"Leiningen!" he shouted. "You're insane! They're not creatures you can fight--they're an elemental--an 'act of God!' Ten miles long, two miles wide--ants, nothing but ants! And every single one of them a fiend from hell..." -- from Leiningen Versus the Ants by Carl Stephenson
Leiningen is for automating Clojure projects without setting your hair on fire.
If your preferred package manager has a relatively recent version of Leiningen, try that first. Otherwise you can install by hand:
Leiningen bootstraps itself using the
lein shell script;
there is no separate install script. It installs its dependencies
upon the first run on unix, so the first run will take longer.
- Download the script.
- Place it on your path. (I like to use
- Set it to be executable. (
chmod 755 ~/bin/lein)
On Windows most users can get
the batch file.
If you have wget.exe or curl.exe already installed and in PATH, you
can just run
lein self-install, otherwise get the standalone jar from the
If you have Cygwin you should be able to use
the shell script above rather than the batch file.
master branch is currently undergoing massive changes for
Leiningen 2.0; you should not expect it to work. If you want to build
from source for everyday use, use the
The tutorial has a detailed walk-through of the steps involved in creating a new project, but here are the commonly-used tasks:
$ lein new NAME # generate a new project skeleton $ lein test [TESTS] # run the tests in the TESTS namespaces, or all tests $ lein repl # launch an interactive REPL session and socket server $ lein jar # package up the whole project as a .jar file $ lein install [NAME VERSION] # install a project $ lein search ... # find jars for your project.clj dependencies
lein help to see a complete list.
lein help $TASK shows the
usage for a specific task.
You can also chain tasks together in a single command by using commas:
$ lein clean, test foo.test-core, jar
Most tasks need to be run from somewhere inside a project directory to
work, but some (
version, and the
two-argument version of
install) may run from anywhere.
The install task places shell scripts in the
directory for projects that include them, so if you want to take
advantage of this, you should put it on your
project.clj file in the project root should look like this:
(defproject myproject "0.5.0-SNAPSHOT" :description "A project for doing things." :url "http://github.com/technomancy/myproject" :dependencies [[org.clojure/clojure "1.2.1"] [org.clojure/clojure-contrib "1.2.0"]] :plugins [[lein-ring "0.4.5"]])
To find specific versions of a dependency, use
lein new task generates a project skeleton with an
appropriate starting point from which you can work. See the
file for a detailed listing of configuration options.
You can also have user-level configuration that applies for all
~/.lein/init.clj file will be loaded every time
Leiningen launches; any arbitrary code may go there. This code is
executed inside Leiningen itself, not in your project. Set the
:repl-init key in project.clj to point to a namespace if
you want code executed inside your project.
You can change the configuration of your project by applying various profiles. Each profile is defined as a map which gets merged into your project map.
Profiles are read from 3 different locations: (in order of precedence)
:profilesentry in the project map
Each of these should be a map of profile names to profile maps.
Note that profiles have special logic when they are merged into your
project map: maps get merged recursively, but sets are
other collections are
concatenated. Other values are simply
replaced. Profiles take precedence in the order they are specified.
To activate a profile for a given run, use the
$ lein with-profile qa test :database
Multiple profiles may be specified with commas:
$ lein with-profile qa,user test :database
with-profile call does not apply across task comma-chains.
with-profile calls, the
:user profiles are
active by default.
Leiningen supports plugins which may contain both new tasks and hooks
that modify behaivour of existing tasks. See
the plugins wiki page
for a full list. If a plugin is needed for successful test or build
runs, (such as
lein-tar) then it should be added to
project.clj, but if it's for your own convenience (such as
swank-clojure) then it should be added to the
:plugins list in the
:user profile from
explains how to write plugins.
Q: How do you pronounce Leiningen?
A: It's LINE-ing-en. ['laɪnɪŋən]
Q: What's a group ID? How do snapshots work?
A: See the tutorial for background.
Q: How should I pick my version numbers?
A: Use semantic versioning.
Q: What if my project depends on jars that aren't in any repository?
