Advanced Vim macros

Vim’s massive command set in both normal and command mode makes the concept of a macro especially powerful. Most Vim users, if they ever use macros at all, will perhaps quickly record an edit to one line, starting with qq and finishing with q, executing with @q, and otherwise never give the concept much thought.

For slightly more advanced Vim users, macros may be more frequently useful, but they perhaps still believe that macros are a niche Vim function unto themselves, and not really open to the deft manipulation of text that pretty much everything else in Vim is.

As is typical in Vim, the rabbit hole of functionality goes much deeper than most users will ever plumb.

Vanilla Vim macros

Suppose I had a plaintext table loaded into a Vim buffer containing the name, subject matter expertise, birth year, and nationality of a few well-known programmers:

Stallman  Richard GNU 1953  USA
Wall  Larry   Perl  1954  USA
Moolenar  Bram  Vim 1961  Netherlands
Tridgell  Andrew  Samba  1967  Australia
Matsumoto  Yukihiro  Ruby  1965  Japan
Ritchie  Dennis  C  1941  USA
Thompson  Ken  Unix  1943  USA

Actually, that’s kind of untidy. Let’s start by formatting it a bit, by running it through Unix’s column tool.

:%!column -t

Stallman   Richard   GNU    1953  USA
Wall       Larry     Perl   1954  USA
Moolenar   Bram      Vim    1961  Netherlands
Tridgell   Andrew    Samba  1967  Australia
Matsumoto  Yukihiro  Ruby   1965  Japan
Ritchie    Dennis    C      1941  USA
Thompson   Ken       Unix   1943  USA

May as well sort it by surname too:

:%!sort -k1

Matsumoto  Yukihiro  Ruby   1965  Japan
Moolenar   Bram      Vim    1961  Netherlands
Ritchie    Dennis    C      1941  USA
Stallman   Richard   GNU    1953  USA
Thompson   Ken       Unix   1943  USA
Tridgell   Andrew    Samba  1967  Australia
Wall       Larry     Perl   1954  USA

That’s better.

Now, suppose we’ve got the task of replacing the fourth column of this table with the approximate age of the person, which we can get naturally enough by sutracting their birth year from the current year. This is a little awkward to do in pure ex, so we’ll record a macro for doing it on one line.

Experimenting a bit, we find that the following works well:

03wdei^R=2012-^R"^M^[0j

Broken down, this does the following:

  • 0 — Move to the start of the line
  • 3w — Skip three words, in this case to the fourth column
  • de — Delete to the end of the word
  • i — Enter insert mode
  • ^R= — Insert the contents of the special = register, which accepts an expression to evaluate
  • 2012-^R"^M — Enter the expression 2012-(birth year) and press Enter (literal ^M), which completes the operation, and inserts the result
  • ^[ — Leave insert mode
  • 0 — Return to the start of the line
  • j — Move down a line

So we record it into a macro a (to stand for “age”, no other reason) as we fix up the first line:

qa03wdei^R=2012-^R"^M^[0jq

Matsumoto  Yukihiro  Ruby   47  Japan
Moolenar   Bram      Vim    1961  Netherlands
Ritchie    Dennis    C      1941  USA
Stallman   Richard   GNU    1953  USA
Thompson   Ken       Unix   1943  USA
Tridgell   Andrew    Samba  1967  Australia
Wall       Larry     Perl   1954  USA

This now means that for each line, we can run the macro by just tapping @a a few times:

Matsumoto  Yukihiro  Ruby   47  Japan
Moolenar   Bram      Vim    51  Netherlands
Ritchie    Dennis    C      71  USA
Stallman   Richard   GNU    59  USA
Thompson   Ken       Unix   69  USA
Tridgell   Andrew    Samba  45  Australia
Wall       Larry     Perl   58  USA

That’s all pretty stock-standard macro stuff that you’ll likely have learned in other tutorials. The only thing that’s slightly voodoo (and certainly not vi-compatible) is the arithmetic done with the special = register. You can read about that in :help @=, if you’re curious.

