How can a clojure script recognise it is running as a script?

[Kelvin Ward]

java -cp clojure.jar clojure.main foo.clj

I'm wondering if the code in foo.clj has anyway to know it is being
executed as a script. In python there's the idiom:

def main(): ...

if __name__ == "__main__":
main()

I can then import the file at the repl and execute main() only if
want. I can also have main called by executing it as a script.

I'm guessing passing a property to the clojure script is the best way
to do this, e.g.:

java -cp clojure.jar -Dclojure.mainscript=foo.clj clojure.main foo.clj

foo.clj:

(defn main []
; ...
)

(if (= (System/getProperty "clojure.mainscript") "foo.clj")
(main))

Any thoughts?

Thanks.

[David Nolen]

The source itself cannot know the way a Python knows. However you can understand how to achieve pretty much the same effect with the following:

http://clojure.org/compilation

[Stuart Sierra]

On Sep 18, 6:46 am, Kelvin Ward <kelvin.d.w...@googlemail.com> wrote:
> java -cp clojure.jar clojure.main foo.clj
>
> I'm wondering if the code in foo.clj has anyway to know it is being
> executed as a script. In python there's the idiom:

This doesn't exist right now. The closest equivalent is:

(ns my-namespace
(:gen-class))

(defn -main [& args]
(println "I was run at the command line."))

This has been discussed at length before. Clojure isn't really a
scripting language, so it may never support this kind of idiom.

-SS

[Kelvin Ward]

Thanks for the help guys, I'll look at compilation.

[ataggart]

Just for my own edification (not being versed in python), what's the
point of knowing that?

[David Nolen]

So that you can write python code that can function both as a shell script and as a library transparently.