@c This is part of the Emacs manual.
-@c Copyright (C) 1985-1987, 1993-1995, 1997, 1999-2012
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1985-1987, 1993-1995, 1997, 1999-2015 Free Software
+@c Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Files
@chapter File Handling
inhibit this insertion by changing the variable
@code{insert-default-directory} to @code{nil} (@pxref{Minibuffer
File}). Regardless, Emacs always assumes that any relative file name
-is relative to the default directory, e.g. entering a file name
+is relative to the default directory, e.g., entering a file name
without a directory specifies a file in the default directory.
@findex cd
buffer name from the file name, omitting the directory name. For
example, a file named @file{/usr/rms/emacs.tex} is visited in a buffer
named @samp{emacs.tex}. If there is already a buffer with that name,
-Emacs constructs a unique name; the normal method is to append
-@samp{<2>}, @samp{<3>}, and so on, but you can select other methods.
-@xref{Uniquify}.
+Emacs constructs a unique name; the normal method is to add a suffix
+based on the directory name (e.g., @samp{<rms>}, @samp{<tmp>},
+and so on), but you can select other methods. @xref{Uniquify}.
@cindex creating files
To create a new file, just visit it using the same command, @kbd{C-x
moves or copies the file into the displayed directory. For details,
see @ref{Drag and Drop}, and @ref{Misc Dired Features}.
+ On text-mode terminals and on graphical displays when Emacs was
+built without a GUI toolkit, you can visit files via the menu-bar
+``File'' menu, which has a ``Visit New File'' item.
+
Each time you visit a file, Emacs automatically scans its contents
to detect what character encoding and end-of-line convention it uses,
and converts these to Emacs's internal encoding and end-of-line
backup.
@vindex make-backup-file-name-function
- If you define the variable @code{make-backup-file-name-function} to
-a suitable Lisp function, that overrides the usual way Emacs
+ If you set the variable @code{make-backup-file-name-function} to
+a suitable Lisp function, you can override the usual way Emacs
constructs backup file names.
@node Backup Deletion
final newlines.
@vindex write-region-inhibit-fsync
- When Emacs saves a file, it invokes the @code{fsync} system call to
-force the data immediately out to disk. This is important for safety
-if the system crashes or in case of power outage. However, it can be
-disruptive on laptops using power saving, as it may force a disk
-spin-up each time you save a file. If you accept an increased risk of
-data loss, you can set @code{write-region-inhibit-fsync} to a
-non-@code{nil} value to disable the synchronization.
+ Normally, when a program writes a file, the operating system briefly
+caches the file's data in main memory before committing the data to
+disk. This can greatly improve performance; for example, when running
+on laptops, it can avoid a disk spin-up each time a file is written.
+However, it risks data loss if the operating system crashes before
+committing the cache to disk.
+
+ To lessen this risk, Emacs can invoke the @code{fsync} system call
+after saving a file. Using @code{fsync} does not eliminate the risk
+of data loss, partly because many systems do not implement
+@code{fsync} properly, and partly because Emacs's file-saving
+procedure typically relies also on directory updates that might not
+survive a crash even if @code{fsync} works properly.
+
+ The @code{write-region-inhibit-fsync} variable controls whether
+Emacs invokes @code{fsync} after saving a file. The variable's
+default value is @code{nil} when Emacs is interactive, and @code{t}
+when Emacs runs in batch mode.
+
+ Emacs never uses @code{fsync} when writing auto-save files, as these
+files might lose data anyway.
@node Interlocking
@subsection Protection against Simultaneous Editing
@cindex locking files
When you make the first modification in an Emacs buffer that is
visiting a file, Emacs records that the file is @dfn{locked} by you.
-(It does this by creating a specially-named symbolic link in the same
-directory.) Emacs removes the lock when you save the changes. The
-idea is that the file is locked whenever an Emacs buffer visiting it
-has unsaved changes.
+(It does this by creating a specially-named symbolic link@footnote{If
+your file system does not support symbolic links, a regular file is
+used.} with special contents in the same directory.) Emacs removes the lock
+when you save the changes. The idea is that the file is locked
+whenever an Emacs buffer visiting it has unsaved changes.
@vindex create-lockfiles
You can prevent the creation of lock files by setting the variable
multiple names, Emacs does not prevent two users from editing it
simultaneously under different names.
- A lock file cannot be written in some circumstances, e.g. if Emacs
-lacks the system permissions or the system does not support symbolic
-links. In these cases, Emacs can still detect the collision when you
-try to save a file, by checking the file's last-modification date. If
-the file has changed since the last time Emacs visited or saved it,
-that implies that changes have been made in some other way, and will
-be lost if Emacs proceeds with saving. Emacs then displays a warning
-message and asks for confirmation before saving; answer @kbd{yes} to
-save, and @kbd{no} or @kbd{C-g} cancel the save.
