How to attach character to the next N lines using Emacs?

Using emacs24 I'd like to attach for example # at the beginning of the next five lines. So having this:

Line1
line2
line3

get this:

#Line1
#line2
#line3

for the number of lines that I specify. How can I do that? Thanks!

Solution

While there may be something built in to Emacs that does this, and you can certainly write a little Lisp to get it done, I would usually use "rectangular editing" features to get this done. Imagine that the buffer contains the following, with . representing the point (where your cursor is)

.Line1
line2
line3

Set the mark

Press C-n twice. This is the state of the buffer now:

Line1
line2
.line3

Press C-x r t.

Type #.

Press enter.

I would find this much more natural than entering a value for the number of times to repeat a command, because you can visually select the lines you want to edit. YMMV

Edit

Here's how to do this using a bit of Emacs Lisp. Note that although I've been using Emacs for a few years now, I only recently began learning how to actually use Emacs Lisp, so this code might not be that great! It does get the job done.

(defun insert-n-times (s n)
  (interactive "Mstring:\nNtimes:")
  (while (> n 0)
    (insert s)
    (goto-char (- (point) 1))
    (next-line)
    (setq n (- n 1))))

Use it by doing the following: M-x insert-n-times RET <type a string> RET <type a number>