How to insert spaces up to column X to line up things in columns?

The other answers here are great, especially @nelstrom's comment for Tabular.vim and his excellent screencast.

But if I were feeling too lazy to install any Vim plugins, yet somehow willing to use Vim macros, I'd use macros.

The algorithm:

For each line,
    Add tons of spaces before the symbol =
    Go to the column you want to align to
    Delete all text up to =, thereby shifting the = into the spot you want.

For your example,

foo = rhs.foo;
foobar = rhs.foobar;
bar = rhs.bar;
toto = rhs.toto;

Position the cursor anywhere on the first line and record the macro for that line by typing, in normal mode:

qa0f=100i <Esc>8|dwjq

Which translates to:

1. qa -- Record a macro in hotkey a
2. 0 -- Go to the beginning of the line
3. f= -- Go to the first equals sign
4. 100i <Esc> -- (There's a single space after the i, and the <Esc> means press escape, don't type "<Esc>".) Insert 100 spaces
5. 8| -- Go to the 8th column (sorry, you'll have to manually figure out which column to align to)
6. dw -- Delete until the next non-space character
7. j -- Go to the next line
8. q -- Stop recording.

Then run the macro stored at hotkey a, 3 times (for the 3 remaining lines), by putting the cursor on the second line and pressing:

3@a

If you are using a unix-like environment, you can use the command line tool column. Mark your lines using visual mode, then:

:'<,'>!column -t

This pastes the selected text into the stdin of the command after '<,'>!. Note that '<,'>! is inserted automatically when you hit : in visual mode.

There is a nice plugin which does exactly that and more, called Align.vim

For you case, you would need to select your expression and then type :Align =. It will align everything, using = as a separator and reference.

(There is a lots of options to align, left, right, cyclically, etc)

You can also check Tabular.vim which provides similar features. See the screencast there for a demo.

A quick, simple way to proceed is to add X spaces and then delete back to column X. For example, if X=40, type

40a<Space><Esc>d40|

An alternative solution is to perform two consecutive substitutions:

%s/=/     =/
%s/\%>7c *//

The trick is the column pattern \%>7c that matches white spaces * only after the 7th column. Here foobar is the longest variable name with 6 characters so we need 7 in the regex.