I want to have basically the same as :read ![external command], but instead the external command I want to read the output from an internal command.


Shells echo / external command: :read !echo 0x539 -> output: 0x539

Vims echo / internal command: :read echo 0x539 -> output: 1337

More explanation

The second example will obviously fail, because thats not vim syntax. But is there an equivalent how I can archive this in vim/neovim? I know that you can generally output the result from vimscript commands in the "= register. (In case you don't know, you can press CTRL-R and then = while being in insert mode to get into the expression register). But I don't know how to use echo with it.

So if you have any ideas, I would be glad to hear them :)

2 Answers 2


One version:

:put =execute('echo 0x539')

though I would probably do i<C-v>u0539<esc>.

You can also redir => {var} into a variable, which can be more readable than the execute() function (different from the command!) if there are multiple lines of script.

  • Thank you that is exactly what I wanted. And I know I could use i<CTRL-V>... but I have a lot of hex numbers and I think to use the vim-echo command is the best way to convert them all. I just took 0x539 just as an example, but still thanks :) And btw you can use <CTRL-R>=execute('echo abc') (in insert mode) too :))
    – Bog
    Nov 28, 2022 at 16:12
  • 1
    You can maybe use something like :%s/0x[a-fA-F0-9]\+/\=submatch(0)->str2nr(16)/ @Pixelbog; that finds all hex numbers starting with 0x and replaced it with the decimal variant. Nov 28, 2022 at 16:19
  • oh wow thank you very much. I learned 3 new things from you :) 1. the submatch(0) thing. 2. the whole line, really interesting what you can all do in vim. Vim is really beautiful isnt it? :) And 3. for some reason if I try to use the exact same line in neovim, it does not work. So I have now more to learn :D Thank you very much :))
    – Bog
    Nov 28, 2022 at 16:53
  • 1
    @Pixelbog yes I'm aware of i_CTRL-R. For brevity I would be inclined to use the pattern 0x\x\+.
    – D. Ben Knoble
    Nov 28, 2022 at 18:49
  • Oh wow thats so cool :D I learned something new again. I didn't know that there is an hexadecimal escape, thanks :))
    – Bog
    Nov 29, 2022 at 9:49

But I don't know how to use echo with it.

You don't.

What comes after :help :echo is an expression but :echo <expr> is not the only way to consume expressions. As it stands, the "= register that you use with :help i_ctrl-r is called "expression register" for a reason: it expects an expression, like :echo.

0x0539 is the expression you want to consume so, in insert mode, <C-r>=0x0539<CR> inserts 1337 at the cursor, as expected.

  • First of all, dude I see you almost all over the internet, if it has to do something with vim xD I love it haha. And second, maybe it is a stupid question, but do you know if I can write multiple hex numbers seperated by a comma or in an array?
    – Bog
    Nov 29, 2022 at 9:59
  • Nevermind. I should have first tested it before writing a comment haha. The Answer is yes it is possible, in array of strings seperated by commas. Like this: =['0x539', '0x45', '0x2a'] :)
    – Bog
    Nov 29, 2022 at 10:01
  • @Pixelbog a list of numbers should work, but the expression register typically turns lists into multiple lines.
    – D. Ben Knoble
    Nov 29, 2022 at 13:23

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