Emacs copy with regex
emacs
Solution
inspired by the already given comments (the Charles answer doesn't work as I would want it), I added a new function to the isearch/isearch-regexp mode map which puts only the matching string into the kill ring (whereas Charles proposal kills from current point to end of matching string):
(defun hack-isearch-kill ()
"Push current matching string into kill ring."
(interactive)
(kill-new (buffer-substring (point) isearch-other-end))
(isearch-done))
(define-key isearch-mode-map (kbd "M-w") 'hack-isearch-kill)
The nice thing about the isearch/isearch-regexp approach (which you can enable with `C-s` and `C-M-s` respectively) is that you can see your search string growing and you can copy it with `M-w` as soon as you are satisfied (and go back to where you have been before with `C-u C-Space`).
This works for me with Emacs 23.1. Don't know if it will work in all situations. Anyway I hope you find it useful :)
UPDATE: going through the emacswiki I stumbled over KillISearchMatch which suggests more or less the same (plus some more tips ...).
Cheers, Daniel
Problem
I have a text file. Can Emacs select text based on regex and put it in kill-ring, so I can copy it somewhere else? Something like regex-kill-ring-save?