23.2 Visiting Files

C-x C-f

Visit a file (find-file).

C-x C-r

Visit a file for viewing, without allowing changes to it (find-file-read-only).

C-x C-v

Visit a different file instead of the one visited last (find-alternate-file).

C-x 4 f

Visit a file, in another window (find-file-other-window). Don't alter what is displayed in the selected window.

C-x 5 f

Visit a file, in a new frame (find-file-other-frame). Don't alter what is displayed in the selected frame.

M-x find-file-literally

Visit a file with no conversion of the contents.

Visiting a file means reading its contents into an Emacs buffer so you can edit them. Emacs makes a new buffer for each file that you visit. We often say that this buffer “is visiting” that file, or that the buffer's “visited file” is that file. Emacs constructs the buffer name from the file name by throwing away the directory, keeping just the name proper. For example, a file named ‘/usr/rms/emacs.tex’ would get a buffer named ‘emacs.tex’. If there is already a buffer with that name, Emacs constructs a unique name—the normal method is to append ‘<2>’, ‘<3>’, and so on, but you can select other methods (voir la section Making Buffer Names Unique).

Each window's mode line shows the name of the buffer that is being displayed in that window, so you can always tell what buffer you are editing.

The changes you make with editing commands are made in the Emacs buffer. They do not take effect in the file that you visited, or any permanent place, until you save the buffer. Saving the buffer means that Emacs writes the current contents of the buffer into its visited file. Voir la section Saving Files.

If a buffer contains changes that have not been saved, we say the buffer is modified. This is important because it implies that some changes will be lost if the buffer is not saved. The mode line displays two stars near the left margin to indicate that the buffer is modified.

To visit a file, use the command C-x C-f (find-file). Follow the command with the name of the file you wish to visit, terminated by a <RET>.

The file name is read using the minibuffer (voir la section The Minibuffer), with defaulting and completion in the standard manner (voir la section File Names). While in the minibuffer, you can abort C-x C-f by typing C-g. File-name completion ignores certain file names; for more about this, see Completion Options.

Your confirmation that C-x C-f has completed successfully is the appearance of new text on the screen and a new buffer name in the mode line. If the specified file does not exist and you could not create it, or exists but you can't read it, then you get an error, with an error message displayed in the echo area.

If you visit a file that is already in Emacs, C-x C-f does not make another copy. It selects the existing buffer containing that file. However, before doing so, it checks whether the file itself has changed since you visited or saved it last. If the file has changed, Emacs offers to reread it.

If you try to visit a file larger than large-file-warning-threshold (the default is 10000000, which is about 10 megabytes), Emacs will ask you for confirmation first. You can answer y to proceed with visiting the file. Note, however, that Emacs cannot visit files that are larger than the maximum Emacs buffer size, which is around 256 megabytes on 32-bit machines (voir la section Using Multiple Buffers). If you try, Emacs will display an error message saying that the maximum buffer size has been exceeded.

On graphical displays there are two additional methods for visiting files. Firstly, when Emacs is built with a suitable GUI toolkit, commands invoked with the mouse (by clicking on the menu bar or tool bar) use the toolkit's standard File Selection dialog instead of prompting for the file name in the minibuffer. On Unix and GNU/Linux platforms, Emacs does that when built with GTK, LessTif, and Motif toolkits; on MS-Windows and Mac, the GUI version does that by default. For information on how to customize this, see Using Dialog Boxes.

Secondly, Emacs supports “drag and drop”; dropping a file into an ordinary Emacs window visits the file using that window. However, dropping a file into a window displaying a Dired buffer moves or copies the file into the displayed directory. For details, see Drag and Drop, and Other Dired Features.

What if you want to create a new file? Just visit it. Emacs displays ‘(New file)’ in the echo area, but in other respects behaves as if you had visited an existing empty file. If you make any changes and save them, the file is created.

