Default: nil

If non-nil, ``uninteresting'' files are not listed. Uninteresting files are those whose filenames match regexp dired-omit-files, plus those ending with extensions in dired-omit-extensions. M-o (dired-omit-toggle) toggles its value, which is buffer-local. Put

(setq dired-omit-files-p t)

inside your dired-mode-hook to have omitting initially turned on in every Dired buffer (See Installation). You can then use M-o to unomit in that buffer.

To enable omitting automatically only in certain directories one can use Dired Local Variables and put

Local Variables:
dired-omit-files-p: t
End:

into a file `.dired' (the default value of dired-local-variables-file) in that directory (See Local Variables).

Default: "^#\\|\\.$"

Filenames matching this buffer-local regexp will not be displayed. This only has effect when dired-omit-files-p is t.

The default value omits the special directories `.' and `..' and autosave files (plus other files ending in ``.'') (See Omitting Examples).

Default: The elements of completion-ignored-extensions (as defined in the file `loaddefs.el' of the GNU Emacs distribution), dired-latex-unclean-extensions, dired-bibtex-unclean-extensions and dired-texinfo-unclean-extensions.

If non-nil, a list of extensions (strings) to omit from Dired listings. Its format is the same as that of completion-ignored-extensions.

Default: 'no-dir

The localp argument dired-omit-expunge passes to dired-get-filename. If it is 'no-dir, omitting is much faster, but you can only match against the non-directory part of the filename. Set it to nil if you need to match the whole pathname or t to match the pathname relative to the buffer's top-level directory.

Default: C-o

Temporary marker used by by Dired to implement omitting. Should never be used as marker by the user or other packages. There is one exception to this rule: by doing

(setq dired-mark-keys "\C-o")
;; i.e., the value of dired-omit-marker-char
;; (which is not defined yet)

anywhere in your `~/.emacs', you will bind the C-o key to insert a C-o marker, thus causing these files to be omitted in addition to the usually omitted files. Unfortunately the files you omitted manually this way will show up again after reverting the buffer, unlike the others.