[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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 Buffers, and those related to backups and auto-saving are described in 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’. See section Functions that Expand Filenames.
35.1 Visiting Files | Reading files into Emacs buffers for editing. | |
35.2 Saving Buffers | Writing changed buffers back into files. | |
35.3 Reading from Files | Reading files into buffers without visiting. | |
35.4 Writing to Files | Writing new files from parts of buffers. | |
35.5 File Locks | Locking and unlocking files, to prevent simultaneous editing by two people. | |
35.6 Information about Files | Testing existence, accessibility, size of files. | |
35.7 Changing File Names and Attributes | Renaming files, changing protection, etc. | |
35.8 File Names | Decomposing and expanding file names. | |
35.9 Contents of Directories | Getting a list of the files in a directory. | |
35.10 Creating and Deleting Directories | ||
35.11 Making Certain File Names “Magic” | Defining "magic" special handling for certain file names. | |
35.12 Partial Files | Treating a section of a buffer as a file. | |
35.13 File Format Conversion | Conversion to and from various file formats. | |
35.14 Files and MS-DOS | Distinguishing text and binary files on MS-DOS. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
35.1.1 Functions for Visiting Files | The usual interface functions for visiting. | |
35.1.2 Subroutines of Visiting | Lower-level subroutines that they use. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This section describes the functions normally used to visit files. For historical reasons, these functions have names starting with ‘find-’ rather than ‘visit-’. See section 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.
See section Reading from Files.
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 Displaying Buffers in Windows.)
When find-file
is called interactively, it prompts for
filename in the minibuffer.
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 nowarn 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 (see section 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> |
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 Displaying Buffers in Windows.
When this command is called interactively, it prompts for filename.
This command selects a buffer visiting the file filename, like
find-file
, but it marks the buffer as read-only. See section Read-Only Buffers, for related functions and variables.
When this command is called interactively, it prompts for 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
. See section Hooks.
When view-file
is called interactively, it prompts for
filename.
With non-nil
prefix arg other-window-p, visit filename
in another window.
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.
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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 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
(see section Creating Buffers).
This function sets the buffer major mode, and parses local variables
(see section How XEmacs Chooses a Major Mode). It is called by find-file-noselect
and by the default revert function (see section 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
.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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:
save-buffer
function marks this version of the file to be
backed up when the buffer is next saved.
save-buffer
function unconditionally backs up the previous
version of the file before saving it.
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.
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
.
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
.
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. See section 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.
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.
This normal hook runs after a buffer has been saved in its visited file.
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. See section Backup by Renaming or by Copying?. 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.
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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. See section File Format Conversion. It also calls the functions in
the list after-insert-file-functions
; see Saving Text Properties in Files.
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 start 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
Making Certain File Names “Magic”.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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.
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
.
See section File Format Conversion. It also calls the functions in the list
write-region-annotate-functions
; see Saving Text Properties in Files.
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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 Comparison of Modification Time.
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 |
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.
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.
This function is called when the user tries to modify filename, but it is locked by another user named other-user. The value it returns determines what happens next:
t
says to grab the lock on the file. Then
this user may edit the file and other-user loses the lock.
nil
says to ignore the lock and let this
user edit the file anyway.
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: filename other-user |
where filename 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’.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
35.6.1 Testing Accessibility | Is a given file readable? Writable? | |
35.6.2 Distinguishing Kinds of Files | Is it a directory? A symbolic link? | |
35.6.3 Truenames | Eliminating symbolic links from a file name. | |
35.6.4 Other Information about Files | How large is it? Any other names? Etc. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
These functions test for permission to access a file in specific ways.
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
.
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 |
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.
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 |
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.
This function returns t
if deleting the file filename and
then creating it anew would keep the file’s owner unchanged.
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. See section Other Information about Files.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This section describes how to distinguish various kinds of files, such as directories, symbolic links, and ordinary files.
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" |
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 |
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).
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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.
See section Buffer File Name, for related information.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This section describes the functions for getting detailed information about a file, other than its contents. This information includes the mode bits that control access permission, the owner and group numbers, the number of names, the inode number, the size, and the times of access and modification.
This function returns the mode bits of filename, as an integer. The mode bits are also called the file permissions, and they specify access control in the usual Unix fashion. If the low-order bit is 1, then the file is executable by all users, if the second-lowest-order bit is 1, then the file is writable by all users, etc.
