file-name-extension

[bpt/emacs.git] / man / dired.texi

@c This is part of the Emacs manual.
@c Copyright (C) 1985, 86, 87, 93, 94, 95, 97, 2000
@c   Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Dired, Calendar/Diary, Rmail, Top
@chapter Dired, the Directory Editor
@cindex Dired

  Dired makes an Emacs buffer containing a listing of a directory, and
optionally some of its subdirectories as well.  You can use the normal
Emacs commands to move around in this buffer, and special Dired commands
to operate on the files listed.

@menu
* Enter: Dired Enter.         How to invoke Dired.
* Commands: Dired Commands.   Commands in the Dired buffer.
* Deletion: Dired Deletion.   Deleting files with Dired.
* Flagging Many Files::       Flagging files based on their names.
* Visit: Dired Visiting.      Other file operations through Dired.
* Marks vs Flags::	      Flagging for deletion vs marking.
* Operating on Files::	      How to copy, rename, print, compress, etc.
			        either one file or several files.
* Shell Commands in Dired::   Running a shell command on the marked files.
* Transforming File Names::   Using patterns to rename multiple files.
* Comparison in Dired::	      Running `diff' by way of Dired.
* Subdirectories in Dired::   Adding subdirectories to the Dired buffer.
* Subdirectory Motion::	      Moving across subdirectories, and up and down.
* Hiding Subdirectories::     Making subdirectories visible or invisible.
* Updating: Dired Updating.   Discarding lines for files of no interest.
* Find: Dired and Find.	      Using `find' to choose the files for Dired.
* Extra Features for Dired::  Dired-X provides more features.
@end menu

@node Dired Enter
@section Entering Dired

@findex dired
@kindex C-x d
@vindex dired-listing-switches
  To invoke Dired, do @kbd{C-x d} or @kbd{M-x dired}.  The command reads
a directory name or wildcard file name pattern as a minibuffer argument
to specify which files to list.  Where @code{dired} differs from
@code{list-directory} is in putting the buffer into Dired mode so that
the special commands of Dired are available.

  The variable @code{dired-listing-switches} specifies the options to
give to @code{ls} for listing directory; this string @emph{must} contain
@samp{-l}.  If you use a numeric prefix argument with the @code{dired}
command, you can specify the @code{ls} switches with the minibuffer
before you enter the directory specification.

@findex dired-other-window
@kindex C-x 4 d
@findex dired-other-frame
@kindex C-x 5 d
  To display the Dired buffer in another window rather than in the
selected window, use @kbd{C-x 4 d} (@code{dired-other-window}) instead
of @kbd{C-x d}.  @kbd{C-x 5 d} (@code{dired-other-frame}) uses a
separate frame to display the Dired buffer.

@node Dired Commands
@section Commands in the Dired Buffer

    The Dired buffer is ``read-only,'' and inserting text in it is not
useful, so ordinary printing characters such as @kbd{d} and @kbd{x} are
used for special Dired commands.  Some Dired commands @dfn{mark} or
@dfn{flag} the @dfn{current file} (that is, the file on the current
line); other commands operate on the marked files or on the flagged
files.

@kindex C-n @r{(Dired)}
@kindex C-p @r{(Dired)}
  All the usual Emacs cursor motion commands are available in Dired
buffers.  Some special-purpose cursor motion commands are also
provided.  The keys @kbd{C-n} and @kbd{C-p} are redefined to put the
cursor at the beginning of the file name on the line, rather than at the
beginning of the line.

@kindex SPC @r{(Dired)}
  For extra convenience, @key{SPC} and @kbd{n} in Dired are equivalent
to @kbd{C-n}.  @kbd{p} is equivalent to @kbd{C-p}.  (Moving by lines is
so common in Dired that it deserves to be easy to type.)  @key{DEL}
(move up and unflag) is often useful simply for moving up.

@node Dired Deletion
@section Deleting Files with Dired
@cindex flagging files (in Dired)
@cindex deleting files (in Dired)

  The primary use of Dired is to @dfn{flag} files for deletion and then
delete the files previously flagged.

@table @kbd
@item d
Flag this file for deletion.
@item u
Remove deletion flag on this line.
@item @key{DEL}
Move point to previous line and remove the deletion flag on that line.
@item x
Delete the files that are flagged for deletion.
@end table

@kindex d @r{(Dired)}
@findex dired-flag-file-deletion
  You can flag a file for deletion by moving to the line describing the
file and typing @kbd{d} (@code{dired-flag-file-deletion}).  The deletion flag is visible as a @samp{D} at
the beginning of the line.  This command moves point to the next line,
so that repeated @kbd{d} commands flag successive files.  A numeric
argument serves as a repeat count.
@vindex dired-recursive-deletes
The variable @code{dired-recursive-deletes} determines if the delete
command will delete non-empty directories recursively.  The default
is to delete only empty directories.

