I'm trying to write a custom command in Vim to make setting the makeprg variable for an out-of-source build easier. Having read the command manual, so far I've got as far as this
command! -complete=file -nargs=1 Cmakeprg call set makeprg=cmake --build <args><CR>
but it isn't working. How do I call "set" within the command?
You :call functions, :set is an Ex command just like :call (as it's invoked with the : prefix).
A complication with :set is that whitespace must be escaped with \, but that can be avoided by using :let with the &option, and <q-args> automatically quotes the passed command arguments.
You also don't need <CR>; this isn't a mapping. Taken all together:
command! -complete=file -nargs=1 Cmakeprg let &makeprg = 'cmake --build ' . <q-args>
Add a colon in front of "set" and use a <CR> to execute it: :set … <CR>
Do not use call.
