clojure.java.io/writer

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Type: function Added: Clojure 1.2 Examples: 3 Runnable: 1

([x & opts])

Attempts to coerce its argument into an open java.io.Writer. Default implementations always return a java.io.BufferedWriter.

Default implementations are provided for Writer, BufferedWriter, OutputStream, File, URI, URL, Socket, and String.

If the argument is a String, it tries to resolve it first as a URI, then as a local file name. URIs with a 'file' protocol are converted to local file names.

Should be used inside with-open to ensure the Writer is properly closed.

Examples

by weiyongqing123 on 2012-02-15 ▶

;; This example shows the use of the ':append' option (defn write-file [] (with-open [w (clojure.java.io/writer "f:/w.txt" :append true)] (.write w (str "hello" "world"))))

by phreed on 2015-06-16 . May have evaluation errors. ▶

;; This example shows the use of the ':encoding' option. (require '(clojure.data.xml :as xml)) (let [tags (xml/element :foo {:foo-attr "foo value"} (xml/element :bar {:bar-attr "bar value"} (xml/element :baz {} "The baz value")))] (with-open [out-file (clojure.java.io/writer "/temp/bar.xml" :encoding "UTF-8")] (xml/emit tags out-file)) (with-open [input (clojure.java.io/reader "/temp/bar.xml")] (xml/parse input))) ;;=> #clojure.data.xml.Element{:tag :foo, :attrs {:foo-attr "foo value"}, ;; :content ;; (#clojure.data.xml.Element{:tag :bar, :attrs {:bar-attr "bar value"}, ;; :content ;; (#clojure.data.xml.Element{:tag :baz, :attrs {}, :content ("The baz value")})})}

by jasonmm on 2017-05-24 . May have evaluation errors. ▶

;; When a Writer is created from a Socket using `with-open`, the ;; underlying Socket is closed along with the Writer. ;; Create the Socket. (require '[clojure.java.io :as io]) (def socket (java.net.Socket.)) (.connect socket (java.net.InetSocketAddress. "www.google.com" 80)) (.isClosed socket) ;;=> false ;; Write to the Socket. (with-open [w (io/writer socket)] (.write w "GET / HTTP/1.0\n\n") (.flush w)) (.isClosed socket) ;;=> true ;; Attempt to read from the Socket. (with-open [r (io/reader socket) s (java.io.StringWriter.)] (io/copy r s)) ;;=> java.net.SocketException: Socket is closed

See also

• clojure.java.io/reader (0)
• clojure.java.io/IOFactory
• clojure.java.io/output-stream
• clojure.core/spit (1)

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