perm url with update: http://xahlee.org/emacs/whitespace-mode.html.
How to use and setup Emacs's whitespace-mode
Xah Lee, 2009-08-14
This pages tells you how to setup emacs's whitespace-mode, and how to use it.
Emacs 23 has this whitespace-mode feature. It renders spaces, tabs, newlines characters with a visible glyph.
This feature is useful for working with “tab separated values” (CSV) that's a common format for importing/exporting address books or spreadsheets. It's also important in whitespace-significant langs such as Python.
Type “Alt+x whitespace-mode” to toggle it on and off. Type “Alt+x global-whitespace-mode” to toggle it globally. There is also whitespace-newline-mode and global-whitespace-newline-mode. They only show newline chars.
The default rendering of whitespace-mode, pretty unreadable. Different placement and mix of whitespaces are rendered with different colors. Also, long lines are colored dark purple. (download whitespace_sample_file.txt)
How to clean whitespaces in one shot?
Select a region then type “Alt+x whitespace-cleanup”, which will delete spaces or tabs in a smart way. (call describe-function to see detail.)
You can also use delete-trailing-whitespace, delete-whitespace-rectangle. Both works on a region.
For more fine control of deleting whitespaces, you can use use query-replace, query-replace-regexp, to replace whitespaces.
How to insert Tab or Newline char?
To insert a literal tab char, press “Ctrl+q Tab”. To type a newline char, type “Ctrl+q Ctrl+j”.
How to reduce colors in whitespace-mode?
Put the following in your emacs init file:
; make whitespace-mode use just basic coloring (setq whitespace-style (quote ( spaces tabs newline space-mark tab-mark newline-mark)))
How to make whitespace-mode use the pilcrow sign “¶” for newline instead of the dollar sign?
Put the following in your “.emacs”:
(setq whitespace-display-mappings '( (space-mark 32  ) ; normal space (space-mark 160  ) (space-mark 2208  ) (space-mark 2336  ) (space-mark 3616  ) (space-mark 3872  ) (newline-mark 10 [182 10]) ; newlne (tab-mark 9 [9655 9] [92 9]) ; tab ))
In the above, the numbers are unicode points. Depending on your choice of font, some glyph may not show up with your font. You may explore with the following unicode chars.
- “·”, MIDDLE DOT, 183
- “¶”, PILCROW SIGN, 182
- “↵”, DOWNWARDS ARROW WITH CORNER LEFTWARDS, 8629
- “▷”, WHITE RIGHT POINTING TRIANGLE, 9655
- “▶”, BLACK RIGHT-POINTING TRIANGLE, 9654
- “→”, RIGHTWARDS ARROW, 8594
- “↦”, RIGHTWARDS ARROW FROM BAR, 8614
- “⇥”, RIGHTWARDS ARROW TO BAR, 8677
A clean setup for whitespace-mode. Spaces are displayed by “·” (MIDDLE DOT; unicode 183), Tabs are displayed by “▷” (WHITE RIGHT POINTING TRIANGLE; unicode 9655), Newline are displayed as “¶” (PILCROW SIGN; unicode 182). Distinction of various mix of types of whitespaces are removed.