This is ../info/lispref.info, produced by makeinfo version 4.0b from lispref/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.  File: lispref.info, Node: Changing File Attributes, Next: File Names, Prev: Information about Files, Up: Files Changing File Names and Attributes ================================== The functions in this section rename, copy, delete, link, and set the modes of files. In the functions that have arguments NEWNAME and OK-IF-ALREADY-EXISTS, if a file by the name of NEWNAME already exists, the actions taken depend on the value of OK-IF-ALREADY-EXISTS: * Signal a `file-already-exists' error if OK-IF-ALREADY-EXISTS is `nil'. * Request confirmation if OK-IF-ALREADY-EXISTS is a number. This is what happens when the function is invoked interactively. * Replace the old file without confirmation if OK-IF-ALREADY-EXISTS is any other value. - Command: add-name-to-file filename newname &optional ok-if-already-exists This function gives the file named FILENAME the additional name NEWNAME. This means that NEWNAME becomes a new "hard link" to FILENAME. Both these arguments must be strings. In the first part of the following example, we list two files, `foo' and `foo3'. % ls -l fo* -rw-rw-rw- 1 rms 29 Aug 18 20:32 foo -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3 Then we evaluate the form `(add-name-to-file "~/lewis/foo" "~/lewis/foo2")'. Again we list the files. This shows two names, `foo' and `foo2'. (add-name-to-file "~/lewis/foo1" "~/lewis/foo2") => nil % ls -l fo* -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo -rw-rw-rw- 2 rms 29 Aug 18 20:32 foo2 -rw-rw-rw- 1 rms 24 Aug 18 20:31 foo3 Finally, we evaluate the following: (add-name-to-file "~/lewis/foo" "~/lewis/foo3" t) and list the files again. Now there are three names for one file: `foo', `foo2', and `foo3'. The old contents of `foo3' are lost. (add-name-to-file "~/lewis/foo1" "~/lewis/foo3") => nil % ls -l fo* -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo2 -rw-rw-rw- 3 rms 29 Aug 18 20:32 foo3 This function is meaningless on non-Unix systems, where multiple names for one file are not allowed. See also `file-nlinks' in *Note File Attributes::. - Command: rename-file filename newname &optional ok-if-already-exists This command renames the file FILENAME as NEWNAME. If FILENAME has additional names aside from FILENAME, it continues to have those names. In fact, adding the name NEWNAME with `add-name-to-file' and then deleting FILENAME has the same effect as renaming, aside from momentary intermediate states. In an interactive call, this function prompts for FILENAME and NEWNAME in the minibuffer; also, it requests confirmation if NEWNAME already exists. - Command: copy-file filename newname &optional ok-if-already-exists time This command copies the file FILENAME to NEWNAME. An error is signaled if FILENAME does not exist. If TIME is non-`nil', then this functions gives the new file the same last-modified time that the old one has. (This works on only some operating systems.) In an interactive call, this function prompts for FILENAME and NEWNAME in the minibuffer; also, it requests confirmation if NEWNAME already exists. - Command: delete-file filename This command deletes the file FILENAME, like the shell command `rm FILENAME'. If the file has multiple names, it continues to exist under the other names. A suitable kind of `file-error' error is signaled if the file does not exist, or is not deletable. (On Unix, a file is deletable if its directory is writable.) See also `delete-directory' in *Note Create/Delete Dirs::. - Command: make-symbolic-link filename newname &optional ok-if-already-exists This command makes a symbolic link to FILENAME, named NEWNAME. This is like the shell command `ln -s FILENAME NEWNAME'. In an interactive call, this function prompts for FILENAME and NEWNAME in the minibuffer; also, it requests confirmation if NEWNAME already exists. - Function: set-file-modes filename mode This function sets mode bits of FILENAME to MODE (which must be an integer). Only the low 12 bits of MODE are used. - Function: set-default-file-modes mode This function sets the default file protection for new files created by XEmacs and its subprocesses. Every file created with XEmacs initially has this protection. On Unix, the default protection is the bitwise complement of the "umask" value. The argument MODE must be an integer. Only the low 9 bits of MODE are used. Saving a modified version of an existing file does not count as creating the file; it does not change the file's mode, and does not use the default file protection. - Function: default-file-modes This function returns the current default protection value. 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 `.com', `.bat' or `.exe'. This is reflected in the values returned by `file-modes' and `file-attributes'.  