Yes, please let me know if `tmux capture-pane -J` works. In that case we could simplify
```viml
function! tmuxcomplete#init()
    let s:capture_args = get(g:, 'tmuxcomplete#capture_args', '?')
    if s:capture_args == '?'
        call system('tmux capture-pane -J &> /dev/null') " check for -J flag
        let s:capture_args = v:shell_error == 0 ? '-J' : ''
    endif
endfunction
```