RE: Format of directories list in dired

[Drew Adams]

  But I want set omit temp files by default.
  Can I do it?

`C-h k M-o' displays this;

 M-o runs the command dired-omit-mode
   which is an interactive compiled Lisp function in `dired-x'.
 It is bound to M-o.
 (dired-omit-mode &optional arg)

 Toggle Dired-Omit mode.
 With numeric arg, enable Dired-Omit mode if arg is positive, disable
 otherwise. Enabling and disabling is buffer-local.
 If enabled, "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'.

So, put this in your .emacs to start up in omit mode:

(dired-omit-mode 1)