How do I use parameters within a custom command?

Question

I want to define a global search and replace with confirmation command, something like:

command Gfr :s/<parameter1>/<parameter2>/gc

So I can type:

:Gfr foo bar

and Vim will find all occurrences of 'foo' in the document and ask for each whether I want to replace it with 'bar'.

Googling has led me to some tantalising hints that this is possible, but no definitive answer.

Answer 1

I would do:

function! Gfr(search, replace)
  execute '%s/' .. a:search .. '/' .. a:replace .. '/gc'
endfunction

command! -nargs=+ Gfr call Gfr(<f-args>)

To pass multiple parameters I propose to use a function and the <f-args> placeholder that converts the argument part of the command into a list of strings that a function can take.

The -nargs=+ force the user to have at least one argument (you cannot force exactly 2 with that parameters)