exec-path-from-shell

A GNU Emacs library to ensure environment variables inside Emacs look the same as in the user's shell.

Motivation

Ever find that a command works in your shell, but not in Emacs?

This happens a lot on OS X, where an Emacs instance launched as a GUI app inherits a default minimal set of environment variables that are probably not the ones you see in a terminal window. Similarly, if you start Emacs as a daemon from systemd or launchd, it will run with a default set of environment variables.

This library solves this problem by copying important environment variables from the user's shell: it works by asking your shell to print out the variables of interest, then copying them into the Emacs environment.

Compatibility

If the path printed by evaluating (getenv "SHELL") in Emacs points at bash or zsh, this should work fine.

At a minimum, this package assumes that your shell is at least UNIX-y: if (getenv "SHELL") evaluates to something like ".../cmdproxy.exe", this package probably isn't for you.

Further, if you use a non-POSIX-standard shell such as tcsh or fish, your shell will be asked to execute sh as a subshell in order to print out the variables in a format which can be reliably parsed. sh must be a POSIX-compliant shell in this case.

Note that shell variables which have not been exported as environment variables (e.g. using the "export" keyword) may not be visible to `exec-path-from-shell'.

Installation

Installable packages are available via MELPA: do M-x package-install RET exec-path-from-shell RET.

Alternatively, download the latest release or clone the repository, and install exec-path-from-shell.el with M-x package-install-file.

Usage

Add the following to your init.el (after calling package-initialize):

(when (memq window-system '(mac ns x))
  (exec-path-from-shell-initialize))

This sets $MANPATH, $PATH and exec-path from your shell, but only when executed in a GUI frame on OS X and Linux.

If you launch Emacs as a daemon from systemd or similar, you might like to use the following snippet:

(when (daemonp)
  (exec-path-from-shell-initialize))

You can copy values of other environment variables by customizing exec-path-from-shell-variables before invoking exec-path-from-shell-initialize, or by calling exec-path-from-shell-copy-env, e.g.:

(exec-path-from-shell-copy-env "PYTHONPATH")

This function may also be called interactively.

The author uses the following configuration snippet before calling exec-path-from-shell-initialize:

(dolist (var '("SSH_AUTH_SOCK" "SSH_AGENT_PID" "GPG_AGENT_INFO" "LANG" "LC_CTYPE" "NIX_SSL_CERT_FILE" "NIX_PATH"))
  (add-to-list 'exec-path-from-shell-variables var))

Setting up your shell startup files correctly

Note that your shell will inherit Emacs's environment variables when it is run by exec-path-from-shell -- to avoid surprises your config files should therefore set the environment variables to their exact desired final values, i.e. don't do this:

export PATH=/usr/local/bin:$PATH

but instead do this:

export PATH=/usr/local/bin:/usr/bin:/bin

To be safe, exec-path-from-shell starts an interactive (and login) shell by default, but this can be much slower than necessary. Interactive shells often have fancy features enabled that are only helpful when one interacts directly with the shell, and this can frequently cause startup time to exceed 750ms. This can be avoided:

• Follow best practice by setting your environment variables so that they are available to both interactive and non-interactive shells. In practical terms, for most people this means setting them in ~/.profile, ~/.bash_profile, ~/.zshenv instead of ~/.bashrc and ~/.zshrc.
• Once a non-interactive shell sets your environment variables correctly, adjust exec-path-from-shell-arguments appropriately (often to nil) before calling exec-path-from-shell-initialize so that it will start a non-interactive shell.

To learn more about how popular shells load start-up files, read this helpful article.

Making exec-path-from-shell faster

If evaluation takes more than exec-path-from-shell-warn-duration-millis (500ms by default) then exec-path-from-shell will print a warning.

• Non-interactive shells start up faster. Follow the steps in the section above so that you can run your shell without -i and still get the right environment variable settings. When "-i" is then removed from exec-path-from-shell-arguments, this package becomes more efficient.
• Invoking the shell has a non-trivial overhead in any case. Don't call exec-path-from-shell-copy-env repeatedly, since each invocation starts a shell. Instead, set exec-path-from-shell-variables to the full list of vars you want, and call exec-path-from-shell-initialize once.

Further help

• C-h f exec-path-from-shell-initialize
• C-h f exec-path-from-shell-copy-env

💝 Support this project and my other Open Source work via Patreon

💼 LinkedIn profile

✍ sanityinc.com

🐦 @sanityinc