[vim] How do I use vim registers?

I only know of one instance using registers is via CtrlR* whereby I paste text from a clipboard.

What are other uses of registers? How to use them?

Everything you know about VI registers (let's focus on vi 7.2) -- share with us.

From vim's help page:

CTRL-R {0-9a-z"%#:-=.}                  *c_CTRL-R* *c_<C-R>*
        Insert the contents of a numbered or named register.  Between
        typing CTRL-R and the second character '"' will be displayed
        <...snip...>
        Special registers:
            '"' the unnamed register, containing the text of
                the last delete or yank
            '%' the current file name
            '#' the alternate file name
            '*' the clipboard contents (X11: primary selection)
            '+' the clipboard contents
            '/' the last search pattern
            ':' the last command-line
            '-' the last small (less than a line) delete
            '.' the last inserted text
                            *c_CTRL-R_=*
            '=' the expression register: you are prompted to
                enter an expression (see |expression|)
                (doesn't work at the expression prompt; some
                things such as changing the buffer or current
                window are not allowed to avoid side effects)
                When the result is a |List| the items are used
                as lines.  They can have line breaks inside
                too.
                When the result is a Float it's automatically
                converted to a String.
        See |registers| about registers.  {not in Vi}
        <...snip...>

If you ever want to paste the contents of the register in an ex-mode command, hit <C-r><registerletter>.

Why would you use this? I wanted to do a search and replace for a longish string, so I selected it in visual mode, started typing out the search/replace expression :%s/[PASTE YANKED PHRASE]//g and went on my day.

If you only want to paste a single word in ex mode, can make sure the cursor is on it before entering ex mode, and then hit <C-r><C-w> when in ex mode to paste the word.

• q5 records edits into register 5 (next q stops recording)
• :reg show all registers and any contents in them
• @5 execute register 5 macro (recorded edits)

Use registers in commands with @. E.g.:

echo @a
echo @0
echo @+

Set them in command:

let @a = 'abc'

Now "ap will paste abc.

I use the default register to grep for text in my vim window without having to reach for the mouse.

1. yank text
2. :!grep "<CTRL-R>0"<CR>

My favorite register is the ':' register. Running @: in Normal mode allows me to repeat the previously ran ex command.

My favorite feature is the ability to append into registers by using capital letters. For example, say you want to move a subset of imports from buffer X to buffer Y.

1. Go to line x1 in buffer X.
2. Type "ayy to replace register a with the content of line x1.
3. Go to line x5.
4. Type "Ayy (capital A) to append line x5 at the end of register a.
5. Go to buffer Y and type "ap to paste

<content of line x1>
<content of line x5>

Other useful registers:

"* or "+ - the contents of the system clipboard

"/ - last search command

": - last command-line command.

Note with vim macros, you can edit them, since they are just a list of the keystrokes used when recording the macro. So you can write to a text file the macro (using "ap to write macro a) and edit them, and load them into a register with "ay$. Nice way of storing useful macros.

One of my favorite parts about registers is using them as macros!

Let's say you are dealing with a tab-delimited value file as such:

ID  Df  %Dev    Lambda
1   0   0.000000    0.313682
2   1   0.023113    0.304332
3   1   0.044869    0.295261
4   1   0.065347    0.286460
5   1   0.084623    0.277922
6   1   0.102767    0.269638
7   1   0.119845    0.261601

Now you decide that you need to add a percentage sign at the end of the %Dev field (starting from 2nd line). We'll make a simple macro in the (arbitrarily selected) m register as follows:

1. Press: qm: To start recording macro under m register.

2. EE: Go to the end of the 3rd column.

3. a: Insert mode to append to the end of this column.

4. %: Type the percent sign we want to add.

5. <ESC>: Get back into command mode.

6. j0: Go to beginning of next line.

7. q: Stop recording macro

We can now just type @m to run this macro on the current line. Furthermore, we can type @@ to repeat, or 100@m to do this 100 times! Life's looking pretty good.

At this point you should be saying, "But what does this have to do with registers?"

Excellent point. Let's investigate what is in the contents of the m register by typing "mp. We then get the following:

EEa%<ESC>j0

At first this looks like you accidentally opened a binary file in notepad, but upon second glance, it's the exact sequence of characters in our macro!

You are a curious person, so let's do something interesting and edit this line of text to insert a ! instead of boring old %.

EEa!<ESC>j0

Then let's yank this into the n register by typing B"nyE. Then, just for kicks, let's run the n macro on a line of our data using @n....

It added a !.

Essentially, running a macro is like pressing the exact sequence of keys in that macro's register. If that isn't a cool register trick, I'll eat my hat.

My friend Brian wrote a comprehensive article on this. I think it is a great intro to how to use topics. https://www.brianstorti.com/vim-registers/

I was pleased when I discovered the 0 register. If you yank text without assigning it to a particular register, then it will be assigned to the 0 register, as well as being saved in the default " register. The difference between the 0 and " registers is that 0 is only populated with yanked text, whereas the default register is also populated with text deleted using d/D/x/X/c/C/s/S commands.

I find this useful when I want to copy some text, delete something and replace it with the copied text. The following steps illustrate an example:

• Yank the text you want to copy with y[motion] - this text is saved in " and 0 registers
• Delete the text you want to replace with d[motion] - this text is saved in " register
• Paste the yanked text with "0p

where " is the command to use a register for the next command.

On the final step, if you were to paste from the default register (with p), it would use the text that you had just deleted (probably not what you intended).

Note that p or P pastes from the default register. The longhand equivalent would be ""p (or ""P) and "0 holds the last yank, "1holds the last delete or change.

For more info see :help registers.

A big source of confusion is the default register ". It is important to know the way it works. It is much better if the default register is avoided most of the times. The explanation from the Vim documentation:

Vim fills this register with text deleted with the "d", "c", "s", "x" commands
or copied with the yank "y" command, regardless of whether or not a specific
register was used (e.g.  "xdd).  This is like the unnamed register is pointing
to the last used register.

So the default register is actually a pointer to the last used register. When you delete, or yank something this register is going to point to other registers. You can test that by checking the registers. There is always another register that is exactly the same as the default register: the yank register ("0) , the first delete register("1) , small delete register("-) or any other register that was used to delete or yank.

The only exception is the black hole register. Vim doc says:

An exception is the '_' register: "_dd does not store the deleted text in any
register.

Usually you are much better off by using directly: "0, "- and "1-"9 default registers or named registers.

I think the secret guru register is the expression = register. It can be used for creative mappings.

:inoremap  \d The current date <c-r>=system("date")<cr>

You can use it in conjunction with your system as above or get responses from custom VimL functions etc.

or just ad hoc stuff like

<c-r>=35+7<cr>

The black hole register _ is the /dev/null of registers.

I use it in my vimrc to allow deleting single characters without updating the default register:

noremap x "_x

and to paste in visual mode without updating the default register:

vnoremap p "_dP

One overlooked register is the '.' dot register which contains the last inserted text no matter how it was inserted eg ct] (change till ]). Then you realise you need to insert it elsewhere but can't use the dot repeat method.

 :reg .
 :%s/fred/<C-R>./

A cool trick is to use "1p to paste the last delete/change (, and then use . to repeatedly to paste the subsequent deletes. In other words, "1p... is basically equivalent to "1p"2p"3p"4p.

You can use this to reverse-order a handful of lines: dddddddddd"1p....