File: lispref.info, Node: File Names, Next: Contents of Directories, Prev: Changing File Attributes, Up: Files File Names ========== Files are generally referred to by their names, in XEmacs as elsewhere. File names in XEmacs are represented as strings. The functions that operate on a file all expect a file name argument. In addition to operating on files themselves, XEmacs Lisp programs often need to operate on the 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, these functions understand MS-DOS file-name syntax as well as Unix syntax. This is so that all the standard Lisp libraries can specify file names in Unix syntax and work properly on all systems without change. Similarly for other operating systems. * Menu: * File Name Components:: The directory part of a file name, and the rest. * Directory Names:: A directory's name as a directory is different from its name as a file. * Relative File Names:: Some file names are relative to a current directory. * 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. * User Name Completion:: Finding the completions for a given user name.  File: lispref.info, Node: File Name Components, Next: Directory Names, Up: File Names File Name Components -------------------- 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, XEmacs considers a file name as having two main parts: the "directory name" part, and the "nondirectory" part (or "file name within the directory"). Either part may be empty. Concatenating these two parts reproduces the original file name. On Unix, the directory part is everything up to and including the last slash; the nondirectory part is the rest. For some purposes, the nondirectory part is further subdivided into the name proper and the "version number". On Unix, only backup files have version numbers in their names. - Function: file-name-directory filename This function returns the directory part of FILENAME (or `nil' if FILENAME does not include a directory part). On Unix, the function returns a string ending in a slash. (file-name-directory "lewis/foo") ; Unix example => "lewis/" (file-name-directory "foo") ; Unix example => nil - Function: file-name-nondirectory filename This function returns the nondirectory part of FILENAME. (file-name-nondirectory "lewis/foo") => "foo" (file-name-nondirectory "foo") => "foo" - Function: file-name-sans-versions filename &optional keep-backup-version This function returns FILENAME without any file version numbers, backup version numbers, or trailing tildes. If KEEP-BACKUP-VERSION is non-`nil', we do not remove backup version numbers, only true file version numbers. (file-name-sans-versions "~rms/foo.~1~") => "~rms/foo" (file-name-sans-versions "~rms/foo~") => "~rms/foo" (file-name-sans-versions "~rms/foo") => "~rms/foo" - Function: file-name-sans-extension filename This function returns FILENAME minus its "extension," if any. The extension, in a file name, is the part that starts with the last `.' in the last name component. For example, (file-name-sans-extension "foo.lose.c") => "foo.lose" (file-name-sans-extension "big.hack/foo") => "big.hack/foo"  File: lispref.info, Node: Directory Names, Next: Relative File Names, Prev: File Name Components, Up: File Names Directory Names --------------- A "directory name" is the name of a directory. A directory is a kind of file, and 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 Unix, this is simple: a directory name ends in a slash, whereas the directory's name as a file lacks that slash. The difference between a directory name and its name as a file is subtle but crucial. When an XEmacs variable or function argument is described as being a directory name, a file name of a directory is not acceptable. The following two functions convert between directory names and file names. They do nothing special with environment variable substitutions such as `$HOME', and the constructs `~', and `..'. - Function: file-name-as-directory filename This function returns a string representing FILENAME in a form that the operating system will interpret as the name of a directory. In Unix, this means appending a slash to the string. (file-name-as-directory "~rms/lewis") => "~rms/lewis/" - Function: directory-file-name dirname This function returns a string representing DIRNAME in a form that the operating system will interpret as the name of a file. On Unix, this means removing a final slash from the string. (directory-file-name "~lewis/") => "~lewis" 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, XEmacs shows users the abbreviation instead. If you wish to convert a directory name to its abbreviation, use this function: - Function: abbreviate-file-name filename &optional hack-homedir This function applies abbreviations from `directory-abbrev-alist' to its argument, and substitutes `~' for the user's home directory. If HACK-HOMEDIR is non-`nil', then this also substitutes `~' for the user's home directory. - Variable: directory-abbrev-alist The variable `directory-abbrev-alist' contains an alist of abbreviations to use for file directories. Each element has the form `(FROM . TO)', and says to replace FROM with TO when it appears in a directory name. The FROM string is actually a regular expression; it should always start with `^'. The function `abbreviate-file-name' performs these substitutions. You can set this variable in `site-init.el' to describe the abbreviations appropriate for your site. Here's an example, from a system on which file system `/home/fsf' and so on are normally accessed through symbolic links named `/fsf' and so on. (("^/home/fsf" . "/fsf") ("^/home/gp" . "/gp") ("^/home/gd" . "/gd"))  File: lispref.info, Node: Relative File Names, Next: File Name Expansion, Prev: Directory Names, Up: File Names Absolute