I use igrep, but it seems to be broken on Windows with emacs 23. I'd like to
switch to grep.
The manual says:
If you specify a prefix argument for M-x grep, it finds the tag ...
There's no sample code for how to actually set the prefix argument. I
know I can type C-u every time, but how do I assign it to a key
(global-set-key)?
C-u is a key. ;-)
Many commands that change their behavior based on a prefix arg use the prefix
arg as one of their arguments. E.g.:
(defun foo (arg)
(interactive "P)
;; Do something according to the value of ARG,
;; which is the same as variable `current-prefix-arg'.
)
If that is the case, and you want a command that _always_ performs `foo' as if
you had used `C-u' interactively, you can write a command that does that:
(defun my-foo ()
(interactive)
(foo arg))
In some cases it is a bit more involved than that. For example, `foo' might do
things differently depending on whether it is called interactively or from Lisp.
More germane to your question, `foo' (`grep' in this case) might not provide any
argument that corresponds one-to-one with the `current-prefix-arg'. You need to
look at the source code for the command to see how it works interactively.
In the case of `grep', you can do this to get what you want:
(defun my-grep ()
"..."
(interactive)
(let ((current-prefix-arg t))
(call-interactively #'grep)))
HTH.
You might also be interested in the version of Emacs `grep' provided by
library `grep+.el'.
http://www.emacswiki.org/emacs/GrepPlus
http://www.emacswiki.org/emacs/grep%2b.el
