Foundation instead of in the original English.
\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.
+
+\1f
File: lispref.info, Node: File Attributes, Prev: Truenames, Up: Information about Files
Other Information about Files
completion-ignored-extensions
=> (".o" ".elc" "~" ".dvi")
-\1f
-File: lispref.info, Node: User Name Completion, Prev: File Name Completion, Up: File Names
-
-User Name Completion
---------------------
-
- This section describes low-level subroutines for completing a user
-name. For other completion functions, see *Note Completion::.
-
- - Function: user-name-all-completions partial-username
- This function returns a list of all possible completions for a user
- whose name starts with PARTIAL-USERNAME. The order of the
- completions is unpredictable and conveys no useful information.
-
- The argument PARTIAL-USERNAME must be a partial user name
- containing no tilde character and no slash.
-
- - Function: user-name-completion username
- This function completes the user name USERNAME. It returns the
- longest prefix common to all user names that start with USERNAME.
-
- If only one match exists and USERNAME matches it exactly, the
- function returns `t'. The function returns `nil' if no user name
- starting with USERNAME exists.
-
- - Function: user-name-completion-1 username
- This function completes the user name USERNAME, like
- `user-name-completion', differing only in the return value. This
- function returns the cons of the completion returned by
- `user-name-completion', and a boolean indicating whether that
- completion was unique.
-
-\1f
-File: lispref.info, Node: Contents of Directories, Next: Create/Delete Dirs, Prev: File Names, Up: Files
-
-Contents of Directories
-=======================
-
- A directory is a kind of file that contains other files entered under
-various names. Directories are a feature of the file system.
-
- XEmacs can list the names of the files in a directory as a Lisp list,
-or display the names in a buffer using the `ls' shell command. In the
-latter case, it can optionally display information about each file,
-depending on the value of switches passed to the `ls' command.
-
- - Function: directory-files directory &optional full-name match-regexp
- nosort files-only
- This function returns a list of the names of the files in the
- directory DIRECTORY. By default, the list is in alphabetical
- order.
-
- If FULL-NAME is non-`nil', the function returns the files'
- absolute file names. Otherwise, it returns just the names
- relative to the specified directory.
-
- If MATCH-REGEXP is non-`nil', this function returns only those
- file names that contain that regular expression--the other file
- names are discarded from the list.
-
- If NOSORT is non-`nil', `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.
-
- If FILES-ONLY is the symbol `t', then only the "files" in the
- directory will be returned; subdirectories will be excluded. If
- FILES-ONLY is not `nil' and not `t', then only the subdirectories
- will be returned. Otherwise, if FILES-ONLY is `nil' (the default)
- then both files and subdirectories will be returned.
-
- (directory-files "~lewis")
- => ("#foo#" "#foo.el#" "." ".."
- "dired-mods.el" "files.texi"
- "files.texi.~1~")
-
- An error is signaled if DIRECTORY is not the name of a directory
- that can be read.
-
- - Function: insert-directory file switches &optional wildcard
- full-directory-p
- This function inserts (in the current buffer) a directory listing
- for directory FILE, formatted with `ls' according to SWITCHES. It
- leaves point after the inserted text.
-
- The argument FILE may be either a directory name or a file
- specification including wildcard characters. If WILDCARD is
- non-`nil', that means treat FILE as a file specification with
- wildcards.
-
- If FULL-DIRECTORY-P is non-`nil', that means FILE is a directory
- and switches do not contain `-d', so that the listing should show
- the full contents of the directory. (The `-d' option to `ls' says
- to describe a directory itself rather than its contents.)
-
- This function works by running a directory listing program whose
- name is in the variable `insert-directory-program'. If WILDCARD is
- non-`nil', it also runs the shell specified by `shell-file-name',
- to expand the wildcards.
-
- - Variable: insert-directory-program
- This variable's value is the program to run to generate a
- directory listing for the function `insert-directory'.
