Keyboard macros are a truly classic emacs feature. Still, I only started to use them years after I got sucked into emacs – not so uncommon for emacs features… There may be more people like me, so let's raise the awareness a bit.
Keyboard macros allow you to record a number of keystrokes, and replay those at some later point. This can be a great time-saver when you need to do repetitive things. In many cases, they are an easy alternative to writing some elisp to get a job done. Note, keyboard macros are should not be confused with elisp-macros, which are something else altogether.
So, when would we want to use a keyboard macro? Let's take some tedious task -- for example, we have a list of a few hundred names:
Newton, Isaac Einstein, Albert Maxwell, James Turing, Alan ...
and we want to turn that into:
Isaac Newton James Maxwell Alan Turing ...
so, roughly, put the last name after the first name, and remove the comma.
We can solve this in different ways; we could simple change each line by hand. That's a fine solution if there are only a few lines, but it gets boring rather quickly.
Another way is to use regular expressions (see Building regular expressions); in this case, it's fairly easy to come up with one (assuming you know regular expressions). But let's see how we can solve it with a keyboard macro.
Schematically, we can solve this with the following:
|go to beginning of a line||C-a|
|kill (cut) the first word||M-d|
|delete the next two characters||DEL DEL|
|go to the end of the line||C-e|
|insert a space||SPC|
|go to the next line||C-n|
This may look like some magical incantation, but it comes quite natural when you are actually doing the editing.
An important thing to remember when working with keyboard macros is that you
do your commands in such a way that they can be repeated for each line. Suppose
you would select
Newton with shift-select, i.e.,
C-SPC at the beginning of
the line and pressing the right arrow key 6 times – that works for
but not for
Einstein. Instead, we need to use
defining a macro
Now that we have solved the problem for a single line, let's make a keyboard macro.
We move the cursor to the first line, and start the definition by pressing
C-x (, or alternatively,
F3. Then, we press the commands
C-n (as in the list above). To finish the
C-x ), (or
Hurray, we have our macro. Now, let's use it.
using the macro
Now, to execute the last defined macro, you press
C-x e. We could repeat that
for our whole list, but fortunately there's an easier way to repeat a macro n
times, using a prefix argument. For example, to repeat the macro 123 times,
you first press
C-u 123 and then
There's a slightly shorter way to do this: instead of
C-u 123 we can write
M-123, and for
C-x e we can use
You can even repeat the macro until the end of the buffer is reached with
C-u 0 C-x e; this only makes sense if the macros ever reaches the end of the buffer
of course. (Remember that you can always terminate with
You can also apply your keyboard macro to all lines in the selected area
M-x apply-macro-to-region-lines (or
C-x C-k r). Important to
remember: this will actually move the cursor (point) to the start of each line,
and then execute the macro. If you want your macro like that, the
go-to-the-next-line should not be part of your macro, or you will be skipping
saving macros for later use
If you want to use multiple macros, you can name them. You can do this with
M-x name-last-kbd-macro. If you name your macro, say,
foo (inventive as we
are), you can then execute it after that as
M-x foo, which will be available
until you exit emacs.
If you want to have the macro for future emacs sessions as well, you can use
insert-kbd-macro, which will give you an elisp version of your macro. For our
example, this will look like:
(fset 'foo [?\C-a ?\M-d delete delete ?\C-e ? ?\C-y ?\C-n])
Not very readable, but we can put this in
.emacs, and we can use it the next
time we start emacs as well. We can also add a key binding for this, for
(global-set-key (kbd "C-c f") 'foo)
This will bind
Keyboard macros can be useful and easy, but they are fundamentally connected
to key presses – so, if you remap your keys to something different, your
macros may not work anymore. Also, the macros are pretty much write-only in
the way we use them here. You can edit them in the macro editor though, with
M-x edit-kbd-macro M-x foo; we'll then get something like:
;; Keyboard Macro Editor. Press C-c C-c to finish; press C-x k RET to cancel. ;; Original keys: C-a M-d 2*<delete> C-e SPC C-y C-n Command: foo Key: none Macro: C-a ;; move-beginning-of-line M-d ;; kill-word 2*<delete> ;; delete-char C-e ;; move-end-of-line SPC ;; self-insert-command C-y ;; yank C-n ;; next-line
Keyboard macros can be quite a useful trick in your arsenal. And I have not
even gone into more advanced tricks like macros with variations or the
macro ring. Please refer to the section Keyboard macros in the emacs
C-h r) for all the details.
And, finally, don't let the text-based example limit your imagination – you can turn just about any repetitive sequence of tasks into a macro.