Emacs function to add new path elements to the $PATH environment variable

A very simple eLisp function to add new path elements to the PATH environment variable. Very useful for adding new comint executables from within .emacs/init.el files.

(defun my-add-path (path-element)
 "Add the specified path element to the Emacs PATH"
  (interactive "DEnter directory to be added to path: ")
  (if (file-directory-p path-element)
    (setenv "PATH"
       (concat (expand-file-name path-element)
               path-separator (getenv "PATH")))))

Quickly diff the changes made in the current buffer with its file

Update (23rd Jan 2010): Separated the key-assignment and  function definition.

A simple function to quickly do a diff of the current buffer contents with its underlying file. Very useful if the file has been changed outside (e.g., a log file).

;; Diff the current buffer with the file contents
(defun my-diff-current-buffer-with-disk ()
 "Compare the current buffer with it's disk file."
 (interactive)
 (diff-buffer-with-file (current-buffer)))
(global-set-key (kbd "C-c w") 'my-diff-current-buffer-with-disk)

Google Search from within Emacs

A quick and dirty eLisp function for searching on the internet from within Emacs. The default is to search using Google, but you can add to the *internet-search-urls* variable to setup additional search URLs.

By default, the search term is appended at end of the URL – however, you can also encode the specific search term insertion point in the URL by marking the position using the “%s” marker.

;;; The custom search URLs
(defvar *internet-search-urls*
 (quote ("http://www.google.com/search?ie=utf-8&oe=utf-8&q=%s"
         "http://en.wikipedia.org/wiki/Special:Search?search=")))

;;; Search a query on the Internet using the selected URL.
(defun search-in-internet (arg)
 "Searches the internet using the ARGth custom URL for the marked text.

If a region is not selected, prompts for the string to search on.

The prefix number ARG indicates the Search URL to use. By default the search URL at position 1 will be used."
 (interactive "p")

 ;; Some sanity check.
 (if (> arg (length *internet-search-urls*))
      (error "There is no search URL defined at position %s" arg))

  (let ((query                          ; Set the search query first.
    (if (region-active-p)
      (buffer-substring (region-beginning) (region-end))
    (read-from-minibuffer "Search for: ")))

  ;; Now get the Base URL to use for the search
  (baseurl (nth (1- arg) *internet-search-urls*)))

  ;; Add the query parameter
  (let ((url
    (if (string-match "%s" baseurl)
      ;; If the base URL has a %s embedded, then replace it
         (replace-match query t t baseurl)
    ;; Else just append the query string at end of the URL
      (concat baseurl query))))
 
   (message "Searching for %s at %s" query url)
   ;; Now browse the URL
   (browse-url url))))