Emacs recognizes from the contents of a file which end-of-line convention it uses to separate lines—newline (used on GNU/Linux and on Unix), carriage-return linefeed (used on Microsoft systems), or just carriage-return (used on the Macintosh)—and automatically converts the contents to the normal Emacs convention, which is that the newline character separates lines. This is a part of the general feature of coding system conversion (@pxref{Coding Systems}), and makes it possible to edit files imported from different operating systems with equal convenience. If you change the text and save the file, Emacs performs the inverse conversion, changing newlines back into carriage-return linefeed or just carriage-return if appropriate.

If the file you specify is actually a directory, C-x C-f invokes Dired, the Emacs directory browser, so that you can “edit” the contents of the directory (voir la section Dired, the Directory Editor). Dired is a convenient way to view, delete, or operate on the files in the directory. However, if the variable find-file-run-dired is nil, then it is an error to try to visit a directory.

Files which are actually collections of other files, or file archives, are visited in special modes which invoke a Dired-like environment to allow operations on archive members. Voir la section File Archives, for more about these features.

If the file name you specify contains shell-style wildcard characters, Emacs visits all the files that match it. (On case-insensitive filesystems, Emacs matches the wildcards disregarding the letter case.) Wildcards include ‘?’, ‘*’, and ‘[…]’ sequences. To enter the wild card ‘?’ in a file name in the minibuffer, you need to type C-q ?. Voir la section Quoted File Names, for information on how to visit a file whose name actually contains wildcard characters. You can disable the wildcard feature by customizing find-file-wildcards.

If you visit a file that the operating system won't let you modify, or that is marked read-only, Emacs makes the buffer read-only too, so that you won't go ahead and make changes that you'll have trouble saving afterward. You can make the buffer writable with C-x C-q (toggle-read-only). Voir la section Miscellaneous Buffer Operations.

If you want to visit a file as read-only in order to protect yourself from entering changes accidentally, visit it with the command C-x C-r (find-file-read-only) instead of C-x C-f.

If you visit a nonexistent file unintentionally (because you typed the wrong file name), use the C-x C-v command (find-alternate-file) to visit the file you really wanted. C-x C-v is similar to C-x C-f, but it kills the current buffer (after first offering to save it if it is modified). When C-x C-v reads the file name to visit, it inserts the entire default file name in the buffer, with point just after the directory part; this is convenient if you made a slight error in typing the name.

C-x 4 f (find-file-other-window) is like C-x C-f except that the buffer containing the specified file is selected in another window. The window that was selected before C-x 4 f continues to show the same buffer it was already showing. If this command is used when only one window is being displayed, that window is split in two, with one window showing the same buffer as before, and the other one showing the newly requested file. Voir la section Multiple Windows.

C-x 5 f (find-file-other-frame) is similar, but opens a new frame, or makes visible any existing frame showing the file you seek. This feature is available only when you are using a window system. @xref{Frames}.

If you wish to edit a file as a sequence of ASCII characters with no special encoding or conversion, use the M-x find-file-literally command. It visits a file, like C-x C-f, but does not do format conversion (voir la section Editing Formatted Text), character code conversion (@pxref{Coding Systems}), or automatic uncompression (voir la section Accessing Compressed Files), and does not add a final newline because of require-final-newline. If you already have visited the same file in the usual (non-literal) manner, this command asks you whether to visit it literally instead.

Two special hook variables allow extensions to modify the operation of visiting files. Visiting a file that does not exist runs the functions in the list find-file-not-found-functions; this variable holds a list of functions, and the functions are called one by one (with no arguments) until one of them returns non-nil. This is not a normal hook, and the name ends in ‘-functions’ rather than ‘-hook’ to indicate that fact.

Successful visiting of any file, whether existing or not, calls the functions in the list find-file-hook, with no arguments. This variable is a normal hook. In the case of a nonexistent file, the find-file-not-found-functions are run first. Voir la section Hooks.

There are several ways to specify automatically the major mode for editing the file (voir la section How Major Modes are Chosen), and to specify local variables defined for that file (voir la section Local Variables in Files).

Ce document a été généré par Eric Reinbold le 23 Février 2009 en utilisant texi2html 1.78.