The highest value returnable is 4095 (7777 octal), meaning that everyone has read, write, and execute permission, that the SUID bit is set for both others and group, and that the sticky bit is set.
(file-modes "~/junk/diffs")
⇒ 492 ; Decimal integer.
(format "%o" 492)
⇒ "754" ; Convert to octal.
(set-file-modes "~/junk/diffs" 438) ⇒ nil (format "%o" 438)
⇒ "666" ; Convert to octal.
% ls -l diffs -rw-rw-rw- 1 lewis 0 3063 Oct 30 16:00 diffs |
This functions returns the number of names (i.e., hard links) that
file filename has. If the file does not exist, then this function
returns nil
. Note that symbolic links have no effect on this
function, because they are not considered to be names of the files they
link to.
% ls -l foo* -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo -rw-rw-rw- 2 rms 4 Aug 19 01:27 foo1 (file-nlinks "foo") ⇒ 2 (file-nlinks "doesnt-exist") ⇒ nil |
This function returns a list of attributes of file filename. If
the specified file cannot be opened, it returns nil
.
The elements of the list, in order, are:
t
for a directory, a string for a symbolic link (the name
linked to), or nil
for a text file.
add-name-to-file
function
(see section Changing File Names and Attributes).
current-time
; see Time of Day.)
t
if the file’s GID would change if file were
deleted and recreated; nil
otherwise.
For example, here are the file attributes for ‘files.texi’:
(file-attributes "files.texi") ⇒ (nil 1 2235 75 (8489 20284) (8489 20284) (8489 20285) 14906 "-rw-rw-rw-" nil 129500 -32252) |
and here is how the result is interpreted:
nil
is neither a directory nor a symbolic link.
1
has only one name (the name ‘files.texi’ in the current default directory).
2235
is owned by the user with UID 2235.
75
is in the group with GID 75.
(8489 20284)
was last accessed on Aug 19 00:09. Use format-time-string
to
! convert this number into a time string. See section Time Conversion.
(8489 20284)
was last modified on Aug 19 00:09.
(8489 20285)
last had its inode changed on Aug 19 00:09.
14906
is 14906 characters long.
"-rw-rw-rw-"
has a mode of read and write access for the owner, group, and world.
nil
would retain the same GID if it were recreated.
129500
has an inode number of 129500.
-32252
is on file system number -32252.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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:
file-already-exists
error if
ok-if-already-exists is nil
.
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 Other Information about Files.
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.
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.
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 Creating and Deleting Directories.
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.
This function sets mode bits of filename to mode (which must be an integer). Only the low 12 bits of mode are used.
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.
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
.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
35.8.1 File Name Components | The directory part of a file name, and the rest. | |
35.8.2 Directory Names | A directory’s name as a directory is different from its name as a file. | |
35.8.3 Absolute and Relative File Names | Some file names are relative to a current directory. | |
35.8.4 Functions that Expand Filenames | Converting relative file names to absolute ones. | |
35.8.5 Generating Unique File Names | Generating names for temporary files. | |
35.8.6 File Name Completion | Finding the completions for a given file name. | |
35.8.7 User Name Completion | Finding the completions for a given user name. |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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
|
This function returns the nondirectory part of filename.
(file-name-nondirectory "lewis/foo") ⇒ "foo" (file-name-nondirectory "foo") ⇒ "foo" |
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" |
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" |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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 ‘..’.
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/" |
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:
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.
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")) |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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 |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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/../’.
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.
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") |
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/" |
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" |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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.
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
.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This section describes low-level subroutines for completing a file name. For other completion functions, see Completion.
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") |
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 |
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") |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This section describes low-level subroutines for completing a user name. For other completion functions, see Completion.
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.
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.
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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.
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.
This variable’s value is the program to run to generate a directory listing
for the function insert-directory
.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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.)
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
This variable holds a list of handlers whose use is presently inhibited for a certain operation.
The operation for which certain handlers are presently inhibited.
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
.
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
.
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
35.12.1 Intro to Partial Files | ||
35.12.2 Creating a Partial File | ||
35.12.3 Detached Partial Files |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
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.
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:
The name of this format.
A documentation string for the format.
A regular expression which is used to recognize files represented in this format.
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.
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:
(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.
A flag, t
if the encoding function modifies the buffer, and
nil
if it works by returning a list of annotations.
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
.
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.
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.
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
.
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
(see section 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
.
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.
[ << ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This document was generated by Aidan Kehoe on December 27, 2016 using texi2html 1.82.