@kindex u @r{(Dired deletion)}
@kindex DEL @r{(Dired)}
  The files are flagged for deletion rather than deleted immediately to
reduce the danger of deleting a file accidentally.  Until you direct
Dired to expunge the flagged files, you can remove deletion flags using
the commands @kbd{u} and @key{DEL}.  @kbd{u} (@code{dired-unmark}) works
just like @kbd{d}, but removes flags rather than making flags.
@key{DEL} (@code{dired-unmark-backward}) moves upward, removing flags;
it is like @kbd{u} with argument @minus{}1.

@kindex x @r{(Dired)}
@findex dired-expunge
@cindex expunging (Dired)
  To delete the flagged files, type @kbd{x} (@code{dired-expunge}).
This command first displays a list of all the file names flagged for
deletion, and requests confirmation with @kbd{yes}.  If you confirm,
Dired deletes the flagged files, then deletes their lines from the text
of the Dired buffer.  The shortened Dired buffer remains selected.

  If you answer @kbd{no} or quit with @kbd{C-g} when asked to confirm, you
return immediately to Dired, with the deletion flags still present in
the buffer, and no files actually deleted.

@node Flagging Many Files
@section Flagging Many Files at Once

@table @kbd
@item #
Flag all auto-save files (files whose names start and end with @samp{#})
for deletion (@pxref{Auto Save}).

@item ~
Flag all backup files (files whose names end with @samp{~}) for deletion
(@pxref{Backup}).

@item &
Flag for deletion all files with certain kinds of names, names that
suggest you could easily create the files again.

@item .@: @r{(Period)}
Flag excess numeric backup files for deletion.  The oldest and newest
few backup files of any one file are exempt; the middle ones are
flagged.

@item % d @var{regexp} @key{RET}
Flag for deletion all files whose names match the regular expression
@var{regexp}.
@end table

  The @kbd{#}, @kbd{~}, @kbd{&}, and @kbd{.} commands flag many files for
deletion, based on their file names.  These commands are useful
precisely because they do not themselves delete any files; you can
remove the deletion flags from any flagged files that you really wish to
keep.@refill

@kindex & @r{(Dired)}
@findex dired-flag-garbage-files
@vindex dired-garbage-files-regexp
  @kbd{&} (@code{dired-flag-garbage-files}) flags files whose names
match the regular expression specified by the variable
@code{dired-garbage-files-regexp}.  By default, this matches certain
files produced by @TeX{}, and the @samp{.orig} and @samp{.rej} files
produced by @code{patch}.

@kindex # @r{(Dired)}
@kindex ~ @r{(Dired)}
@findex dired-flag-auto-save-files
@findex dired-flag-backup-files
  @kbd{#} (@code{dired-flag-auto-save-files}) flags for deletion all
files whose names look like auto-save files (@pxref{Auto Save})---that
is, files whose names begin and end with @samp{#}.  @kbd{~}
(@code{dired-flag-backup-files}) flags for deletion all files whose
names say they are backup files (@pxref{Backup})---that is, whose names
end in @samp{~}.

@kindex . @r{(Dired)}
@vindex dired-kept-versions
@findex dired-clean-directory
  @kbd{.} (period, @code{dired-clean-directory}) flags just some of the
backup files for deletion: all but the oldest few and newest few backups
of any one file.  Normally @code{dired-kept-versions} (@strong{not}
@code{kept-new-versions}; that applies only when saving) specifies the
number of newest versions of each file to keep, and
@code{kept-old-versions} specifies the number of oldest versions to
keep.

  Period with a positive numeric argument, as in @kbd{C-u 3 .},
specifies the number of newest versions to keep, overriding
@code{dired-kept-versions}.  A negative numeric argument overrides
@code{kept-old-versions}, using minus the value of the argument to
specify the number of oldest versions of each file to keep.

@findex dired-flag-files-regexp
@kindex % d @r{(Dired)}
  The @kbd{% d} command flags all files whose names match a specified
regular expression (@code{dired-flag-files-regexp}).  Only the
non-directory part of the file name is used in matching.  You can use
@samp{^} and @samp{$} to anchor matches.  You can exclude subdirectories
by hiding them (@pxref{Hiding Subdirectories}).

@node Dired Visiting
@section Visiting Files in Dired

  There are several Dired commands for visiting or examining the files
listed in the Dired buffer.  All of them apply to the current line's
file; if that file is really a directory, these commands invoke Dired on
that subdirectory (making a separate Dired buffer).

