a window; see *Note Displaying Buffers::.
-
- When this command is called interactively, it prompts for FILENAME.
-
- - Command: find-file-read-only FILENAME
- This command selects a buffer visiting the file FILENAME, like
- `find-file', but it marks the buffer as read-only. *Note Read
- Only Buffers::, for related functions and variables.
-
- When this command is called interactively, it prompts for FILENAME.
-
- - Command: view-file FILENAME
- This command visits FILENAME in View mode, and displays it in a
- recursive edit, returning to the previous buffer when done. View
- mode is a mode that allows you to skim rapidly through the file
- but does not let you modify it. Entering View mode runs the
- normal hook `view-mode-hook'. *Note Hooks::.
-
- When `view-file' is called interactively, it prompts for FILENAME.
-
- - Variable: find-file-hooks
- The value of this variable is a list of functions to be called
- after a file is visited. The file's local-variables specification
- (if any) will have been processed before the hooks are run. The
- buffer visiting the file is current when the hook functions are
- run.
-
- This variable works just like a normal hook, but we think that
- renaming it would not be advisable.
-
- - Variable: find-file-not-found-hooks
- The value of this variable is a list of functions to be called when
- `find-file' or `find-file-noselect' is passed a nonexistent file
- name. `find-file-noselect' calls these functions as soon as it
- detects a nonexistent file. It calls them in the order of the
- list, until one of them returns non-`nil'. `buffer-file-name' is
- already set up.
-
- This is not a normal hook because the values of the functions are
- used and they may not all be called.
-
-\1f
-File: lispref.info, Node: Subroutines of Visiting, Prev: Visiting Functions, Up: Visiting Files
-
-Subroutines of Visiting
------------------------
-
- The `find-file-noselect' function uses the `create-file-buffer' and
-`after-find-file' functions as subroutines. Sometimes it is useful to
-call them directly.
-
- - Function: create-file-buffer FILENAME
- This function creates a suitably named buffer for visiting
- FILENAME, and returns it. It uses FILENAME (sans directory) as
- the name if that name is free; otherwise, it appends a string such
- as `<2>' to get an unused name. See also *Note Creating Buffers::.
-
- *Please note:* `create-file-buffer' does *not* associate the new
- buffer with a file and does not select the buffer. It also does
- not use the default major mode.
-
- (create-file-buffer "foo")
- => #<buffer foo>
- (create-file-buffer "foo")
- => #<buffer foo<2>>
- (create-file-buffer "foo")
- => #<buffer foo<3>>
-
- This function is used by `find-file-noselect'. It uses
- `generate-new-buffer' (*note Creating Buffers::.).
-
- - Function: after-find-file &optional ERROR WARN NOAUTO
- This function sets the buffer major mode, and parses local
- variables (*note Auto Major Mode::.). It is called by
- `find-file-noselect' and by the default revert function (*note
- Reverting::.).
-
- If reading the file got an error because the file does not exist,
- but its directory does exist, the caller should pass a non-`nil'
- value for ERROR. In that case, `after-find-file' issues a warning:
- `(New File)'. For more serious errors, the caller should usually
- not call `after-find-file'.
-
- If WARN is non-`nil', then this function issues a warning if an
- auto-save file exists and is more recent than the visited file.
-
- If NOAUTO is non-`nil', then this function does not turn on
- auto-save mode; otherwise, it does.
-
- The last thing `after-find-file' does is call all the functions in
- `find-file-hooks'.
-
-\1f
-File: lispref.info, Node: Saving Buffers, Next: Reading from Files, Prev: Visiting Files, Up: Files
-
-Saving Buffers
-==============
-
- When you edit a file in XEmacs, you are actually working on a buffer
-that is visiting that file--that is, the contents of the file are
-copied into the buffer and the copy is what you edit. Changes to the
-buffer do not change the file until you "save" the buffer, which means
-copying the contents of the buffer into the file.
-
- - Command: save-buffer &optional BACKUP-OPTION
- This function saves the contents of the current buffer in its
- visited file if the buffer has been modified since it was last
- visited or saved. Otherwise it does nothing.
-
- `save-buffer' is responsible for making backup files. Normally,
- BACKUP-OPTION is `nil', and `save-buffer' makes a backup file only
- if this is the first save since visiting the file. Other values
- for BACKUP-OPTION request the making of backup files in other
- circumstances:
-
- * With an argument of 4 or 64, reflecting 1 or 3 `C-u''s, the
- `save-buffer' function marks this version of the file to be
- backed up when the buffer is next saved.
-
- * With an argument of 16 or 64, reflecting 2 or 3 `C-u''s, the
- `save-buffer' function unconditionally backs up the previous
- version of the file before saving it.
