“boot” is a build tooling command for the Clojure programming language. It helps in the development and deployment of Clojure projects. This article provides various use cases of the “boot” command and how to use them.

Use case 1: Start a REPL session either with the project or standalone

Code:

boot repl

Motivation: When working with Clojure projects, it is often necessary to test code snippets or interact with the running project in a REPL (Read-Evaluate-Print Loop) session. This allows for quick experimentation and debugging.

Explanation: The “repl” command is used to start a REPL session. When executed, it launches a Clojure REPL environment where you can interactively evaluate expressions, define functions, and run code.

Example OUTPUT:

nREPL server started on port 54321 on host localhost - nrepl://localhost:54321
REPL-y 0.4.4, nREPL 0.8.0
Clojure 1.10.3

Use case 2: Build a single ‘uberjar’

Code:

boot jar

Motivation: When you want to build a standalone executable JAR file for your Clojure project, the “jar” command comes in handy. This single JAR file contains all the necessary dependencies and can be executed as a standalone application.

Explanation: The “jar” command is used to build an “uberjar” which is a self-contained JAR file that includes both your project’s code and its dependencies. This is useful when you want to distribute your application as a single executable file.

Example OUTPUT:

Building jar...

Use case 3: Learn about a command

Code:

boot cljs --help

Motivation: When working with command-line tools, it is often helpful to have access to proper documentation or help information. The “–help” option provides a quick way to learn about the available options and arguments for a specific command.

Explanation: The “–help” option is used to display the usage information and available options for a command. In this case, it shows the documentation and usage information for the “cljs” command (which is used for ClojureScript-related tasks).

Example OUTPUT:

Usage: boot cljs [options ...]
Options:
  -O, --optimizations OPTIMIZATIONS Option to cljs command
  -C, --compiler-option KEY=VALUE Additional option to cljs.compiler/set-compiler-option!

Use case 4: Generate scaffolding for a new project based on a template

Code:

boot --dependencies boot/new new --template template_name --name project_name

Motivation: Creating a new project from scratch can be time-consuming and error-prone. Using a template provides a pre-configured project structure with best practices, saving time and ensuring a consistent setup.

Explanation: The “new” command with the “boot/new” template is used to generate a new project based on a specified template. The “–template” argument specifies the name of the template, and the “–name” argument specifies the name of the new project.

Example OUTPUT:

Setup a new project using the "web" template? (y/n)

Use case 5: Build for development (if using the boot/new template)

Code:

boot dev

Motivation: During the development phase of a Clojure project, it is common to have a development build that provides features like live reloading and hot code replacement for faster iterations and easier debugging.

Explanation: The “dev” command is used to build a project specifically optimized for development. It typically enables features like live reloading, hot code replacement, and verbose error messages to aid in the development process.

Example OUTPUT:

Building dev...

Use case 6: Build for production (if using the boot/new template)

Code:

boot prod

Motivation: When preparing a Clojure project for production deployment, it is essential to create an optimized build that minimizes the application’s size, removes development-specific features, and ensures high performance.

Explanation: The “prod” command is used to build a project specifically optimized for production deployment. It typically performs aggressive optimizations, removes debug symbols, and generates a compact and efficient output. The resulting build is suitable for deployment in production environments.

Example OUTPUT:

Building prod...

Conclusion:

The “boot” command provides a range of functionality for building and managing Clojure projects. Whether starting a REPL session, building standalone JAR files, generating project scaffolding, or creating optimized builds for development and production, the “boot” command helps streamline the development and deployment process.