@table @kbd
@item f
@kindex f @r{(Dired)}
@findex dired-find-file
Visit the file described on the current line, like typing @kbd{C-x C-f}
and supplying that file name (@code{dired-find-file}).  @xref{Visiting}.

@item @key{RET}
@kindex RET @r{(Dired)}
Equivalent to @kbd{f}.

@item a
@kindex a @r{(Dired)}
@findex dired-find-alternate-file
Like @kbd{f}, but replaces the contents of the Dired buffer with
that of an alternate file or directory.

@item o
@kindex o @r{(Dired)}
@findex dired-find-file-other-window
Like @kbd{f}, but uses another window to display the file's buffer
(@code{dired-find-file-other-window}).  The Dired buffer remains visible
in the first window.  This is like using @kbd{C-x 4 C-f} to visit the
file.  @xref{Windows}.

@item C-o
@kindex C-o @r{(Dired)}
@findex dired-display-file
Visit the file described on the current line, and display the buffer in
another window, but do not select that window (@code{dired-display-file}).

@item Mouse-2
@findex dired-mouse-find-file-other-window
Visit the file named by the line you click on
(@code{dired-mouse-find-file-other-window}).  This uses another window
to display the file, like the @kbd{o} command.

@item v
@kindex v @r{(Dired)}
@findex dired-view-file
View the file described on the current line, using @kbd{M-x view-file}
(@code{dired-view-file}).

Viewing a file is like visiting it, but is slanted toward moving around
in the file conveniently and does not allow changing the file.
@xref{Misc File Ops,View File}.
@end table

@node Marks vs Flags
@section Dired Marks vs. Flags

@cindex marking in Dired
  Instead of flagging a file with @samp{D}, you can @dfn{mark} the file
with some other character (usually @samp{*}).  Most Dired commands to
operate on files, aside from ``expunge'' (@kbd{x}), look for files
marked with @samp{*}.

  Here are some commands for marking with @samp{*}, or for unmarking or
operating on marks.  (@xref{Dired Deletion}, for commands to flag and
unflag files.)

@table @kbd
@item m
@itemx * m
@kindex m @r{(Dired)}
@kindex * m @r{(Dired)}
@findex dired-mark
Mark the current file with @samp{*} (@code{dired-mark}).  With a numeric
argument @var{n}, mark the next @var{n} files starting with the current
file.  (If @var{n} is negative, mark the previous @minus{}@var{n}
files.)

@item * *
@kindex * * @r{(Dired)}
@findex dired-mark-executables
Mark all executable files with @samp{*}
(@code{dired-mark-executables}).  With a numeric argument, unmark all
those files.

@item * @@
@kindex * @@ @r{(Dired)}
@findex dired-mark-symlinks
Mark all symbolic links with @samp{*} (@code{dired-mark-symlinks}).
With a numeric argument, unmark all those files.

@item * /
@kindex * / @r{(Dired)}
@findex dired-mark-directories
Mark with @samp{*} all files which are actually directories, except for
@file{.} and @file{..} (@code{dired-mark-directories}).  With a numeric
argument, unmark all those files.

@item * s
@kindex * s @r{(Dired)}
@findex dired-mark-subdir-files
Mark all the files in the current subdirectory, aside from @file{.}
and @file{..} (@code{dired-mark-subdir-files}).

@item u
@itemx * u
@kindex u @r{(Dired)}
@kindex * u @r{(Dired)}
@findex dired-unmark
Remove any mark on this line (@code{dired-unmark}).

@item @key{DEL}
@itemx * @key{DEL}
@kindex * DEL @r{(Dired)}
@findex dired-unmark-backward
Move point to previous line and remove any mark on that line
(@code{dired-unmark-backward}).

@item * !
@kindex * ! @r{(Dired)}
@findex dired-unmark-all-files-no-query
Remove all marks from all the files in this Dired buffer
(@code{dired-unmark-all-files-no-query}).

@item * ? @var{markchar}
@kindex * ? @r{(Dired)}
@findex dired-unmark-all-files
Remove all marks that use the character @var{markchar}
(@code{dired-unmark-all-files}).  The argument is a single
character---do not use @key{RET} to terminate it.

With a numeric argument, this command queries about each marked file,
asking whether to remove its mark.  You can answer @kbd{y} meaning yes,
@kbd{n} meaning no, or @kbd{!} to remove the marks from the remaining
files without asking about them.

@item * C-n
@findex dired-next-marked-file
@kindex * C-n @r{(Dired)}
Move down to the next marked file (@code{dired-next-marked-file})
A file is ``marked'' if it has any kind of mark.