-
- - Command: save-some-buffers &optional SAVE-SILENTLY-P EXITING
- This command saves some modified file-visiting buffers. Normally
- it asks the user about each buffer. But if SAVE-SILENTLY-P is
- non-`nil', it saves all the file-visiting buffers without querying
- the user.
-
- The optional EXITING argument, if non-`nil', requests this
- function to offer also to save certain other buffers that are not
- visiting files. These are buffers that have a non-`nil' local
- value of `buffer-offer-save'. (A user who says yes to saving one
- of these is asked to specify a file name to use.) The
- `save-buffers-kill-emacs' function passes a non-`nil' value for
- this argument.
-
- - Variable: buffer-offer-save
- When this variable is non-`nil' in a buffer, XEmacs offers to save
- the buffer on exit even if the buffer is not visiting a file. The
- variable is automatically local in all buffers. Normally, Mail
- mode (used for editing outgoing mail) sets this to `t'.
-
- - Command: write-file FILENAME
- This function writes the current buffer into file FILENAME, makes
- the buffer visit that file, and marks it not modified. Then it
- renames the buffer based on FILENAME, appending a string like `<2>'
- if necessary to make a unique buffer name. It does most of this
- work by calling `set-visited-file-name' and `save-buffer'.
-
- - Variable: write-file-hooks
- The value of this variable is a list of functions to be called
- before writing out a buffer to its visited file. If one of them
- returns non-`nil', the file is considered already written and the
- rest of the functions are not called, nor is the usual code for
- writing the file executed.
-
- If a function in `write-file-hooks' returns non-`nil', it is
- responsible for making a backup file (if that is appropriate). To
- do so, execute the following code:
-
- (or buffer-backed-up (backup-buffer))
-
- You might wish to save the file modes value returned by
- `backup-buffer' and use that to set the mode bits of the file that
- you write. This is what `save-buffer' normally does.
-
- Even though this is not a normal hook, you can use `add-hook' and
- `remove-hook' to manipulate the list. *Note Hooks::.
-
- - Variable: local-write-file-hooks
- This works just like `write-file-hooks', but it is intended to be
- made local to particular buffers. It's not a good idea to make
- `write-file-hooks' local to a buffer--use this variable instead.
-
- The variable is marked as a permanent local, so that changing the
- major mode does not alter a buffer-local value. This is
- convenient for packages that read "file" contents in special ways,
- and set up hooks to save the data in a corresponding way.
-
- - Variable: write-contents-hooks
- This works just like `write-file-hooks', but it is intended for
- hooks that pertain to the contents of the file, as opposed to
- hooks that pertain to where the file came from. Such hooks are
- usually set up by major modes, as buffer-local bindings for this
- variable. Switching to a new major mode always resets this
- variable.
-
- - Variable: after-save-hook
- This normal hook runs after a buffer has been saved in its visited
- file.
-
- - Variable: file-precious-flag
- If this variable is non-`nil', then `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. *Note
- 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 set this variable non-`nil' locally in particular
- buffers.
-
- - User Option: require-final-newline
- This variable determines whether files may be written out that do
- *not* end with a newline. If the value of the variable is `t',
- then `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-`nil', but not `t', then
- `save-buffer' asks the user whether to add a newline each time the
- case arises.
-
- If the value of the variable is `nil', then `save-buffer' doesn't
- add newlines at all. `nil' is the default value, but a few major
- modes set it to `t' in particular buffers.
-
-\1f
-File: lispref.info, Node: Reading from Files, Next: Writing to Files, Prev: Saving Buffers, Up: Files
-
-Reading from Files
-==================
-
- You can copy a file from the disk and insert it into a buffer using
-the `insert-file-contents' function. Don't use the user-level command
-`insert-file' in a Lisp program, as that sets the mark.
-
- - Function: insert-file-contents FILENAME &optional VISIT BEG END
- REPLACE
- This function inserts the contents of file 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 FILENAME is not the name of a file that can be read.
-
- The function `insert-file-contents' checks the file contents
- against the defined file formats, and converts the file contents if
- appropriate. *Note Format Conversion::. It also calls the
- functions in the list `after-insert-file-functions'; see *Note
- Saving Properties::.
-
- If VISIT is non-`nil', this function additionally marks the buffer
- as unmodified and sets up various fields in the buffer so that it
- is visiting the file FILENAME: these include the buffer's visited
- file name and its last save file modtime. This feature is used by
- `find-file-noselect' and you probably should not use it yourself.
-
- If BEG and END are non-`nil', they should be integers specifying
- the portion of the file to insert. In this case, VISIT must be
- `nil'. For example,
-
- (insert-file-contents filename nil 0 500)
-
- inserts the first 500 characters of a file.
