Emacs is ignoring my path when it runs a compile command

Question

I'm trying to get a compile command (rake cucumber) to run with a specific ruby version on my Mac OS X system, I use rvm to do this currently in the terminal. My ~/.MacOSX/environment.plist has the correct path in it, but emacs insists on prepending to this path and therefore making it useless. I've also tried:

(when (equal system-type 'darwin)
  (setenv "PATH" (concat "/Users/fearoffish/.rvm/bin:/Users/fearoffish/.rvm/rubies/ruby-1.8.7-p249/bin:/Users/fearoffish/.rvm/gems/ruby-1.8.7-p249/bin:/Users/fearoffish/.rvm/gems/ruby-1.8.7-p249%global/bin:/Users/fearoffish/.rvm/bin"))
  (push "/Users/fearoffish/.rvm/bin" exec-path)
  (push "/Users/fearoffish/.rvm/rubies/ruby-1.8.7-p249/bin" exec-path)
  (push "/Users/fearoffish/.rvm/gems/ruby-1.8.7-p249/bin" exec-path)
  (push "/Users/fearoffish/.rvm/gems/ruby-1.8.7-p249%global/bin" exec-path)
  (push "/Users/fearoffish/.rvm/bin" exec-path))

It was the desperate attempt of an emacs beginner to get what I wanted. It still prepends in front of it, so my path ends up being:

/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/Users/fearoffish/.rvm/bin:/Users/fearoffish/.rvm/rubies/ruby-1.8.7-p249/bin:/Users/fearoffish/.rvm/gems/ruby-1.8.7-p249/bin:/Users/fearoffish/.rvm/gems/ruby-1.8.7-p249%global/bin

I don't want /usr/bin and others prepending, I want my path first and the emacs prepended path to be at the end, I reckon this would fix my problem.

I test this by simply opening Aquamacs and running meta-x compile and then echo $PATH.

Any ideas?

Answer 1

Everyone seems to have misunderstood the original issue: the path is already setup correctly in Emacs, and the correct path is already passed to the shell started by the compile command! So what gives? Here is the answer:

In MacOS X, there is a small tool called path_helper(1). It is called by default from /etc/profile, which is executed by Bash on shell startup. When you start a compilation from Emacs, it launches a shell (which by default is Bash on MacOS X), and therefore executes this path_helper tool. And here comes the key point: path_helper rearranges your path, moving the standard directories like /usr/bin in front of your custom added directories, no matter where you originally added them. Try this yourself by opening a shell and first having a look at what PATH is, and then execute /usr/lib/path_helper and have look at the resulting PATH!

The brute force solution for you might be to simply comment out the call to path_helper in /etc/profile. Note however that then you won't automatically get the paths in /etc/paths.d setup by path_helper, which is the tool's main purpose.

Answer 2

A small modification to the solution by sanityinc (couldn't find a way to enter it in the comments above -- is that just me?)

• I use -l option to the shell to force a login shell (which reads .profile or .bash_profile), rather than an interactive shell (which only reads .bashrc).
• I do some string trimming on the returned path (as inspection shows a newline sneaking in).

Modified code:

(defun set-exec-path-from-shell-PATH ()
  (let ((path-from-shell 
      (replace-regexp-in-string "[[:space:]\n]*$" "" 
        (shell-command-to-string "$SHELL -l -c 'echo $PATH'"))))
    (setenv "PATH" path-from-shell)
    (setq exec-path (split-string path-from-shell path-separator))))
(when (equal system-type 'darwin) (set-exec-path-from-shell-PATH))

Answer 3

I don't have a Mac, so I cannot test this directly, but this can all be found in the *info* page Interactive Inferior Shell.

When you start a shell in Emacs, the process that gets spawned is the program in the Emacs variable explicit-shell-file-name (and if that is nil, the environment variables ESHELL and SHELL are used).

It then sends the contents of ~/.emacs_*shellname* (e.g. if your shell is csh, then ~/.emacs_csh would be sent over. Also, the appropriate .rc files for csh program is sourced, so you can update that as well (in my case .cshrc). Additionally, you can wrap customizations in the .rc file with a check for the environment variable INSIDE_EMACS (which which Emacs sets before it runs a shell).

You need to update those files to change the path in the shell, not the Emacs variable exec-path. exec-path - which is just a list of directories Emacs uses to find executable programs. The behavior of the executables are not affected by changes to exec-path.