@item * C-p
@findex dired-prev-marked-file
@kindex * C-p @r{(Dired)}
Move up to the previous marked file (@code{dired-prev-marked-file})

@item * t
@kindex * t @r{(Dired)}
@findex dired-do-toggle
Toggle all marks (@code{dired-do-toggle}): files marked with @samp{*}
become unmarked, and unmarked files are marked with @samp{*}.  Files
marked in any other way are not affected.

@item * c @var{old} @var{new}
@kindex * c @r{(Dired)}
@findex dired-change-marks
Replace all marks that use the character @var{old} with marks that use
the character @var{new} (@code{dired-change-marks}).  This command is
the primary way to create or use marks other than @samp{*} or @samp{D}.
The arguments are single characters---do not use @key{RET} to terminate
them.

You can use almost any character as a mark character by means of this
command, to distinguish various classes of files.  If @var{old} is a
space (@samp{ }), then the command operates on all unmarked files; if
@var{new} is a space, then the command unmarks the files it acts on.

To illustrate the power of this command, here is how to put @samp{D}
flags on all the files that have no marks, while unflagging all those
that already have @samp{D} flags:

@example
* c D t  * c SPC D  * c t SPC
@end example

This assumes that no files are marked with @samp{t}.

@item % m @var{regexp} @key{RET}
@itemx * % @var{regexp} @key{RET}
@findex dired-mark-files-regexp
@kindex % m @r{(Dired)}
@kindex * % @r{(Dired)}
Mark (with @samp{*}) all files whose names match the regular expression
@var{regexp} (@code{dired-mark-files-regexp}).  This command is like
@kbd{% d}, except that it marks files with @samp{*} instead of flagging
with @samp{D}.  @xref{Flagging Many Files}.

Only the non-directory part of the file name is used in matching.  Use
@samp{^} and @samp{$} to anchor matches.  Exclude subdirectories by
hiding them (@pxref{Hiding Subdirectories}).

@item % g @var{regexp} @key{RET}
@findex dired-mark-files-containing-regexp
@kindex % m @r{(Dired)}
Mark (with @samp{*}) all files whose @emph{contents} contain a match for
the regular expression @var{regexp}
(@code{dired-mark-files-containing-regexp}).  This command is like
@kbd{% m}, except that it searches the file contents instead of the file
name.

@item C-_
@kindex C-_ @r{(Dired)}
@findex dired-undo
Undo changes in the Dired buffer, such as adding or removing
marks (@code{dired-undo}).
@end table

@node Operating on Files
@section Operating on Files
@cindex operating on files in Dired

  This section describes the basic Dired commands to operate on one file
or several files.  All of these commands are capital letters; all of
them use the minibuffer, either to read an argument or to ask for
confirmation, before they act.  All of them give you several ways to
specify which files to manipulate:

@itemize @bullet
@item
If you give the command a numeric prefix argument @var{n}, it operates
on the next @var{n} files, starting with the current file.  (If @var{n}
is negative, the command operates on the @minus{}@var{n} files preceding
the current line.)

@item
Otherwise, if some files are marked with @samp{*}, the command operates
on all those files.

@item
Otherwise, the command operates on the current file only.
@end itemize

  Here are the file-manipulating commands that operate on files in this
way.  (Some other Dired commands, such as @kbd{!} and the @samp{%}
commands, also use these conventions to decide which files to work on.)

@table @kbd
@findex dired-do-copy
@kindex C @r{(Dired)}
@item C @var{new} @key{RET}
Copy the specified files (@code{dired-do-copy}).  The argument @var{new}
is the directory to copy into, or (if copying a single file) the new
name.
@vindex dired-recursive-copies
The variable @code{dired-recursive-copies} determines if directories are
copied recursively.  The default is to not copy recursively.

@vindex dired-copy-preserve-time
If @code{dired-copy-preserve-time} is non-@code{nil}, then copying with
this command sets the modification time of the new file to be the same
as that of the old file.

@item D
@findex dired-do-delete
@kindex D @r{(Dired)}
Delete the specified files (@code{dired-do-delete}).  Like the other
commands in this section, this command operates on the @emph{marked}
files, or the next @var{n} files.  By contrast, @kbd{x}
(@code{dired-expunge}) deletes all @dfn{flagged} files.

@findex dired-do-rename
@kindex R @r{(Dired)}
@item R @var{new} @key{RET}
Rename the specified files (@code{dired-do-rename}).  The argument
@var{new} is the directory to rename into, or (if renaming a single
file) the new name.

