Read and write file in Clojure

file1.clj

(use '[clojure.string :only [split]])
(require '[clojure.java.io :as io])

(def format-str "%1$-255s%2$09d%3$-255s%4$-1000s%5$-1s")

(defn format-line
  [line]
  (let [[v1 v2 v3 v4 v5] (split line #",")]
    (format format-str v1 (read-string v2) v3 v4 v5)))

(defn -main [file]
  (let [lines (split (slurp file) #"\n")]
    (with-open [wrt (io/writer (str file ".txt"))]
      (doseq [line lines]
        (.write wrt (str (format-line line) "\n"))))))