-
-\1f
-File: lispref.info, Node: Create/Delete Dirs, Next: Magic File Names, Prev: Contents of Directories, Up: Files
-
-Creating and Deleting Directories
-=================================
-
- Most XEmacs Lisp file-manipulation functions get errors when used on
-files that are directories. For example, you cannot delete a directory
-with `delete-file'. These special functions exist to create and delete
-directories.
-
- - Command: make-directory dirname &optional parents
- This function creates a directory named DIRNAME. Interactively,
- the default choice of directory to create is the current default
- directory for file names. That is useful when you have visited a
- file in a nonexistent directory.
-
- Non-interactively, optional argument PARENTS says whether to
- create parent directories if they don't exist. (Interactively, this
- always happens.)
-
- - Command: delete-directory dirname
- This function deletes the directory named DIRNAME. The function
- `delete-file' does not work for files that are directories; you
- must use `delete-directory' in that case.
-
-\1f
-File: lispref.info, Node: Magic File Names, Next: Partial Files, Prev: Create/Delete Dirs, Up: Files
-
-Making Certain File Names "Magic"
-=================================
-
- You can implement special handling for certain file names. This is
-called making those names "magic". 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
-XEmacs file operations for file names that do match.
-
- The variable `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:
-
- (REGEXP . HANDLER)
-
-All the XEmacs primitives for file access and file name transformation
-check the given file name against `file-name-handler-alist'. If the
-file name matches REGEXP, the primitives handle that file by calling
-HANDLER.
-
- The first argument given to HANDLER is the name of the primitive;
-the remaining arguments are the arguments that were passed to that
-operation. (The first of these arguments is typically the file name
-itself.) For example, if you do this:
-
- (file-exists-p FILENAME)
-
-and FILENAME has handler HANDLER, then HANDLER is called like this:
-
- (funcall HANDLER 'file-exists-p FILENAME)
-
- Here are the operations that a magic file name handler gets to
-handle:
-
-`add-name-to-file', `copy-file', `delete-directory', `delete-file',
-`diff-latest-backup-file', `directory-file-name', `directory-files',
-`dired-compress-file', `dired-uncache', `expand-file-name',
-`file-accessible-directory-p', `file-attributes', `file-directory-p',
-`file-executable-p', `file-exists-p', `file-local-copy', `file-modes',
-`file-name-all-completions', `file-name-as-directory',
-`file-name-completion', `file-name-directory', `file-name-nondirectory',
-`file-name-sans-versions', `file-newer-than-file-p', `file-readable-p',
-`file-regular-p', `file-symlink-p', `file-truename', `file-writable-p',
-`get-file-buffer', `insert-directory', `insert-file-contents', `load',
-`make-directory', `make-symbolic-link', `rename-file', `set-file-modes',
-`set-visited-file-modtime', `unhandled-file-name-directory',
-`verify-visited-file-modtime', `write-region'.
-
- Handlers for `insert-file-contents' typically need to clear the
-buffer's modified flag, with `(set-buffer-modified-p nil)', if the
-VISIT argument is non-`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:
-
- (defun my-file-handler (operation &rest args)
- ;; First check for the specific operations
- ;; that we have special handling for.
- (cond ((eq operation 'insert-file-contents) ...)
- ((eq operation 'write-region) ...)
- ...
- ;; 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)))))
-
- 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
-`inhibit-file-name-handlers' and `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.
-
- - Variable: inhibit-file-name-handlers
- This variable holds a list of handlers whose use is presently
- inhibited for a certain operation.
-
- - Variable: inhibit-file-name-operation
- The operation for which certain handlers are presently inhibited.
-
- - Function: find-file-name-handler file operation
- This function returns the handler function for file name FILE, or
- `nil' if there is none. The argument 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 `inhibit-file-name-operation'.
-
- - Function: file-local-copy filename
- This function copies file FILENAME to an ordinary non-magic file,
- if it isn't one already.
-
- If FILENAME specifies a "magic" file name, which programs outside
- Emacs cannot directly read or write, this copies the contents to
- an ordinary file and returns that file's name.