Dired automatically changes the visited file name of buffers associated
with renamed files so that they refer to the new names.

@findex dired-do-hardlink
@kindex H @r{(Dired)}
@item H @var{new} @key{RET}
Make hard links to the specified files (@code{dired-do-hardlink}).  The
argument @var{new} is the directory to make the links in, or (if making
just one link) the name to give the link.

@findex dired-do-symlink
@kindex S @r{(Dired)}
@item S @var{new} @key{RET}
Make symbolic links to the specified files (@code{dired-do-symlink}).
The argument @var{new} is the directory to make the links in, or (if
making just one link) the name to give the link.

@findex dired-do-chmod
@kindex M @r{(Dired)}
@item M @var{modespec} @key{RET}
Change the mode (also called ``permission bits'') of the specified files
(@code{dired-do-chmod}).  This uses the @code{chmod} program, so
@var{modespec} can be any argument that @code{chmod} can handle.

@findex dired-do-chgrp
@kindex G @r{(Dired)}
@item G @var{newgroup} @key{RET}
Change the group of the specified files to @var{newgroup}
(@code{dired-do-chgrp}).

@findex dired-do-chown
@kindex O @r{(Dired)}
@item O @var{newowner} @key{RET}
Change the owner of the specified files to @var{newowner}
(@code{dired-do-chown}).  (On most systems, only the superuser can do
this.)

@vindex dired-chown-program
The variable @code{dired-chown-program} specifies the name of the
program to use to do the work (different systems put @code{chown} in
different places).

@findex dired-do-print
@kindex P @r{(Dired)}
@item P @var{command} @key{RET}
Print the specified files (@code{dired-do-print}).  You must specify the
command to print them with, but the minibuffer starts out with a
suitable guess made using the variables @code{lpr-command} and
@code{lpr-switches} (the same variables that @code{lpr-buffer} uses;
@pxref{Hardcopy}).

@findex dired-do-compress
@kindex Z @r{(Dired)}
@item Z
Compress the specified files (@code{dired-do-compress}).  If the file
appears to be a compressed file already, it is uncompressed instead.

@findex dired-do-load
@kindex L @r{(Dired)}
@item L
Load the specified Emacs Lisp files (@code{dired-do-load}).
@xref{Lisp Libraries}.

@findex dired-do-byte-compile
@kindex B @r{(Dired)}
@item B
Byte compile the specified Emacs Lisp files
(@code{dired-do-byte-compile}).  @xref{Byte Compilation,, Byte
Compilation, elisp, The Emacs Lisp Reference Manual}.

@kindex A @r{(Dired)}
@findex dired-do-search
@item A @var{regexp} @key{RET}
Search all the specified files for the regular expression @var{regexp}
(@code{dired-do-search}).

This command is a variant of @code{tags-search}.  The search stops at
the first match it finds; use @kbd{M-,} to resume the search and find
the next match.  @xref{Tags Search}.

@kindex Q @r{(Dired)}
@findex dired-do-query-replace
@item Q @var{from} @key{RET} @var{to} @key{RET}
Perform @code{query-replace-regexp} on each of the specified files,
replacing matches for @var{from} (a regular expression) with the string
@var{to} (@code{dired-do-query-replace}).

This command is a variant of @code{tags-query-replace}.  If you exit the
query replace loop, you can use @kbd{M-,} to resume the scan and replace
more matches.  @xref{Tags Search}.

@kindex a @r{(Dired)}
@findex dired-do-apply
@item a @var{function} @kbd{RET}
Apply an arbitrary Lisp function to the name of each marked file
(@code{dired-do-apply}).
@end table

@kindex + @r{(Dired)}
@findex dired-create-directory
  One special file-operation command is @kbd{+}
(@code{dired-create-directory}).  This command reads a directory name and
creates the directory if it does not already exist.

@node Shell Commands in Dired
@section Shell Commands in Dired
@cindex shell commands, Dired

@findex dired-do-shell-command
@kindex ! @r{(Dired)}
The dired command @kbd{!} (@code{dired-do-shell-command}) reads a shell
command string in the minibuffer and runs that shell command on all the
specified files.  You can specify the files to operate on in the usual
ways for Dired commands (@pxref{Operating on Files}).  There are two
ways of applying a shell command to multiple files:

@itemize @bullet
@item
If you use @samp{*} in the shell command, then it runs just once, with
the list of file names substituted for the @samp{*}.  The order of file
names is the order of appearance in the Dired buffer.

Thus, @kbd{! tar cf foo.tar * @key{RET}} runs @code{tar} on the entire
list of file names, putting them into one tar file @file{foo.tar}.

