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.
: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 tabnew silent put=message set nomodified endfunction command! -nargs=+ -complete=command TabMessage call TabMessage(<q-args>)
Note that :redir can use a variable instead of a register, as shown above.
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:
ie, if you didn't know the :retab command (as for a long time I didn't), you could expand tabs using basic unix commands like ":%! expand -t 4". Wish I'd known this a long time ago, so I'm posting it here in the hopes that others might find it :-)
The answer is (for example):
:read !ls ~
and :help :read for more information.