java - Capturing System/out in Clojure -

i'm working java package outputs text console , need capture text in string, i'm not sure how this. looking @ clojure documentation seemed have wrap java call in with-out-str isn't working me.

minimal code example: if try

(with-out-str   (.println (system/out) "foo")) 

i'm hoping string value "foo", it's still outputting console instead. doing wrong?

java's system.out.println(...) call println method of printstream instance. need replace system.out stream own instance , capture content:

(import [java.io bytearrayoutputstream printstream])  (def out-buffer (java.io.bytearrayoutputstream.))  (system/setout (java.io.printstream. out-buffer true "utf-8"))  (defn out-str []   (.tostring out-buffer "utf-8")) 

watch out in repl though because uses system.out print results when replace globally, break repl instance.

you can write macro capture content of system.out , restore original printstream instance:

(defmacro with-system-out-str [& body]   `(let [out-buffer# (bytearrayoutputstream.)          original-out# system/out          tmp-out# (printstream. out-buffer# true "utf-8")]      (try        (system/setout tmp-out#)        ~@body        (finally          (system/setout original-out#)))      (.tostring out-buffer# "utf-8")))  (with-system-out-str   (.println system/out "hi")) ;; => "hi\n"