Repeating Vim macros

As a first very simple hint, if you’re running a macro several times, don’t forget that you can prepend a count to it; in our case, 6@a would have fixed up all the remaining lines. To take advantage of this, it’s good practice to compose your macros so that they make sense when run multiple times; in the example above, note that the end of the macro is moving down onto the next line, ready to run the macro again if appropriate.

Similarly, if you’ve already run a macro once, you can run the same one again by just tapping the @ key twice, @@. This repeats the last run macro. Again, you can prepend a count to this, @a5@@.

The true nature of Vim macros

The registers that hold macros are the same registers that you probably use more frequently for operations like deleting, yanking, and pasting. Running a macro is simply instructing Vim to take the contents of a register and execute them as keystrokes, as if you were actually typing them. Thinking about macros this way has a couple of interesting consequences.

First of all, it means you needn’t restrict yourself to the single-keystroke vi commands for Vim when you compose macros. You can include ex commands as well, for example to run a substitution during a macro:

qb:s/foo/bar/g^Mq
@b

Secondly, and more interestingly, all of the operations that you can apply to registers in general work with what we normally call macros, with the old standards, delete, yank, and paste. You can test this with the example macro demonstrated above, by typing "ap, which will dump the raw text straight into the buffer. Also like other registers, it’ll show up in the output of the :registers command.

All this means is that like everything else in Vim, macros are just text, and all of Vim’s clever tools can be used to work with them.

Editing Vim macros in a buffer

If you’ve used macros even a little bit you’ll be very familiar with how frustrating they are to record. For some reason, as soon as you press qa to start recording a macro into register a, your normal fluency with Vim commands goes out the window and you keep making mistakes that will make the macro unsuitable to apply.

So, don’t compose macros on the fly. Just stop doing it. I recommend that if a macro is more than three keystrokes, you should compose it directly in a scratch Vim buffer so that you can test it iteratively.

Here’s an example using the macro above; suppose I realise partway through writing it that I made a mistake in typing 2011 instead of 2012. I finish recording the rest of the macro anyway, and dump the broken keystrokes into a new scratch buffer:

:enew
"ap

This gives me the contents of the macro in plain text in the buffer:

qa03wdei^R=2011-^R"^M^[0jq

So now all I have to do is change that bad year to 2012, and then yank the whole thing back into register a:

^"ay$

Now I can test it directly with @a on the appropriate file, and if it’s still wrong, I just jump back to my scratch buffer and keep fixing it up until it works.

One potential snag here is that you have to enter keystrokes like Ctrl+R as literal characters, but once you know you can enter any keystroke in Vim literally in insert or command mode by prefixing it with Ctrl+V, that isn’t really a problem. So to enter a literal Ctrl+R in insert mode, you type Ctrl+V, then Ctrl+R.

Running a Vim macro on a set of lines

It’s occasionally handy to be able to run a macro that you’ve got ready on a specific subset of lines of the file, or perhaps just for every line. Fortunately, there’s a way to do this, too.

Using the :normal command, you’re able to run macros from the ex command line:

:normal @a

All it takes is prefixing this with any sort of range definition to allow you to run a macro on any set of lines that you’re able to define.

Run the macro on each line of the whole buffer:

:% normal @a

Between lines 10 and 20:

:10,20 normal @a

On the lines in the current visual selection:

:'<,'> normal @a

On the lines containing the pattern vim:

:g/vim/ normal @a

When you get confident using this, :norm is a nice abbreviation to use.

Moving a Vim macro into a function

For really useful macros of your own devising, it’s occasionally handy to put it into a function for use in scripts or keystroke mappings. Here again the :normal command comes in handy.

Suppose I wanted to keep the age calculation macro defined above for later use on spreadsheets of this kind. I’d start by dumping it into a new buffer:

:enew
"ap

The macro appears as raw text:

03wdei^R=2012-^R"^M^[0j

I prefix it with a :normal call, and wrap a function definition around it:

function! CalculateAge()
    normal 03wdei^R=2012-^R"^M^[0j 
endfunction

Then all I need to do is include that in a file that gets loaded during Vim’s startup, possibly just .vimrc. I can call it directly from ex:

:call CalculateAge()

But given that I wanted it to be a quick-access macro, maybe it’s better to bind it to \a, or whatever your chosen <leader> character is:

nnoremap <leader>a :call CalculateAge()<CR>

Saving a Vim macro

If you want to have a macro always available to you, that is, always loaded into the appropriate register at startup, that can be done in your .vimrc file with a call to let to fill the register with the literal characters required:

let @a='03wdei^R=2012-^R"^M^[0j'

Appending extra keystrokes to a Vim macro

If you just want to tack extra keystrokes onto an existing macro and don’t care to edit it in a Vim buffer, you can do that by recording into it with its capital letter equivalent. So, if you wanted to add more keystrokes into the register b, start recording with qB, and finish with the usual q.