and Relative File Names -------------------------------- All the directories in the file system form a tree starting at the root directory. A file name can specify all the directory names starting from the root of the tree; then it is called an "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 "relative" file name. On Unix, an absolute file name starts with a slash or a tilde (`~'), and a relative one does not. - Function: file-name-absolute-p filename This function returns `t' if file FILENAME is an absolute file name, `nil' otherwise. (file-name-absolute-p "~rms/foo") => t (file-name-absolute-p "rms/foo") => nil (file-name-absolute-p "/user/rms/foo") => t  File: lispref.info, Node: File Name Expansion, Next: Unique File Names, Prev: Relative File Names, Up: File Names Functions that Expand Filenames ------------------------------- "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 `./' and `NAME/../'. - Function: expand-file-name filename &optional directory This function converts FILENAME to an absolute file name. If DIRECTORY is supplied, it is the directory to start with if FILENAME is relative. (The value of DIRECTORY should itself be an absolute directory name; it may start with `~'.) Otherwise, the current buffer's value of `default-directory' is used. For example: (expand-file-name "foo") => "/xcssun/users/rms/lewis/foo" (expand-file-name "../foo") => "/xcssun/users/rms/foo" (expand-file-name "foo" "/usr/spool/") => "/usr/spool/foo" (expand-file-name "$HOME/foo") => "/xcssun/users/rms/lewis/$HOME/foo" Filenames containing `.' or `..' are simplified to their canonical form: (expand-file-name "bar/../foo") => "/xcssun/users/rms/lewis/foo" `~/' at the beginning is expanded into the user's home directory. A `/' or `~' following a `/'. Note that `expand-file-name' does _not_ expand environment variables; only `substitute-in-file-name' does that. - Function: file-relative-name filename &optional directory This function does the inverse of expansion--it tries to return a relative name that is equivalent to FILENAME when interpreted relative to DIRECTORY. If DIRECTORY is `nil' or omitted, the value of `default-directory' is used. (file-relative-name "/foo/bar" "/foo/") => "bar") (file-relative-name "/foo/bar" "/hack/") => "../foo/bar") - Variable: default-directory The value of this buffer-local variable is the default directory for the current buffer. It should be an absolute directory name; it may start with `~'. This variable is local in every buffer. `expand-file-name' uses the default directory when its second argument is `nil'. On Unix systems, the value is always a string ending with a slash. default-directory => "/user/lewis/manual/" - Function: substitute-in-file-name filename This function replaces environment variable references in FILENAME with the environment variable values. Following standard Unix shell syntax, `$' is the prefix to substitute an environment variable value. The environment variable name is the series of alphanumeric characters (including underscores) that follow the `$'. If the character following the `$' is a `{', then the variable name is everything up to the matching `}'. Here we assume that the environment variable `HOME', which holds the user's home directory name, has value `/xcssun/users/rms'. (substitute-in-file-name "$HOME/foo") => "/xcssun/users/rms/foo" After substitution, a `/' or `~' following a `/' is taken to be the start of an absolute file name that overrides what precedes it, so everything before that `/' or `~' is deleted. For example: (substitute-in-file-name "bar/~/foo") => "~/foo" (substitute-in-file-name "/usr/local/$HOME/foo") => "/xcssun/users/rms/foo"  File: lispref.info, Node: Unique File Names, Next: File Name Completion, Prev: File Name Expansion, Up: File Names Generating Unique File Names ---------------------------- Some programs need to write temporary files. Here is the usual way to construct a name for such a file: (make-temp-name (expand-file-name NAME-OF-APPLICATION (temp-directory))) Here we use `(temp-directory)' to specify a directory for temporary files--under Unix, it will normally evaluate to `"/tmp/"'. The job of `make-temp-name' is to prevent two different users or two different processes from trying to use the same name. - Function: temp-directory This function returns the name of the directory to use for temporary files. Under Unix, this will be the value of `TMPDIR', defaulting to `/tmp'. On Windows, this will be obtained from the `TEMP' or `TMP' environment variables, defaulting to `/'. Note that the `temp-directory' function does not exist under FSF Emacs. - Function: make-temp-name prefix This function generates a temporary file name starting with PREFIX. The Emacs process number forms part of the result, so there is no danger of generating a name being used by another process. (make-temp-name "/tmp/foo") => "/tmp/fooGaAQjC" In addition, this function makes an attempt to choose a name that does not specify an existing file. To make this work, PREFIX should be an absolute file name. To avoid confusion, each Lisp application should preferably use a unique PREFIX to `make-temp-name'.  