+ A lock file cannot be written in some circumstances, e.g., if Emacs
+lacks the system permissions or cannot create lock files for some
+other reason. In these cases, Emacs can still detect the collision
+when you try to save a file, by checking the file's last-modification
+date. If the file has changed since the last time Emacs visited or
+saved it, that implies that changes have been made in some other way,
+and will be lost if Emacs proceeds with saving. Emacs then displays a
+warning message and asks for confirmation before saving; answer
+@kbd{yes} to save, and @kbd{no} or @kbd{C-g} cancel the save.
If you are notified that simultaneous editing has already taken
place, one way to compare the buffer to its file is the @kbd{M-x
restores the contents from its auto-save file @file{#@var{file}#}.
You can then save with @kbd{C-x C-s} to put the recovered text into
@var{file} itself. For example, to recover file @file{foo.c} from its
-auto-save file @file{#foo.c#}, do:@refill
+auto-save file @file{#foo.c#}, do:
@example
M-x recover-file @key{RET} foo.c @key{RET}
buffer named @file{*diff*}. This works by running the @command{diff}
program, using options taken from the variable @code{diff-switches}.
The value of @code{diff-switches} should be a string; the default is
-@code{"-c"} to specify a context diff. @xref{Top,, Diff, diff,
-Comparing and Merging Files}, for more information about the
-@command{diff} program.
+@code{"-c"} to specify a context diff.
+@c Note that the actual name of the info file is diffutils.info,
+@c but it adds a dir entry for diff too.
+@c On older systems, only "info diff" works, not "info diffutils".
+@xref{Top,, Diff, diff, Comparing and Merging Files}, for more
+information about the @command{diff} program.
The output of the @code{diff} command is shown using a major mode
called Diff mode. @xref{Diff Mode}.
You can edit a Diff mode buffer like any other buffer. (If it is
read-only, you need to make it writable first. @xref{Misc Buffer}.)
Whenever you change a hunk, Diff mode attempts to automatically
-correct the line numbers in the hunk headers, to ensure that the diff
+correct the line numbers in the hunk headers, to ensure that the patch
remains ``correct''. To disable automatic line number correction,
change the variable @code{diff-update-on-the-fly} to @code{nil}.
@item C-c C-a
@findex diff-apply-hunk
+@cindex patches, applying
Apply this hunk to its target file (@code{diff-apply-hunk}). With a
prefix argument of @kbd{C-u}, revert this hunk.
functions that are deleted by the patch.
@end table
- By default, Diff mode highlights trailing whitespace on modified
-lines, so that they are more obvious. This is done by enabling
-Whitespace mode in the Diff buffer (@pxref{Useless Whitespace}). Diff
-mode buffers are set up so that Whitespace mode avoids highlighting
-trailing whitespace occurring in the diff context.
+@c Trailing whitespace is NOT shown by default.
+@c Emacs's dir-locals file enables this (for some reason).
+@cindex trailing whitespace, in patches
+@findex diff-delete-trailing-whitespace
+ Patches sometimes include trailing whitespace on modified lines, as
+an unintentional and undesired change. There are two ways to deal
+with this problem. Firstly, if you enable Whitespace mode in a Diff
+buffer (@pxref{Useless Whitespace}), it automatically highlights
+trailing whitespace in modified lines. Secondly, you can use the
+command @kbd{M-x diff-delete-trailing-whitespace}, which searches for
+trailing whitespace in the lines modified by the patch, and removes
+that whitespace in both the patch and the patched source file(s).
+This command does not save the modifications that it makes, so you can
+decide whether to save the changes (the list of modified files is
+displayed in the echo area). With a prefix argument, it tries to
+modify the original source files rather than the patched source files.
@node Misc File Ops
@section Miscellaneous File Operations
@var{new} are on different file systems, the file @var{old} is copied
and deleted. If the argument @var{new} is just a directory name, the
real new name is in that directory, with the same non-directory
-component as @var{old}. For example, @kbd{M-x rename-file RET ~/foo
-RET /tmp RET} renames @file{~/foo} to @file{/tmp/foo}. The same rule
-applies to all the remaining commands in this section. All of them
-ask for confirmation when the new file name already exists, too.
+component as @var{old}. For example, @kbd{M-x rename-file @key{RET}
+~/foo @key{RET} /tmp @key{RET}} renames @file{~/foo} to
+@file{/tmp/foo}. The same rule applies to all the remaining commands
+in this section. All of them ask for confirmation when the new file
+name already exists, too.
@ifnottex
If a file is under version control (@pxref{Version Control}), you
@var{target} at the time the opening is done, or will get an error if
the name @var{target} is nonexistent at that time. This command does
not expand the argument @var{target}, so that it allows you to specify
-a relative name as the target of the link. Not all systems support
-symbolic links; on systems that don't support them, this command is
-not defined.
+a relative name as the target of the link. On MS-Windows, this
+command works only on MS Windows Vista and later.
