Redirect the output of a Vim or external command into a scratch buffer

redir.md

Redirect the output of a Vim or external command into a scratch buffer

Usage (any shell)

Show the full output of command :hi in a scratch buffer:

:Redir hi

Show the full output of command :!ls -al in a scratch buffer:

:Redir !ls -al

Show the full output of the previous command in a scratch buffer:

:Redir!

Additional usage (depends on non-standard shell features so YMMV)

Evaluate the current line with node and show the full output in a scratch buffer:

" current line
console.log(Math.random());

" Ex command
:.Redir !node

" scratch window
0.03987581000754448

Evaluate the current buffer + positional parameters with bash and show the full output in a scratch buffer:

" content of buffer
echo ${1}
echo ${2}

" Ex command
:%Redir !bash -s foo bar

" scratch window
foo
bar

---

My Vim-related gists.

redir.vim

function! Redir(cmd = '', rng = 0, start = 1, end = 1, bang = '')
    let cmd = a:cmd->trim()
    for win in range(1, winnr('$'))
        if getwinvar(win, 'scratch')
            execute win . 'windo close'
        endif
    endfor
    if a:bang == '!' && cmd->empty()
        let cmd = expand(@:)->trim()
    endif
    if cmd =~ '^!'
        let ext_cmd = cmd =~' %'
                \ ? matchstr(substitute(cmd, ' %', ' ' . shellescape(escape(expand('%:p'), '\')), ''), '^!\zs.*')
                \ : matchstr(cmd, '^!\zs.*')
        if a:rng == 0
            let output = systemlist(ext_cmd)
        else
            let joined_lines = join(getline(a:start, a:end), '\n')
            let cleaned_lines = substitute(shellescape(joined_lines), "'\\\\''", "\\\\'", 'g')
            let output = systemlist(ext_cmd . " <<< $" . cleaned_lines)
        endif
    else
        redir => output
        execute cmd
        redir END
        let output = split(output, "\n")
    endif
    vnew
    let w:scratch = 1
    setlocal buftype=nofile bufhidden=wipe nobuflisted noswapfile
    call setline(1, output)
endfunction


" This command definition includes -bar, so that it is possible to "chain" Vim commands.
" Side effect: double quotes can't be used in external commands
command! -nargs=? -complete=command -bar -range -bang Redir silent call Redir(<q-args>, <range>, <line1>, <line2>, '<bang>')

" This command definition doesn't include -bar, so that it is possible to use double quotes in external commands.
" Side effect: Vim commands can't be "chained".
command! -nargs=? -complete=command -range -bang Redir silent call Redir(<q-args>, <range>, <line1>, <line2>, '<bang>')

In fact, things can be easier now use the vim command read. For example, :read !ls -arlh can exec the external shell command ls -arlh to the buffer in one step directly. If you wanna redirect the command result from the vim ex mode, you can also use the vim command like :put=execute('ls') or :put=execute('buffers'). The variable put is very special in vim. I have used this feature to make my "quickfix" with ripgrep. Here is my vim config -> https://github.com/HCY-ASLEEP/NVIM-Config/blob/main/init.vim.

Well… of course :read !foo can be used to insert the output of external command foo in the buffer, or :put=execute('hi') to insert the output of Ex command :hi. But that's, like… in the current buffer, and 10% of what this :Redir does.

:Redir !foo is functionally similar to the following crude command:

:vnew | read !foo

and :Redir foo is functionally "similar" to:

:vnew | put=execute('foo')

which is already a bit more than :read.

That is more or less what I did for years but it had a bunch of issues that I fixed gradually to obtain this command, which now fits my workflow perfectly. Those issues, in no particular order:

• Whether you do :read or :0read, you always end up with an extraneous empty line, which is something I don't like at all. My first attempt to fix that was to switch to :put, which allowed me to use system() or :redir, which allowed me to add a third command that removed the extra line:

  :vnew | :put=system('foo') | 1d_
  

  Which worked, but it started to become quite a mouthful. That is the point where you start to consider turning it into a an Ex command. And of course, it couldn't be turned into a command as-is because, depending on whether the command was internal or external, I would have to decide whether to use system() or :redir.

  Note that I wrote this command before execute() was introduced, but that wouldn't change much. :redir is perfectly fine.

  Taking one path or another depending on the argument is not super hard, mind you, but solving that specific "extra line" issue, made the problem—and the solution—a little bit more complex than a "simple" :read or a "simple" :put.

• The resulting buffer lingered behind because it was a regular one. Since I intended it to be a "scratch buffer", I had to set a few options. Once again, that's not hard, but that's more complexity added to the mix. It makes the whole thing much cleaner, though, so the added complexity is very much worth it.

  And that's one more step further away from a simple :read or :put.

• In some cases, :read changes the alternate file, which is something I wanted to avoid in this scenario but not all the time. Another reason why suggesting a simple :read as an alternative would be disingenuous at best.

• I didn't want the command to spawn more than one scratch window. Solving it was, again, relatively easy, but that's still more complexity than that mythical :read.

• I wanted my command to be usable as a filter, which, yet again, added more complexity because I needed to handle ranges.

• Etc.

So no, :read and :put don't make things easier at all.

Thanks for your serious reply, now that I have a better understanding of these commands, I'm considering taking your methods to improve my config.

guys can you give me something in luascript?!

guys can you give me something in luascript?!

Thanks romainl for amazing work! I implement this command with lua script, with some extra commands to get repl-like features.

Also, this lua implementations support vertical and horizontal modifiers.

And note that this lua script doesn't use sh -c to do things, it spawns process directly, so no shell commands available but also no shell escaping needed.

My implementation in lua

Thanks, @Leenuus.

@gachikuku it looks like your wish came true.

Thank you @Leenuus! 🤗
@romainl it did.

Thank you @Leenuus! 🤗 @romainl it did.

Thanks, @Leenuus.

@gachikuku it looks like your wish came true.

Hi, @gachikuku , I rewrite my ugly codes and write a README like @romainl did.

And with vim.uv power, this implementation is totally async.

Split direction and stderr are handled too.

Can't thank @romainl more for such a simple, elegant, and powerful solution.

My gist here

You are very welcome, @Leenuus. Your gist seems almost plugin-ready.

You are very welcome, @Leenuus. Your gist seems almost plugin-ready.

Hope that I don't overengineer. 😂

@Leenuus @romainl is right!
That thing reserves a repo not a gist.
Plus it would be easier for folks to set it up, so make it a plugin.

@romainl Would you be open to turning this gist into a plugin? I would do it (even just for my own convenience), but not being the author, I couldn't properly license it.

any idea how to do this when you're already in the 'hit-enter' / 'more-prompt'

@MicahMartin The output of the previous command is not accessible so we have to re-run it. I have added that feature: at the "hit enter" or "more" prompt, do :Redir!.

FWIW, I already refactored this into a plugin some time ago. I finally published it here.

awesome!