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 full output of command :hi in scratch window:

:Redir hi

Show full output of command :!ls -al in scratch window:

:Redir !ls -al 

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

Evaluate current line with node and show full output in scratch window:

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

" Ex command
:.Redir !node

" scratch window
0.03987581000754448

Evaluate visual selection + positional parameters with bash and show full output in scratch window:

" 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, start, end)
	for win in range(1, winnr('$'))
		if getwinvar(win, 'scratch')
			execute win . 'windo close'
		endif
	endfor
	if a:cmd =~ '^!'
		let cmd = a:cmd =~' %'
			\ ? matchstr(substitute(a:cmd, ' %', ' ' . shellescape(escape(expand('%:p'), '\')), ''), '^!\zs.*')
			\ : matchstr(a:cmd, '^!\zs.*')
		if a:rng == 0
			let output = systemlist(cmd)
		else
			let joined_lines = join(getline(a:start, a:end), '\n')
			let cleaned_lines = substitute(shellescape(joined_lines), "'\\\\''", "\\\\'", 'g')
			let output = systemlist(cmd . " <<< $" . cleaned_lines)
		endif
	else
		redir => output
		execute a: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=1 -complete=command -bar -range Redir silent call Redir(<q-args>, <range>, <line1>, <line2>)

" 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=1 -complete=command -range Redir silent call Redir(<q-args>, <range>, <line1>, <line2>)

Checking for % my be of some interest, too:

[...]
if cmd =~ '^!'
    if cmd =~' %'
        let cmd = substitute(cmd, ' %', ' ' . expand('%:p'), '')
    endif
    let output = system(matchstr(cmd, '^!\zs.*'))
else
[...]

Can you paste the full script? Sorry, I can't execute if after insert your snippets. Thank you.

097115's snippet incorrectly uses cmd instead of a:cmd. Check the main snippet for a working version.

Checking for % my be of some interest, too:

[...]
if cmd =~ '^!'
    if cmd =~' %'
        let cmd = substitute(cmd, ' %', ' ' . expand('%:p'), '')
    endif
    let output = system(matchstr(cmd, '^!\zs.*'))
else
[...]

Can you paste the full script? Sorry, I can't execute if after insert your snippets. Thank you.

097115's snippet incorrectly uses cmd instead of a:cmd. Check the main snippet for a working version.

It works! Thank you for this. It has wasted me several hours.

I'm curious why you added the -bar option to the command definition?
Im on both MacOS and Windows -- with most of my time in Windows. When I try to redirect a shell command that has an argument with a space, it fails because the " I try to use just becomes the beginning of the Ex command's comment.

:Redir !p4 annotate -u "file with spaces"

Ends up trying to invoke:

system('p4 annotate -u')

...because the <q-args> never includes anything from the first " onwards.

Do you have a use case of invoking this command in a | joined chain of commands?

Side note...

I also changed the expand('%:p') to be "more" compatible for windows, into: shellescape(escape(expand('%:p'), '\'))
I "think" this change would still remain compatible with the *nix systems most people use most of the time.

@nebbish The use case for -bar is to allow things like:

:Redir <cmd> | v/foo/d    " insert output of <cmd> in the buffer then delete every line matching foo
:Redir !<cmd> | $    " insert output of <cmd> in the buffer then move cursor to some arbitrary line

With -bar I can "postprocess" the buffer on the command-line using Vim tools. That's the whole point.

The problem is that I overlooked this sentence from :help :command-bar:

Also checks for a " to start a comment.

which is not super intuitive when using something called -bar.

Anyway, right now I don't see a possible middle ground:

• on one hand, I really want to be able to do the things described above,
• on the other hand, your example is very real and reasonable and should work and -bar prevents it.

For now, I think I'm going to keep the -bar and provide a non-bar alternative.

---

As for your escaping snippets… my gists often miss that kind of refinement because I usually stop at "works for me" and "me". A plugin would be treated differently :-). It seems to work fine on my end so I will add it ASAP.

Thank you.

👍

How to capture the output of the job? In this case, redir is finished before out_cb is called.

call job_start("python -m this", {'out_cb': {_, msg -> execute('echom ' .. msg)}})

@younger-1 Redir() would have to be rewritten to make that possible. As of now, it is 100% synchronous.

not exactly the same, but similar in vim9script: https://github.com/habamax/vim-shout

The same in Vim9script:

export def g:Redir(cmd: string, rng: number, start: number, end: number)
	for win in range(1, winnr('$'))
		if !empty(getwinvar(win, 'scratch'))
			execute win .. 'windo close'
		endif
	endfor
        var output = []
	if cmd =~ '^!'
		var cmd_filt = cmd =~ ' %'
			\ ? matchstr(substitute(cmd, ' %', ' ' .. shellescape(escape(expand('%:p'), '\')), ''), '^!\zs.*')
			\ : matchstr(cmd, '^!\zs.*')
		if rng == 0
			output = systemlist(cmd_filt)
		else
			var joined_lines = join(getline(start, end), '\n')
			var cleaned_lines = substitute(shellescape(joined_lines), "'\\\\''", "\\\\'", 'g')
			output = systemlist(cmd_filt .. " <<< $" .. cleaned_lines)
		endif
	else
                var tmp: string
		redir => tmp
		execute cmd
		redir END
		output = split(tmp, "\n")
	endif
	vnew
	w:scratch = 1
	setlocal buftype=nofile bufhidden=wipe nobuflisted noswapfile
	setline(1, output)
enddef

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?!