@item
If the command string doesn't contain @samp{*}, then it runs once
@emph{for each file}, with the file name added at the end.

For example, @kbd{! uudecode @key{RET}} runs @code{uudecode} on each
file.
@end itemize

What if you want to run the shell command once for each file but with
the file name inserted in the middle?  Or if you want to use the file
names in a more complicated fashion?  Use a shell loop.  For example,
this shell command would run @code{uuencode} on each of the specified
files, writing the output into a corresponding @file{.uu} file:

@example
for file in *; do uuencode $file $file >$file.uu; done
@end example

@noindent
In simple cases you can instead use @samp{?} in the command.  This is
similar to @samp{*} but the command will be run on each file
individually.

The working directory for the shell command is the top-level directory
of the Dired buffer.

The @kbd{!} command does not attempt to update the Dired buffer to show
new or modified files, because it doesn't really understand shell
commands, and does not know what files the shell command changed.  Use
the @kbd{g} command to update the Dired buffer (@pxref{Dired
Updating}).

@node Transforming File Names
@section Transforming File Names in Dired

  Here are commands that alter file names in a systematic way:

@table @kbd
@findex dired-upcase
@kindex % u @r{(Dired)}
@item % u
Rename each of the selected files to an upper-case name
(@code{dired-upcase}).  If the old file names are @file{Foo}
and @file{bar}, the new names are @file{FOO} and @file{BAR}.

@item % l
@findex dired-downcase
@kindex % l @r{(Dired)}
Rename each of the selected files to a lower-case name
(@code{dired-downcase}).  If the old file names are @file{Foo} and
@file{bar}, the new names are @file{foo} and @file{bar}.

@item % R @var{from} @key{RET} @var{to} @key{RET}
@kindex % R @r{(Dired)}
@findex dired-do-rename-regexp
@itemx % C @var{from} @key{RET} @var{to} @key{RET}
@kindex % C @r{(Dired)}
@findex dired-do-copy-regexp
@itemx % H @var{from} @key{RET} @var{to} @key{RET}
@kindex % H @r{(Dired)}
@findex dired-do-hardlink-regexp
@itemx % S @var{from} @key{RET} @var{to} @key{RET}
@kindex % S @r{(Dired)}
@findex dired-do-symlink-regexp
These four commands rename, copy, make hard links and make soft links,
in each case computing the new name by regular-expression substitution
from the name of the old file.
@end table

  The four regular-expression substitution commands effectively perform
a search-and-replace on the selected file names in the Dired buffer.
They read two arguments: a regular expression @var{from}, and a
substitution pattern @var{to}.

  The commands match each ``old'' file name against the regular
expression @var{from}, and then replace the matching part with @var{to}.
You can use @samp{\&} and @samp{\@var{digit}} in @var{to} to refer to
all or part of what the pattern matched in the old file name, as in
@code{replace-regexp} (@pxref{Regexp Replace}).  If the regular expression
matches more than once in a file name, only the first match is replaced.

  For example, @kbd{% R ^.*$ @key{RET} x-\& @key{RET}} renames each
selected file by prepending @samp{x-} to its name.  The inverse of this,
removing @samp{x-} from the front of each file name, is also possible:
one method is @kbd{% R ^x-\(.*\)$ @key{RET} \1 @key{RET}}; another is
@kbd{% R ^x- @key{RET} @key{RET}}.  (Use @samp{^} and @samp{$} to anchor
matches that should span the whole filename.)

  Normally, the replacement process does not consider the files'
directory names; it operates on the file name within the directory.  If
you specify a numeric argument of zero, then replacement affects the
entire absolute file name including directory name.

  Often you will want to select the set of files to operate on using the
same @var{regexp} that you will use to operate on them.  To do this,
mark those files with @kbd{% m @var{regexp} @key{RET}}, then use the
same regular expression in the command to operate on the files.  To make
this easier, the @kbd{%} commands to operate on files use the last
regular expression specified in any @kbd{%} command as a default.

@node Comparison in Dired
@section File Comparison with Dired

  Here are two Dired commands that compare specified files using
@code{diff}.

@table @kbd
@item =
@findex dired-diff
@kindex = @r{(Dired)}
Compare the current file (the file at point) with another file (the file
at the mark) using the @code{diff} program (@code{dired-diff}).  The
file at the mark is the first argument of @code{diff}, and the file at
point is the second argument.

@findex dired-backup-diff
@kindex M-= @r{(Dired)}
@item M-=
Compare the current file with its latest backup file
(@code{dired-backup-diff}).  If the current file is itself a backup,
compare it with the file it is a backup of; this way, you can compare
a file with any backup version of your choice.

