Pretty printing XML files on Emacs
You don't even need to write your own function - sgml-mode (a gnu emacs core module) has a built-in pretty printing function called (sgml-pretty-print ...) which takes region beginning and end arguments.
If you are cutting and pasting xml and you find your terminal is chopping the lines in arbitrary places you can use this pretty printer which fixes broken lines first.
If you only need pretty indenting without introducing any new line-breaks, you can apply the indent-region command to the entire buffer with these keystrokes:
C-x hC-M-\If you also need to introduce line-breaks, so that opening and closing tags are on separate lines, you could use the following very nice elisp function, written by Benjamin Ferrari. I found it on his blog and hope it's ok for me to reproduce it here:
(defun bf-pretty-print-xml-region (begin end) "Pretty format XML markup in region. You need to have nxml-modehttp://www.emacswiki.org/cgi-bin/wiki/NxmlMode installed to dothis. The function inserts linebreaks to separate tags that havenothing but whitespace between them. It then indents the markupby using nxml's indentation rules." (interactive "r") (save-excursion (nxml-mode) (goto-char begin) (while (search-forward-regexp "\>[ \\t]*\<" nil t) (backward-char) (insert "\n") (setq end (1+ end))) (indent-region begin end)) (message "Ah, much better!"))This doesn't rely on an external tool like Tidy.