-
- If FILENAME is an ordinary file name, not magic, then this function
- does nothing and returns `nil'.
-
- - Function: unhandled-file-name-directory filename
- This function returns the name of a directory that is not magic.
- It uses the directory part of FILENAME if that is not magic.
- Otherwise, it asks the handler what to do.
-
- 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.
-
-\1f
-File: lispref.info, Node: Partial Files, Next: Format Conversion, Prev: Magic File Names, Up: Files
-
-Partial Files
-=============
-
-* Menu:
-
-* Intro to Partial Files::
-* Creating a Partial File::
-* Detached Partial Files::
-
-\1f
-File: lispref.info, Node: Intro to Partial Files, Next: Creating a Partial File, Up: Partial Files
-
-Intro to Partial Files
-----------------------
-
- A "partial file" is a section of a buffer (called the "master
-buffer") that is placed in its own buffer and treated as its own file.
-Changes made to the partial file are not reflected in the master buffer
-until the partial file is "saved" using the standard buffer save
-commands. Partial files can be "reverted" (from the master buffer)
-just like normal files. When a file part is active on a master buffer,
-that section of the master buffer is marked as read-only. Two file
-parts on the same master buffer are not allowed to overlap. Partial
-file buffers are indicated by the words `File Part' in the modeline.
-
- The master buffer knows about all the partial files that are active
-on it, and thus killing or reverting the master buffer will be handled
-properly. When the master buffer is saved, if there are any unsaved
-partial files active on it then the user will be given the opportunity
-to first save these files.
-
- When a partial file buffer is first modified, the master buffer is
-automatically marked as modified so that saving the master buffer will
-work correctly.
-
-\1f
-File: lispref.info, Node: Creating a Partial File, Next: Detached Partial Files, Prev: Intro to Partial Files, Up: Partial Files
-
-Creating a Partial File
------------------------
-
- - Function: make-file-part &optional start end name buffer
- Make a file part on buffer BUFFER out of the region. Call it
- NAME. This command creates a new buffer containing the contents
- of the region and marks the buffer as referring to the specified
- buffer, called the "master buffer". When the file-part buffer is
- saved, its changes are integrated back into the master buffer.
- When the master buffer is deleted, all file parts are deleted with
- it.
-
- When called from a function, expects four arguments, START, END,
- NAME, and BUFFER, all of which are optional and default to the
- beginning of BUFFER, the end of BUFFER, a name generated from
- BUFFER name, and the current buffer, respectively.
-
-\1f
-File: lispref.info, Node: Detached Partial Files, Prev: Creating a Partial File, Up: Partial Files
-
-Detached Partial Files
-----------------------
-
- Every partial file has an extent in the master buffer associated
-with it (called the "master extent"), marking where in the master
-buffer the partial file begins and ends. If the text in master buffer
-that is contained by the extent is deleted, then the extent becomes
-"detached", meaning that it no longer refers to a specific region of
-the master buffer. This can happen either when the text is deleted
-directly or when the master buffer is reverted. Neither of these should
-happen in normal usage because the master buffer should generally not be
-edited directly.
-
- Before doing any operation that references a partial file's master
-extent, XEmacs checks to make sure that the extent is not detached. If
-this is the case, XEmacs warns the user of this and the master extent is
-deleted out of the master buffer, disconnecting the file part. The file
-part's filename is cleared and thus must be explicitly specified if the
-detached file part is to be saved.
-
-\1f
-File: lispref.info, Node: Format Conversion, Next: Files and MS-DOS, Prev: Partial Files, Up: Files
-
-File Format Conversion
-======================
-
- The variable `format-alist' defines a list of "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.
-
- - Variable: format-alist
- This list contains one format definition for each defined file
- format.
-
- Each format definition is a list of this form:
-
- (NAME DOC-STRING REGEXP FROM-FN TO-FN MODIFY MODE-FN)
-
- Here is what the elements in a format definition mean:
-
-NAME
- The name of this format.
