External Programs And Emacs

The Emacs philosophy is “do everything in Emacs.” To that end, there are many emacs modes that act as frontends to external command-line programs such as ledger. One common problem is that, depending on how you start your Emacs, it might complain about being unable to find those external programs. This is a common problem if you start Emacs as a systemd service or if you use the GUI version on a Mac.

The Problem

By default, Emacs sets its path to whatever the path is in the environment where Emacs is started. If you start Emacs from your terminal, Emacs inherits the $PATH you’ve already set. If you start Emacs from the Mac GUI program, it’ll inherit the default $PATH, which doesn’t include any custom setup you’ve done in your .bashrc or any other user-specific path info. Similarly with systemd - you only get the default $PATH. The default $PATH doesn’t point to any of your user-specific binaries, and that’s why Emacs can’t find them.

The Solution

You can, in systemd, set a custom path as part of the service definition, but there’s a better way. Steve Purcell has come out with a little Emacs package called [exec-path-from-shell](https://github.com/purcell/exec-path-from-shell) that reads your environment variables, such as your $PATH and adds them to Emacs.

To use it(along with package.el) add the following to your init.el:

(use-package exec-path-from-shell
    :config
    (when (memq window-system '(mac ns x))
    (exec-path-from-shell-initialize))
    :defer 0)

If you don’t use package.el, then install it yourself and just use the third and fourth lines.