Set Emacs executables PATH to the one used by interactive shells

emacs-path-from-interactive-shell.el

;;; Put this in your .emacs file.

;;; PATH used by default in emacs is not that used in interactive shells. Thus, it would miss
;;; paths set in the shell's rc file.

;;; The login shell could print warnings or errors on initialization, so we isolate the PATH and
;;; use a simple regexp to get the real value
(let ((interactive-shell-path (shell-command-to-string "$SHELL -l -i -c 'echo \"***\n$PATH\n***\"'")))
  (string-match ".*\\*\\*\\*\\\n\\(.*\\)\n\\*\\*\\*.*" interactive-shell-path)
  (let ((clean-shell-path (match-string 1 interactive-shell-path)))
    (setenv "PATH" clean-shell-path) ;;; normal PATH
    (setq eshell-path-env clean-shell-path) ;;; PATH in eshell
    (setq exec-path (split-string clean-shell-path path-separator)) ;;; exec-path
    )
  )

This is based on http://www.verious.com/qa/how-to-make-emacs-to-use-my-bashrc-file/