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Java example source code file (shell.clj)

This example Java source code file (shell.clj) is included in the "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bytearrayoutputstream, defaults, eclipse, hickey, iso-8859-1, passes, reader, runtime/getruntime, sets, string, stringwriter, utf-8

The shell.clj Java example source code

;   Copyright (c) Rich Hickey. All rights reserved.
;   The use and distribution terms for this software are covered by the
;   Eclipse Public License 1.0 (
;   which can be found in the file epl-v10.html at the root of this distribution.
;   By using this software in any fashion, you are agreeing to be bound by
;   the terms of this license.
;   You must not remove this notice, or any other, from this software.

  ^{:author "Chris Houser, Stuart Halloway",
    :doc "Conveniently launch a sub-process providing its stdin and
collecting its stdout"}
  (:use [ :only (as-file copy)])
  (:import ( ByteArrayOutputStream StringWriter)
           (java.nio.charset Charset)))

(def ^:dynamic *sh-dir* nil)
(def ^:dynamic *sh-env* nil)

(defmacro with-sh-dir
  "Sets the directory for use with sh, see sh for details."
  {:added "1.2"}
  [dir & forms]
  `(binding [*sh-dir* ~dir]

(defmacro with-sh-env
  "Sets the environment for use with sh, see sh for details."
  {:added "1.2"}
  [env & forms]
  `(binding [*sh-env* ~env]
(defn- aconcat
  "Concatenates arrays of given type."
  [type & xs]
  (let [target (make-array type (apply + (map count xs)))]
    (loop [i 0 idx 0]
      (when-let [a (nth xs i nil)]
        (System/arraycopy a 0 target idx (count a))
        (recur (inc i) (+ idx (count a)))))

(defn- parse-args
  (let [default-encoding "UTF-8" ;; see sh doc string
        default-opts {:out-enc default-encoding :in-enc default-encoding :dir *sh-dir* :env *sh-env*}
        [cmd opts] (split-with string? args)]
    [cmd (merge default-opts (apply hash-map opts))]))

(defn- ^"[Ljava.lang.String;" as-env-strings 
  "Helper so that callers can pass a Clojure map for the :env to sh."
   (nil? arg) nil
   (map? arg) (into-array String (map (fn [[k v]] (str (name k) "=" v)) arg))
   true arg))

(defn- stream-to-bytes
  (with-open [bout (ByteArrayOutputStream.)]
    (copy in bout)
    (.toByteArray bout)))

(defn- stream-to-string
  ([in] (stream-to-string in (.name (Charset/defaultCharset))))
  ([in enc]
     (with-open [bout (StringWriter.)]
       (copy in bout :encoding enc)
       (.toString bout))))

(defn- stream-to-enc
  [stream enc]
  (if (= enc :bytes)
    (stream-to-bytes stream)
    (stream-to-string stream enc)))

(defn sh
  "Passes the given strings to Runtime.exec() to launch a sub-process.

  Options are

  :in      may be given followed by any legal input source for
 , e.g. InputStream, Reader, File, byte[],
           or String, to be fed to the sub-process's stdin.
  :in-enc  option may be given followed by a String, used as a character
           encoding name (for example \"UTF-8\" or \"ISO-8859-1\") to
           convert the input string specified by the :in option to the
           sub-process's stdin.  Defaults to UTF-8.
           If the :in option provides a byte array, then the bytes are passed
           unencoded, and this option is ignored.
  :out-enc option may be given followed by :bytes or a String. If a
           String is given, it will be used as a character encoding
           name (for example \"UTF-8\" or \"ISO-8859-1\") to convert
           the sub-process's stdout to a String which is returned.
           If :bytes is given, the sub-process's stdout will be stored
           in a byte array and returned.  Defaults to UTF-8.
  :env     override the process env with a map (or the underlying Java
           String[] if you are a masochist).
  :dir     override the process dir with a String or

  You can bind :env or :dir for multiple operations using with-sh-env
  and with-sh-dir.

  sh returns a map of
    :exit => sub-process's exit code
    :out  => sub-process's stdout (as byte[] or String)
    :err  => sub-process's stderr (String via platform default encoding)"
  {:added "1.2"}
  [& args]
  (let [[cmd opts] (parse-args args)
        proc (.exec (Runtime/getRuntime) 
               ^"[Ljava.lang.String;" (into-array cmd)
               (as-env-strings (:env opts))
               (as-file (:dir opts)))
        {:keys [in in-enc out-enc]} opts]
    (if in
        (with-open [os (.getOutputStream proc)]
          (copy in os :encoding in-enc)))
      (.close (.getOutputStream proc)))
    (with-open [stdout (.getInputStream proc)
                stderr (.getErrorStream proc)]
      (let [out (future (stream-to-enc stdout out-enc))
            err (future (stream-to-string stderr))
            exit-code (.waitFor proc)]
        {:exit exit-code :out @out :err @err}))))


(println (sh "ls" "-l"))
(println (sh "ls" "-l" "/no-such-thing"))
(println (sh "sed" "s/[aeiou]/oo/g" :in "hello there\n"))
(println (sh "sed" "s/[aeiou]/oo/g" :in ( "hello there\n")))
(println (sh "cat" :in "x\u25bax\n"))
(println (sh "echo" "x\u25bax"))
(println (sh "echo" "x\u25bax" :out-enc "ISO-8859-1")) ; reads 4 single-byte chars
(println (sh "cat" "myimage.png" :out-enc :bytes)) ; reads binary file into bytes[]
(println (sh "cmd" "/c dir 1>&2"))


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