The backup file is the first file given to @code{diff}.
@end table

@node Subdirectories in Dired
@section Subdirectories in Dired
@cindex subdirectories in Dired
@cindex expanding subdirectories in Dired

  A Dired buffer displays just one directory in the normal case;
but you can optionally include its subdirectories as well.

  The simplest way to include multiple directories in one Dired buffer is
to specify the options @samp{-lR} for running @code{ls}.  (If you give a
numeric argument when you run Dired, then you can specify these options
in the minibuffer.)  That produces a recursive directory listing showing
all subdirectories at all levels.

  But usually all the subdirectories are too many; usually you will
prefer to include specific subdirectories only.  You can do this with
the @kbd{i} command:

@table @kbd
@findex dired-maybe-insert-subdir
@kindex i @r{(Dired)}
@item i
@cindex inserted subdirectory (Dired)
@cindex in-situ subdirectory (Dired)
Insert the contents of a subdirectory later in the buffer.
@end table

Use the @kbd{i} (@code{dired-maybe-insert-subdir}) command on a line
that describes a file which is a directory.  It inserts the contents of
that directory into the same Dired buffer, and moves there.  Inserted
subdirectory contents follow the top-level directory of the Dired
buffer, just as they do in @samp{ls -lR} output.

If the subdirectory's contents are already present in the buffer, the
@kbd{i} command just moves to it.

In either case, @kbd{i} sets the Emacs mark before moving, so @kbd{C-u
C-@key{SPC}} takes you back to the old position in the buffer (the line
describing that subdirectory).

Use the @kbd{l} command (@code{dired-do-redisplay}) to update the
subdirectory's contents.  Use @kbd{k} to delete the subdirectory.
@xref{Dired Updating}.

@node Subdirectory Motion
@section Moving Over Subdirectories

  When a Dired buffer lists subdirectories, you can use the page motion
commands @kbd{C-x [} and @kbd{C-x ]} to move by entire directories.

@cindex header line (Dired)
@cindex directory header lines
  The following commands move across, up and down in the tree of
directories within one Dired buffer.  They move to @dfn{directory header
lines}, which are the lines that give a directory's name, at the
beginning of the directory's contents.

@table @kbd
@findex dired-next-subdir
@kindex C-M-n @r{(Dired)}
@item C-M-n
Go to next subdirectory header line, regardless of level
(@code{dired-next-subdir}).

@findex dired-prev-subdir
@kindex C-M-p @r{(Dired)}
@item C-M-p
Go to previous subdirectory header line, regardless of level
(@code{dired-prev-subdir}).

@findex dired-tree-up
@kindex C-M-u @r{(Dired)}
@item C-M-u
Go up to the parent directory's header line (@code{dired-tree-up}).

@findex dired-tree-down
@kindex C-M-d @r{(Dired)}
@item C-M-d
Go down in the directory tree, to the first subdirectory's header line
(@code{dired-tree-down}).

@findex dired-prev-dirline
@kindex < @r{(Dired)}
@item <
Move up to the previous directory-file line (@code{dired-prev-dirline}).
These lines are the ones that describe a directory as a file in its
parent directory.

@findex dired-next-dirline
@kindex > @r{(Dired)}
@item >
Move down to the next directory-file line (@code{dired-prev-dirline}).
@end table

@node Hiding Subdirectories
@section Hiding Subdirectories

@cindex hiding in Dired (Dired)
  @dfn{Hiding} a subdirectory means to make it invisible, except for its
header line, via selective display (@pxref{Selective Display}).

@table @kbd
@item $
@findex dired-hide-subdir
@kindex $ @r{(Dired)}
Hide or reveal the subdirectory that point is in, and move point to the
next subdirectory (@code{dired-hide-subdir}).  A numeric argument serves
as a repeat count.

@item M-$
@findex dired-hide-all
@kindex M-$ @r{(Dired)}
Hide all subdirectories in this Dired buffer, leaving only their header
lines (@code{dired-hide-all}).  Or, if any subdirectory is currently
hidden, make all subdirectories visible again.  You can use this command
to get an overview in very deep directory trees or to move quickly to
subdirectories far away.
@end table

  Ordinary Dired commands never consider files inside a hidden
subdirectory.  For example, the commands to operate on marked files
ignore files in hidden directories even if they are marked.  Thus you
can use hiding to temporarily exclude subdirectories from operations
without having to remove the markers.

  The subdirectory hiding commands toggle; that is, they hide what was
visible, and show what was hidden.

