Writing clojure maps/arrays to a file and reading them back

Question

I need to save clojure maps to a file and read them back later to process them.

This is what I could come up with. Is there a better way to accomplish the same thing?

Answer 1

Yes - spit and prn-str for writing, slurp and read-string for reading.

user=> (def a [1 2 3 4])
#'user/a
user=> (prn-str a)
"[1 2 3 4]\n"
user=> (spit "stored-array.dat" (prn-str a))
nil

(in a new REPL session)

user=> (require 'clojure.edn)
nil
user=> (slurp "stored-array.dat")
"[1 2 3 4]\n"
user=> (clojure.edn/read-string (slurp "stored-array.dat"))
[1 2 3 4]

I used a vector for that example, but any data (e.g. maps) should work just as well.

Note that there is a read-string in the main Clojure language, but this is explicitly documented as not being safe for untrusted data, so it's better to use the version from clojure.edn.