running external command on contents of register

Question

I know I can use ranges/marks with the ! command like so:

%! column -t

etc. Is there any way to pass a register to the external command instead of the current buffer? I imagine it would look something like this @n! column -t but this just prints the contents of n with the "not an editor command" error. Do I just have to resort to putting the contents of the register in a temporary buffer and then running the command?

Answer 1

Not with the ! command. You'll have to use system instead. From :h system():

system({expr} [, {input}])              *system()* *E677*
        Get the output of the shell command {expr} as a string.  See
        |systemlist()| to get the output as a List.

        When {input} is given and is a string this string is written
        to a file and passed as stdin to the command.  The string is
        written as-is, you need to take care of using the correct line
        separators yourself.
        If {input} is given and is a |List| it is written to the file
        in a way |writefile()| does with {binary} set to "b" (i.e.
        with a newline between each list item with newlines inside
        list items converted to NULs).
        When {input} is given and is a number that is a valid id for
        an existing buffer then the content of the buffer is written
        to the file line by line, each line terminated by a NL and
        NULs characters where the text has a NL.

So putting this all together, you could do

:call system("column -t", getreg("@n"))

Now, unfortunately, this on it's own doesn't produce any output into the buffer. So if you want it to go into your buffer, you'll have to use put

:put =system("column -t", getreg("@n"))