How to move `n` number char <left> in vim command line?

Question

My init.vim code

autocmd FileType cpp nnoremap <F4> :RunWithFile ~/Downloads/ > output.txt && cat output.txt

I want my cursor position to be exact 31 times <left> in command line.
or after ~/Downloads/

Like this

PS: I got this idea from this shortcut nmap <leader>s :%s/\<<C-r><C-w>\>/<C-r><C-w>/gI<Left><Left><Left>
here the cursor goes 3 char left in command line

but if i use <left> it will take 31 left's in my init.vim code to go in that position
I couldn't find any simple solution. Maybe you folks can help me out a bit.

Answer 1

There is no straightforward way to tell vim to land the cursor at a particular place in the cmdline during a map, but there are a number of workarounds.

1. Direct positioning

autocmd FileType cpp nnoremap <F4> :RunWithFile ~/Downloads/ > output.txt && cat output.txt<c-r>=setcmdpos(getcmdpos()-31)[1]<cr>

You can use setcmdpos() to place the cursor anywhere on the cmdline in an expression. The only trick here is to have it not enter any text by indexing [1] (which is invalid, and returns empty string).

2. Alternative to <left>

autocmd FileType cpp nnoremap <F4> :RunWithFile ~/Downloads/ > output.txt && cat output.txt<s-left><s-left><s-left><s-left><s-left><left>

shift-left moves more than left, thus you will need fewer movements.

3. Using repeat()

autocmd FileType cpp execute 'nnoremap <F4> :RunWithFile ~/Downloads/ > output.txt && cat output.txt' . repeat('<left>', 31)

You can create the sequence of <left>s with an expression using the expression register. The map itself will still be quite ugly but the code is cleaner.

Answer 2

1. Normally prefer :h ftplugin over autocmd FileType. If still want autocmd, at least, put it into augroup.
2. Use :h map-<buffer> to define a local mapping. Otherwise it will affect all other buffers/windows too.
3. Typing foo[cursor]bar is as simple as bar<C-B>foo.