Temporarily set the `default-directory` for `start-process`

Question

Is it possible to set the default-directory temporarily (e.g., let-bound) when using start-process? If so, how please.

(let ((default-directory "/Users/HOME/Desktop/tmp"))
  (start-process "touch-file" nil "touch" "test.txt"))

start-process ignores a let-bound default-directory.

Answer 1

default-directory has to be a directory, not the filename of a directory. In other words it has to end with a slash. In some places it does not matter whether a directory path ends with a slash or not, here it does.

(let ((default-directory "/some/directory/"))
  ...)

Answer 2

Just expand the file name:

(let ((default-directory "/Users/HOME/Desktop/tmp"))
  (start-process "touch-file" nil "touch"
                 (expand-file-name "test.txt")))