Setting the search pattern to just a portion of a regex pattern

Question

I'm not sure if the title makes sense, but I'll try to explain what I'm trying to do.

I have a file with some code like:

some_var = 3;
...
func(some_var);

The file has a bunch of calls to func and I'd like to find all occurrences of the variable passed to each call. In this case I'd like to find some_var on the line where it is assigned as well as where it is passed to the function. Unfortunately the variable name may differ in each instance, so I can't just search for the variable name directly.

Is there some way to search for the call to the function, capture the argument passed to it and then set the search pattern to that argument?

I tried the following, but it seems sub-expressions don't work with the :g command:

:g/func(\(\w\+\))/let @/ = \1

Answer 1

I'd probably use a simple macro for this:

qq/func(./e<CR>#q

N.B In the above, <CR> is a single press of your Return key.

Broken down:

• qq Start recording a macro into the "q register,
• /func(./e<CR> Search for the function, leaving the cursor on the first character of the argument .
• # Search backwards for the variable
• q Stop recording the macro.

You can then press n if necessary, to continue searching backwards for the variable, in case it is assigned to more than once.

When you've finished inspecting that variable, press Ctrl-O to step back through the jumplist until you're back at the function call, and then press @q to replay the macro to find the next call to the function and the argument that is passed to it.