# Leiningen — Automate Clojure Projects Without Losing Your Mind

> Leiningen is the de facto build tool for Clojure. It handles dependency management, project scaffolding, REPL launching, testing, and packaging with a single command-line interface.

## Install

Save as a script file and run:

# Leiningen — Automate Clojure Projects Without Losing Your Mind

## Quick Use
```bash
# Install
curl -o /usr/local/bin/lein https://raw.githubusercontent.com/technomancy/leiningen/stable/bin/lein
chmod +x /usr/local/bin/lein
lein new app myproject
cd myproject && lein run
```

## Introduction
Leiningen is the most widely used build tool in the Clojure ecosystem. It handles the entire project lifecycle—from scaffolding a new project to managing dependencies, running tests, starting a REPL, and building deployable artifacts—all driven by a declarative `project.clj` file.

## What Leiningen Does
- Resolves and downloads dependencies from Maven Central and Clojars repositories
- Scaffolds new projects from templates via `lein new <template> <name>`
- Launches a Clojure REPL with the project classpath fully configured
- Runs tests with `lein test` and generates reports
- Builds uberjars (standalone JARs with all dependencies bundled) for deployment

## Architecture Overview
Leiningen is a Clojure application distributed as a shell script bootstrap. The bootstrap downloads the Leiningen core JAR on first run and delegates to it. Projects are configured through `project.clj`, a Clojure data structure. Dependency resolution uses Apache Maven's Aether library under the hood. Leiningen's plugin architecture allows the community to extend it with tasks for code formatting, Docker builds, ClojureScript compilation, and more.

## Self-Hosting & Configuration
- Install by downloading the `lein` script and placing it on your PATH
- All project settings live in `project.clj` at the project root
- User-level settings go in `~/.lein/profiles.clj` for global plugins and JVM options
- Repositories are configurable: add private Maven repos or S3-backed repositories
- JVM options are set via `:jvm-opts` in `project.clj` or via `LEIN_JVM_OPTS` environment variable

## Key Features
- Template-based project creation with community templates for web apps, libraries, and more
- nREPL integration for connecting editors like Emacs (CIDER), IntelliJ (Cursive), and VS Code (Calva)
- Profile system for environment-specific configuration (dev, test, production)
- Plugin ecosystem covering tasks like `lein-ring` for web servers and `lein-cljsbuild` for ClojureScript
- Offline mode and local repository caching for reproducible builds without network access

## Comparison with Similar Tools
- **Clojure CLI (deps.edn)** — official tool focused on dependency management; Leiningen provides a broader task runner and plugin system
- **Boot** — alternative Clojure build tool using a pipeline model; less widely adopted than Leiningen
- **Maven** — Java build tool; Leiningen wraps Maven's resolver but uses a simpler Clojure-native configuration
- **Gradle** — powerful but complex; Leiningen is purpose-built for Clojure with less configuration overhead

## FAQ
**Q: Should I use Leiningen or the official Clojure CLI?**
A: Leiningen is better for projects that need a full build lifecycle with plugins. The Clojure CLI is lighter and preferred for library development and simple dependency management.

**Q: Can Leiningen build ClojureScript projects?**
A: Yes. Use the `lein-cljsbuild` plugin or `lein-shadow` (wrapping shadow-cljs) for ClojureScript compilation.

**Q: Does Leiningen work with Java dependencies?**
A: Yes. Leiningen resolves dependencies from Maven Central and any Maven-compatible repository, so all Java libraries are accessible.

**Q: How do I create a standalone executable?**
A: Run `lein uberjar` to produce a self-contained JAR file that includes all dependencies and can be run with `java -jar`.

## Sources
- https://github.com/technomancy/leiningen
- https://leiningen.org

---
Source: https://tokrepo.com/en/workflows/asset-de62b9aa
Author: Script Depot