How to redirect ex command output into current buffer or file?

Question

How can I redirect or pipe the output of an ex command into my current buffer or a file?

For example, I want to read the contents of all the registers into the current buffer, which in ex mode is shown using :registers.

Answer 1

:redir >name_of_registers_file
:registers
:redir END
:r name_of_registers_file
:help redir

The last command is very useful, since there are lots of options for redirection: to variables, to registers, how to append, further cornucopia.

I still find it weird and annoying that it uses END that way, but since everything else that can follow redir has to start with a non-word-character, at least it's not ambiguous.

PS AFAIK (which is pretty far in this case) there's no way to read it directly into the buffer: you have to store it in a register or a variable first. Check the help for the various options of how to do that.

PPS If you do want to do this using a variable —maybe to encapsulate it in a function and avoid clobbering registers or global variables— you'll have to convert the multiline string that gets written to the variable into a list. EG

:call append( '.', split(variable_you_redirected_to, "\n") )

Otherwise (if you just do append('.',var)) you end up with ^@'s (nulls) instead of newlines, since that's what vimscript uses to represent newlines in String variables.

edit: as @Bill Odom mentions, using :put =variable_you_redirected_to is a lot easier than the complicated append() expression. Thanks, Bill!

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PPPS

I've written a snippet to make this stuff more convenient. It declares a function Redir(command, target) and a command R.

The command parses the last series of non-space characters as a redirection target and passes that to the function, which does the boilerplate to redirect the command output to the redirection target.

The command is everything after R and before the last space.

EG

" Store the vim buffer list in buffer_list.txt
:R ls >buffer_list.txt
" Store error messages emitted by a function being debugged
"   in the 'unnamed register'
:R call FunctionBeingDebugged() @">

There are a few limitations with this: for example you won't be able to write to a filename that contains a space. The upside to this is that you don't have to quote your command. I've got it posted on gist.github.com, and I'll try to keep it updated if I end up improving it. Or you can fork it yourself</noeuphemism>!

Anyway the snippet is available here. It can be dropped into a .vimrc file or into a file in ~/.vim/plugins.