Capture ex command output

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created 2001 · complexity intermediate · version 7.0

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Ever want to capture the output of an ex command like :set all into a Vim text buffer for easy viewing? This is actually a very easy thing to accomplish!

You can use the :redir command to redirect the output of an ex command to a register and then paste the contents of the register into a Vim buffer.

For example:

:redir @a
:set all
:redir END

Now, register 'a' will have the output of the "set all" ex command. You can paste this into a Vim buffer, using "ap.

You can also write a Vim function to do the above. Since you probably don't want your command output to mess up your carefully constructed window layout, this function will pipe the output of a command into a new tab, allowing you to simply close the tab when done. If you don't like using tab pages, or you don't have tab support because you didn't compile with it or your Vim version is less than 7.0, you could modify this function to use a new split window instead:

function! TabMessage(cmd)
  redir => message
  silent execute a:cmd
  redir END
  if empty(message)
    echoerr "no output"
  else
    " use "new" instead of "tabnew" below if you prefer split windows instead of tabs
    tabnew
    setlocal buftype=nofile bufhidden=wipe noswapfile nobuflisted nomodified
    silent put=message
  endif
endfunction
command! -nargs=+ -complete=command TabMessage call TabMessage(<q-args>)

Example usage:

:TabMessage highlight

Note that :redir can use a variable instead of a register, as shown above.

Note also that :redir will capture silenced messages as well. While this won't be problematic with most builtin commands that echo stuff that we are interested in, this is quite problematic when we execute a sequence of several commands. Since version 7.4-2008, Vim provides an execute() function that'll simplify things and avoid side-effects.

References

• :help :redir
• :help execute()

Related scripts

• Decho

Comments

This may be obvious to experts, but it took me a very long time to figure it out, because Google searches on terms like 'pipe', 'buffer', 'shell', etc never brought it to my attention. However, you can pipe the contents of the file currently being edited (the current buffer) to a shell command, and replace the current file/buffer with the output of that command, using this:

:%! [cmd]

That is, if you didn't know about the :retab command, you could expand tabs using basic Unix commands like :%! expand -t 4.

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The answer is (for example):

:read !ls ~

and :help :read for more information.

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Here is a function that inserts the output of an Ex command into a split window:

function! OutputSplitWindow(...)
  " this function output the result of the Ex command into a split scratch buffer
  let cmd = join(a:000, ' ')
  let temp_reg = @"
  redir @"
  silent! execute cmd
  redir END
  let output = copy(@")
  let @" = temp_reg
  if empty(output)
    echoerr "no output"
  else
    new
    setlocal buftype=nofile bufhidden=wipe noswapfile nobuflisted
    put! =output
  endif
endfunction
command! -nargs=+ -complete=command Output call OutputSplitWindow(<f-args>)

Example: :Output echo strftime("%H:%M")

I think I incorporated the useful stuff out of this script into the tip. I did not see much in the way of important differences, and in some ways the tip was better. --Fritzophrenic (talk) 18:00, June 3, 2015 (UTC)

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