A: The deploy guide explains how to set up a private repository. If you are not sharing them with a team you could also just install locally.
Q: I want to hack two projects in parallel, but it's annoying to switch between them.
A: If you create a directory called
checkouts in your project
root and symlink some other project roots into it, Leiningen will
allow you to hack on them in parallel. That means changes in the
dependency will be visible in the main project without having to go
through the whole install/switch-projects/deps/restart-repl cycle,
and the copy in
checkouts will take precedence over the dependency
declared in project.clj. Note that this is not a replacement for
listing the project in
:dependencies; it simply supplements that for
Q: Is it possible to exclude indirect dependencies?
A: Yes. Some libraries, such as log4j, depend on projects that are not included in public repositories and unnecessary for basic functionality. Projects listed as
:dependencies may exclude
any of their dependencies by using the
:exclusions key. See
lein help sample for details.
Q: What does
java.lang.NoSuchMethodError: clojure.lang.RestFn.<init>(I)V mean?
A: It means you have some code that was AOT (ahead-of-time) compiled with a different version of Clojure than the one you're currently using. If it persists after running
lein clean then it
is a problem with your dependencies. Note that for
your own project that AOT compilation in Clojure is much less
important than it is in other languages. There are a few
language-level features that must be AOT-compiled to work, generally
for Java interop. If you are not using any of these features, you
should not AOT-compile your project if other projects may depend
Q: I'm behind an HTTP proxy; how can I fetch my dependencies?
A: TODO: document aether proxy setup.
Q: What can be done to speed up launch?
A: The main delay involved in Leiningen comes from starting the JVM. Most people use a development cycle that involves keeping a single process running for as long as you're working on that project. Depending on your editor you may be able to do this via its Clojure integration. (See swank-clojure or VimClojure, for example.) Otherwise you can use the basic
Q: Still too slow; what else can make startup faster?
A: If you are running an older version of Leiningen (before 1.7) you can
export LEIN_JVM_OPTS=-XX:+TieredCompilation to improve
boot time. This requires Hotspot version 20 or newer. On newer versions
of Leiningen it is enabled automatically.
Q: I don't have access to stdin inside my project.
A: There's a problem in the library that Leiningen uses to spawn new processes that blocks access to console input. This means that functions like
read-line will not work as expected in most
contexts, though the
repl task necessarily includes a
workaround. You can also use the
trampoline task to
launch your project's JVM after Leiningen's has exited rather than
launching it as a subprocess. TODO: document in-process classloader
Please report issues on the
Github issue tracker
or the mailing list.
Personal email addresses are not appropriate for bug reports. See
the readme for the
leiningen-core library and
more details on how Leiningen's codebase is structured.
Patches are preferred as Github pull requests, though patches from
git format-patch are also welcome on the mailing list. Please use
topic branches when sending pull requests rather than committing
directly to master in order to minimize unnecessary merge commit
Contributors who have had a single patch accepted may request commit rights on the mailing list or in IRC. Please use your judgment regarding potentially-destabilizing work and branches. Other contributors will usually be glad to review topic branches before merging if you ask on IRC or the mailing list.
Contributors are also welcome to request a free Leiningen sticker by asking on the mailing list and mailing a SASE.
You don't need to "build" Leiningen per se, but when you're using a checkout you will need to get its dependencies in place.
Using Leiningen 1.x, run
lein deps in the
subproject directory. Once you do that in most cases a
self-install will usually get you what you need. However, this will
occasionally fail for very new SNAPSHOT versions since the standalone
jar will not have been uploaded yet.
Source Copyright © 2009-2012 Phil Hagelberg, Alex Osborne, Dan Larkin, and other contributors. Distributed under the Eclipse Public License, the same as Clojure uses. See the file COPYING.
Thanks to Stuart Halloway for Lancet and Tim Dysinger for convincing me that good builds are important.
Images Copyright © 2010 Phil Hagelberg. Distributed under the Creative Commons Attribution + ShareAlike License. Full-size version available.