@node Dired Updating
@section Updating the Dired Buffer

  This section describes commands to update the Dired buffer to reflect
outside (non-Dired) changes in the directories and files, and to delete
part of the Dired buffer.

@table @kbd
@item g
Update the entire contents of the Dired buffer (@code{revert-buffer}).

@item l
Update the specified files (@code{dired-do-redisplay}).

@item k
Delete the specified @emph{file lines}---not the files, just the lines
(@code{dired-do-kill-lines}).

@item s
Toggle between alphabetical order and date/time order
(@code{dired-sort-toggle-or-edit}).

@item C-u s @var{switches} @key{RET}
Refresh the Dired buffer using @var{switches} as
@code{dired-listing-switches}.
@end table

@kindex g @r{(Dired)}
@findex revert-buffer @r{(Dired)}
  Type @kbd{g} (@code{revert-buffer}) to update the contents of the
Dired buffer, based on changes in the files and directories listed.
This preserves all marks except for those on files that have vanished.
Hidden subdirectories are updated but remain hidden.

@kindex l @r{(Dired)}
@findex dired-do-redisplay
  To update only some of the files, type @kbd{l}
(@code{dired-do-redisplay}).  This command applies to the next @var{n}
files, or to the marked files if any, or to the current file.  Updating
them means reading their current status from the file system and
changing the buffer to reflect it properly.

  If you use @kbd{l} on a subdirectory header line, it updates the
contents of the corresponding subdirectory.

@kindex k @r{(Dired)}
@findex dired-do-kill-lines
  To delete the specified @emph{file lines}---not the files, just the
lines---type @kbd{k} (@code{dired-do-kill-lines}).  With a numeric
argument @var{n}, this command applies to the next @var{n} files;
otherwise, it applies to the marked files.

  If you kill the line for a file that is a directory, the directory's
contents are also deleted from the buffer.  Typing @kbd{C-u k} on the
header line for a subdirectory is another way to delete a subdirectory
from the Dired buffer.

  The @kbd{g} command brings back any individual lines that you have
killed in this way, but not subdirectories---you must use @kbd{i} to
reinsert each subdirectory.

@cindex Dired sorting
@cindex sorting Dired buffer
@kindex s @r{(Dired)}
@findex dired-sort-toggle-or-edit
  The files in a Dired buffers are normally listed in alphabetical order
by file names.  Alternatively Dired can sort them by date/time.  The
Dired command @kbd{s} (@code{dired-sort-toggle-or-edit}) switches
between these two sorting modes.  The mode line in a Dired buffer
indicates which way it is currently sorted---by name, or by date.

  @kbd{C-u s @var{switches} @key{RET}} lets you specify a new value for
@code{dired-listing-switches}.

@node Dired and Find
@section Dired and @code{find}
@cindex @code{find} and Dired

  You can select a set of files for display in a Dired buffer more
flexibly by using the @code{find} utility to choose the files.

@findex find-name-dired
  To search for files with names matching a wildcard pattern use
@kbd{M-x find-name-dired}.  It reads arguments @var{directory} and
@var{pattern}, and chooses all the files in @var{directory} or its
subdirectories whose individual names match @var{pattern}.

  The files thus chosen are displayed in a Dired buffer in which the
ordinary Dired commands are available.

@findex find-grep-dired
  If you want to test the contents of files, rather than their names,
use @kbd{M-x find-grep-dired}.  This command reads two minibuffer
arguments, @var{directory} and @var{regexp}; it chooses all the files in
@var{directory} or its subdirectories that contain a match for
@var{regexp}.  It works by running the programs @code{find} and
@code{grep}.  See also @kbd{M-x grep-find}, in @ref{Compilation}.
Remember to write the regular expression for @code{grep}, not for Emacs.

@findex find-dired
  The most general command in this series is @kbd{M-x find-dired}, which
lets you specify any condition that @code{find} can test.  It takes two
minibuffer arguments, @var{directory} and @var{find-args}; it runs
@code{find} in @var{directory}, passing @var{find-args} to tell
@code{find} what condition to test.  To use this command, you need to
know how to use @code{find}.

@vindex find-ls-option
  The format of listing produced by these commands is controlled by the
variable @code{find-ls-option}, whose default value specifies using
options @samp{-ld} for @code{ls}.  If your listings are corrupted, you
may need to change the value of this variable.

@node Extra Features for Dired
@section Extra Features for Dired---The Dired-X Package

The Dired-X package provides various extra features for Dired mode.  You
can load it with @code{M-x load-library} or customize
@code{dired-load-hook} to add @samp{(require@w{ }'dired-x)}.
@xref{Top, Introduction, Dired Extra Version 2 User's Manual, dired-x}.