Elisp: exec-path, External Program Search Paths

exec-path

exec-path

List of dir paths to search external programs. An element may be nil, it means default-directory.

By default the last element of this list is exec-directory (the emacs bin dir.) .

Emacs uses exec-path to find executable binary programs.

For example,

• Alt+x diff tries to find unix diff
• Alt+x grep tries to find unix grep
• Alt+x shell tries to find unix bash if emacs is on linux.
• Alt+x dired-do-compress tries to find unix gzip
• Alt+x ispell-word tries to find unix ispell or aspell

By default, emacs copies the value of (getenv "PATH") to exec-path. So, their values should be identical.

Here's a example of setting exec-path:

(when (eq system-type 'windows-nt) (push (expand-file-name "~/bin/oxipng/") exec-path))

• Emacs Init: Environment Variables

Difference between exec-path and PATH

• The value of environment variable “PATH” is used by emacs when you are trying to call a linux command from a shell in emacs.
• The exec-path is used by emacs itself to find programs it needs for its features, such as spell checking, file compression, compiling, grep, diff, etc.

The value of (getenv "PATH") and exec-path do not need to be the same.