Vim watch file for changes

Question

Is there a way I can have vim watch something like /tmp/my-vim for changes whenever vim is opened to edit any other file and then run a function when the change occurs?

I am looking for a way to tie my sxhkd shortcut for switching modes (dark/light, which changes other applications themes) to change currently running vim colorschemes.

Answer 1

Using a timer that regularly read the file for what colour mode is in use I solved the question.

Here is the script that reads and calls the changes:

" Set colour scheme (and more) to light mode
function! ColorModeLight()
    colorscheme onehalflight
    let g:color_mode_light=1
    ...
endfunction

" Set colour scheme (and more) to dark mode
function! ColorModeDark()
    colorscheme onehalfdark
    let g:color_mode_light=0
    ...
endfunction

" Check for system colour mode changed
function! ColorModeCheck(timer)
    for line in readfile('/tmp/SYSTEM_LIGHT_MODE', '', 1)
        if line =~ '0' && get(g:, 'color_mode_light', 0) == 1
            call ColorModeDark()
        elseif line =~ '1' && get(g:, 'color_mode_light', 0) == 0
            call ColorModeLight()
        endif
    endfor
endfunction

" Set default colour
colorscheme onehalfdark
let g:color_mode_light=0

...

" Regularly check file for changes
let timer = timer_start(500, 'ColorModeCheck', {'repeat': -1})

My sxhkd runs a script that truncates and writes either 1 or 0 to /tmp/SYSTEM_LIGHT_MODE when called by toggling between the two, after this script is fired vim will soon read that a change occurred and update the colorscheme (lightline and more).