Using Clojure tools

The clojure command provided by installing Clojure CLI tools can be used to evaluate code, run Clojure applications and start a REPL for a Clojure editor or a command line REPL UI.

Clojure CLI tools are extended by adding aliases for community tools, e.g. practicalli/clojure-deps-edn

Editor used for majority of developer workflows

A REPL connected Editor provides the richest developer workflow for Clojure

Common tasks for Clojure development

Commands to use for common tasks and where their aliases are included in Clojure CLI tools or require an alias (either in a project or user-wide deps.edn file).

Task Command Built-in
Run Command Line REPL clojure or clj if rlwrap binary installed Yes
Run Command Line REPL with Rebel clojure -M:repl/rebel Add alias
Run REPL process with nREPL editor support clojure -M:middleware/cider-clj Add alias
Create project (clojure exec) clojure -X:new :template app :name practicalli/my-app Add alias
Create project (clojure main) clojure -M:new app practicalli/my-app Add alias
Download dependencies clojure -Spath or clojure -P (plus optional aliases) Yes
Run the project clojure -M -m domain.main-namespace Yes
Run the project clojure -X:project/run -m domain.main-namespace Add alias
Find libraries (mvn & git) clojure -M:project/find-deps library-name Add alias
Check for new dependency versions clojure -M:project/outdated Add alias
Run tests clojure -M:test/runner Add alias
Package library clojure -X:project/jars Add alias
Deploy library locally clojure -X:deps mvn-install Yes
Package application clojure -X:project/uberjar Add alias

Clojure CLI tools can also be used for evaluating an expressions or running Clojure from files as scripts, although these approaches are less common.

What version of Clojure CLI tools are installed?

The deps.edn file allows you to specify a particular version of the Clojure language the REPL and project use. You can also evaluate *clojure-version* in a REPL to see which version of the Clojure language is being used.

clojure -Sdescribe will show you the version of the Clojure CLI tools that is currently installed.

clojure cli tools - describe install version

clojure -Sverbose will also show the version of Clojure CLI tools used and then run a REPL

Clojure CLI main flag options

The most used flags for the clojure command

Flag Purpose Config used
-M Run Clojure project with clojure.main deps, path, :main-opts & command line args
-P Prepare / dry run (CI servers, Containers) deps, path
-P -M:aliases Prepare / dry run including alias deps and paths deps, path
-P -X:aliases Prepare / dry run including alias deps and paths deps, path
-X Execute a qualified function, optional default arguments deps, path, :exec-fn, :exec-args & :key val args
-J Java Virtual Machine specific options (heap size, etc)
  • deps = :deps, :extra-deps, replace-deps
  • path = :path, :extra-paths, replace-paths

Which flag to use?

The -M flag should work with all community tools, at they are typically support the Clojure.main approach with free-form string options as arguments.

The -X flag should be used for the new built-in aliases and for any tools supporting Clojure exec approach, with arguments passed as key/value pairs. More tools should start adopting the -X flag and supporting key/value arguments in future.

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