File: lispref.info, Node: File Name Completion, Next: User Name Completion, Prev: Unique File Names, Up: File Names File Name Completion -------------------- This section describes low-level subroutines for completing a file name. For other completion functions, see *Note Completion::. - Function: file-name-all-completions partial-filename directory This function returns a list of all possible completions for files whose name starts with PARTIAL-FILENAME in directory 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 PARTIAL-FILENAME must be a file name containing no directory part and no slash. The current buffer's default directory is prepended to DIRECTORY, if DIRECTORY is not absolute. File names which end with any member of `completion-ignored-extensions' are not considered as possible completions for PARTIAL-FILENAME unless there is no other possible completion. `completion-ignored-extensions' is not applied to the names of directories. In the following example, suppose that the current default directory, `~rms/lewis', has five files whose names begin with `f': `foo', `file~', `file.c', `file.c.~1~', and `file.c.~2~'. (file-name-all-completions "f" "") => ("foo" "file~" "file.c.~2~" "file.c.~1~" "file.c") (file-name-all-completions "fo" "") => ("foo") - Function: file-name-completion partial-filename directory This function completes the file name PARTIAL-FILENAME in directory DIRECTORY. It returns the longest prefix common to all file names in directory DIRECTORY that start with PARTIAL-FILENAME. If only one match exists and PARTIAL-FILENAME matches it exactly, the function returns `t'. The function returns `nil' if directory DIRECTORY contains no name starting with PARTIAL-FILENAME. File names which end with any member of `completion-ignored-extensions' are not considered as possible completions for PARTIAL-FILENAME unless there is no other possible completion. `completion-ignored-extensions' is not applied to the names of directories. In the following example, suppose that the current default directory has five files whose names begin with `f': `foo', `file~', `file.c', `file.c.~1~', and `file.c.~2~'. (file-name-completion "fi" "") => "file" (file-name-completion "file.c.~1" "") => "file.c.~1~" (file-name-completion "file.c.~1~" "") => t (file-name-completion "file.c.~3" "") => nil - User Option: completion-ignored-extensions `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 or when a buffer showing all possible completions is displayed. A typical value might look like this: completion-ignored-extensions => (".o" ".elc" "~" ".dvi")  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 name starting 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 partial-username This function completes a user name from PARTIAL-USERNAME. It returns the longest prefix common to all user names that start with PARTIAL-USERNAME. If only one match exists and PARTIAL-USERNAME matches it exactly, the function returns `t'. The function returns `nil' if no user name starting with PARTIAL-USERNAME exists. - Function: user-name-completion-1 partial-username This function completes the partial user name PARTIAL-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.  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'.  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.  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 filename &optional operation This function returns the handler function for file name FILENAME, 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.  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::  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.  File: lispref.info, Node: Creating a Partial File, Next: Detached Partial Files, Prev: Intro to Partial Files, Up: Partial Files Creating a Partial File ----------------------- - Command: 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's name, and the current buffer, respectively.  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.  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. - Command: 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. - Command: 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 for FORMAT specifies `nil'. - Command: format-insert-file file format &optional start end This command inserts the contents of file FILE, converting it according to format FORMAT. If START 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 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.  File: lispref.info, Node: Files and MS-DOS, Prev: Format Conversion, Up: Files Files and MS-DOS ================ Emacs on MS-DOS makes a distinction between text files and binary files. This is necessary because ordinary text files on MS-DOS use a two character sequence between lines: carriage-return and linefeed (CRLF). Emacs expects just a newline character (a linefeed) between lines. When Emacs reads or writes a text file on MS-DOS, it needs to convert the line separators. This means it needs to know which files are text files and which are binary. It makes this decision when visiting a file, and records the decision in the variable `buffer-file-type' for use when the file is saved. *Note MS-DOS Subprocesses::, for a related feature for subprocesses. - Variable: buffer-file-type This variable, automatically local in each buffer, records the file type of the buffer's visited file. The value is `nil' for text, `t' for binary. - Function: find-buffer-file-type