-
- If the argument REPLACE is non-`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.
-
- If you want to pass a file name to another process so that another
-program can read the file, use the function `file-local-copy'; see
-*Note Magic File Names::.
-
-\1f
-File: lispref.info, Node: Writing to Files, Next: File Locks, Prev: Reading from Files, Up: Files
-
-Writing to Files
-================
-
- You can write the contents of a buffer, or part of a buffer, directly
-to a file on disk using the `append-to-file' and `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.
-
- - Command: append-to-file START END FILENAME
- This function appends the contents of the region delimited by
- START and END in the current buffer to the end of file FILENAME.
- If that file does not exist, it is created. If that file exists
- it is overwritten. This function returns `nil'.
-
- An error is signaled if FILENAME specifies a nonwritable file, or
- a nonexistent file in a directory where files cannot be created.
-
- - Command: write-region START END FILENAME &optional APPEND VISIT
- This function writes the region delimited by START and END in the
- current buffer into the file specified by FILENAME.
-
- If START is a string, then `write-region' writes or appends that
- string, rather than text from the buffer.
-
- If APPEND is non-`nil', then the specified text is appended to the
- existing file contents (if any).
-
- If VISIT is `t', then XEmacs 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 FILENAME's modtime, and marks the buffer as not
- modified. This feature is used by `save-buffer', but you probably
- should not use it yourself.
-
- If VISIT is a string, it specifies the file name to visit. This
- way, you can write the data to one file (FILENAME) while recording
- the buffer as visiting another file (VISIT). The argument VISIT
- is used in the echo area message and also for file locking; VISIT
- is stored in `buffer-file-name'. This feature is used to
- implement `file-precious-flag'; don't use it yourself unless you
- really know what you're doing.
-
- The function `write-region' converts the data which it writes to
- the appropriate file formats specified by `buffer-file-format'.
- *Note Format Conversion::. It also calls the functions in the list
- `write-region-annotate-functions'; see *Note Saving Properties::.
-
- Normally, `write-region' displays a message `Wrote file FILENAME'
- in the echo area. If VISIT is neither `t' nor `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.
-
-\1f
-File: lispref.info, Node: File Locks, Next: Information about Files, Prev: Writing to Files, Up: Files
-
-File Locks
-==========
-
- When two users edit the same file at the same time, they are likely
-to interfere with each other. XEmacs tries to prevent this situation
-from arising by recording a "file lock" when a file is being modified.
-XEmacs can then detect the first attempt to modify a buffer visiting a
-file that is locked by another XEmacs process, and ask the user what to
-do.
-
- File locks do not work properly when multiple machines can share
-file systems, such as with NFS. Perhaps a better file locking system
-will be implemented in the future. When file locks do not work, it is
-possible for two users to make changes simultaneously, but XEmacs can
-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 *Note Modification Time::.
-
- - Function: file-locked-p &optional FILENAME
- This function returns `nil' if the file FILENAME is not locked by
- this XEmacs process. It returns `t' if it is locked by this
- XEmacs, and it returns the name of the user who has locked it if it
- is locked by someone else.
-
- (file-locked-p "foo")
- => nil
-
- - Function: lock-buffer &optional FILENAME
- This function locks the file FILENAME, if the current buffer is
- modified. The argument 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.
-
- - Function: 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.
-
- - Function: ask-user-about-lock FILE OTHER-USER
- This function is called when the user tries to modify FILE, but it
- is locked by another user named OTHER-USER. The value it returns
- determines what happens next:
-
- * A value of `t' says to grab the lock on the file. Then this
- user may edit the file and OTHER-USER loses the lock.
-
- * A value of `nil' says to ignore the lock and let this user
- edit the file anyway.
-
- * This function may instead signal a `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:
-
- error--> File is locked: FILE OTHER-USER
-
- where `file' is the name of the file and OTHER-USER is the
- name of the user who has locked the file.
-
- The default definition of this function asks the user to choose
- what to do. If you wish, you can replace the `ask-user-about-lock'
- function with your own version that decides in another way. The
- code for its usual definition is in `userlock.el'.
-
-\1f
-File: lispref.info, Node: Information about Files, Next: Changing File Attributes, Prev: File Locks, Up: Files
-
-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 `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.
-
-\1f
-File: lispref.info, Node: Testing Accessibility, Next: Kinds of Files, Up: Information about Files
-
-Testing Accessibility
----------------------
-
- These functions test for permission to access a file in specific
-ways.
-
- - Function: file-exists-p FILENAME
- This function returns `t' if a file named FILENAME appears to
- exist. This does not mean you can necessarily read the file, only
- that you can find out its attributes. (On Unix, 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 `nil'.
