clojure - 如何用 "~"替换主页路径？

Question

如果我从命令行传入路径，“~”将扩展到我的主目录:

(defn -main
  "I don't do a whole lot ... yet."
  [& args]
  (doseq [arg args]
    (println arg)))

britannia:uberjar srseverance$ java -jar args-0.1.0-SNAPSHOT-standalone.jar ~/158.clj 
/Volumes/Macintosh HD/Users/srseverance/158.clj

但是如果我尝试使用包含 ~ 的路径文件，我将找不到该文件。

user> (with-open [r (clojure.java.io/reader "~/158.clj")]
        (doall (line-seq r)))
FileNotFoundException ~/158.clj (No such file or directory)  java.io.FileInputStream.open0 (FileInputStream.java:-2)

如何获取“~/158.clj”之类的字符串并返回 clojure.java.io/reader 可以使用的内容，例如“/Volumes/Macintosh HD/Users/srseverance/158.clj”？

Answer 1

您可以定义

(defn expand-home [s]
  (if (.startsWith s "~")
    (clojure.string/replace-first s "~" (System/getProperty "user.home"))
    s))

并用它来解析主目录:

(clojure.java.io/reader (expand-home "~/158.clj"))]

您还可以查看fs expand-home 的库定义，它解决了下面 bfontaine 评论中概述的 ~foo 问题:

(let [homedir (io/file (System/getProperty "user.home"))
      usersdir (.getParent homedir)]
  (defn home
    "With no arguments, returns the current value of the `user.home` system
     property. If a `user` is passed, returns that user's home directory. It
     is naively assumed to be a directory with the same name as the `user`
     located relative to the parent of the current value of `user.home`."
    ([] homedir)
    ([user] (if (empty? user) homedir (io/file usersdir user)))))

(defn expand-home
  "If `path` begins with a tilde (`~`), expand the tilde to the value
  of the `user.home` system property. If the `path` begins with a
  tilde immediately followed by some characters, they are assumed to
  be a username. This is expanded to the path to that user's home
  directory. This is (naively) assumed to be a directory with the same
  name as the user relative to the parent of the current value of
  `user.home`."
  [path]
  (let [path (str path)]
    (if (.startsWith path "~")
      (let [sep (.indexOf path File/separator)]
        (if (neg? sep)
          (home (subs path 1))
          (io/file (home (subs path 1 sep)) (subs path (inc sep)))))
      path)))