How do I delete the newline from a process output?

问题

I call git get the toplevel dir (according to Is there a way to get the git root directory in one command? ).

(let ((tmpbuffer (get-buffer-create (make-temp-name "git"))))
  (call-process "git" nil tmpbuffer nil "rev-parse" "--show-toplevel")
  (with-current-buffer tmpbuffer
    (with-output-to-string
      (princ (buffer-string))
      (kill-buffer))))

But there's a trailing newline in the string returned. I'm not sure how to get rid of it.

回答1:

I think you can do

(replace-regexp-in-string "\n$" "" 
              (shell-command-to-string "git rev-parse --show-toplevel"))

回答2:

If you only want to remove a newline at the very end of the output, use

(replace-regexp-in-string "\n\\'" "" 
  (shell-command-to-string "git rev-parse --show-toplevel"))

The accepted answer also replaces pairs of newlines ("\n\n") in the output by single newlines ("\n"), because $ matches at the end of the string or after a newline, while \\' only matches at the end of the string.

回答3:

Assuming it is stored in a variable output-string, the final newline at the end can be removed this way:

(substring output-string 0 -1)

With the shell-command way, it would look like this:

(substring
  (shell-command-to-string "git rev-parse --show-toplevel")
  0 -1)

来源：https://stackoverflow.com/questions/14074912/how-do-i-delete-the-newline-from-a-process-output