@kindex C-x i
@findex insert-file
@findex file-cache-minibuffer-complete
You can use the @dfn{file name cache} to make it easy to locate a
file by name, without having to remember exactly where it is located.
-When typing a file name in the minibuffer, @kbd{C-@key{tab}}
+When typing a file name in the minibuffer, @kbd{C-@key{TAB}}
(@code{file-cache-minibuffer-complete}) completes it using the file
-name cache. If you repeat @kbd{C-@key{tab}}, that cycles through the
+name cache. If you repeat @kbd{C-@key{TAB}}, that cycles through the
possible completions of what you had originally typed. (However, note
-that the @kbd{C-@key{tab}} character cannot be typed on most text
+that the @kbd{C-@key{TAB}} character cannot be typed on most text
terminals.)
The file name cache does not fill up automatically. Instead, you
@findex image-mode
@findex image-toggle-display
-@findex image-toggle-animation
+@findex image-next-file
+@findex image-previous-file
@cindex images, viewing
-@cindex image animation
-@cindex animated images
Visiting image files automatically selects Image mode. In this
major mode, you can type @kbd{C-c C-c} (@code{image-toggle-display})
to toggle between displaying the file as an image in the Emacs buffer,
support for displaying such images. If the displayed image is wider
or taller than the frame, the usual point motion keys (@kbd{C-f},
@kbd{C-p}, and so forth) cause different parts of the image to be
-displayed. If the image can be animated, the command @kbd{RET}
+displayed. You can press @kbd{n} (@code{image-next-file}) and @kbd{p}
+(@code{image-previous-file}) to visit the next image file and the
+previous image file in the same directory, respectively.
+
+@findex image-toggle-animation
+@findex image-next-frame
+@findex image-previous-frame
+@findex image-goto-frame
+@findex image-increase-speed
+@findex image-decrease-speed
+@findex image-reset-speed
+@findex image-reverse-speed
+@vindex image-animate-loop
+@cindex image animation
+@cindex animated images
+ If the image can be animated, the command @key{RET}
(@code{image-toggle-animation}) starts or stops the animation.
Animation plays once, unless the option @code{image-animate-loop} is
-non-@code{nil}. Currently, Emacs only supports animation in GIF
-files.
+non-@code{nil}. With @kbd{f} (@code{image-next-frame}) and @kbd{b}
+(@code{image-previous-frame}) you can step through the individual
+frames. Both commands accept a numeric prefix to step through several
+frames at once. You can go to a specific frame with @kbd{F}
+(@code{image-goto-frame}). Typing @kbd{a +}
+(@code{image-increase-speed}) increases the speed of the animation,
+@kbd{a -} (@code{image-decrease-speed}) decreases it, and @kbd{a r}
+(@code{image-reverse-speed}) reverses it. The command @kbd{a 0}
+(@code{image-reset-speed}) resets the speed to the original value.
@cindex ImageMagick support
- If your Emacs was compiled with ImageMagick support, it is possible
-to view a much wider variety of image types in Image mode, by
-rendering the images via ImageMagick. However, this feature is
-currently disabled by default. To enable it, add the following line
-to your init file:
-
-@example
-(imagemagick-register-types)
-@end example
+@vindex imagemagick-enabled-types
+@vindex imagemagick-types-inhibit
+ If Emacs was compiled with support for the ImageMagick library, it
+can use ImageMagick to render a wide variety of images. The variable
+@code{imagemagick-enabled-types} lists the image types that Emacs may
+render using ImageMagick; each element in the list should be an
+internal ImageMagick name for an image type, as a symbol or an
+equivalent string (e.g., @code{BMP} for @file{.bmp} images). To
+enable ImageMagick for all possible image types, change
+@code{imagemagick-enabled-types} to @code{t}. The variable
+@code{imagemagick-types-inhibit} lists the image types which should
+never be rendered using ImageMagick, regardless of the value of
+@code{imagemagick-enabled-types} (the default list includes types like
+@code{C} and @code{HTML}, which ImageMagick can render as an ``image''
+but Emacs should not). To disable ImageMagick entirely, change
+@code{imagemagick-types-inhibit} to @code{t}.
@findex thumbs-mode
@findex mode, thumbs
@node Filesets
@section Filesets
@cindex filesets
+@cindex sets of files
@findex filesets-init
If you regularly edit a certain group of files, you can define them
@findex filesets-remove-buffer
The simplest way to define a fileset is by adding files to it one at
a time. To add a file to fileset @var{name}, visit the file and type
-@kbd{M-x filesets-add-buffer @kbd{RET} @var{name} @kbd{RET}}. If
+@kbd{M-x filesets-add-buffer @key{RET} @var{name} @key{RET}}. If
there is no fileset @var{name}, this creates a new one, which
initially contains only the current file. The command @kbd{M-x
filesets-remove-buffer} removes the current file from a fileset.