Swank/slime support for clojure
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Swank Clojure

Swank Clojure is a server that allows SLIME (the Superior Lisp Interaction Mode for Emacs) to connect to Clojure projects.


The simplest way is to just jack-in from an existing project using Leiningen:

  • Install clojure-mode either from Marmalade or from git.
  • lein plugin install swank-clojure 1.3.2
  • From inside a project, invoke M-x clojure-jack-in

That's all it takes! There are no extra install steps beyond clojure-mode on the Emacs side and the swank-clojure plugin on the Leiningen side.

SLIME Commands

Commonly-used SLIME commands:

  • C-c TAB: Autocomplete symbol at point
  • C-x C-e: Eval the form under the point
  • C-c C-k: Compile the current buffer
  • C-c C-l: Load current buffer and force required namespaces to reload
  • M-.: Jump to the definition of a var
  • C-c S-i: Inspect a value
  • C-c C-m: Macroexpand the call under the point
  • C-c C-d C-d: Look up documentation for a var
  • C-c C-z: Switch from a Clojure buffer to the repl buffer
  • C-c M-p: Switch the repl namespace to match the current buffer
  • C-c C-w c: List all callers of a given function

Pressing "v" on a stack trace a debug buffer will jump to the file and line referenced by that frame if possible.

If you need help with Emacs in general, try pressing C-h t (control-h followed by regular t) for the introductory tutorial. You may also find the commercial PeepCode Emacs screencast helpful.

Note that SLIME was designed to work with Common Lisp, which has a distinction between interpreted code and compiled code. Clojure has no such distinction, so the load-file functionality is overloaded to add :reload-all behaviour.

Alternate Usage

There are other ways to use Swank for different specific circumstances. For each of these methods you will have to install slime and slime-repl manually as outlined in "Connecting with SLIME" below.

Standalone Server

If you just want a standalone swank server with no third-party libraries, you can use the shell wrapper that Leiningen installs for you:

$ lein plugin install swank-clojure 1.3.2
$ ~/.lein/bin/swank-clojure

M-x slime-connect

If you put ~/.lein/bin on your $PATH it's even more convenient.

Manual Swank in Project

You can also start a swank server from inside your project but launch the server from outside Emacs (so that it can stay up longer than you have Emacs open, or so you can debug from a remote machine), you can use lein swank:

$ lein swank # you can specify PORT and HOST optionally

If you're using Maven, add this to your pom.xml under the <dependencies> section:


Then you can launch a swank server like so:

$ mvn clojure:swank

Note that due to a bug in clojure-maven-plugin, you currently cannot include it as a test-scoped dependency; it must be compile-scoped. You also cannot change the port from Maven; it's hard-coded to 4005.

Put this in your Emacs configuration to get syntax highlighting in the slime repl:

(add-hook 'slime-repl-mode-hook 'clojure-mode-font-lock-setup)

Connecting with SLIME

If you're not using the M-x clojure-jack-in method mentioned above, you'll have to install SLIME yourself. The easiest way is to use package.el. If you are using Emacs 24 or the Emacs Starter Kit, then you have it already. If not, get it from Emacs's own repository.

Then add Marmalade as an archive source in your Emacs config:

(require 'package)
(add-to-list 'package-archives
             '("marmalade" . "http://marmalade-repo.org/packages/") t)

Then you can do M-x package-list-packages. Go down to slime-repl and mark it with i. Execute the installation by pressing x.

When you perform the installation, you will see warnings related to the byte-compilation of the packages. This is normal; the packages will work just fine even if there are problems byte-compiling it upon installation.

Slime defaults to iso-8895-1 encoding if you aren't using M-x clojure-jack-in because that's what Common Lisp uses. You'll need to fix this when connecting to Clojure:

(setq slime-net-coding-system 'utf-8-unix)

Then you should be able to connect to the swank server you launched:

M-x slime-connect

It will prompt you for your host (usually localhost) and port. It may also warn you that your SLIME version doesn't match your Swank version; this should be OK.

Known Issues

Currently having multiple versions of swank-clojure on the classpath can cause issues when running "lein swank" or "lein jack-in". It's recommended to not put swank-clojure in your :dev-dependencies but have users run "lein plugin install" to have it installed globally.

Having old versions of SLIME installed either manually or using a system-wide package manager like apt-get may cause issues. Also the official CVS version of SLIME is not supported; it often breaks compatibility with Clojure.

Not all SLIME functionality from Common Lisp is available in Clojure at this time; in particular only a small subset of the cross-reference commands are implemented.

Swank-clojure and SLIME are only tested with GNU Emacs; forks such as Aquamacs and XEmacs may work but are untested.


You can embed Swank Clojure in your project, start the server from within your own code, and connect via Emacs to that instance:

(ns my-app
  (:require [swank.swank]))
(swank.swank/start-server) ;; optionally takes a port argument

Then use M-x slime-connect to connect from within Emacs.

You can also start the server directly from the "java" command-line launcher if you AOT-compile it and specify "swank.swank" as your main class.


You can set repl-aware breakpoints using swank.core/break. For now, see Hugo Duncan's blog for an explanation of this excellent feature.

CDT (included in Swank Clojure since 1.4.0) is a more comprehensive debugging tool that includes support for stepping, seting breakpoints, catching exceptions, and eval clojure expressions in the context of the current lexical scope.


The mailing list and clojure channel on Freenode are the best places to bring up questions/issues.

Contributions are preferred as either Github pull requests or using "git format-patch". Please use standard indentation with no tabs, trailing whitespace, or lines longer than 80 columns. See this post on submitting good patches for some tips. If you've got some time on your hands, reading this style guide wouldn't hurt either.


Copyright (C) 2008-2011 Jeffrey Chu, Phil Hagelberg, Hugo Duncan, and contributors

Licensed under the EPL. (See the file COPYING.)