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October 1, 2022

Clojure Goodness: Writing Text File Content With spit

In a previous post we learned how to read text file contents with the slurp function. To write text file content we use the spit function. We content is defined in the second argument of the function. The first argument allows several types that will turn into a Writer object used for writing the content to. For example a string argument is used as URI and if that is not valid as a file name of the file to read. A File instance can be used directly as argument as well. But also Writer, BufferedWriter, OutputStream, URI, URL and Socket. As an option we can specify the encoding used to write the file content using the :encoding keyword. The default encoding is UTF-8 if we don't specify the encoding option. With the option :append we can define if content needs to be appended to an existing file or the content should overwrite existing content in the file.

In the following example we use the spit function with several types for the first argument:

(ns mrhaki.sample.spit
  (:import ( FileWriter FilterWriter StringWriter File)))

;; With spit we can write string content to a file.
;; spit treats the first argument as file name if it is a string.
(spit "files/data/output.txt" (println-str "Clojure rocks!"))

;; We can add the option :append if we want to add text
;; to a file, instead of overwriting the content of a file.
(spit "files/data/output.txt" (println-str "And makes the JVM functional.") :append true)

;; Another option is the :encoding option which is UTF-8 by default
(spit "files/data/output.txt" (str "Clojure rocks!") :encoding "UTF-8")

;; The first argument can also be a File.
(spit (File. "files/data/file.xt") "Sample")

;; We can pass a writer we create ourselves as well.
(spit (FileWriter. "files/data/output.txt" true) "Clojure rocks")

;; Or use a URL or URI instance.
(spit (new "file:files/data/url.txt") "So many options...")
(spit ( "file:files/data/url.txt") "And they all work!" :append true)

Written with Clojure 1.11.1.