Recursive Vim macros

If you’re crazy enough to need this, and I never have, there’s an excellent Vim Tip for it. But personally, I think if you need recursion in your text processing then it’s time to bust out a real programming language and not Vimscript to solve your problem.

If the issue for which you think you need recursion is running a macro on every line of a buffer with an arbitrary number of lines, then you don’t need recursion; just record a one-line version of the macro and call it with :% normal @a to run it on every line.

Vim macro gotchas

Here are a few gotchas which will save you some frustration if you know about them ahead of time:

  • When you have a hammer, everything starts to look like a nail. Don’t try to solve problems with macros when there are better solutions in the ex command set, or available in external programs. See the Vim koans page for a couple of examples.
  • You need to insert keystrokes like Enter as literal Ctrl+M, so that they look like ^M. The convenience abbreviations in mappings, like <CR>, simply don’t work. You’re likely to find yourself chording Ctrl+V a lot.
  • Macros tend to stop, sometimes for apparently no reason and with no warning messages, as soon as they hit some sort of error. One particularly annoying instance of this is when you’re performing several substitutions in a macro, because if it doesn’t find any instances of a pattern it will throw an error and stop executing. You can prevent this by adding the e flag to the substitution call:

    :s/foo/bar/e
    

Thanks to user bairui for suggesting a safer alternative for yanking macro lines from buffers, which I’ve changed. He’s written a whole blog post replying to this one. It’s a good read if you’re interested in going in to even more depth about when to use macros in Vim.

Vi mode in tmux

tmux offers a set of vi-like bindings for navigating a buffer in a window. These allow you to not only navigate through the buffer beyond what your screen is currently showing, but also to search all the output generated thus far, and to select and copy text that can be pasted in any other window in the tmux session.

You can enable this as a default setting in .tmux.conf with the following:

set-window-option -g mode-keys vi

You can confirm this is working by pressing Ctrl+B and then : in a tmux session to bring up the command line, and typing:

list-keys -t vi-copy

This will bring up a complete list of the vi-like functionality available to you in this mode.

With this done, within a tmux instance, pressing Ctrl+B and then [ will enter copy mode, allowing you to copy text or view the history of the buffer, including searching with / and ?. Most of the basic vi movements work, including screenwise vertical movement commands like Ctrl+F and Ctrl+B. You can leave this mode just by pressing Enter, or you can start a selection by pressing Space on a character, moving to another, and then pressing Enter. If you have text copied like this you can paste it into any tmux window in that session by pressing Ctrl+B and then ].

If you don’t mind artifically introducing a few Vim-only features to the vi mode, you can set things up so that v starts a selection and y finishes it in the same way that Space and Enter do, more like Vim:

bind-key -t vi-copy 'v' begin-selection
bind-key -t vi-copy 'y' copy-selection

A possible snag to remember here is that for most older versions, tmux selections don’t include the character under the cursor, whereas Vim visual selections do include it unless you change the exclusive option from its default of no. This has been fixed in more recent builds of tmux, however, so if you find it as jarring as I did and your package manager has a version of tmux older than 1.5, you may like to consider upgrading or compiling tmux locally.

Even if you’re using a terminal emulator in a GUI environment, if you get good at using this you’ll find it’s much faster and more precise than clicking and dragging to select text to copy and paste it. It keeps you from having to move to the mouse, and additionally eliminates the problem of copying whole lines split into more than one panes.

Note that all of the above assumes that your prefix is the default of Ctrl+B, which many tmux users, myself included, seem to prefer to change to the old GNU Screen prefix key of Ctrl+A.