$ cljClojure 1.12.0user=>

user=> (+ 2 3)   # press the `enter` key after typing the expression to evaluate it5                # result of expressionuser=>           # type Ctrl-D here to exit the REPL (does not print)$

{:deps {clojure.java-time/clojure.java-time {:mvn/version "1.1.0"}}}

$ clj -X:deps find-versions :lib clojure.java-time/clojure.java-time...omitted{:mvn/version "1.0.0"}{:mvn/version "1.1.0"}

$ cljDownloading: clojure/java-time/clojure.java-time/1.1.0/clojure.java-time-1.1.0.pom from clojarsDownloading: clojure/java-time/clojure.java-time/1.1.0/clojure.java-time-1.1.0.jar from clojarsClojure 1.12.0user=> (require '[java-time.api :as t])niluser=> (str (t/instant))"2022-10-07T16:06:50.067221Z"

$ mkdir hello-world$ cp deps.edn hello-world$ cd hello-world$ mkdir src

(ns hello  (:require [java-time.api :as t]))(defn time-str  "Returns a string representation of a datetime in the local time zone."  [instant]  (t/format    (t/with-zone (t/formatter "hh:mm a") (t/zone-id))    instant))(defn run [opts]  (println "Hello world, the time is" (time-str (t/instant))))

$ clj -X hello/runHello world, the time is 12:19 PM

├── time-lib│   ├── deps.edn│   └── src│       └── hello_time.clj└── hello-world    ├── deps.edn    └── src        └── hello.clj

(ns hello-time  (:require [java-time.api :as t]))(defn now  "Returns the current datetime"  []  (t/instant))(defn time-str  "Returns a string representation of a datetime in the local time zone."  [instant]  (t/format    (t/with-zone (t/formatter "hh:mm a") (t/zone-id))    instant))

(ns hello  (:require [hello-time :as ht]))(defn run [opts]  (println "Hello world, the time is" (ht/time-str (ht/now))))

{:deps {time-lib/time-lib {:local/root "../time-lib"}}}

$ clj -X hello/runHello world, the time is 12:22 PM

cd ../time-libgit initgit add deps.edn srcgit commit -m 'init'

git tag -a 'v0.0.1' -m 'initial release'git push --tags

{:deps {io.github.yourname/time-lib {:git/tag "v0.0.1" :git/sha "4c4a34d"}}}

$ clj -X hello/runCloning: https://github.com/yourname/time-libChecking out: https://github.com/yourname/time-lib at 4c4a34dHello world, the time is 02:10 PM

Typically, the project classpath includes only the project source, not its test source by default. You can add extra paths as modifications to the primary classpath in the make-classpath step of the classpath construction. To do so, add an alias:test that includes the extra relative source path"test":

Apply that classpath modification and examine the modified classpath by invokingclj -A:test -Spath:

Note that the test dir is now included in the classpath.

You can extend the:test alias in the previous section to include the cognitect-labstest-runner for running all clojure.test tests:

Extend the:test alias:

And then execute the test runner using the default config (run all tests in -test namespaces under the test/ dir):

Aliases in thedeps.edn file can also be used to add optional dependencies that affect the classpath:

Here the:bench alias is used to add an extra dependency, namely the criterium benchmarking library.

You can add this dependency to your classpath by adding the:bench alias to modify the dependency resolution:clj -A:bench.

It can be helpful to experiment with a library without adding it to an existingdeps.edn file or creating one.

Note that due to escaping rules, it’s best to wrap the config data in single quotes.

Some dependencies will require a preparation step before they can be used on the classpath. These libs should state this need in theirdeps.edn:

Including the top-level key:deps/prep-lib tells the tools.deps classpath construction that something extra is needed to prepare this lib and that can be performed by invoking thecompile function in the:build alias. Once the prepare step has been done, it should create the path"target/classes" and that can be checked for completion.

You depend on this library like any other source-based library (could be git or local):

If you then try to include that library on your classpath you’ll see an error:

You can then tell the CLI to prep using this command (this is a 1-time action for a particular lib version):

You can use multiple aliases in combination. For example thisdeps.edn file defines two aliases -:old-async to force the use of an older core.async version and:bench to add an extra dependency:

Activate both aliases as follows:clj -A:bench:old-async.

Occasionally you may need to refer directly to a jar on disk that is not present in a Maven repository, such as a database driver jar.

Specify local jar dependencies with a local coordinate that points directly to a jar file instead of a directory:

When usinggen-class orgen-interface, the Clojure source must be ahead-of-time compiled to generate the java class(es).

This can be done by callingcompile. The default destination for compiled class files isclasses/, which needs to be created and added to the classpath:

Editdeps.edn to add"classes" to the paths:

Declare a class with gen-class insrc/my_class.clj:

Then you can reference the class with:import in another source filesrc/hello.clj. Notice that the namespace is also added in:require so compilation can automatically find all dependent namespaces and compile them.

You can compile in the REPL or run a script to do the compilation:

And then run the hello namespace:

SeeCompilation and Class Generation for a complete reference.

Clojure provides built-in support for runningsocket servers, and in particular using them to host remote REPLs.

To configure a socket server repl, add the following base configuration to yourdeps.edn:

And then start the server by invoking with the alias:

If you like, you can also override the default parameters (or add additional options) on the command line:

You can use netcat to connect from another terminal:

Use Ctrl-D to exit the repl and Ctrl-C to exit the server.

There are several helpful tools in the built-in:deps alias to explore the full set of transitive deps used by your project (and their licenses).

Tolist the full set of all the deps included on your classpath, useclj -X:deps list. For example in thehello-world application at the top of this guide, you would see something like this:

The full set of transitive dependencies used by your application is listed in alphabetical order with version and license. See the api docs for additional printing options.

If you want to understand thetree structure of your dependencies and how version selection choices were made, useclj -X:deps tree:

There were no version selections made here, but seethe docs for more on how choices are explained in the tree if needed.

Both of these helper functions take an optional:aliases argument if you wish to examine the dependency list or tree with one or more aliases applied, such asclj -X:deps list :aliases '[:alias1 :alias2]'.