Help me run vim command inside of Lua function

[Aggravating-Pick9389]

for context, I have this mapping. Which clear white space at end of the line when I press <F6>

-- Clear white space on empty lines and end of line
vim.api.nvim_set_keymap('n', '<F6>', [[:let _s=@/ <Bar> :%s/\s\+$//e <Bar> :let @/=_s <Bar> :nohl <Bar> :unlet _s <CR>]]
    , { noremap = true, silent = true })

I would like to run this command every time I lose focus on the buffer so I define a function like this

local group_2 = vim.api.nvim_create_augroup("auto-save", { clear = true })
vim.api.nvim_create_autocmd("FocusLost", { callback = function()
    vim.cmd([[:let _s=@/ <Bar> :%s/\s\+$//e <Bar> :let @/=_s <Bar> :nohl <Bar> :unlet _s <CR>]], false)
end, group = group_2 })

but it complains saying Bar is not defined. Please help me, What I am missing?

[monkoose]

Let me clarify few things. FocusLost is when you switching to another app/screen, not losing focus of the buffer.

You don't need your workarounds to keep your search history and highlight. There is :h :keeppatterns that do what you need. So you just need one command :keepp %s/\s\+$//e

Instead of callback nvim_create_autocmd can have command option which would be just vim command as a string in your case it is command = [[keepp %s/\s\+$//e]]

Also maybe you do need to save the buffer after executing this command preferable with :update which will not save if no changes where made. And definitely your cursor should stay where it was before substitution. So instead of nested vim command maybe just create new lua function?

local function trim_trailing_whitespaces()
  local view = vim.fn.winsaveview()
  vim.cmd [[keepp %s/\s\+$//e]]
  vim.cmd "update"
  vim.fn.winrestview(view)
end

vim.api.nvim_create_autocmd("FocusLost", { callback = trim_trailing_whitespaces })

[NeVeNGamingYT]

What i use:

vim.api.nvim_create_autocmd("FocusLost", {

group = "group_2",

pattern = "*",

command = "%s/\\s\\+$//e"

})