Don't expand `%` in external grep call

Question

I try to search for {% amount in all files under the current directory.

Using ag, this works fine:

ag -Q '{% amount'

(-Q specify to not use any regex, try to match text literally)

I have this in my .vimrc:

grepprg=ag --nogroup --nocolor --column

And when I use :grep -Q '{% amount' I get the following error:

E499: Empty file name for '%' or '#', only works with ":p:h"

Which (in my understanding) mean that Vim try to expand % and fail (because I've not opened any file).

My question is: How to search for a litteral % when using external grep program?

---

Note: thanks to statox I know that the following works:

:vimgrep /%/ *

Answer 1

In the Vim command line, the % is a special placeholder for the current buffer name. See :help cmdline-special. To avoid the expansion, just escape the character with a backslash: :grep -Q '{\% amount'