-
- - Function: file-readable-p FILENAME
- This function returns `t' if a file named FILENAME exists and you
- can read it. It returns `nil' otherwise.
-
- (file-readable-p "files.texi")
- => t
- (file-exists-p "/usr/spool/mqueue")
- => t
- (file-readable-p "/usr/spool/mqueue")
- => nil
-
- - Function: file-executable-p FILENAME
- This function returns `t' if a file named FILENAME exists and you
- can execute it. It returns `nil' otherwise. 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.
-
- - Function: file-writable-p FILENAME
- This function returns `t' if the file FILENAME can be written or
- created by you, and `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, `foo' is not writable because the
- parent directory does not exist, even though the user could create
- such a directory.
-
- (file-writable-p "~/foo")
- => t
- (file-writable-p "/foo")
- => nil
- (file-writable-p "~/no-such-dir/foo")
- => nil
-
- - Function: file-accessible-directory-p DIRNAME
- This function returns `t' if you have permission to open existing
- files in the directory whose name as a file is DIRNAME; otherwise
- (or if there is no such directory), it returns `nil'. The value
- of DIRNAME may be either a directory name or the file name of a
- directory.
-
- Example: after the following,
-
- (file-accessible-directory-p "/foo")
- => nil
-
- we can deduce that any attempt to read a file in `/foo/' will give
- an error.
-
- - Function: file-ownership-preserved-p FILENAME
- This function returns `t' if deleting the file FILENAME and then
- creating it anew would keep the file's owner unchanged.
-
- - Function: file-newer-than-file-p FILENAME1 FILENAME2
- This function returns `t' if the file FILENAME1 is newer than file
- FILENAME2. If FILENAME1 does not exist, it returns `nil'. If
- FILENAME2 does not exist, it returns `t'.
-
- In the following example, assume that the file `aug-19' was written
- on the 19th, `aug-20' was written on the 20th, and the file
- `no-file' doesn't exist at all.
-
- (file-newer-than-file-p "aug-19" "aug-20")
- => nil
- (file-newer-than-file-p "aug-20" "aug-19")
- => t
- (file-newer-than-file-p "aug-19" "no-file")
- => t
- (file-newer-than-file-p "no-file" "aug-19")
- => nil
-
- You can use `file-attributes' to get a file's last modification
- time as a list of two numbers. *Note File Attributes::.
-
-\1f
-File: lispref.info, Node: Kinds of Files, Next: Truenames, Prev: Testing Accessibility, Up: Information about Files
-
-Distinguishing Kinds of Files
------------------------------
-
- This section describes how to distinguish various kinds of files,
-such as directories, symbolic links, and ordinary files.
-
- - Function: file-symlink-p FILENAME
- If the file FILENAME is a symbolic link, the `file-symlink-p'
- function returns the file name to which it is linked. This may be
- the name of a text file, a directory, or even another symbolic
- link, or it may be a nonexistent file name.
-
- If the file FILENAME is not a symbolic link (or there is no such
- file), `file-symlink-p' returns `nil'.
-
- (file-symlink-p "foo")
- => nil
- (file-symlink-p "sym-link")
- => "foo"
- (file-symlink-p "sym-link2")
- => "sym-link"
- (file-symlink-p "/bin")
- => "/pub/bin"
-
-
- - Function: file-directory-p FILENAME
- This function returns `t' if FILENAME is the name of an existing
- directory, `nil' otherwise.
-
- (file-directory-p "~rms")
- => t
- (file-directory-p "~rms/lewis/files.texi")
- => nil
- (file-directory-p "~rms/lewis/no-such-file")
- => nil
- (file-directory-p "$HOME")
- => nil
- (file-directory-p
- (substitute-in-file-name "$HOME"))
- => t
-
- - Function: file-regular-p FILENAME
- This function returns `t' if the file FILENAME exists and is a
- regular file (not a directory, symbolic link, named pipe,
- terminal, or other I/O device).
-
-\1f
-File: lispref.info, Node: Truenames, Next: File Attributes, Prev: Kinds of Files, Up: Information about Files
-
-Truenames
----------
-
- The "truename" of a file is the name that you get by following
-symbolic links until none remain, then expanding to get rid of `.' and
-`..' as components. Strictly speaking, a file need not 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.
-
- - Function: file-truename FILENAME &optional DEFAULT
- The function `file-truename' returns the true name of the file
- FILENAME. This is the name that you get by following symbolic
- links until none remain.
-
- If the filename is relative, DEFAULT is the directory to start
- with. If DEFAULT is `nil' or missing, the current buffer's value
- of `default-directory' is used.
-
- *Note Buffer File Name::, for related information.
-
projects / chise / xemacs-chise.git / blobdiff