filename This function determines whether file FILENAME is a text file or a binary file. It returns `nil' for text, `t' for binary. - User Option: file-name-buffer-file-type-alist This variable holds an alist for distinguishing text files from binary files. Each element has the form (REGEXP . TYPE), where REGEXP is matched against the file name, and TYPE may be is `nil' for text, `t' for binary, or a function to call to compute which. If it is a function, then it is called with a single argument (the file name) and should return `t' or `nil'. - User Option: default-buffer-file-type This variable specifies the default file type for files whose names don't indicate anything in particular. Its value should be `nil' for text, or `t' for binary. - Command: find-file-text filename Like `find-file', but treat the file as text regardless of its name. - Command: find-file-binary filename Like `find-file', but treat the file as binary regardless of its name.  File: lispref.info, Node: Backups and Auto-Saving, Next: Buffers, Prev: Files, Up: Top Backups and Auto-Saving *********************** Backup files and auto-save files are two methods by which XEmacs tries to protect the user from the consequences of crashes or of the user's own errors. Auto-saving preserves the text from earlier in the current editing session; backup files preserve file contents prior to the current session. * Menu: * Backup Files:: How backup files are made; how their names are chosen. * Auto-Saving:: How auto-save files are made; how their names are chosen. * Reverting:: `revert-buffer', and how to customize what it does.  File: lispref.info, Node: Backup Files, Next: Auto-Saving, Up: Backups and Auto-Saving Backup Files ============ A "backup file" is a copy of the old contents of a file you are editing. XEmacs makes a backup file the first time you save a buffer into its visited file. Normally, this means that the backup file contains the contents of the file as it was before the current editing session. The contents of the backup file normally remain unchanged once it exists. Backups are usually made by renaming the visited file to a new name. Optionally, you can specify that backup files should be made by copying the visited file. This choice makes a difference for files with multiple names; it also can affect whether the edited file remains owned by the original owner or becomes owned by the user editing it. By default, XEmacs makes a single backup file for each file edited. You can alternatively request numbered backups; then each new backup file gets a new name. You can delete old numbered backups when you don't want them any more, or XEmacs can delete them automatically. * Menu: * Making Backups:: How XEmacs makes backup files, and when. * Rename or Copy:: Two alternatives: renaming the old file or copying it. * Numbered Backups:: Keeping multiple backups for each source file. * Backup Names:: How backup file names are computed; customization.  File: lispref.info, Node: Making Backups, Next: Rename or Copy, Up: Backup Files Making Backup Files ------------------- - Function: backup-buffer This function makes a backup of the file visited by the current buffer, if appropriate. It is called by `save-buffer' before saving the buffer the first time. - Variable: buffer-backed-up This buffer-local variable indicates whether this buffer's file has been backed up on account of this buffer. If it is non-`nil', then the backup file has been written. Otherwise, the file should be backed up when it is next saved (if backups are enabled). This is a permanent local; `kill-local-variables' does not alter it. - User Option: make-backup-files This variable determines whether or not to make backup files. If it is non-`nil', then XEmacs creates a backup of each file when it is saved for the first time--provided that `backup-inhibited' is `nil' (see below). The following example shows how to change the `make-backup-files' variable only in the `RMAIL' buffer and not elsewhere. Setting it `nil' stops XEmacs from making backups of the `RMAIL' file, which may save disk space. (You would put this code in your `.emacs' file.) (add-hook 'rmail-mode-hook (function (lambda () (make-local-variable 'make-backup-files) (setq make-backup-files nil)))) - Variable: backup-enable-predicate This variable's value is a function to be called on certain occasions to decide whether a file should have backup files. The function receives one argument, a file name to consider. If the function returns `nil', backups are disabled for that file. Otherwise, the other variables in this section say whether and how to make backups. The default value is this: (lambda (name) (or (< (length name) 5) (not (string-equal "/tmp/" (substring name 0 5))))) - Variable: backup-inhibited If this variable is non-`nil', backups are inhibited. It records the result of testing `backup-enable-predicate' on the visited file name. It can also coherently be used by other mechanisms that inhibit backups based on which file is visited. For example, VC sets this variable non-`nil' to prevent making backups for files managed with a version control system. This is a permanent local, so that changing the major mode does not lose its value. Major modes should not set this variable--they should set `make-backup-files' instead.