I wrote a small "hello world" program on Linux to get started with the language.
Now I'd like to run it and see what it outputs.
How can I run this code? What command should I run?
Create a new Clojure project with Leiningen. Build the project to create an executable JAR file. Execute the JAR file. Execute code in a Clojure REPL.
CLJ files mostly belong to Clojure by Rich Hickey, Open Source Project Sponsor. Clojure is a dynamic programming language that targets the Java Virtual Machine. It is designed to be a general-purpose language and is a compiled language - it compiles directly to JVM bytecode, yet remains completely dynamic.
FWIW, I'm interpreting the question here as specifically asking how to run a single file, like a script, versus as a part of a compiled project. Obviously though, there's a relationship between how and why you would want to run a single file, and how you would want to build a full project, so I weigh that in some as well.
clj
tooling Docs are here:
https://clojure.org/guides/deps_and_cli
This is an official part of the Clojure project, which by itself is a pretty good reason to go this route. However, it has a couple of advantages over the other solutions here:
deps.edn
~/.clojure/deps.edn
seems to do a better job of cleanly providing reusable functionality via its aliass than ~/.lein/profiles.clj
clj
won't choke on a borked src file, like lein repl
doesSimply
clj your-code-file.clj
Or if you have dependencies
clj -Sdeps '{:deps {clj-time {:mvn/version "0.14.2"}}} your-code-file.clj
Works well as a shebang in scripts as well!
#!clj -deps '{:deps {clj-time {:mvn/version "0.14.2"}}} (ns my-crazy-script! (:require ...)) ...
I recommend installing with homebrew, which now works on both Mac and Linux. If you're on Windows I'd recommend using the WSL+brew.
The one advantage I see of lein
(see below) tooling over clj
generally is that lein
handles a little more of the process of building and packaging your code base, when you get to that point. However, there are other ways of handing that (see pack, uberdeps or cambada), and the advantages of clj
mentioned above outweigh IMHO.
If you are trying to run a single file, as apposed to an entire project, there's a good chance your in "scripting territory". Unfortunately, the JVM takes a while to boot up, as does Clojure itself. Via the magic of GraalVM and the SCI, Babashka is able to support most of the Clojure language with blazing fast startup times. It also comes with quite a few "batteries included" for typical scripting tasks, making it a perfect complement to clj
when you want fast-executing, short lived processes.
Once you install it you can simply bb you-code-file.clj
, or use #!bb
in your shebang. See the docs for more usage instructions:
https://babashka.org/
lein
& lein-exec
If you prefer lein
tooling, or have a ~/.lein/profiles.clj
file handy already and don't want to invest in learning clj
/deps.edn
, you can consider looking at lein-exec
.
If you already have a project.clj
set up with dependencies, you can of course run lein run -m <yer-namespace>[/<yer-main-fn>]
.
As mentioned above, the one advantage of lein
over clj
is that it is a complete build tool, and can make jars/uberjars for you with lein jar
or lein uberjar
, do deploys and such.
I'd recommend http://planck-repl.org/. It now supports (bootstrapped) quick launching of ClojureScript scripts without having to fire up the JVM or Clojure. Like babashka, this makes it great for scripting. However, I find babashka both more powerful and more natural for scripting, so I'd start there unless you have a particular reason for wanting to use Cljs (more familiarity with JS/node, need of certain cljs libraries, etc).
For more substantial projects (beyond scripting), you may want to look at Shadlow-CLJS, for its ease of incorporating vanilla JS projects. And FWIW, Shadow nicely integrates with both deps and lein, and has it's own built in hode code reloading, like figwheel.
java
You can, of course, as has been suggested in another answer, use
java -cp clojure.jar clojure.main file.clj
But you don't see that in the wild too often, because it's a pain to have to find the path to your clojure.jar
and manually composing classpaths for dependencies sucks. But, you know, to each their own.
You can run script with following command:
java -cp clojure.jar clojure.main file.clj
but it's better to use leiningen, especially when you'll start to add dependencies to your project. lein provides number of commands to run your code (with all necessary dependencies), pack code into archive with lein jar
, or create complete, independent archives with lein uberjar
that you can run with:
java -jar your_app.jar
command
P.S. You can read how to use lein
in following article - it describes base tasks & configurations
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