-
-DOC-STRING
- A documentation string for the format.
-
-REGEXP
- A regular expression which is used to recognize files represented
- in this format.
-
-FROM-FN
- A function to call to decode data in this format (to convert file
- data into the usual Emacs data representation).
-
- The FROM-FN is called with two args, BEGIN and 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, FROM-FN should return the modified end position.
-
- One responsibility of FROM-FN is to make sure that the beginning
- of the file no longer matches REGEXP. Otherwise it is likely to
- get called again.
-
-TO-FN
- A function to call to encode data in this format (to convert the
- usual Emacs data representation into this format).
-
- The TO-FN is called with two args, BEGIN and END, which specify
- the part of the buffer it should convert. There are two ways it
- can do the conversion:
-
- * By editing the buffer in place. In this case, TO-FN should
- return the end-position of the range of text, as modified.
-
- * By returning a list of annotations. This is a list of
- elements of the form `(POSITION . STRING)', where POSITION is
- an integer specifying the relative position in the text to be
- written, and STRING is the annotation to add there. The list
- must be sorted in order of position when TO-FN returns it.
-
- When `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.
-
-MODIFY
- A flag, `t' if the encoding function modifies the buffer, and
- `nil' if it works by returning a list of annotations.
-
-MODE
- A mode function to call after visiting a file converted from this
- format.
-
- The function `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 `find-file-noselect' or the commands that use
-it, performs conversion likewise (because it calls
-`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 `buffer-file-format'.
-
- - Variable: 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 local in all buffers.
-
- When `write-region' writes data into a file, it first calls the
-encoding functions for the formats listed in `buffer-file-format', in
-the order of appearance in the list.
-
- - Function: format-write-file file format
- This command writes the current buffer contents into the file FILE
- in format FORMAT, and makes that format the default for future
- saves of the buffer. The argument FORMAT is a list of format
- names.
-
- - Function: format-find-file file format
- This command finds the file FILE, converting it according to
- format FORMAT. It also makes FORMAT the default if the buffer is
- saved later.
-
- The argument FORMAT is a list of format names. If FORMAT is
- `nil', no conversion takes place. Interactively, typing just
- <RET> for FORMAT specifies `nil'.
-
- - Function: format-insert-file file format &optional beg end
- This command inserts the contents of file FILE, converting it
- according to format FORMAT. If BEG and END are non-`nil', they
- specify which part of the file to read, as in
- `insert-file-contents' (*note Reading from Files::).
-
- The return value is like what `insert-file-contents' returns: a
- list of the absolute file name and the length of the data inserted
- (after conversion).
-
- The argument FORMAT is a list of format names. If FORMAT is
- `nil', no conversion takes place. Interactively, typing just
- <RET> for FORMAT specifies `nil'.
-
- - Function: format-find-file file format
- This command finds the file FILE, converting it according to
- format FORMAT. It also makes FORMAT the default if the buffer is
- saved later.
-
- The argument FORMAT is a list of format names. If FORMAT is
- `nil', no conversion takes place. Interactively, typing just
- <RET> for FORMAT specifies `nil'.
-
- - Function: format-insert-file file format &optional beg end
- This command inserts the contents of file FILE, converting it
- according to format FORMAT. If BEG and END are non-`nil', they
- specify which part of the file to read, as in
- `insert-file-contents' (*note Reading from Files::).
-
- The return value is like what `insert-file-contents' returns: a
- list of the absolute file name and the length of the data inserted
- (after conversion).
-
- The argument FORMAT is a list of format names. If FORMAT is
- `nil', no conversion takes place. Interactively, typing just
- <RET> for FORMAT specifies `nil'.
-
- - Variable: 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
- `buffer-file-format'; but it is used instead of
- `buffer-file-format' for writing auto-save files. This variable
- is always local in all buffers.
-
projects / chise / xemacs-chise.git / blobdiff