emacs

Emacs Integration

Interact with your running Emacs server via emacsclient. Evaluate Emacs Lisp expressions, read and write buffer contents, execute commands, and access your Emacs environment.

Requirements

• Emacs server running: Start with emacs --daemon or add (server-start) to your init.el
• emacsclient installed: Usually comes with Emacs

Verify: emacsclient -e "(+ 1 2)" should return 3

When NOT to Use This Skill

For reading/writing files on disk: Use the built-in Claude tools instead:

• Read files: Use the Read tool (more efficient, no Emacs dependency)
• Write/edit files: Use the Write/Edit tools (direct file manipulation)
• Search files: Use Grep/Glob tools (optimized for codebase search)

This skill is best reserved for Emacs-only operations:

• Buffers without files (scratch, Messages, etc.)
• Evaluating Emacs Lisp expressions
• Querying Emacs state (variables, configuration, metadata)
• Working with Emacs-specific data (Org entries, buffer lists, etc.)

Even if a buffer has a file backing it, use the Read/Write tools for the file content—they're simpler and don't require a running Emacs instance.

Quick Reference

Evaluate Emacs Lisp

emacsclient -e "(+ 1 2)"
emacsclient -e "(buffer-name)"
emacsclient -e "(symbol-value 'load-path)"

Read Buffers

# Current buffer
emacsclient -e "(buffer-substring-no-properties (point-min) (point-max))"

# Specific buffer
emacsclient -e "(with-current-buffer \"myfile.org\" (buffer-substring-no-properties (point-min) (point-max)))"

Write to Buffers

# Replace buffer contents
emacsclient -e "(with-current-buffer \"scratch\" (erase-buffer) (insert \"new content\"))"

# Append to buffer
emacsclient -e "(with-current-buffer \"notes\" (goto-char (point-max)) (insert \"\\nNew line\"))"

Get/Set Variables

# Get variable
emacsclient -e "(symbol-value 'user-full-name)"

# Set variable
emacsclient -e "(setq fill-column 100)"

Execute Commands

# Save buffer
emacsclient -e "(call-interactively 'save-buffer)"

# Switch to buffer
emacsclient -e "(switch-to-buffer \"*scratch*\")"

Common Patterns

Insert code from Claude into Emacs

(with-current-buffer "myfile.el"
  (goto-char (point-max))
  (newline)
  (insert "(defun my-function () \"docstring\" ())"))

Get project files via Emacs

(directory-files "/path/to/project" t "\\.el$")

Query Org mode structure

(org-map-entries (lambda () (org-get-heading t t)))

Get file metadata

; File exists?
(file-exists-p "/path/to/file")

; File size
(file-attribute-size (file-attributes "/path/to/file"))

; Modification time
(file-attribute-modification-time (file-attributes "/path/to/file"))

List all open buffers

(mapcar #'buffer-name (buffer-list))

Advanced: Org Mode Integration

Extract TODO items from your Emacs notes:

(org-map-entries (lambda () 
  (cons (org-get-heading t t) 
        (org-get-property-block (point)))))

Insert a new TODO into your inbox:

(with-current-buffer "inbox.org"
  (goto-char (point-max))
  (insert "\n* TODO ")
  (insert "YOUR TASK HERE"))

Error Handling

Error	Solution
emacsclient: can't find socket	Start Emacs: emacs --daemon
Symbol's value as variable is void	Check variable name spelling
Buffer ... does not exist	Verify buffer name: emacsclient -e "(buffer-list)"
Wrong number of arguments	Review Emacs Lisp docs for function signature

Tips

• Escaping: Use \\n for newlines in string literals
• Large buffers: Reading/writing 10MB+ may be slow
• Character encoding: UTF-8 is assumed
• Security: Only use with trusted Emacs configurations

See Also

• Emacs Manual: Emacs Server
• Org Mode Manual
• Emacs Lisp Reference